Substream - sub_gw_impact_oceans

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  2. 01-09-2003 eco nws - global warming - system - atmosphere - co2 - water - impact - oceans - acidification - Greenhouse gases may be acidifying the oceans - as well as changing the climate, researchers have found. They warned that if carbon dioxide emissions continued unabated seas may turn more acidic than they have been for 300 million years. This could prove a serious threat to marine life. Many marine organisms, such as corals, are highly sensitive to acidity changes. Acidity and alkalinity is measured using the pH scale. The lower the pH, the higher the acidity. When carbon dioxide dissolves in water, the pH drops. Researchers from the Lawrence Livermore National Laboratory in California compared actual changes in ocean pH from geological and historical records with those predicted by a theoretical model. Ocean surface pH was 8.3 after the last ice age, and 8.2 before carbon dioxide emissions took off in the industrial era. Today, it is 8.1. (ananova)

  3. 15-07-2004 eco nws - global warming - system - atmosphere - co2 - impact - oceans - oceans absorbed missing co2 - Nearly half the excess carbon dioxide spilled into the air by humans over the past two centuries has been taken up by the ocean, a study says. If the process continues, it could damage the ability of many ocean creatures to make their shells, says an accompanying report. Carbon dioxide, produced by burning fossil fuels and other industrial processes, is one of the most important 'greenhouse' gasses that many scientists fear may be causing global warming by trapping heat in the Earth's atmosphere. The atmosphere currently includes about 380 parts per million of carbon dioxide, up from 280 parts per million in 1800, according to scientists. But that accounts for only about half the CO2 released into the air in that period, causing researchers to speculate about what had happened to the rest. A team led by Christopher L. Sabine of the National Oceanic and Atmospheric Administration reports in Friday's issue of the journal Science that the missing gas is dissolved in the ocean. (wired)

  4. 15-07-2004 eco nws - global warming - system - atmosphere - impact - oceans - one third of ocean co2 storage capacity used - Humans have used up about one-third of the potential of the world's oceans to absorb the greenhouse gas carbon dioxide generated by human activities such as burning coal for electricity and gasoline for transportation. The first comprehensive study of the ocean storage of carbon dioxide derived from human activities - anthropogenic CO2 - determined that the oceans have taken up some 118 billion metric tons of this carbon dioxide between 1800 and 1994. The international team of scientists who completed the survey said this total is approximately one-third of the oceans' long-term potential. The research team, which included scientists from the United States, South Korea, Australia, Canada, Japan, Spain, and Germany, based the study on a 10 year survey of global ocean carbon distributions in the 1990s. (earthhope)

  5. 11-12-2004 eco nws - global warming - impact - oceans - sea level - report - nef - Rich nations are prepared to spend up to $32bn to protect the European coastline from sea level rise - but have promised only $0.41bn to help poor nations confront climate change, according to a new report launched yesterday. In fact, the cost of defending the coastline of just one nation, Tanzania, from a one metre rise in sea level could total more than $14bn. Cast Adrift, a report from the pressure groups Greenpeace and the New Economic Foundation, highlights the gap between the developing and developed worlds as the latest round of climate change talks gather pace in Argentina. Global average temperatures have been rising for more than a decade, increasing the risk of more frequent windstorms, floods, droughts and even ice storms. These would mean extra insurance liability and business risk, additional construction costs, warning systems, sea and river defences, and greater spending on water, health, agriculture and tourism. (guardian)

  6. 24-01-2005 eco nws - global warming - impact - oceans - report - icct - The world may have little more than a decade to avert catastrophic climate change, politicians and scientists say. A report by the International Climate Change Taskforce says it is vital that global temperatures do not rise by more than 2C above pre-industrial levels. Atmospheric carbon dioxide levels that would trigger this rise could possibly be reached in about 10 years or so. (bbc)

  7. 02-02-2005 eco nws - global warming - impact - oceans - climate - chance of gulf stream change now 50% - The chance of the Gulf Stream, which brings warm waters around the British Isles, being halted, sending temperatures plummeting by more than 5C, is now more than 50%, a scientific conference on climate change was told yesterday. The conference, called by Tony Blair to inform world leaders about the urgency of reducing carbon dioxide emissions, was told of a series of new research findings which showed that climate change was speeding up and would be worse than hitherto expected. Only five years ago the scientists on the UN's Intergovernmental Panel on Climate Change were confident that Antarctica was a 'slumbering giant' and its vast ice sheets so cold that they would not begin to melt for centuries, even if the climate changed elsewhere. This conference was told 'the giant is awakening', and areas of the ice-bound continent melting, causing faster sea-level rise than expected. (guardian)

  8. 17-02-2005 eco nws - global warming - evidence - impact - oceans - 'compelling' evidence that ocean warming over the past 40 years can be linked to the industrial release of carbon dioxide. US researchers compared the rise in ocean temperatures with predictions from climate models and found human activity was the most likely cause. 'This is perhaps the most compelling evidence yet that global warming is happening right now and it shows that we can successfully simulate its past and likely future evolution,' said lead author Tim Barnett, of the climate research division at the Scripps Institution of Oceanography in San Diego, California. (bbc)

  9. 01-04-2005 eco nws - global warming - impact - oceans - atlantic current shutdown scenario - If the North Atlantic Ocean's circulation system is shut down -- an apocalyptic global-warming scenario -- the impact on the world's food supplies would be disastrous, a study said Thursday. The shutdown would cause global stocks of plankton, a vital early link in the food chain, to decline by a fifth while plankton stocks in the North Atlantic itself would shrink by more than half, it said. 'A massive decline of plankton stocks could have catastrophic effects on fisheries and human food supply in the affected regions,' warned the research, authored by Andreas Schmittner of Oregon State University. The circulation system is like a conveyor belt, taking warm water from the Caribbean in the tropical western Atlantic to the cold latitudes of the northeastern Atlantic. There, the warm surface water cools and sinks, gradually getting hauled around back to the southwest, where it warms again and rises to the surface. This movement is vital for northwestern Europe, for the warm water brings the region balmy, wet weather. Without it, Ireland, Britain, parts of France, Belgium, the Netherlands and Germany would be plunged into prolonged, bitter winters. The circulation is also essential for plankton, providing an upwelling of deep-water nutrients on which these tiny creatures feed. In turn, the plankton feed fish and other marine animals, which in turn are harvested by humans. Schmittner, writing in the British weekly science journal Nature, said his computer model of plankton loss was based on a disruption of the circulation system over 500 years, during which the conveyor belt lost more than 80 percent of its power. (earth hope)

  10. 24-05-2005 eco nws - global warming - impact - water - oceans - ice - arctic ice - Antarctic buffers sea level rise - The ice sheet covering the interior of Antarctica is thickening, researchers report in the journal Science. This bulge, which was recorded by satellite, may temporarily buffer rising sea levels, they believe. Antarctica's 'weight gain' is due to extra snowfall, caused by rising temperatures, the US-UK team thinks. (bbc)

  11. 03-06-2005 eco nws - global warming - impact - oceans - human cause of ocean warming - Scientists collected detailed data on ocean temperatures across the globe, going back 40 years, and compared them with results generated by computer climate models. Only when they included climate changes caused by people - the dumping of the greenhouse gas carbon dioxide into the atmosphere through fossil-fuel burning and other activities, and sulfate pollution - did they find a match between the real data and the models. 'It was a distinctive signal, and for the models to capture it so well is quite remarkable,' said co-author Tim Barnett of the Scripps Institution of Oceanography in La Jolla, Calif. (earth hope)

  12. 16-02-2006 eco nws - global warming - impact - oceans - Greenland ice swells ocean rise - BBC News science reporter, St Louis Greenland's glaciers are sliding towards the sea much faster than previously believed, scientists have told a conference in St Louis, US. It was thought the entire Greenland ice sheet could melt in about 1,000 years, but the latest evidence suggests that could happen much sooner. It implies that sea levels will rise a great deal faster as well. Details of the study, by Nasa and University of Kansas researchers, are also reported in the journal Science. The comprehensive analysis found that the amount of ice dumped into the Atlantic Ocean has doubled in the last five years. If the Greenland ice sheet melted completely, it would raise global sea levels by about 7m. Greenland's contribution to global sea level rise today is two to three times greater than it was in 1996. 'We are concerned because we know that sea levels have been able to rise much faster in the past - 10 times faster. This is a big gorilla. If sea level rise is multiplied by 10 or more, I'm not sure we can deal with that,' co-author Eric Rignot, from the US space agency's (Nasa) Jet Propulsion Laboratory in California, told the BBC News website. Previous estimates suggested it would take many hundreds of years for the Greenland ice sheet to melt completely. The new data will cut this timescale, but by how much is uncertain. It takes a long time to build and melt an ice sheet, but glaciers can react quickly to temperature changes Dr Eric Rignot, Nasa 'It depends on how fast the glaciers can go and how sustainable the acceleration can be,' said Dr Rignot. He added: 'It takes a long time to build and melt an ice sheet, but glaciers can react quickly to temperature changes.' In 1996, Greenland was losing about 100 cubic km per year in mass from its ice sheet. In 2005, this had increased to about 220 cubic km. By comparison, the city of Los Angeles uses about one cubic km of water per year. Rising surface air-temperatures seem to be behind the increases in glacier speed in the southern half of Greenland since 1996; but the northward spread of warmer temperatures may be responsible for a rapid increase in glacier speed further north after 2000. Over the past 20 years, the air temperature in south-east Greenland has risen by 3C. Warmer temperatures cause more surface melt water to reach the base of the ice sheet where it meets the rock. This is thought to serve as a lubricant, easing the glaciers' march to the sea. The study's results come from satellites that monitor glacier movement from space. Rignot and colleague Pannir Kanagaratnam, from the University of Kansas, built up a glacier speed map from the data for 2000 and then used measurements from 1996-2005 to determine how glacier velocity had changed in the last decade. The researchers plan to continue their monitoring of the Greenland glaciers using satellite data. The Greenland ice sheet covers 1.7 million sq km and is up to 3km thick. The scientists described their results at the annual meeting of the American Association for the Advancement of Science. (bbc)

  13. 23-03-2006 eco nws - global warming - impact - oceans - Sea rise could be 'catastrophic' - Earth could be headed for catastrophic sea level rise in the next few centuries if greenhouse gases continue to rise at present rates, experts say. A study in the US journal Science suggests a threshold triggering a rise in sea level of several metres could be reached before the end of the century. Scientists used an ancient period of warming to predict future changes. Greenland could be as warm by 2100 as it was 130,000 years ago, when melting ice raised sea levels by 3-4m. The implication is that Greenland would - eventually - melt by as much in response to present warming. The findings come from two studies published in Science by Dr Jonathan Overpeck, of the University of Arizona in Tucson, and colleagues. Their computer models show that, in addition to widespread melting of the Greenland ice sheet, this rate of warming could also lead to the collapse of about half of the West Antarctic ice sheet in 500 years. Dr Overpeck's team used computer models to simulate the climate 130,000 years ago. Because Earth was tilted slightly more than today on its axis, more solar radiation hit the northern latitudes, driving warming there. The researchers found that melting of the Greenland ice sheet could have raised sea levels by 2-3.5m. But they also concluded that the rest could have come from the West Antarctic ice sheet. It was not as warm here, but much of the ice sheet remains below sea level. This, they believe, allowed warming ocean waters along with rising sea levels to destabilise it. 'The simulated climate warming agreed well with the observed climate warming,' Dr Overpeck told the BBC News website. 'So, we had a firm estimate of how much warmth was necessary to cause that much sea level rise.' The researchers then compared this with simulations of future warming to learn how much sea level rise would be expected in future. They estimate peak rates of sea level rise exceeding 1m per century. (bbc)

  14. 06-12-2006 eco nws - global warming - system - atmosphere - co2 - impact - oceans - biodiversity - animal life - co2 uptake & life - SeaWIFS data - Global warming is reducing ocean life, increasing atmospheric C02 - Alarming new satellite data show that the warming of the world�s oceans is reducing ocean life while contributing to increased global warming. The ocean�s food chain is based upon the growth of billions upon billions of microscopic plants. New satellite data show that ocean warming is reducing these plants �� thus imperiling ocean fisheries and marine life, according to an article in the Nov. 7 issue of the scientific journal Nature. �We show on a global scale that the growth of these plants, called phytoplankton, is strongly tied to changes in the warming of the ocean,� said David Siegel, co-author and professor of marine science in the Department of Geography at the University of California, Santa Barbara. Siegel is also director of the Institute for Computational Earth System Science (ICESS). �Phytoplankton grow faster in a cool ocean and slower in a warm one,� said Siegel. �The scary part is that the oceans are warming now �� probably caused by our emissions of greenhouse gases like carbon dioxide.� These microscopic plants are predicted to grow even slower in the warmer oceans of the future. This in turn will reduce the food available to fish and other organisms, including marine birds and mammals, which are supported by the ocean�s food chain. Phytoplankton are responsible for about the same amount of photosynthesis each year as all the plants on land combined. Another disturbing result of reduced phytoplankton is that our atmosphere depends on the consumption of atmospheric carbon dioxide by these plants. Reduced phytoplankton means less carbon dioxide is taken up by the ocean, which could speed global warming, contributing to a vicious cycle of increased warming. �Rising levels of carbon dioxide in the atmosphere play a big part in global warming,� said lead author Michael Behrenfeld of Oregon State University. �This study shows that as the climate warms, phytoplankton growth rates go down and along with them the amount of carbon dioxide these ocean plants consume. That allows carbon dioxide to accumulate more rapidly in the atmosphere, which would produce more warming.� The findings are from a NASA-funded analysis of data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) instrument on the OrbView-2 spacecraft, launched in 1997. The uninterrupted nine-year record shows in great detail the ups and downs of marine biological activity or productivity from month to month and year to year. Captured at the start of this data record was a major, rapid rebound in ocean biological activity after a major El Ni�o event. El Ni�o and La Ni�a are major warming or cooling events, respectively, that occur approximately every three to seven years in the eastern Pacific Ocean and are known to change weather patterns around the world. Scientists made their discovery by comparing the SeaWiFS record of the rise and fall of global ocean plant life to different measures of recent global climate change. The climate records included several factors that directly affect ocean conditions, such as changes in sea surface temperature and surface winds. The results support computer model predictions of what could happen to the world's oceans as the result of prolonged future climate warming. 'When we compared changes in phytoplankton activity with simultaneous changes in climate conditions, the agreement between the two records was simply astonishing,' Behrenfeld said. (science blog)

  15. 02-02-2007 eco nws - global warming - system - impact - oceans - biodiversity - animal life - fish - atmosphere - other stressors - report - ipcc - Climate Change Only One Symptom of a Stressed Planet Earth - In releasing its latest comprehensive report, the Intergovernmental Panel on Climate Change (IPCC) focuses an important spotlight on the current state of the Earth�s climate. Climate change is just one of the many symptoms exhibited by a planet under pressure from human activities. 'Global environmental change, which includes climate change, threatens to irreversibly alter our planet,' says Kevin Noone, Executive Director of the International Geosphere-Biosphere Programme (IGBP). Global studies by IGBP show that human-driven environmental changes are affecting many parts of the Earth�s system, in addition to its climate. For example: - Half of Earth�s land surface is now domesticated for direct human use. / - 75 percent of the world�s fisheries are fully or over-exploited. / - The composition of today�s atmosphere is well outside the range of natural variability the Earth has maintained over the last 650,000 years. / - The Earth is now in the midst of its sixth great extinction event. / (science blog)

  16. 08-03-2007 eco nws - global warming - impact - oceans - acidification - biodiversity - animal life - Global warming or not, CO2 levels threaten marine life - Like a piece of chalk dissolving in vinegar, marine life with hard shells is in danger of being dissolved by increasing acidity in the oceans. Ocean acidity is rising as sea water absorbs more carbon dioxide released into the atmosphere from power plants and automobiles. The higher acidity threatens marine life, including corals and shellfish, which may become extinct later this century from the chemical effects of carbon dioxide, even if the planet warms less than expected. A new study by University of Illinois atmospheric scientist Atul Jain, graduate student Long Cao and Carnegie Institution scientist Ken Caldeira suggests that future changes in ocean acidification are largely independent of climate change. The researchers report their findings in a paper accepted for publication in the journal Geophysical Research Letters, and posted on its Web site. 'Before our study, there was speculation in the academic community that climate change would have a big impact on ocean acidity,' Jain said. 'We found no such impact.' In previous studies, increasing levels of carbon dioxide in the atmosphere led to a reduction in ocean pH and carbonate ions, both of which damage marine ecosystems. What had not been studied before was how climate change, in concert with higher concentrations of carbon dioxide, would affect ocean chemistry and biology. To investigate changes in ocean chemistry that could result from higher temperatures and carbon-dioxide concentrations, the researchers used an Earth-system model called the Integrated Science Assessment Model. Developed by Jain and his graduate students, the model includes complex physical and chemical interactions among carbon-dioxide emissions, climate change, and carbon-dioxide uptake by oceans and terrestrial ecosystems. The ocean-surface pH has been reduced by about 0.1 during the past two centuries. Using ISAM, the researchers found ocean pH would decline a total of 0.31 by the end of this century, if carbon-dioxide emissions continue on a trajectory to ultimately stabilize at 1,000 parts per million. During the last 200 years, the concentration of atmospheric carbon dioxide increased from about 275 parts per million to about 380 parts per million. Unchecked, it could surpass 550 parts per million by mid-century. 'As the concentration of carbon dioxide increases, ocean water will become more acidic; which is bad news for marine life,' Cao said. 'Fortunately, the effects of climate change will not further increase this acidity.' There are a number of effects and feedback mechanisms built into the ocean-climate system, Jain said. 'Warmer water, for example, directly reduces the ocean pH due to temperature effect on the reaction rate in the carbonate system. At the same time, warmer water also absorbs less carbon dioxide, which makes the ocean less acidic. These two climate effects balance each other, which results in negligible net climate effect on ocean pH.' The addition of carbon dioxide into the oceans also affects the carbonate mineral system by decreasing the availability of carbonate ions. Calcium carbonate is used in forming shells. With less carbonate ions available, the growth of corals and shellfish could be significantly reduced. (science blog)

  17. 03-12-2009 eco nws - global warming - impact - oceans - ocean acidification - nitrogen - interplay - Elevated Carbon Dioxide Levels May Mitigate Losses of Biodiversity from Nitrogen Pollution - ScienceDaily (Dec. 3, 2009) � Rising levels of carbon dioxide may overheat the planet and cause other environmental problems, but fears that rising CO2 levels could directly reduce plant biodiversity can be allayed, according to a new study by a University of Minnesota scientist Peter Reich. In fact, rising CO2 may actually help counteract losses of diversity from another environmental villain: the global rain of nitrogen from fertilizers and exhaust fumes. The study, published in December 4 in the journal Science, involved a 10-year open-air outdoor experiment in which 48 plots planted with 16 different species of plants were tested using ambient and elevated levels of nitrogen and carbon dioxide. Researchers measured the number of species observed in each plot, the plant biomass both above and below ground, as well as factors related to soil, water and light that might affect plant growth. Over time, the diversity of plants growing in the research plots changed significantly, depending on the combinations of plants and the way added CO2 and nitrogen affected the health of different species. One of the study's key findings is that while the combination of ambient carbon dioxide and nitrogen pollution reduces species richness by 16 percent, adding more CO2 to the mix reduces that change by half. "From a biodiversity perspective, there was no evidence to support the worst-case scenario, in which impacts of rising CO2 and nitrogen deposition combine to suppress diversity by 30 percent, 40 percent or even 50 percent or more," Reich said. "Instead, their interaction ameliorated the diversity loss due to nitrogen enrichment that occurs under ambient CO2. Given the importance of biodiversity to the effective health and function of our ecosystems this is good news, or perhaps better labeled as "not quite as bad" news." Reich, a Regents professor in the department of forest resources, notes that "while it is a relief to find out that rising CO2 and nitrogen may not directly cause enormous losses of diversity, this finding does not detract from the urgent need for us to curb CO2 emissions given the other critical CO2 effects, such as overheating the planet and threatening marine life through ocean acidification."

  18. 22-05-2010 eco nws - global warming - impact - oceans - warming - Ocean Stored Significant Warming Over Last 16 Years, Study Finds - ScienceDaily (May 22, 2010) � The upper layer of the world's ocean has warmed since 1993, indicating a strong climate change signal, according to a new study. The energy stored is enough to power nearly 500 100-watt light bulbs per each of the roughly 6.7 billion people on the planet. "We are seeing the global ocean store more heat than it gives off," said John Lyman, an oceanographer at NOAA's Joint Institute for Marine and Atmospheric Research, who led an international team of scientists that analyzed nine different estimates of heat content in the upper ocean from 1993 to 2008. The team combined the estimates to assess the size and certainty of growing heat storage in the ocean. Their findings are published in the May 20 edition of the journal Nature. The scientists are from NOAA, NASA, the Met Office Hadley Centre in the United Kingdom, the University of Hamburg in Germany and the Meteorological Research Institute in Japan. "The ocean is the biggest reservoir for heat in the climate system," said Josh Willis, an oceanographer at NASA's Jet Propulsion Laboratory and one of the scientists who contributed to the study. "So as the planet warms, we're finding that 80 to 90 percent of the increased heat ends up in the ocean." A warming ocean is a direct cause of global sea level rise, since seawater expands and takes up more space as it heats up. The scientists say that this expansion accounts for about one-third to one-half of global sea level rise. Combining multiple estimates of heat in the upper ocean -- from the surface to about 2,000 feet down -- the team found a strong multi-year warming trend throughout the world's ocean. According to measurements by an array of autonomous free-floating ocean floats called Argo as well as by earlier devices called expendable bathythermographs or XBTs that were dropped from ships to obtain temperature data, ocean heat content has increased over the last 16 years. The team notes that there are still some uncertainties and some biases. "The XBT data give us vital information about past changes in the ocean, but they are not as accurate as the more recent Argo data," said Gregory Johnson, an oceanographer at NOAA's Pacific Marine Environmental Laboratory. "However, our analysis of these data gives us confidence that on average, the ocean has warmed over the past decade and a half, signaling a climate imbalance." Data from the array of Argo floats� -- deployed by NOAA and other U.S. and international partners �- greatly reduce the uncertainties in estimates of ocean heat content over the past several years, the team said. There are now more than 3,200 Argo floats distributed throughout the world's ocean sending back information via satellite on temperature, salinity, currents and other ocean properties.

  19. 10-06-2010 eco nws - global warming - impact - oceans - sea level - Sea Levels May Rise by as Much as One Meter Before the End of This Century - ScienceDaily (June 10, 2010) � Sea levels may rise by as much as one metre before the end of this century, according to new predictions. Melting glaciers may contribute more to the rise in sea levels than scientists have previously realised. - 150 million people will be affected - Sea levels can be expected to rise by between 0.5 and 1.5 metres before the next century, according to the report Melting Snow and Ice: A Call for Action, published by the Norwegian Polar Institute, which attracted a lot of attention at the Copenhagen Climate Change Conference in December last year. "Melting glaciers and the melting ice sheets in the Arctic and Antarctic will account for 75% of the rise in sea levels, while expansion of the water as it warms will account for 25 %," said Director Jan-Gunnar Winther of the Norwegian Polar Institute. Such a rise in sea levels will have a tremendous impact on coastal communities around the world. There are 150 million people who live within one metre of the current coastline, and who will be severely affected, said Professor Tim Naish of the Victoria University of Wellington in New Zealand. Professor Naish is doing research on ice cores from the West Antarctic Ice Sheet -- an area of particular interest with respect to rising sea levels. - New estimates of ice loss - The loss of mass from the West Antarctic Ice Sheet and the area around the Amundsen Sea is much higher than previously suspected, according to Postdoctoral Researcher Mike Willis from Cornell University. Using state-of-the-art satellite technology and modern GPS technology, he has produced new and accurate measurements of the ice masses in Antarctica. "As glaciers grow and shrink, the earth moves up and down. By monitoring the earth's movement with GPS technology, we can take the earth out of the equation and come up with more accurate measures of the ice masses," he said. Sue Nelson's popular science session on the first day of the conference also included an interview with scientist Tom Jordan, whose group presented the first images ever of the Gamburtsev Subglacial Mountains earlier in the afternoon. Dr Steve Rintoul from the Antarctic Climate & Ecosystems Cooperative Research Centre talked about his research, which involves attaching motion sensors to elephant seals that spend the winter feeding beneath the sea ice in order to record data on the water quality of the Southern Ocean.

  20. 19-06-2010 eco nws - global warming - impact - oceans - warming - people - Ocean Changes May Have Dire Impact on People - ScienceDaily (June 19, 2010) � The first comprehensive synthesis on the effects of climate change on the world's oceans has found they are now changing at a rate not seen for several million years. In an article published June 18 in Science magazine, scientists reveal the growing atmospheric concentrations of man-made greenhouse gases are driving irreversible and dramatic changes to the way the ocean functions, with potentially dire impacts for hundreds of millions of people across the planet. The findings of the report emerged from a synthesis of recent research on the world's oceans, carried out by two of the world's leading marine scientists, one from The University of Queensland in Australia, and one from The University of North Carolina at Chapel Hill, in the USA. Professor Ove Hoegh-Guldberg, lead author of the report and Director of The University of Queensland's Global Change Institute, says the findings have enormous implications for mankind, particularly if the trend continues. He said that the Earth's ocean, which produces half of the oxygen we breathe and absorbs 30% of human-generated CO2, is equivalent to its heart and lungs. "Quite plainly, the Earth cannot do without its ocean. This study, however, shows worrying signs of ill health. "It's as if the Earth has been smoking two packs of cigarettes a day!" He went on to say, "We are entering a period in which the very ocean services upon which humanity depends are undergoing massive change and in some cases beginning to fail," says Prof. Hoegh-Guldberg. "Further degradation will continue to create enormous challenges and costs for societies worldwide." He warned that we may soon see "sudden, unexpected changes that have serious ramifications for the overall well-being of humans," including the capacity of the planet to support people. "This is further evidence that we are well on the way to the next great extinction event." The "fundamental and comprehensive" changes to marine life identified in the report include rapidly warming and acidifying oceans, changes in water circulation and expansion of dead zones within the ocean depths. These are driving major changes in marine ecosystems: less abundant coral reefs, sea grasses and mangroves (important fish nurseries); fewer, smaller fish; a breakdown in food chains; changes in the distribution of marine life; and more frequent diseases and pests among marine organisms. Report co-author, Dr John F. Bruno, an Associate Professor at The University of North Carolina, says greenhouse gas emissions are modifying many physical and geochemical aspects of the planet's oceans, in ways "unprecedented in nearly a million years." "This is causing fundamental and comprehensive changes to the way marine ecosystems function," Dr Bruno said. "We are becoming increasingly certain that the world's marine ecosystems are approaching tipping points. These tipping points are where change accelerates and causes unrelated impacts on other systems, the results of which we really have no power or model to foresee." The authors conclude: "These challenges underscore the urgency with which world leaders must act to limit further growth of greenhouse gases and thereby reduce the risk of these events occurring. Ignoring the science is not an option." In their study, the researchers sought to address a gap in previous studies that have often overlooked the affects of climate change on marine ecosystems, due to the fact that they are complex and can be logistically difficult to study. According to leading US marine scientist, the University of Maine's School of Marine Services Professor Robert S. Steneck, the study provides a valuable indicator of the ecological risk posed by climate change, particularly to coastal regions. "While past studies have largely focused on single global threats such as 'global warming', Hoegh-Guldberg and Bruno make a compelling case for the cumulative impacts of multiple planet-scale threats," Prof. Steneck said.

  21. 04-11-2010 eco nws - global warming - impact - oceans - circulation - Current Global Warming May Reverse Circulation in Atlantic Ocean, as It Did 20,000 Years Ago - ScienceDaily (Nov. 4, 2010) � Universitat Aut�noma de Barcelona scientists have researched how ocean currents in the Atlantic were affected by climate change in the past. The study shows that there was a period when the flow of deep waters in the Atlantic was reversed. The results are relevant for the near future since similar changes are expected to occur in the course of climate warming over the next 100 years. The Atlantic Ocean circulation (termed meridional overturning circulation, MOC) is an important component of the climate system. Warm currents, such as the Gulf Stream, transport energy from the tropics to the subpolar North Atlantic and influence regional weather and climate patterns. Once they arrive in the North the currents cool, their waters sink and with them they transfer carbon from the atmosphere to the abyss. These processes are important for climate but the way the Atlantic MOC responds to climate change is not well known yet. An international team of investigators under the leadership of two researchers from the UAB now demonstrates the response of the Atlantic MOC to climate change in the past. The new research results will be published on 4 November 2010 in the journal Nature. The research project was led by Rainer Zahn (ICREA researcher) and Pere Masque, both of the UAB at the Institut de Ci�ncia i Tecnologia Ambientals (ICTA) and Department of Physics. With collaborators at the universities of Seville, Oxford and Cardiff (UK) they investigated the distribution of isotopes in the Atlantic Ocean that are generated from the natural decay of uranium in seawater and are distributed with the flow of deep waters across the Atlantic basin. The young investigator Cesar Negre studied the natural abundance of these isotopes in the seafloor sediments 2.5 km deep in the South Atlantic and achieved a PhD degree in the Environmental Science and Technology doctoral programme at ICTA. The study shows that the ocean circulation was very different in the past and that there was a period when the flow of deep waters in the Atlantic was reversed. This happened when the climate of the North Atlantic region was substantially colder and deep convection was weakened. At that time the balance of seawater density between the North and South Atlantic was shifted in such a way that deep water convection was stronger in the South Polar Ocean. Recent computer models simulate a reversal of the deep Atlantic circulation under such conditions while it is only now with the new data generated by UAB scientists and their colleagues from Seville and the UK that the details of the circulation reversal become apparent. This situation occurred during the ice age 20,000 years ago. Although this was far back in time the results are relevant for our climate today and in the near future. The new study shows that the Atlantic MOC in the past was very sensitive to changes in the salt balance of Atlantic Ocean currents. Similar changes in seawater salt concentration are expected to occur in the North Atlantic in the course of climate warming over the next 100 years. Therefore the data to be published in Nature offer the climate modelling community the opportunity to calibrate their models and improve their capacity to predict reliably future ocean and climate changes.

  22. 21-12-2010 eco nws - global warming - impact - oceans - nitrogen - Ocean Acidification Changes Nitrogen Cycling in World Seas - ScienceDaily (Dec. 21, 2010) � Increasing acidity in the sea's waters may fundamentally change how nitrogen is cycled in them, say marine scientists who published their findings in this week's issue of the journal Proceedings of the National Academy of Sciences (PNAS). Nitrogen is one of the most important nutrients in the oceans. All organisms, from tiny microbes to blue whales, use nitrogen to make proteins and other important compounds. Some microbes can also use different chemical forms of nitrogen as a source of energy. One of these groups, the ammonia oxidizers, plays a pivotal role in determining which forms of nitrogen are present in the ocean. In turn, they affect the lives of many other marine organisms. "Ocean acidification will have widespread effects on marine ecosystems, but most of those effects are still unknown," says David Garrison, director of the National Science Foundation (NSF)'s Biological Oceanography Program, which funded the research along with NSF's Chemical Oceanography Program. "This report that ocean acidification decreases nitrification (the amount of nitrogen) is extremely important," says Garrison, "because of the crucial role of the nitrogen cycle in biogeochemical processes-processes that take place throughout the oceans." Very little is known about how ocean acidification may affect critical microbial groups like the ammonia oxidizers, "key players in the ocean's nitrogen cycle," says Michael Beman of the University of Hawaii and lead author of the PNAS paper. In six experiments spread across two oceans, Beman and colleagues looked at the response of ammonia oxidation rates to ocean acidification. In every case where the researchers experimentally increased the amount of acidity in ocean waters, ammonia oxidation rates decreased. These declines were remarkably similar in different regions of the ocean indicating that nitrification rates may decrease globally as the oceans acidify in coming decades, says David Hutchins of the University of Southern California, a co-author of the paper. Oceanic nitrification is a major natural component of production of the greenhouse gas nitrous oxide. From the seas, nitrous oxide then enters the atmosphere, says Beman. "All else being equal, decreases in nitrification rates therefore have the potential to reduce nitrous oxide emissions to the atmosphere." Oceanic emissions of nitrous oxide are second only to soils as a global source of nitrous oxide. With a pH decrease of 0.1 in ocean waters (making the waters more acidic), the scientists estimate a decrease in nitrous oxide emissions comparable to all current nitrous oxide emissions from fossil fuel combustion and industrial activity. An important caveat, they say, is that nitrous oxide emissions from oceanic nitrification may be altered by other forms of global environmental change such as increased deposition of nitrogen to the ocean, or loss of oxygen in some key areas. "That could offset any decrease due to ocean acidification, and needs to be studied in more detail," says Hutchins. Another major implication of the findings is equally complex, the researchers say, but just as important. As human-derived carbon dioxide permeates the sea, ammonia-oxidizing organisms will be at a significant disadvantage in competing for ammonia. Over time, that would shift the available form of dissolved nitrogen in the surface oceans away from forms like nitrate that are produced by nitrification, and toward regenerated ammonium. With a decrease in average ocean pH from 8.1 to 8.0 (greater acidity), the scientists estimate that up to 25 percent of the ocean's primary production could shift from nitrate- to ammonium-supported. The consequences of such a shift are not easily predicted, says Hutchins, but would likely favor certain drifting, microscopic plant species over others, with cascading effects throughout marine food webs. "What makes ocean acidification such a challenging scientific and societal issue is that we're engaged in a global, unreplicated experiment," says Beman, "one that's difficult to study--and has many unknown consequences."

  23. 11-01-2011 eco nws - global warming - impact - oceans - sea-level - Mountain Glacier Melt to Contribute 12 Centimeters to World Sea-Level Increases by 2100 - ScienceDaily (Jan. 11, 2011) � Melt off from small mountain glaciers and ice caps will contribute about 12 centimetres to world sea-level increases by 2100, according to UBC research published this week in Nature Geoscience. The largest contributors to projected global sea-level increases are glaciers in Arctic Canada, Alaska and landmass bound glaciers in the Antarctic. Glaciers in the European Alps, New Zealand, the Caucasus, Western Canada and the Western United Sates--though small absolute contributors to global sea-level increases--are projected to lose more than 50 per cent of their current ice volume. The study modelled volume loss and melt off from 120,000 mountain glaciers and ice caps, and is one of the first to provide detailed projections by region. Currently, melt from smaller mountain glaciers and ice caps is responsible for a disproportionally large portion of sea level increases, even though they contain less than one per cent of all water on Earth bound in glacier ice. "There is a lot of focus on the large ice sheets but very few global scale studies quantifying how much melt to expect from these smaller glaciers that make up about 40 percent of the entire sea-level rise that we observe right now," says Valentina Radic, a postdoctoral researcher with the Department of Earth and Ocean Sciences and lead author of the study. Increases in sea levels caused by the melting of the Greenland and Antarctic ice sheets, and the thermal expansion of water, are excluded from the results. Radic and colleague Regine Hock at the University of Alaska, Fairbanks, modelled future glacier melt based on temperature and precipitation projections from 10 global climate models used by the Intergovernmental Panel on Climate Change. "While the overall sea level increase projections in our study are on par with IPCC studies, our results are more detailed and regionally resolved," says Radic. "This allows us to get a better picture of projected regional ice volume change and potential impacts on local water supplies, and changes in glacier size distribution." Global projections of sea level rises from mountain glacier and ice cap melt from the IPCC range between seven and 17 centimetres by the end of 2100. Radic's projections are only slightly higher, in the range of seven to 18 centimetres. Radic's projections don't include glacier calving--the production of icebergs. Calving of tide-water glaciers may account for 30 per cent to 40 per cent of their total mass loss. "Incorporating calving into the models of glacier mass changes on regional and global scale is still a challenge and a major task for future work," says Radic. However, the new projections include detailed projection of melt off from small glaciers surrounding the Greenland and Antarctic ice sheets, which have so far been excluded from, or only estimated in, global assessments.

  24. 15-02-2011 eco nws - global warming - impact - oceans - sea level - Rising Seas Will Affect Major US Coastal Cities by 2100, New Research Finds - ScienceDaily (Feb. 15, 2011) � Rising sea levels could threaten an average of 9 percent of the land within 180 U.S. coastal cities by 2100, according to new research led by University of Arizona scientists. The Gulf and southern Atlantic coasts will be particularly hard hit. Miami, New Orleans, Tampa, Fla., and Virginia Beach, Va. could lose more than 10 percent of their land area by 2100. The research is the first analysis of vulnerability to sea-level rise that includes every U.S. coastal city in the lower 48 with a population of 50,000 or more. The latest scientific projections indicate that by 2100, the sea level will rise about 1 meter -- or even more. One meter is about 3 feet. At the current rate of global warming, sea level is projected to continue rising after 2100 by as much as 1 meter per century. "According to the most recent sea-level-rise science, that's where we're heading," said lead researcher Jeremy L. Weiss, a senior research specialist in the UA's department of geosciences. "Impacts from sea-level rise could be erosion, temporary flooding and permanent inundation." The coastal municipalities the team identified had 40.5 million people living in them, according to the 2000 U.S. Census. Twenty of those cities have more than 300,000 inhabitants. Weiss and his colleagues examined how much land area from the 180 municipalities could be affected by 1 to 6 meters of sea-level rise. "With the current rate of greenhouse gas emissions, the projections are that the global average temperature will be 8 degrees Fahrenheit warmer than present by 2100," said Weiss, who is also a UA doctoral candidate in geosciences. "That amount of warming will likely lock us into at least 4 to 6 meters of sea-level rise in subsequent centuries, because parts of the Greenland and Antarctic ice sheets will slowly melt away like a block of ice on the sidewalk in the summertime." At 3 meters (almost 10 feet), on average more than 20 percent of land in those cities could be affected. Nine large cities, including Boston and New York, would have more than 10 percent of their current land area threatened. By 6 meters (about 20 feet), about one-third of the land area in U.S. coastal cities could be affected. "Our work should help people plan with more certainty and to make decisions about what level of sea-level rise, and by implication, what level of global warming, is acceptable to their communities and neighbors," said co-author Jonathan T. Overpeck, a UA professor of geosciences and of atmospheric sciences and co-director of UA's Institute of the Environment. Weiss, Overpeck and Ben Strauss of Climate Central in Princeton, N.J., are publishing their paper, "Implications of Recent Sea Level Rise Science for Low-Elevation Areas in Coastal Cities of the Conterminous U.S.A.," in Climatic Change Letters. Weiss and Overpeck had previously developed maps of how increases in sea level could affect the U.S. coastline. Strauss suggested adding the boundaries of municipalities to focus on how rising seas would affect coastal towns and cities. For the detailed maps needed for the new project, the researchers turned to the National Elevation Dataset produced by the U.S. Geological Survey. The NED provides a high-resolution digital database of elevations for the entire U.S. The high resolution let Weiss and his colleagues identify the elevation of a piece of land as small as 30 meters (about 100 feet) on a side -- about the size of an average house lot. The researchers used the USGS database to create detailed digital maps of the U.S. coast that delineate what areas could be affected by 1 meter to 6 meters of sea-level rise. The researchers also added the boundaries for all municipalities with more than 50,000 people according to the 2000 U.S. Census. To increase the accuracy of their maps, the team included all pieces of land that had a connection to the sea and excluded low-elevation areas that had no such connection. Rising seas do not just affect oceanfront property -- water moves inland along channels, creeks, inlets and adjacent low-lying areas. "Ours is the first national-scale data set that delineates these low-lying coastal areas for the entire lower 48 at this degree of spatial resolution," Weiss said. The NED data set has some uncertainty, particularly for estimating elevation changes of 1 meter or less. That means the researchers' ability to identify the threat to any particular small piece of land is better for larger amounts of sea-level rise than for smaller amounts of sea-level rise, Weiss said. "As better digital elevation models become available, we'll be using those," Weiss said. "The USGS is always improving the digital elevation models for the U.S." Overpeck said, "The main point of our work is to give people in our coastal towns and cities more information to work with as they decide how to deal with the growing problem of sea-level rise."

  25. 08-03-2011 eco nws - global warming - impact - oceans - sea level - Melting Ice Sheets Now Largest Contributor to Sea Level Rise - ScienceDaily (Mar. 8, 2011) � The Greenland and Antarctic ice sheets are losing mass at an accelerating pace, according to a new NASA-funded satellite study. The findings of the study -- the longest to date of changes in polar ice sheet mass -- suggest these ice sheets are overtaking ice loss from Earth's mountain glaciers and ice caps to become the dominant contributor to global sea level rise, much sooner than model forecasts have predicted. The results of the study will be published this month in Geophysical Research Letters, a journal of the American Geophysical Union. The nearly 20-year study reveals that in 2006, a year in which comparable results for mass loss in mountain glaciers and ice caps are available from a separate study conducted using other methods, the Greenland and Antarctic ice sheets lost a combined mass of 475 gigatonnes a year on average. That's enough to raise global sea level by an average of 1.3 millimeters (.05 inches) a year. (A gigatonne is one billion metric tons, or more than 2.2 trillion pounds.) Ice sheets are defined as being larger than 50,000 square kilometers, or 20,000 square miles, and only exist in Greenland and Antarctica while ice caps are areas smaller than 50,000 square km. The pace at which the polar ice sheets are losing mass was found to be accelerating rapidly. Each year over the course of the study, the two ice sheets lost a combined average of 36.3 gigatonnes more than they did the year before. In comparison, the 2006 study of mountain glaciers and ice caps estimated their loss at 402 gigatonnes a year on average, with a year-over-year acceleration rate three times smaller than that of the ice sheets. "That ice sheets will dominate future sea level rise is not surprising -- they hold a lot more ice mass than mountain glaciers," said lead author Eric Rignot, of NASA's Jet Propulsion Laboratory, Pasadena, California, and the University of California, Irvine. "What is surprising is this increased contribution by the ice sheets is already happening. If present trends continue, sea level is likely to be significantly higher than levels projected by the United Nations Intergovernmental Panel on Climate Change in 2007. Our study helps reduce uncertainties in near-term projections of sea level rise." Rignot's team combined nearly two decades (1992-2009) of monthly satellite measurements with advanced regional atmospheric climate model data to examine changes in ice sheet mass and trends in acceleration of ice loss. The study compared two independent measurement techniques. The first characterized the difference between two sets of data: interferometric synthetic aperture radar data from European, Canadian and Japanese satellites and radio echo soundings, which were used to measure ice exiting the ice sheets; and regional atmospheric climate model data from Utrecht University, The Netherlands, used to quantify ice being added to the ice sheets. The other technique used eight years of data from the NASA/German Aerospace Center's Gravity Recovery and Climate Experiment (Grace) satellites, which track minute changes in Earth's gravity field due to changes in Earth's mass distribution, including ice movement. The team reconciled the differences between techniques and found them to be in agreement, both for total amount and rate of mass loss, over their data sets' eight-year overlapping period. This validated the data sets, establishing a consistent record of ice mass changes since 1992. The team found that for each year over the 18-year study, the Greenland ice sheet lost mass faster than it did the year before, by an average of 21.9 gigatonnes a year. In Antarctica, the year-over-year speedup in ice mass lost averaged 14.5 gigatonnes. "These are two totally independent techniques, so it is a major achievement that the results agree so well," said co-author Isabella Velicogna, also jointly with JPL and UC Irvine. "It demonstrates the tremendous progress that's being made in estimating how much ice the ice sheets are gaining and losing, and in analyzing Grace's time-variable gravity data." The authors conclude that, if current ice sheet melting rates continue for the next four decades, their cumulative loss could raise sea level by 15 centimeters (5.9 inches) by 2050. When this is added to the predicted sea level contribution of 8 centimeters (3.1 inches) from glacial ice caps and 9 centimeters (3.5 inches) from ocean thermal expansion, total sea level rise could reach 32 centimeters (12.6 inches). While this provides one indication of the potential contribution ice sheets could make to sea level in the coming century, the authors caution that considerable uncertainties remain in estimating future ice loss acceleration. Other participating institutions include the Institute for Marine and Atmospheric Research, Utrecht University, The Netherlands; and the National Center for Atmospheric Research, Boulder, Colorado. More on Grace is online at http://www.csr.utexas.edu/grace/ and http://grace.jpl.nasa.gov/.

  26. 21-03-2011 eco nws - global warming - impact - oceans - co2 absorbtion - oceans - North Atlantic Oceanic Currents Play Greater Role in Absorption of Carbon Than Previously Thought - ScienceDaily (Mar. 21, 2011) � The ocean traps carbon through two principal mechanisms: a biological pump and a physical pump linked to oceanic currents. A team of researchers from CNRS, IRD, the Mus�um National d'Histoire Naturelle, UPMC and UBO (1) have managed to quantify the role of these two pumps in an area of the North Atlantic. Contrary to expectations, the physical pump in this region could be nearly 100 times more powerful on average than the biological pump. By pulling down masses of water cooled and enriched with carbon, ocean circulation thus plays a crucial role in deep carbon sequestration in the North Atlantic. These results are published in the Journal of Geophysical Research. The ocean traps around 30% of the carbon dioxide emitted into the atmosphere through human activity and represents, with the terrestrial biosphere, the main carbon sink. Much research has been devoted to understanding the natural mechanisms that regulate this sink. On the one hand, there is the biological pump: the carbon dioxide dissolved in the water is firstly used for the photosynthesis of phytoplankton, microscopic organisms that proliferate in the upper layer of the ocean. The food chain then takes over: the phytoplankton is eaten by zooplankton, itself consumed by larger organisms, and so on. Cast into the depths in the form of organic waste, some of this carbon ends its cycle in sediments at the bottom of the oceans. This biological pump is particularly effective in the North Atlantic, where a spectacular bloom of phytoplankton occurs every year. On the other hand, there is the physical pump which, through oceanic circulation, pulls down surface waters containing dissolved carbon dioxide towards deeper layers, thereby isolating the gas from exchanges with the atmosphere. On the basis of data collected in a specific region of the North Atlantic during the POMME (2) campaigns, the researchers were able to implement high-resolution numerical simulations. They thus carried out the first precise carbon absorption budget of the physical and biological pumps. They succeeded, for the first time, in quantifying the respective proportions of each of the two mechanisms. Surprisingly, their results suggest that in this region of the North Atlantic the biological pump would only absorb a minute proportion of carbon, around one hundredth. The carbon would thus be trapped mainly by the physical pump, which is almost one hundred times more efficient. At this precise location, oceanic circulation pulls down the carbon, in dissolved organic and inorganic form, to depths of between 200 and 400 meters, together with the water masses formed at the surface. The key role of the physical pump in the North Atlantic had never been quantified before. Its importance raises numerous questions: how long does the carbon transported by the physical pump remain trapped at depth before being driven back to the surface by the reverse mechanism? Is this proportion between the biological pump and the physical pump observed in other oceanic regions of the planet? And, last but not least, how will this mechanism evolve with climate change, which affects both the physical mechanism and the biological mechanism?

  27. 27-04-2011 eco nws - global warming - impact - oceans - ocean currents - agulhas ocean current leakage - Agulhas Ocean Current 'Leakage', Fueled by Global Warming, Could Stabilize Atlantic Overturning Circulation - ScienceDaily (Apr. 27, 2011) � The Agulhas Current which runs along the east coast of Africa may not be as well known as its counterpart in the Atlantic, the Gulf Stream, but researchers are now taking a much closer look at this current and its "leakage" from the Indian Ocean into the Atlantic Ocean. In a study published in the journal Nature, April 27, a global team of scientists led by University of Miami (UM) Rosenstiel School of Marine & Atmospheric Science Associate Professor Lisa Beal, suggests that Agulhas leakage could be a significant player in global climate variability. The Agulhas Current transports warm and salty waters from the tropical Indian Ocean to the southern tip of Africa, where most of the water loops around to remain in the Indian Ocean (the Agulhas Retroflection), while some waters leak into the fresher Atlantic Ocean via giant Agulhas rings. Once in the Atlantic, the salty Agulhas leakage waters eventually flow into the Northern Hemisphere and act to strengthen the Atlantic overturning circulation by enhancing deep water formation. Recent research points to an increase in Agulhas leakage over the last few decades caused primarily by human-induced climate change. This finding is profound, because it suggests that increased Agulhas leakage could trigger a strengthening in the Atlantic overturning circulation, at a time when warming and accelerated meltwater input in the North Atlantic has been predicted to weaken it. "This could mean that current IPCC model predictions for the next century are wrong and there will be no cooling in the North Atlantic to partially offset the effects of global climate change over North America and Europe," said Beal, "Instead, increasing Agulhas leakage could stabilize the oceanic heat transport carried by the Atlantic overturning circulation." There is also paleoceanographic data to suggest that dramatic peaks in Agulhas leakage over the past 500,000 years may have triggered the end of glacial cycles. This serves as further evidence that the Agulhas system and its leakage play an important role in the planet's climate. "This study shows that local changes in atmospheric and oceanic conditions in the Southern Hemisphere can affect the strength of the ocean circulation in unexpected ways. Under a warming climate, the Agulhas Current system near the tip of South Africa could bring more warm salty water from the Indian to the Atlantic Ocean and counteract opposing effects from the Arctic Ocean," said Eric Itsweire, director of the National Science Foundation (NSF)'s physical oceanography program, which funded the research. The study establishes the need for additional research in the region that focuses on Agulhas rings, as well as the leakage. Climate modeling experiments are critical, and need to be supported by paleoceanographic data and sustained observations to firmly establish the role of this system in a warming climate. "Our goal now is to get more of the scientific community involved in research of the Agulhas system and its global effects. The emphasis has been too long in the North Atlantic," said Beal.

  28. 18-06-2011 eco nws - global warming - impact - dead zones - biodiversity - oceans - Ocean's Harmful Low-Oxygen Zones Growing, Are Sensitive to Small Changes in Climate - ScienceDaily (June 18, 2011) � Fluctuations in climate can drastically affect the habitability of marine ecosystems, according to a new study by UCLA scientists that examined the expansion and contraction of low-oxygen zones in the ocean. The UCLA research team, led by assistant professor of atmospheric and oceanic sciences Curtis Deutsch, used a specialized computer simulation to demonstrate for the first time that the size of low-oxygen zones created by respiring bacteria is extremely sensitive to changes in depth caused by oscillations in climate. These oxygen-depleted regions, which expand or contract depending on their depth, pose a distinct threat to marine life. "The growth of low-oxygen regions is cause for concern because of the detrimental effects on marine populations -- entire ecosystems can die off when marine life cannot escape the low-oxygen water," said Deutsch. "There are widespread areas of the ocean where marine life has had to flee or develop very peculiar adaptations to survive in low-oxygen conditions." The study, which was published June 9 in the online edition the journal Science and will be available in an upcoming print edition, also showed that in addition to consuming oxygen, marine bacteria are causing the depletion of nitrogen, an essential nutrient necessary for the survival of most types of algae. "We found there is a mechanism that connects climate and its effect on oxygen to the removal of nitrogen from the ocean," Deutsch said. "Our climate acts to change the total amount of nutrients in the ocean over the timescale of decades." Low-oxygen zones are created by bacteria living in the deeper layers of the ocean that consume oxygen by feeding on dead algae that settle from the surface. Just as mountain climbers might feel adverse effects at high altitudes from a lack of air, marine animals that require oxygen to breathe find it difficult or impossible to live in these oxygen-depleted environments, Deutsch said. Sea surface temperatures vary over the course of decades through a climate pattern called the Pacific Decadal Oscillation, during which small changes in depth occur for existing low-oxygen regions, Deutsch said. Low-oxygen regions that rise to warmer, shallower waters expand as bacteria become more active; regions that sink to colder, deeper waters shrink as the bacteria become more sluggish, as if placed in a refrigerator. "We have shown for the first time that these low-oxygen regions are intrinsically very sensitive to small changes in climate," Deutsch said. "That is what makes the growth and shrinkage of these low-oxygen regions so dramatic." Molecular oxygen from the atmosphere dissolves in sea water at the surface and is transported to deeper levels by ocean circulation currents, where it is consumed by bacteria, Deutsch said. "The oxygen consumed by bacteria within the deeper layers of the ocean is replaced by water circulating through the ocean," he said. "The water is constantly stirring itself up, allowing the deeper parts to occasionally take a breath from the atmosphere." A lack of oxygen is not the only thing fish and other marine life must contend with, according to Deutsch. When oxygen is very low, the bacteria will begin to consume nitrogen, one of the most important nutrients that sustain marine life. "Almost all algae, the very base of the food chain, use nitrogen to stay alive," Deutsch said. "As these low-oxygen regions expand and contract, the amount of nutrients available to keep the algae alive at the surface of the ocean goes up and down." Understanding the causes of oxygen and nitrogen depletion in the ocean is important for determining the effect on fisheries and fish populations, he said. Deutsch and his team used a computer model of ocean circulation and biological processes that produce or consume oxygen to predict how the ocean's oxygen distribution has changed over the past half century. The researchers tested their predictions using observations made over the last several decades, specifically targeting areas where oxygen concentration is already low, because marine life in these areas will feel the changes most quickly. - How would rising global temperatures affect these low-oxygen environments? - As temperature increases, less oxygen leaves the atmosphere to dissolve in the ocean, Deutsch explained. Additionally, the shallower levels of the ocean heat up and become more buoyant, slowing the oxygen circulation to lower layers. "In the case of a global temperature increase, we expect that low-oxygen regions will grow in size, similar to what happened at the end of the last ice age 30,000 years ago," Deutsch said. "Since these regions change greatly in size from decade to decade due to the Pacific Decadal Oscillation, more data is required before we can recognize an overall trend. "Global warming will almost certainly influence the amount of oxygen in the ocean, but we expect it to be a slow effect that takes place over long periods of time," he added. "There are huge changes in the volume of this low-oxygen water, but the changes oscillate in a natural cycle instead of a persistent growth as many expected. Oxygen comes and goes in the ocean in a way that is not attributable to the long-term warming of the planet. Instead, it is part of the natural rhythm of the ocean."

  29. 21-06-2011 eco nws - global warming - impact - biodiversity - oceans - Multiple Ocean Stresses Threaten 'Globally Significant' Marine Extinction, Experts Warn - ScienceDaily (June 21, 2011) � An international panel of marine experts warns in a new report that the world's ocean is at high risk of entering a phase of extinction of marine species unprecedented in human history. The preliminary report arises from the first ever interdisciplinary international workshop to consider the cumulative impact of all stressors affecting the ocean. Considering the latest research across all areas of marine science, the workshop examined the combined effects of pollution, acidification, ocean warming, overfishing and hypoxia (deoxygenation). The scientific panel concluded that: - The combination of stressors on the ocean is creating the conditions associated with every previous major extinction of species in Earth's history. - The speed and rate of degeneration in the ocean is far faster than anyone has predicted. - Many of the negative impacts previously identified are greater than the worst predictions. - Although difficult to assess because of the unprecedented speed of change, the first steps to globally significant extinction may have begun with a rise in the extinction threat to marine species such as reef-�forming corals. / Dr Alex Rogers, Scientific Director of the International Programme on the State of the Ocean (IPSO) which convened the workshop said: "The findings are shocking. As we considered the cumulative effect of what humankind does to the ocean the implications became far worse than we had individually realized. This is a very serious situation demanding unequivocal action at every level. We are looking at consequences for humankind that will impact in our lifetime, and worse, our children's and generations beyond that." Marine scientists from institutions around the world gathered at Oxford University under the auspices of IPSO and the International Union for Conservation of Nature (IUCN). The group reviewed recent research by world ocean experts and found firm evidence that the effects of climate change, coupled with other human-�-induced impacts such as over-�-fishing and nutrient run-�-off from farming, have already caused a dramatic decline in ocean health. Increasing hypoxia (low oxygen levels) and anoxia (absence of oxygen, known as ocean dead zones) combined with warming of the ocean and acidification are the three factors which have been present in every mass extinction event in Earth's history. There is strong scientific evidence that these three factors are combining in the ocean again, exacerbated by multiple severe stressors. The scientific panel concluded that a new extinction event was inevitable if the current trajectory of damage continues. As examples, the panel point out: - The rate at which carbon is being absorbed by the ocean is already far greater now than at the time of the last globally significant extinction of marine species, some 55 million years ago, when up to 50% of some groups of deep-sea animals were wiped out. - A single mass coral bleaching event in 1998 killed 16% of all the world's tropical coral reefs. - Overfishing has reduced some commercial fish stocks and populations of by-�catch species by more than 90%. - New science also suggests that pollutants including flame retardant chemicals and synthetic musks found in detergents are being traced in the Polar Seas, and that these chemicals can be absorbed by tiny plastic particles in the ocean which are in turn ingested by marine creatures. / The experts agreed that adding these and other threats together means that the ocean and the ecosystems within it are unable to recover, being constantly bombarded with multiple attacks. The report sets out a series of recommendations and calls on states, regional bodies and the United Nations to enact measures to better conserve ocean ecosystems, and in particular demands the urgent adoption of better governance of the largely unprotected high seas which make up the majority of the world's ocean. Dan Laffoley, Marine Chair of IUCN's World Commission on protected Areas and Senior Advisor on Marine Science and Conservation for IUCN, and co-�-author of the report, said: "The world's leading experts on oceans are surprised by the rate and magnitude of changes we are seeing. The challenges for the future of the ocean are vast, but unlike previous generations we know what now needs to happen. The time to protect the blue heart of our planet is now, today and urgent."

  30. 21-06-2011 eco nws - global warming - impact - sea level - oceans - Fastest Sea-Level Rise in 2,000 Years Linked to Increasing Global Temperatures - ScienceDaily (June 21, 2011) � The rate of sea level rise along the U.S. Atlantic coast is greater now than at any time in the past 2,000 years -- and has shown a consistent link between changes in global mean surface temperature and sea level. The findings are published in the journal Proceedings of the National Academy of Sciences (PNAS). The research, funded by the National Science Foundation (NSF), was conducted by Andrew Kemp, Yale University; Benjamin Horton, University of Pennsylvania; Jeffrey Donnelly, Woods Hole Oceanographic Institution; Michael Mann, Pennsylvania State University; Martin Vermeer, Aalto University School of Engineering, Finland; and Stefan Rahmstorf, Potsdam Institute for Climate Impact Research, Germany. "Having a detailed picture of rates of sea level change over the past two millennia provides an important context for understanding current and potential future changes," says Paul Cutler, program director in NSF's Division of Earth Sciences. "It's especially valuable for anticipating the evolution of coastal systems," he says, "in which more than half the world's population now lives." Adds Kemp, "Scenarios of future rise are dependent on understanding the response of sea level to climate changes. Accurate estimates of past sea-level variability provide a context for such projections." Kemp and colleagues developed the first continuous sea-level reconstruction for the past 2,000 years, and compared variations in global temperature to changes in sea level over that time period. The team found that sea level was relatively stable from 200 BC to 1,000 AD. Then in the 11th century, sea level rose by about half a millimeter each year for 400 years, linked with a warm climate period known as the Medieval Climate Anomaly. Then there was a second period of stable sea level during a cooler period called the Little Ice Age. It persisted until the late 19th century. Since the late 19th century, sea level has risen by more than 2 millimeters per year on average, the steepest rate for more than 2,100 years. "Sea-level rise is a potentially disastrous outcome of climate change," says Horton, "as rising temperatures melt land-based ice, and warm ocean waters." To reconstruct sea level, the scientists used microfossils called foraminifera preserved in sediment cores extracted from coastal salt marshes in North Carolina. The age of the cores was estimated using radiocarbon dating and other techniques. To test the validity of their approach, the team compared its reconstructions with tide-gauge measurements from North Carolina for the past 80 years, and global tide-gauge records for the past 300 years. A second reconstruction from Massachusetts confirmed their findings. The records were corrected for contributions to sea-level rise made by vertical land movements. The reconstructed changes in sea level over the past millennium are consistent with past global temperatures, the researchers say, and can be determined using a model relating the rate of sea level rise to global temperature. "Data from the past helped calibrate our model, and will improve sea level rise projections under scenarios of future temperature increases," says Rahmstorf.

  31. 11-07-2011 eco nws - global warming - impact - oceans - co2 - Climate Change Reducing Ocean's Carbon Dioxide Uptake, New Analysis Shows - ScienceDaily (July 11, 2011) � How deep is the ocean's capacity to buffer against climate change? As one of the planet's largest single carbon absorbers, the ocean takes up roughly one-third of all human carbon emissions, reducing atmospheric carbon dioxide and its associated global changes. But whether the ocean can continue mopping up human-produced carbon at the same rate is still up in the air. Previous studies on the topic have yielded conflicting results, says University of Wisconsin-Madison assistant professor Galen McKinley. In a new analysis published online July 10 in Nature Geoscience, McKinley and her colleagues identify a likely source of many of those inconsistencies and provide some of the first observational evidence that climate change is negatively impacting the ocean carbon sink. "The ocean is taking up less carbon because of the warming caused by the carbon in the atmosphere," says McKinley, an assistant professor of atmospheric and oceanic sciences and a member of the Center for Climatic Research in the Nelson Institute for Environmental Studies. The analysis differs from previous studies in its scope across both time and space. One of the biggest challenges in asking how climate is affecting the ocean is simply a lack of data, McKinley says, with available information clustered along shipping lanes and other areas where scientists can take advantage of existing boat traffic. With a dearth of other sampling sites, many studies have simply extrapolated trends from limited areas to broader swaths of the ocean. McKinley and colleagues at UW-Madison, the Lamont-Doherty Earth Observatory at Columbia University, and the Universite Pierre et Marie Curie in Paris expanded their analysis by combining existing data from a range of years (1981-2009), methodologies, and locations spanning most of the North Atlantic into a single time series for each of three large regions called gyres, defined by distinct physical and biological characteristics. They found a high degree of natural variability that often masked longer-term patterns of change and could explain why previous conclusions have disagreed. They discovered that apparent trends in ocean carbon uptake are highly dependent on exactly when and where you look -- on the 10- to 15-year time scale, even overlapping time intervals sometimes suggested opposite effects. "Because the ocean is so variable, we need at least 25 years' worth of data to really see the effect of carbon accumulation in the atmosphere," she says. "This is a big issue in many branches of climate science -- what is natural variability, and what is climate change?" Working with nearly three decades of data, the researchers were able to cut through the variability and identify underlying trends in the surface CO2 throughout the North Atlantic. During the past three decades, increases in atmospheric carbon dioxide have largely been matched by corresponding increases in dissolved carbon dioxide in the seawater. The gases equilibrate across the air-water interface, influenced by how much carbon is in the atmosphere and the ocean and how much carbon dioxide the water is able to hold as determined by its water chemistry. But the researchers found that rising temperatures are slowing the carbon absorption across a large portion of the subtropical North Atlantic. Warmer water cannot hold as much carbon dioxide, so the ocean's carbon capacity is decreasing as it warms. In watching for effects of increasing atmospheric carbon on the ocean's uptake, many people have looked for indications that the carbon content of the ocean is rising faster than that of the atmosphere, McKinley says. However, their new results show that the ocean sink could be weakening even without that visible sign. "More likely what we're going to see is that the ocean will keep its equilibration but it doesn't have to take up as much carbon to do it because it's getting warmer at the same time," she says. "We are already seeing this in the North Atlantic subtropical gyre, and this is some of the first evidence for climate damping the ocean's ability to take up carbon from the atmosphere." She stresses the need to improve available datasets and expand this type of analysis to other oceans, which are relatively less-studied than the North Atlantic, to continue to refine carbon uptake trends in different ocean regions. This information will be critical for decision-making, since any decrease in ocean uptake may require greater human efforts to control carbon dioxide levels in the atmosphere.

  32. 21-08-2011 eco nws - global warming - impact - oceans - north icelandic jet - nij - weather - Newly Discovered Icelandic Current Could Change North Atlantic Climate Picture - ScienceDaily (Aug. 21, 2011) � An international team of researchers, including physical oceanographers from the Woods Hole Oceanographic Institution (WHOI), has confirmed the presence of a deep-reaching ocean circulation system off Iceland that could significantly influence the ocean's response to climate change in previously unforeseen ways. The current, called the North Icelandic Jet (NIJ), contributes to a key component of the Atlantic Meridional Overturning Circulation (AMOC), also known as the "great ocean conveyor belt," which is critically important for regulating Earth's climate. As part of the planet's reciprocal relationship between ocean circulation and climate, this conveyor belt transports warm surface water to high latitudes where the water warms the air, then cools, sinks, and returns towards the equator as a deep flow. Crucial to this warm-to-cold oceanographic choreography is the Denmark Strait Overflow Water (DSOW), the largest of the deep, overflow plumes that feed the lower limb of the conveyor belt and return the dense water south through gaps in the Greenland-Scotland Ridge. For years it has been thought that the primary source of the Denmark Overflow is a current adjacent to Greenland known as the East Greenland Current. However, this view was recently called into question by two oceanographers from Iceland who discovered a deep current flowing southward along the continental slope of Iceland. They named the current the North Icelandic Jet and hypothesized that it formed a significant part of the overflow water. Now, in a paper published in the Aug. 21 online issue of the journal Nature Geoscience, the team of researchers -- including the two Icelanders who discovered it -- has confirmed that the Icelandic Jet is not only a major contributor to the DSOW but "is the primary source of the densest overflow water." "In our paper we present the first comprehensive measurements of the NIJ," said Robert S. Pickart of WHOI, one of the authors of the study. "Our data demonstrate that the NIJ indeed carries overflow water into Denmark Strait and is distinct from the East Greenland Current. We show that the NIJ constitutes approximately half of the total overflow transport and nearly all of the densest component. The researchers used a numerical model to hypothesize where and how the NIJ is formed. "We've identified a new paradigm," he said. "We're hypothesizing a new, overturning loop" of warm water to cold. The results, Pickart says, have "important ramifications" for ocean circulation's impact on climate. Climate specialists have been concerned that the conveyor belt is slowing down due to a rise in global temperatures. They suggest that increasing amounts of fresh water from melting ice and other warming-related phenomena are making their way into the northern North Atlantic, where it could freeze, which would prevent the water from sinking and decrease the need for the loop to deliver as much warm water as it does now. Eventually, this could lead to a colder climate in the northern hemisphere. While this scenario is far from certain, it is critical that researchers understand the overturning process, he said, to be able to make accurate predictions about the future of climate and circulation interaction. "If a large fraction of the overflow water comes from the NIJ, then we need to re-think how quickly the warm-to-cold conversion of the AMOC occurs, as well as how this process might be altered under a warming climate," Pickart said. "These results implicate local water mass transformation and exchange near Iceland as central contributors to the deep limb of the Atlantic Meridional Overturning Circulation, and raise new questions about how global ocean circulation will respond to future climate change," said Eric Itsweire, program director in the U.S. National Science Foundation (NSF)'s Division of Ocean Sciences, which funded the research. The Research Council of Norway also funded the analysis of the data. Pickart and a team of scientists from the U.S., Iceland, Norway, and the Netherlands are scheduled to embark on Aug. 22 on a cruise aboard the WHOI-operated R/V Knorr to collect new information on the overturning in the Iceland Sea. "During our upcoming cruise on the Knorr we will, for the first time, deploy an array of year-long moorings across the entire Denmark Strait to quantify the NIJ and distinguish it from the East Greenland Current," Pickart said. "Then we will collect shipboard measurements in the Iceland Sea to the north of the mooring line to determine more precisely where and how the NIJ originates." In addition to Pickart, authors of the Nature Geoscience study include Michael A. Spall, and Daniel J. Torres of WHOI, lead author Kjetil V�ge, a graduate of the MIT-WHOI joint program now with University of Bergen, Norway, Svein �sterhus and Tor Eldevik, also of the University of Bergen, Norway, and H��inn Valdimarsson and Steingr�mur J�nsson -- the two discoverers of the NIJ -- of the Marine Research Institute in Reykjavik, Iceland.

  33. 18-09-2011 eco nws - global warming - impact - oceans - atmosphere - temperature - Deep Oceans Can Mask Global Warming for Decade-Long Periods - ScienceDaily (Sep. 18, 2011) � The planet's deep oceans at times may absorb enough heat to flatten the rate of global warming for periods of as long as a decade even in the midst of longer-term warming, according to a new analysis led by the National Center for Atmospheric Research (NCAR). The study, based on computer simulations of global climate, points to ocean layers deeper than 1,000 feet (300 meters) as the main location of the "missing heat" during periods such as the past decade when global air temperatures showed little trend. The findings also suggest that several more intervals like this can be expected over the next century, even as the trend toward overall warming continues. "We will see global warming go through hiatus periods in the future," says NCAR's Gerald Meehl, lead author of the study. "However, these periods would likely last only about a decade or so, and warming would then resume. This study illustrates one reason why global temperatures do not simply rise in a straight line." The research, by scientists at NCAR and the Bureau of Meteorology in Australia, is published online in Nature Climate Change. Funding for the study came from the National Science Foundation, NCAR's sponsor, and the Department of Energy. - Where the missing heat goes - The 2000s were Earth's warmest decade in more than a century of weather records. However, the single-year mark for warmest global temperature, which had been set in 1998, remained unmatched until 2010. Yet emissions of greenhouse gases continued to climb during the 2000s, and satellite measurements showed that the discrepancy between incoming sunshine and outgoing radiation from Earth actually increased. This implied that heat was building up somewhere on Earth, according to a 2010 study published in Science by NCAR researchers Kevin Trenberth and John Fasullo. The two scientists, who are coauthors on the new study, suggested that the oceans might be storing some of the heat that would otherwise go toward other processes, such as warming the atmosphere or land, or melting more ice and snow. Observations from a global network of buoys showed some warming in the upper ocean, but not enough to account for the global build-up of heat. Although scientists suspected the deep oceans were playing a role, few measurements were available to confirm that hypothesis. To track where the heat was going, Meehl and colleagues used a powerful software tool known as the Community Climate System Model, which was developed by scientists at NCAR and the Department of Energy with colleagues at other organizations. Using the model's ability to portray complex interactions between the atmosphere, land, oceans, and sea ice, they performed five simulations of global temperatures. The simulations, which were based on projections of future greenhouse gas emissions from human activities, indicated that temperatures would rise by several degrees during this century. But each simulation also showed periods in which temperatures would stabilize for about a decade before climbing again. For example, one simulation showed the global average rising by about 2.5 degrees Fahrenheit (1.4 degrees Celsius) between 2000 and 2100, but with two decade-long hiatus periods during the century. During these hiatus periods, simulations showed that extra energy entered the oceans, with deeper layers absorbing a disproportionate amount of heat due to changes in oceanic circulation. The vast area of ocean below about 1,000 feet (300 meters) warmed by 18% to 19% more during hiatus periods than at other times. In contrast, the shallower global ocean above 1,000 feet warmed by 60% less than during non-hiatus periods in the simulation. "This study suggests the missing energy has indeed been buried in the ocean," Trenberth says. "The heat has not disappeared, and so it cannot be ignored. It must have consequences." - A pattern like La Ni�a - The simulations also indicated that the oceanic warming during hiatus periods has a regional signature. During a hiatus, average sea-surface temperatures decrease across the tropical Pacific, while they tend to increase at higher latitudes, especially around 30�S and 30�N in the Pacific and between 35�N and 40�N in the Atlantic, where surface waters converge to push heat into deeper oceanic layers. These patterns are similar to those observed during a La Ni�a event, according to Meehl. He adds that El Ni�o and La Ni�a events can be overlaid on top of a hiatus-related pattern. Global temperatures tend to drop slightly during La Ni�a, as cooler waters reach the surface of the tropical Pacific, and they rise slightly during El Ni�o, when those waters are warmer. "The main hiatus in observed warming has corresponded with La Ni�a conditions, which is consistent with the simulations," Trenberth says. The simulations were part of NCAR's contribution to the Coupled Model Intercomparison Project Phase 5 (CMIP5). They were run on supercomputers at NCAR's National Science Foundation-supported Climate Simulation Laboratory, and on supercomputers at Oak Ridge Leadership Computing Facility and the National Energy Research Scientific Computing Center, both supported by the Office of Science of the U.S. Department of Energy.

  34. 17-10-2011 eco nws - global warming - impact - oceans - sea level - Sea Levels to Continue to Rise for 500 Years? Long-Term Climate Calculations Suggest So - ScienceDaily (Oct. 17, 2011) � Rising sea levels in the coming centuries is perhaps one of the most catastrophic consequences of rising temperatures. Massive economic costs, social consequences and forced migrations could result from global warming. But how frightening of times are we facing? Researchers from the Niels Bohr Institute are part of a team that has calculated the long-term outlook for rising sea levels in relation to the emission of greenhouse gases and pollution of the atmosphere using climate models. The results have been published in the scientific journal Global and Planetary Change. "Based on the current situation we have projected changes in sea level 500 years into the future. We are not looking at what is happening with the climate, but are focusing exclusively on sea levels," explains Aslak Grinsted, a researcher at the Centre for Ice and Climate, the Niels Bohr Institute at the University of Copenhagen. - Model based on actual measurements - He has developed a model in collaboration with researchers from England and China that is based on what happens with the emission of greenhouse gases and aerosols and the pollution of the atmosphere. Their model has been adjusted backwards to the actual measurements and was then used to predict the outlook for rising sea levels. The research group has made calculations for four scenarios: a pessimistic one, an optimistic one, and two more realistic ones. In the pessimistic scenario, emissions continue to increase. This will mean that sea levels will rise 1.1 meters by the year 2100 and will have risen 5.5 meters by the year 2500. Even in the most optimistic scenario, which requires extremely dramatic climate change goals, major technological advances and strong international cooperation to stop emitting greenhouse gases and polluting the atmosphere, the sea would continue to rise. By the year 2100 it will have risen by 60 cm and by the year 2500 the rise in sea level will be 1.8 meters. For the two more realistic scenarios, calculated based on the emissions and pollution stabilizing, the results show that there will be a sea level rise of about 75 cm by the year 2100 and that by the year 2500 the sea will have risen by 2 meters. - Rising sea levels for centuries - "In the 20th century sea has risen by an average of 2mm per year, but it is accelerating and over the last decades the rise in sea level has gone approximately 70% faster. Even if we stabilize the concentrations in the atmosphere and stop emitting greenhouse gases into the atmosphere, we can see that the rise in sea level will continue to accelerate for several centuries because of the sea and ice caps long reaction time. So it would be 2-400 years before we returned to the 20th century level of a 2 mm rise per year," says Aslak Grinsted. He points out that even though long-term calculations are subject to uncertainties, the sea will continue to rise in the coming centuries and it will most likely rise by 75 cm by the year 2100 and by the year 2500 the sea will have risen by 2 meters.

  35. 28-11-2011 eco nws - global warming - impact - oceans - biodiversity - Marine Biodiversity Loss Due to Global Warming and Predation, Study Predicts - ScienceDaily (Nov. 28, 2011) � The biodiversity loss caused by climate change will result from a combination of rising temperatures and predation -- and may be more severe than currently predicted, according to a study by University of British Columbia zoologist Christopher Harley. The study, published in the current issue of the journal Science, examined the response of rocky shore barnacles and mussels to the combined effects of warming and predation by sea stars. Harley surveyed the upper and lower temperature limits of barnacles and mussels from the cool west coast of Vancouver Island to the warm shores of the San Juan Islands, where water temperature rose from the relatively cool of the1950s to the much warmer years of 2009 and 2010. "Rocky intertidal communities are ideal test-beds for studying the effects of climatic warming," says Christopher Harley, an associate professor of zoology at UBC and author of the study. "Many intertidal organisms, like mussels, already live very close to their thermal tolerance limits, so the impacts can be easily studied." At cooler sites, mussels and rocky shore barnacles were able to live high on the shore, well beyond the range of their predators. However, as temperatures rose, barnacles and mussels were forced to live at lower shore levels, placing them at the same level as predatory sea stars. Daily high temperatures during the summer months have increased by almost 3.5 degrees Celsius in the last 60 years, causing the upper limits of barnacle and mussels habitats to retreat by 50 centimeters down the shore. However, the effects of predators, and therefore the position of the lower limit, have remained constant. "That loss represents 51 per cent of the mussel bed. Some mussels have even gone extinct locally at three of the sites I surveyed," says Harley. Meanwhile, when pressure from sea star predation was reduced using exclusion cages, the prey species were able to occupy hotter sites where they don't normally occur, and species richness at the sites more than doubled. "A mussel bed is kind of like an apartment complex -- it provides critical habitat for a lot of little plants and animals," says Harley. "The mussels make the habitat cooler and wetter, providing an environment for crabs and other small crustaceans, snails, worms and seaweed." These findings provide a comprehensive look at the effects of warming and predation, while many previous studies on how species ranges will change due to warming assume that species will simply shift to stay in their current temperature range. Harley says the findings show that the combined effects of warming and predation could lead to more widespread extinction than are currently predicted, as animals or plants are unable to shift their habitat ranges. "Warming is not just having direct effects on individual species," says Harley. "This study shows that climate change can also alter interactions between species, and produce unexpected changes in where species can live, their community structure, and their diversity."

  36. 18-01-2012 eco nws - global warming - impact - weather - oceans - Climate Balancing: Sea-Level Rise Vs. Surface Temperature Change Rates - ScienceDaily (Jan. 18, 2012) — Engineering our way out of global climate warming may not be as easy as simply reducing the incoming solar energy, according to a team of University of Bristol and Penn State climate scientists. Designing the approach to control both sea level rise and rates of surface air temperature changes requires a balancing act to accommodate the diverging needs of different locations. "Basic physics and past observations suggest that reducing the net influx of solar energy will cool the Earth," said Peter J. Irvine, graduate student, University of Bristol, UK, and participant in the Worldwide Universities Network Research Mobility Programme to Penn State. "However, surface air temperatures would respond much more quickly and sea levels will respond much more slowly." Current solar radiation management approaches include satellites that block the sun, making Earth's surface more reflective or mimicking the effects of volcanoes by placing aerosol particles in the upper atmosphere. "These solar radiation management approaches could be cheaper than reducing carbon dioxide emissions," said Klaus Keller, associate professor of geosciences, Penn State. "But they are an imperfect substitute for reducing carbon dioxide emissions and carry considerable risks." How well they work at reducing sea level rise or surface air temperatures depends on how they are implemented. "Strategies designed to reverse sea-level rise differ from the strategies designed to limit the rate of temperature changes," said Ryan Sriver, research associate in geosciences, Penn State. To stop or reverse sea-level rise, the incoming solar radiation would have to be decreased rapidly, but this approach would produce rapid cooling. Adopting a more gradual approach would reduce the risks due to rapid cooling, but would allow for considerable sea-level rise. The researchers note that people living close to sea level are likely more concerned about sea-level rise than about the rates of surface temperature changes. In contrast, those living far from the oceans, are likely more concerned about rates of surface temperature changes that can influence agricultural or energy usage. The researchers used a model to analyze the tension between controlling sea level rise and rates of surface temperature changes. They ran 120 scenarios with differing combinations of solar radiation management (SRM) including one called "business as usual," which has no SRM. They note that their model includes many approximations. For example, it does not include a mechanistic representation of ice sheets. They also did not consider scenarios that combine solar radiation management and reducing carbon dioxide emissions. They report in the current issue of Nature Climate Change that the forcing required to stop sea-level rise could cause a rapid cooling with a rate similar to the peak business-as-usual warming rate. "While abrupt cooling may sound like a good idea, it could be more damaging than the increasing temperatures caused by increasing carbon dioxide," said Keller. "The rate of cooling can be a problem if it exceeds the capacity of the plants and animals to adapt," said Sriver. Another consideration when implementing solar radiation management approaches is that these approaches can require a long-term commitment. The researchers showed that "termination of solar radiation management was found to produce warming rates up to five times greater than the maximum rates under the business-as-usual scenario, whereas sea-level rise rates were only 30 percent higher." To avoid such harsh changes, should SRM be discontinued, requires a slow phase out over many decades. This places a commitment on future generations.