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Climate Change Weakens Southern Ocean Convection

02.03.2014
02.03.2014 18:00 Age: 4 yrs

Changes in the salinity of ocean surface waters due to climate change are inhibiting deep ocean mixing, encouraging ocean heat storage and contributing to the so called pause in global warming, according to new research.

Click to enlarge. Icebergs and sea ice floating atop near-freezing surface waters of the Weddell Sea, where deep ocean convection may have been much stronger than at present. Courtesy: Eric Galbraith and Nature.

Click to enlarge. Iceberg floating atop near-freezing surface waters of the Weddell Sea, where deep ocean convection may have been much stronger than at present. Courtesy: Eric Galbraith and Nature.

Abstract and citation for paper are below the two news releases that follow.

Here is a news release issued by McGill University:

Global Warming Felt to Deepest Reaches of Ocean

Study shows climate change has put a freshwater lid on the Antarctic ocean, trapping warm water in ocean depths

From McGill University NewsroomHere is a news release issued by the University of Pennsylvania:

Deep Ocean Current May Slow Due to Climate Change, Penn Research Finds

Abstract

In 1974, newly available satellite observations unveiled the presence of a giant ice-free area, or polynya, within the Antarctic ice pack of the Weddell Sea, which persisted during the two following winters. Subsequent research showed that deep convective overturning had opened a conduit between the surface and the abyssal ocean, and had maintained the polynya through the massive release of heat from the deep sea. Although the polynya has aroused continued interest, the presence of a fresh surface layer has prevented the recurrence of deep convection there since 1976, and it is

now largely viewed as a naturally rare event. Here, we present a new analysis of historical observations and model simulations that suggest deep convection in the Weddell Sea was more active in the past, and has been weakened by anthropogenic forcing. The observations show that surface freshening of the southern polar ocean since the 1950s has considerably enhanced the salinity stratification. Meanwhile, among the present generation of global climate models, deep convection is common in the Southern Ocean under pre-industrial conditions, but weakens and ceases under a climate change scenario owing to surface freshening. A decline of open-ocean convection would reduce the production rate of Antarctic Bottom Waters, with important implications for ocean heat and carbon storage, and may have played a role in recent Antarctic climate change.

Citation

Cessation of deep convection in the open Southern Ocean under anthropogenic climate change by Casimir de Lavergn, Jaime B. Palter, Eric D. Galbraith, Rafaele Bernardello and Irina Marinov published in Nature Climate Change . Published online 2 March 2014. DOI: 10.1038/NCLIMATE2132

 

Source

Nature press release.

McGill news release here.

University of Pensylvania news release here.

 

Note

This story updated to include McGill news release 19.40 2 March 2014.

This story updated to include University of Pennsylvania news release 12.25 23 March 2014.