May 29, 2014
Antarctic Ice Sheet Less Stable Than Previously Believed, New Study Claims
redOrbit Staff & Wire Reports - Your Universe Online
The Antarctic Ice Sheet started melting approximately 5,000 years earlier than previously believed following the last ice age, according to new research appearing in this week’s edition of the journal Nature.The study, which comes in the wake of research suggesting that destabilization of some of the West Antarctic Ice Sheet has already begun, also said that the shrinkage of the ice sheet accelerated and caused rapid sea level increases across eight individual episodes, the researchers said in a statement Wednesday.
As part of their research, scientists from the University of Cologne, Oregon State University, the Alfred-Wegener-Institute, the University of Hawaii at Manoa, the University of Lapland, the University of New South Wales and the University of Bonn examined a pair of sediment cores from the Scotia Sea.
Those sediment cores contained “iceberg-rafted debris” which has been scraped off Antarctica by moving ice and deposited into the sea by icebergs. As the icebergs melted, the minerals they carried were released into seafloor sediments, allowing the researchers to look at how the Antarctic Ice Sheet used to behave.
During periods of rapid increases in iceberg-rafted debris suggest that a greater number of icebergs were being released by the Antarctic Ice Sheet, and the study authors found eight separate occasions during which there were increased amounts of debris. The earlier of those episodes took place as early as 20,000 years ago, even though the melting of the ice sheet was believed to have started just 14,000 years ago.
“Conventional thinking based on past research is that the Antarctic Ice Sheet has been relatively stable since the last ice age, that it began to melt relatively late during the deglaciation process, and that its decline was slow and steady until it reached its present size,” said lead author and University of Cologne scientist Michael Weber. “The sediment record suggests a different pattern – one that is more episodic and suggests that parts of the ice sheet repeatedly became unstable during the last deglaciation.”
In addition, the research provides what is believed to be the first concrete evidence that the Antarctic Ice Sheet contributed to what is known as meltwater pulse 1A, a period of extremely rapid sea level increase that started approximately 14,500 years ago. The largest of the eight episodes detailed the in new study coincides with meltwater pulse 1A, noted co-author Peter Clark.
“During that time, the sea level on a global basis rose about 50 feet in just 350 years – or about 20 times faster than sea level rise over the last century,” said Clark, a professor in the Oregon State University College of Earth, Ocean, and Atmospheric Sciences. “We don’t yet know what triggered these eight episodes or pulses, but it appears that once the melting of the ice sheet began it was amplified by physical processes.”
In order to figure out what caused the large-scale ice-sheet collapses during these periods, Weber, Clark and their colleagues conducted a series of climate modeling experiments. Those simulations suggested that the events could have been triggered by “an unusually strong flow of warm water towards Antarctica,” explained co-author Axel Timmermann, a professor at the University of Hawaii’s International Pacific Research Center.
The episodes abruptly stopped roughly 9,000 years ago, and just as the researchers are not certain how these events started, they are equally uncertain why they came to a sudden halt. Clark said that it was possible that there was no more ice on the sheet that was vulnerable to the physical changes that were occurring. Regardless, he noted that their research demonstrates that the Antarctic Ice Sheet is less stable than experts had realized.