Climate predictions point to the fact that this will change in the future and affect especially the climate in countries of the Mediterranean region, with more dry spells.

As global warming progresses, the North Atlantic will receive more precipitation and a greater amount of water from the melting of glaciers in Greenland, thus reducing the salinity of ocean water and weakening the Gulf Stream's effects.

The article published in Nature describes an alternative approach which suggests that flows from the Indian Ocean to the South Atlantic, near the tip of Africa, also are important in relation to future current systems in the North Atlantic.

The Agulhas Current, located in the southwest of the Indian Ocean, transports high density salt water to the southern tip of Africa, where part of it escapes to the South Atlantic, contributing to the strength of the global circulation of this ocean.

The study describes how this inflow of salt water from the Indian Ocean can compensate the decrease in salinity in the North Atlantic and therefore stabilise the Gulf Stream and the climate in Europe. These processes have been simulated using computational climate models.

The article reviews information available until now and enumerates the steps which must be taken with the aim of carrying out a better assessment of the processes involved in this current system.

To demonstrate the dynamics of the Agulhas Current, its sensitivity to climate change and the way it transmits its signals to the North Atlantic, researchers point out the need to combine long-term studies on temperature variation and salinity of the Agulhas Current, analyses on climate changes in the past and detailed computer simulation models.

The existence of connections between the Agulhas Current and Europe's climate has been the focus of study these past six years of the research group directed by Dr Rainer Zahn.

The authors of the research article are members of a consortium of marine scientists from United States, Germany, The Netherlands, United Kingdom and Spain working together with the objective of studying the effects of the Agulhas Current on regional and global climates.

This group forms part of the Scientific Committee on Oceanic Research (SCOR), member of the International Council for Science. Other member institutions include the US National Science Foundation, the World Climate Research Programme (WCRP), the International Association for the Physical Sciences of the Oceans (IAPSO) and the International Marine Global Change Study (IMAGES). earlier related report
Agulhas leakage could stabilize Atlantic overturning circulation
Miami FL (SPX) Apr 29 - 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 and 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.

The scientific review team included UM's Lisa Beal, Wilhelmus P.M. de Ruijter of Utrecht University in the Netherlands, Arne Biastoch of Leibniz- Institut fur Meereswissenschaften (IFM-GEOMAR) in Germany, and Rainer Zahn of the Universitat Autonoma de Barcelona in Spain, as well as members of SCOR Working Group 136 on the Climatic Importance of the Agulhas System, sponsored by the Scientific Committee for Oceanic Research, the International Association for the Physical Sciences of the Oceans, and the World Climate Research Program.

The Scientific Committee on Oceanic Research is supported by the National Science Foundation, award no. OCE-0938349. Beal is funded by the National Science Foundation through the ACT (Agulhas Current Time-series) project, award no. OCE-0850891.

The ACT ocean observing program was launched in April 2010 to measure the variability of the Agulhas Current using a combination of current meter moorings and satellite data. Beal, who serves as chief scientist, spent one month aboard Research Vessel Knorr in the southwest Indian Ocean deploying oceanographic instruments.

-SPACE STORY-- water-earth slug1 150 23-DEC-49 Predicting and preventing environmental collapse Predicting and preventing environmental collapse wisconsin-lake-runabout-lg.jpg wisconsin-lake-runabout-bg.jpg wisconsin-lake-runabout-sm.jpg Through extensive environmental monitoring, the research team identified the early warning signals of a regime shift in this study lake. Credit: Cascade Project Photo Archive. Cary Institute of Ecosystem Studies
by Staff Writers Millbrook NY (SPX) Apr 29, 2011 By closely monitoring environmental conditions at a remote Wisconsin lake, researchers have found that models used to assess catastrophic changes in economic and medical systems can also predict environmental collapse. Stock market crashes, epileptic seizures, and ecological breakdowns are all preceded by a measurable increase in variance-be it fluctuations in brain waves, the Dow Jones index, or, in the case of the Wisconsin lake, chlorophyll.

In a paper published this week in the journal Science, a team of ecologists is the first to show that by paying attention to variability in key ecosystem processes, scientists can detect the early warning signs that herald environmental collapse.

Insight into regime shifts-the reorganization of an ecosystem from one state to another-is critical to identifying ecosystems that will fail without intervention.

"Early warning signs help you prepare for, and hopefully prevent, the worst case scenario," notes contributing author Jonathan J. Cole, a biogeochemist at the Cary Institute of Ecosystem Studies.

"We are surrounded by problems caused by ecological regime shifts-water supply shortages, fishery declines, unproductive rangeland-our study shows that there is promise in identifying these changes before they reach their tipping point."

The team, led by Stephen Carpenter, a limnologist at the University of Wisconsin-Madison, triggered a regime shift in a Wisconsin lake by introducing a top predator. The study lake was originally dominated by small fish, such as golden shiners, that feed on tiny free-swimming invertebrates. Researchers destabilized the lake by adding largemouth bass.

The goal: to observe the cascade of environmental changes that eventually led to a food web dominated by piscivorous, or fish-eating, fish.

Throughout the lake's three-year manipulation, its chemical, biological, and physical vital signs were continuously monitored to track even the smallest changes. It was in these massive sets of data that researchers were able to detect the signals of the ecosystem's impending collapse.

As the number of bass increased, smaller fish spent more time swimming in groups near the shoreline, to avoid being eaten. Freed from predation, invertebrates living in the open water shifted to forms that were larger in size.

Phytoplankton, the preferred food of these invertebrates, became more variable. Bass populations increased, as they fed on the smaller fish. Within three years the lake's food web had completely shifted to one dominated by fish-eating fish and larger free-swimming invertebrates

significantly, more than a year before the food web transition was complete, variance in chlorophyll measurements was a reliable early warning indicator of the impending food web regime shift.

"The field experiment is a validated statistical early warning system for ecosystem collapse. With more work, this could revolutionize ecosystem management," Carpenter comments.

The catch, however, is that for the early warning system to work, continuous monitoring of an ecosystem's chemistry, physical properties, and biota are required. The chlorophyll red flag would only work for identifying food web shifts in freshwater lakes.

Such an approach may not be practical for every threatened ecosystem, says Carpenter, but he also cites the price of doing nothing: "These regime shifts tend to be hard to reverse. It is like a runaway train once it gets going and the costs, both ecological and economic, are high."

Cole concludes, "Automated sensors, remote sensing technology, and computing are making continuous environmental monitoring much more accessible. And identifying early warning signs across a variety of ecosystems could help us prioritize management efforts."

The project was funded by the National Science Foundation. In addition to Cole and Carpenter, authors include Michael Pace, James Coloso, and David Seekell of the University of Virginia at Charlottesville; James Hodgson of St. Norbert College; and Ryan Batt, Tim Cline, James Kitchell, Laura Smith, and Brian Weidel of UW-Madison.

del.icio.us	Digg	Reddit
YahooMyWeb	Google	Facebook

Memory Foam Mattress Review

SPACE MEDIA NETWORK PROMOTIONS Solar Energy Solutions Tempur-Pedic Mattress Comparison ... Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News