La Niña Cuts 50 Percent of Oceanic Melt in Antarctica
By Julie S | Jan 03, 2014 11:07 AM EST
A new study found that La Niña has cut the oceanic melt in West Antarctica by 50 percent during a three-year observation.
A team of scientists from the British Antarctic Survey and other institutions found that the oceanic melting of the ice in Antarctica diminished by half from 2010 to 2013. They believe that it was caused by a La Niña weather occurrence. During La Niña, the sea surface temperature across the Atlantic Ocean becomes lower than its regular temperature which is 3 to 5 degrees Celsius.
The findings implied that the thinning of Pine Island Glacier is much more susceptible to climatic and ocean variability than previously believed.
The Pine Island Glacier has continuously melted during the past decades due to a deep oceanic inflow of Circumbipolar Deep Water (CDW) on the continental shelf beside the glacier. This warmer water makes it way into a cavity beneath the ice shelf melting from below.
The passage of this warmer water was made easier by the unpinning of the ice shelf from an underwater ridge. The ridge had, in effect, acted as a wall preventing warmer water from getting to the thickest part of the shelf. This ungrounding event was one of the major driving forces behind the glacier's rapid change.
In January 2012, the researchers have observed that the ocean melting of the glacier was the lowest ever recorded. The peak of the thermocline – the layer separating the cold surface water and warm deep waters – was discovered to be roughly 250 meters deeper than any other year.
The observations implied an intricate interaction between climatic, geological, and oceanographic processes.
Dr. Pierre Dutrieux, the lead author of the study said in a press release, “We found ocean melting of the glacier was the lowest ever recorded, and less than half of that observed in 2010. This enormous, and unexpected, variability contradicts the widespread view that a simple and steady ocean warming in the region is eroding the West Antarctic Ice Sheet. These results demonstrate that the sea-level contribution of the ice sheet is influenced by climatic variability over a wide range of time scales.”
Professor Adrian Jenkins, co-author of the study, added, “These new insights suggest that the recent history of ice shelf melting and thinning has been much more variable than hitherto suspected and susceptible to climate variability driven from the tropics.”
The study was published in the January 2 issue of Science.