February 13, 2013
Satellite Confirms Shrinking Arctic Ocean Ice Model
[ Watch the Video: Arctic Sea Ice Changes 2011-2012 ]
Lee Rannals for redOrbit.com — Your Universe Online
A team combined new satellite observations, along with a model created by University of Washington researchers, to confirm the summer minimum in Arctic sea ice is one-fifth of what it was back in 1980, when the model started.
The University of Washington researchers' Pan-Arctic Ice Ocean Modeling and Assimilation System, or PIOMAS, helps to provide a 34-year monthly picture of what has been happening to the total volume of Arctic sea ice. PIOMAS combines weather records, sea-surface temperature and satellite pictures of ice coverage to determine ice volume. After this, it verifies the results with actual thickness measurements from individual moorings, as well as submarines that sit below the ice.
PIOMAS helps check its results against five years of precise ice thickness measurements that were collected by a specialized satellite launched by NASA's Ice, Cloud, and Land Elevation Satellite (ICESat).
ICESat helped measure ice thickness across the Arctic to within 15 inches back until spring of 2008. After this period, ESA's CryoSat-2 satellite helped pick up where ICESat left off, completing ice thickness measurements in 2010.
Co-author of the paper published in Geophysical Research Letters, Axel Schweiger, a polar scientist in the UW Applied Physics Laboratory, says arctic sea ice is shrinking and thinning at the same time, so it is normal for the summer ice volume to drop faster than the area covered.
"From what we know from records pieced together from observations and proxy data, the pan-arctic decline of sea ice is unprecedented for at least a few thousand years," Schweiger told redOrbit. "Sea ice changes over the last 30 year are difficult to explain with what we know about natural variability over that period."
He said the decline of Arctic sea ice has been a robust feature of climate simulations for a long time, and all models show that. Axel added one question we need to be asking is what are the processes driving these changes.
"Although there is discussion in the scientific community about the exact contributions of natural vs. human caused change, I don't think there is any disagreement that by far the largest contributor are greenhouse gases," Schweiger told redOrbit.
Arctic sea ice reached a record low in 2012, and some scientists had speculated for a while it was caused by "The Great Arctic Cyclone of August 2012." However, Schweiger disputed this theory in a paper reported in the same journal.
That team determined cyclone or no cyclone, the Arctic sea ice would have reached this historic sea ice minimum.
“There were a lot of ideas and questions about this which seemed quite plausible,” Schweiger explained to redOrbit. “Science is about following up on those questions in a systematic way. I think we provided a first step here.
“Will a thinning ice pack really be more vulnerable to storms in general or was this a rare event,” he added. “What would happen if the timing of the storm was different? Do we need to account for processes such as bigger waves breaking up ice floes in future model experiments.”