New from Colorado.EDU:
In 2012, temperatures at the summit of Greenland rose above freezing for the first time since 1889, raising questions about what led to the unusual melt episode. Now, a new analysis led by the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder shows that some of the same weather and climate factors were at play in both 1889 and 2012: heat waves thousands of miles upwind in North America, higher-than-average ocean surface temperatures south of Greenland and atmospheric rivers of warm, moist air that streamed toward Greenland’s west coast.
“These rare melt events on the highest elevations of Greenland require an unusual coincidence of factors. Understanding how they come together may help us better forecast the future of Greenland’s ice and snow,” said William Neff, a fellow at CIRES, a joint institute of CU-Boulder and the National Oceanic and Atmospheric Administration. Neff is lead author of the new analysis, accepted for publication in the American Geophysical Union’s Journal of Geophysical Research.
Neff and colleagues at CIRES, NOAA’s Earth System Research Laboratory and Scripps Institution of Oceanography at the University of California San Diego began digging into the underlying reasons for Greenland’s extreme melt year after another research project showed that warm air and thin clouds were key to the 2012 warmth and melt.
To figure out where the warm air and clouds came from, the scientists started with satellite observations of moisture in the air over the Atlantic Ocean, looking for atmospheric rivers. Atmospheric rivers are narrow filaments of water vapor in the atmosphere that can stream significant amounts of moisture northward in the midlatitudes.
The researchers also studied sea-surface temperatures, which might have influenced the temperature and moisture content of air moving toward Greenland. And to better understand atmospheric and oceanic conditions back in 1889, the research team drew on data in the 20th Century Reanalysis, a sophisticated computer reconstruction of the weather going back to 1871.
The original article appears on the Colorado.EDU website. Read it in its entirety here.