The coldest deep ocean water that flows around Antarctica in the Southern Ocean has been strangely disappearing at a high rate for the past few decades, a new study has revealed.
This mass of water is called Antarctic Bottom Water, which is formed in a few distinct locations around Antarctica, where seawater is cooled by the overlying air and made saltier by ice formation (which leaves the salt behind in the unfrozen water).
The cold, salty water is denser than the water around it, causing it to sink to the sea floor where it spreads northward, filling most of the deep ocean around the world as it slowly mixes with warmer waters above it.
The world’s deep ocean currents play a critical role in transporting heat and carbon around the planet, which helps regulate the Earth’s climate.
Previous studies had indicated that this deep water has become warmer and less salty over the past few decades, but a new study has found that significantly less of this water has also been formed during this time.
Oceanographers examined temperature data collected from 1980 to 2011 at about 10-year intervals by an international program of repeated ship-based oceanographic surveys in the Southern Ocean.
They found that Antarctic Bottom Water has been disappearing at an average rate of about 8 million metric tons per second over the past few decades, equivalent to about 50 times the average flow of the Mississippi River, according to statement from the National Oceanic and Atmospheric Administration (NOAA), which helped fund the data collection.
“In every oceanographic survey repeated around the Southern Ocean since about the 1980s, Antarctic Bottom Water has been shrinking at a similar mean rate, giving us confidence that this surprisingly large contraction is robust,” said lead author of the study Sarah Purkey, a graduate student at the University of Washington in Seattle.
What’s causing the reduction and what it means are things the researchers must still investigate.
“We are not sure if the rate of bottom-water reduction we have found is part of a long-term trend or a cycle,” said co-author Gregory C. Johnson, an oceanographer at NOAA’s Pacific Marine Environmental Laboratory in Seattle.
Changes in the temperature, salt content, dissolved oxygen and dissolved carbon dioxide of this prominent water mass have important ramifications for Earth’s climate, including contributions to sea level rise and the rate of Earth’s heat uptake.
“We need to continue to measure the full depth of the oceans, including these deep ocean waters, to assess the role and significance that these reported changes and others like them play in the Earth’s climate,” Johnson added.
http://www.deccanchronicle.com/channels/sci-tech/climate/coldest-deepest-antarctic-water-mysteriously-shrinking-530
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Showing posts with label anarctica. Show all posts
Showing posts with label anarctica. Show all posts
Sunday, March 25, 2012
Sunday, January 8, 2012
Russians DOing Research at Both Poles
The journey
After having drawn a lot of attention from thepress, Koen left form Zaventem Airport on 15 December for Cape Town, where he spent a few days. His departure for the Russian Novolazarevskaya base was delayed due to a violent storm. On 23 December, Koen took his first steps in Antarctica and described his experience as “a marvelous and very special experience. The thermal shock was enormous. The cold stung my hands, feet and nose. It certainly felt like we were on the coldest continent on the planet.”
Arrival at the Princess Elisabeth Station
After another flight leaving from the Russian base Koen was able to reach his final destination: the Princess Elisabeth Station – just in time to celebrate Christmas in Antarctica! Koen arrived at the station at the same time as a team of German scientists from the German Federal Institute for Geosciences and Natural Resources (Bundesanstalt für Geowissenschaften und Rohstoffe - BGR), who will do geophysical research in the Sør Rondane mountains. However the German team had to postpone their research, given that the Mary Arctica, the ship bringing the helicopters they need to get, was blocked 130 km off the coast for several days. The Mary Arctica finally arrived at Crown Bay on 5 January, and Koen left this morning with other members of the station team to help offload equipment from the ship.
Meanwhile in Brussels…
To keep you up to date with Koen’s adventures at the station, an article and a photo gallery will be posted every two weeks during his stay in Antarctica. We are also organizing teacher workshops (one on 25 January for the Flemish Community and one on 1 February for the French-Speaking Community) in the Class Zero Emission space at the headquarters of the International Polar Foundation (IPF) in Brussels. During the workshops, teachers will be able to chat with Koen and ask him questions via Skype video conference.
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