I posted on this a long time agowhen I was trying to determine viable mechanisms able to alter Gulf Stream heattransfer into the Arctic . We knew that during the Bronze Age that thenorthern waters were a full two degrees warmer. It needed a big switch and the South African Current was a good place tostart.
This item is a call to start theprocess of gathering information. Itreally needs to be done and a lot more besides in order to see and plausibly understanddevelopments.
It really shows us though justhow well positioned that current is to cause major change and this should neverbe forgotten. I suspect a simpleseasonal burp there could possibly have brought on the little ice age around 1700AD which then took decades to recover from. At least we have to think it through to see if the dynamics are evenplausible.
If I have learned anything themajor risk in climate is a sudden cooling event, of which we have had several thatcan be detected. Recovery is always slowand we have just now fully recovered from the event in 1700 AD. The time period is not that precise but itwas pretty abrupt.
Water currents of South Africa could stabilize climate in Europe
by Staff Writers
The Agulhas Current, located in the southwest of the Indian Ocean,transports high density salt water to the southern tip of Africa, where part ofit escapes to the South Atlantic, contributing to the strength of the globalcirculation of this ocean.
One of the ocean currents which particularly interests oceanographers andclimatologists is the
Climate predictions point to the fact that this will change in thefuture and affect especially the climate in countries of the Mediterraneanregion, with more dry spells.
As global warming progresses, the North Atlantic will receive moreprecipitation 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 whichsuggests that flows from the Indian Ocean to the South Atlantic, near the tipof 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 ofit escapes to the South Atlantic, contributing to the strength of the globalcirculation of this ocean.
The study describes how this inflow of salt water from the Indian Oceancan compensate the decrease in salinity in the North Atlantic and thereforestabilise 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 thesteps which must be taken with the aim of carrying out a better assessment ofthe processes involved in this current system.
To demonstrate the dynamics of the Agulhas Current, its sensitivity toclimate change and the way it transmits its signals to the North Atlantic,researchers point out the need to combine long-term studies on temperaturevariation and salinity of the Agulhas Current, analyses on climate changes inthe 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 pastsix years of the research group directed by Dr Rainer Zahn.
The authors of the research article are members of a consortium ofmarine scientists from United States ,Germany , The Netherlands , United Kingdom and Spain
This group forms part of the Scientific Committee on Oceanic Research(SCOR), member of the International Council for Science. Other memberinstitutions include the US National Science Foundation, the World ClimateResearch Programme(WCRP), the International Association for the Physical Sciences of the Oceans(IAPSO) and the International Marine Global Change Study (IMAGES). earlierrelated report
Agulhas leakage could stabilize Atlantic overturning circulation
Miami FL (SPX) Apr 29 - The Agulhas Current which runs along the east coast ofAfrica may not be as well known as its counterpart in the Atlantic, the GulfStream, but researchers are now taking a much closer look at this current andits "leakage" from the Indian Ocean into the Atlantic Ocean.
Agulhas leakage could stabilize Atlantic overturning circulation
Miami FL (SPX) Apr 29 - The Agulhas Current which runs along the east coast ofAfrica may not be as well known as its counterpart in the Atlantic, the GulfStream, but researchers are now taking a much closer look at this current andits "leakage" from the Indian Ocean into the Atlantic Ocean.
In a study published in the journal Nature, April 27, a global team ofscientists led by University of Miami (UM) Rosenstiel School
The Agulhas Current transports warm and salty waters from the tropicalIndian Ocean to the southern tip of Africa, where most of the water loopsaround to remain in the Indian Ocean (the Agulhas Retroflection), while somewaters leak into the fresher Atlantic Ocean via giant Agulhas rings.
Once in the Atlantic , the saltyAgulhas leakage waters eventually flow into the Northern Hemisphere and act tostrengthen the Atlantic overturning circulation by enhancing deep waterformation.
Recent research points to an increase in Agulhas leakage over the lastfew decades caused primarily by human-induced climate change. This finding isprofound, because it suggests that increased Agulhas leakage could trigger astrengthening in the Atlantic overturning circulation, at a time when warmingand accelerated meltwater input in the North Atlantic has been predicted to weaken it.
"This could mean that current IPCC model predictions for the nextcentury are wrong and there will be no cooling in the North Atlantic topartially offset the effects of global climate change over North America andEurope," said Beal, "Instead, increasing Agulhas leakage couldstabilize the oceanic heat transport carried by the Atlantic overturningcirculation."
There is also paleoceanographic data to suggest that dramatic peaks inAgulhas leakage over the past 500,000 years may have triggered the end ofglacial cycles. This serves as further evidence that the Agulhas system and itsleakage play an important role in the planet's climate.
"This study shows that local changes in atmospheric and oceanicconditions in the Southern Hemisphere can affect the strength of the oceancirculation in unexpected ways. Under a warming climate, the Agulhas Currentsystem near the tip of South Africa could bring more warm salty water from theIndian to the Atlantic Ocean and counteract opposing effects from the Arctic Ocean,"said Eric Itsweire, director of the National Science Foundation (NSF)'sphysical oceanography program, which funded the research.
The study establishes the need for additional research in the regionthat focuses on Agulhas rings, as well as the leakage. Climate modeling experimentsare critical, and need to be supported by paleoceanographic data and sustainedobservations to firmly establish the role of this system in a warming climate.
"Our goal now is to get more of the scientific community involvedin research of the Agulhas system and its global effects. The emphasis has beentoo long in the North Atlantic ," saidBeal.
The scientific review team included UM's Lisa Beal, Wilhelmus P.M. deRuijter of Utrecht University in the Netherlands, Arne Biastoch of Leibniz-Institut fur Meereswissenschaften (IFM-GEOMAR) in Germany, and Rainer Zahn ofthe Universitat Autonoma de Barcelona in Spain, as well as members of SCORWorking Group 136 on the Climatic Importance of the Agulhas System, sponsoredby the Scientific Committee for Oceanic Research, the International Associationfor the Physical Sciences of the Oceans, and the World Climate ResearchProgram.
The Scientific Committee on Oceanic Research is supported by theNational Science Foundation, award no. OCE-0938349. Beal is funded by theNational 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 measurethe variability of the Agulhas Current using a combination of current metermoorings and satellite data. Beal, who serves as chief scientist, spent onemonth aboard Research Vessel Knorr in the southwest Indian Ocean deploying oceanographic instruments.
-SPACE STORY-- water-earth slug1 150 23-DEC-49 Predicting andpreventing environmental collapse Predicting and preventing environmentalcollapse wisconsin-lake-runabout-lg.jpg wisconsin-lake-runabout-bg.jpg wisconsin-lake-runabout-sm.jpgThrough extensive environmental monitoring, the research team identified theearly warning signals of a regime shift in this study lake. Credit: CascadeProject Photo Archive. Cary Instituteof Ecosystem Studies
by Staff Writers
By closely monitoring environmental conditions at a remote Wisconsin lake, researchers have found that models usedto assess catastrophic changes in economic and medical systems can also predictenvironmental collapse. Stock market crashes, epileptic seizures, andecological breakdowns are all preceded by a measurable increase in variance-beit 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 ofecologists is the first to show that by paying attention to variability in keyecosystem processes, scientists can detect the early warning signs that heraldenvironmental collapse.
Insight into regime shifts-the reorganization of an ecosystem from onestate to another-is critical to identifying ecosystems that will fail withoutintervention.
"Early warning signs help you prepare for, and hopefully prevent,the worst case scenario," notes contributing author Jonathan J. Cole, abiogeochemist at the Cary Institute of Ecosystem Studies.
"We are surrounded by problems caused by ecological regime shifts-watersupply shortages,fishery declines, unproductive rangeland-our study shows that there is promisein identifying these changes before they reach their tipping point."
The team, led by Stephen Carpenter, a limnologist at the University ofWisconsin-Madison, triggered a regime shift in a Wisconsin lake by introducing a top predator. The study lake was originally dominated bysmall fish, such as golden shiners, that feed on tiny free-swimminginvertebrates. Researchers destabilized the lake by adding largemouth bass.
The goal: to observe the cascade of environmental changes thateventually 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 eventhe smallest changes. It was in these massive sets of data that researcherswere able to detect the signals of the ecosystem's impending collapse.
As the number of bass increased, smaller fish spent more time swimmingin groups near the shoreline, to avoid being eaten. Freed from predation,invertebrates living in the open water shifted to forms that were larger insize.
Phytoplankton, the preferred food of these invertebrates, became morevariable. Bass populations increased, as they fed on the smaller fish. Withinthree years the lake's food web had completely shifted to one dominated byfish-eating fish and larger free-swimming invertebrates
significantly, more than a year before the food web transition wascomplete, variance in chlorophyll measurements was a reliable early warningindicator of the impending food web regime shift.
"The field experiment is a validated statistical early warningsystem for ecosystem collapse. With more work, this could revolutionizeecosystem management," Carpenter comments.
The catch, however, is that for the early warning system to work,continuous monitoring of an ecosystem's chemistry, physical properties, andbiota are required. The chlorophyll red flag would only work for identifyingfood 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: "Theseregime shifts tend to be hard to reverse. It is like a runaway train once itgets going and the costs, both ecological and economic, are high."
Cole concludes, "Automated sensors, remote sensing technology, andcomputing are making continuous environmental monitoring much more accessible.And identifying early warning signs across a variety of ecosystems could helpus prioritize management efforts."
The project was funded by the National Science Foundation. In additionto Cole and Carpenter, authors include Michael Pace, James Coloso, and DavidSeekell of the University of Virginia at Charlottesville; James Hodgson of St.Norbert College; and Ryan Batt, Tim Cline, James Kitchell, Laura Smith, andBrian Weidel of UW-Madison.
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