I posted on this a long time ago
when I was trying to determine viable mechanisms able to alter Gulf Stream heat
transfer into the Arctic . We knew that during the Bronze Age that the
northern waters were a full two degrees warmer.
It needed a big switch and the South African Current was a good place to
start.
This item is a call to start the
process of gathering information. It
really needs to be done and a lot more besides in order to see and plausibly understand
developments.
It really shows us though just
how well positioned that current is to cause major change and this should never
be forgotten. I suspect a simple
seasonal burp there could possibly have brought on the little ice age around 1700
AD which then took decades to recover from.
At least we have to think it through to see if the dynamics are even
plausible.
If I have learned anything the
major risk in climate is a sudden cooling event, of which we have had several that
can be detected. Recovery is always slow
and we have just now fully recovered from the event in 1700 AD. The time period is not that precise but it
was 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 of
it escapes to the South Atlantic, contributing to the strength of the global
circulation of this ocean.
One of the ocean currents which particularly interests oceanographers and climatologists is the
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
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 ClimateResearch 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.
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
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
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-watersupply 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.
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