Global warming is replicating conditions that triggered an abrupt sea level rise of several meters in the ocean around Antarctica about 15,000 years ago, a new study has warned.
"The changes that are currently taking place in a disturbing manner resemble those 14,700 years ago," said climate researcher Michael E Weber from University of Bonn in Germany.
At that time, changes in atmospheric-oceanic circulation led to a stratification in the ocean with a cold layer at the surface and a warm layer below.
Under such conditions, ice sheets melt more strongly than when the surrounding ocean is thoroughly mixed.
This is exactly what is presently happening around the Antarctic, researchers said.
"The reason for the layering is that global warming in parts of Antarctica is causing land based ice to melt, adding massive amounts of freshwater to the ocean surface," said Chris Fogwill from the Climate Change Research Centre in Australia.
"At the same time as the surface is cooling, the deeper ocean is warming, which has already accelerated the decline of glaciers in the Amundsen Sea Embayment," said Fogwill.
It appears global warming is replicating conditions that, in the past, triggered significant shifts in the stability of the Antarctic ice sheet.
To investigate the climate changes of the past, the scientists are studying drill cores from the eternal ice. Layer by layer, this frozen "climate archive" reveals its secrets to the experts.
In previous studies, the scientists had found evidence of eight massive melting events in deep sea sediments around the Antarctic, which occurred at the transition from the last ice age to the present warm period.
"The largest melt occurred 14,700 years ago. During this time the Antarctic contributed to a sea level rise of at least three meters within a few centuries," said Weber.
The present discovery is the first direct evidence from the Antarctic continent which confirms the assumed models.
The research team used isotopic analyses of ice cores from the Weddell Sea region, which now flows into the ocean about a quarter of the Antarctic melt.
Through a combination with ice sheet and climate modelling, the isotopic data show that the waters around the Antarctic were heavily layered at the time of the melting events, so that the ice sheets melted at a faster rate.
"The big question is whether the ice sheet will react to these changing ocean conditions as rapidly as it did 14,700 years ago," said co-author Nick Golledge from the Antarctic Research Centre in New Zealand.
The findings were published in the journal Scientific Reports.
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