Using super-sensitive satellite measurements, scientists are developing a more sharply focused picture of what is happening to the ice mass of Antarctica - one of the 800-pound gorillas of global sea level rise.
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Year-to-year rises and falls in snow and ice accumulation in two key regions of West Antarctica - the Antarctic Peninsula and a coastal region along the Amundsen Sea - are the handiwork of the natural climate pattern known as El Nino, an international team of scientists reports.
Ingo Sasgen at the GFZ German Research Center for Geosciences in Postdam and colleagues found clear El Nino-La Nina "signatures" when they compared gravity measurements taken from the German-American twin GRACE satellites from the years 2002 to 2009 with precipitation data from the European Center for Medium Range Weather Forecasts.
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Co-author Maik Thomas described a see-saw pattern between the two regions and the two cool and warm El Nino/Southern Oscillation (ENSO) patterns that are driven by periodic shifts in sea surface temperatures along the equatorial Pacific Ocean.
"The cooler La Nina years lead to a strong low pressure area over the Amundsen Sea, which favors heavy rainfall along the Antarctic Peninsula; the ice mass is increasing there. In contrast, the Amundsen area is dominated by dry air from the interior during this time. El Nino years with their warm phase lead to precisely the opposite pattern: reduced rainfall and mass loss in the Antarctic Peninsula, and an increase in the Amundsen sectorfield, respectively."
Sasgen noted that the new findings, published in the journal Earth and Planetary Science Letters, will help scientists better distinguish between "interannual mass variability and its causes" and longer-term climate change.
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"It is accurate to say that ENSO has a strong influence on the annual mass balance in West Antarctica, but (probably) not on the long-term ice mass trends," Sasgen told Discovery News. "For example, GRACE indicated a negative annual net loss for all years between 2002 and 2009, despite the accumulation variability caused by ENSO."
Climate scientists are keeping wary eyes on signs of accelerating ice mass loss in Antarctica and Greenland because both ice caps, showing signs of climate change, contain enough freshwater to sharply raise sea levels and swamp coastal areas around the globe.
IMAGE: Ingo Sasgen/GFZ