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Seminar: Wednesday, Sept. 19, 2012 at 3:30 pm

Warm Events at Summit, Greenland During 2012 Relative to an
Evolving 25 Year Ice Sheet Temperature Record
Christopher A. Shuman

An evolving temperature record from the Greenland Summit, at approximately 3216 m in elevation, has documented unusual periods of near and above freezing air temperatures especially in July 2012. Since August 2005, data has been collected from well-calibrated and actively-ventilated temperature sensors at a NOAA-ESRL climate observatory. Comparison of these data from a nominal 2 m height above the ice sheet surface over the past seven summers reveals several periods of unusual warmth at the highest elevations of the ice sheet during 2012. Field observations from station personnel indicate slush formed during the period of greatest warmth and an ~2 cm thick ice crust has been preserved in the snow stratigraphy. The warm temperatures at Summit were independently assessed and mapped across Greenland using a combination of SSMIS passive microwave, Oceansat scatterometer, and MODIS infrared data. earth/features/greenland-melt.html

Detailed analysis of the available data indicates that temperatures rose to or above freezing for almost 6.5 hours on July 11 at Summit Station. A maximum air temperature of 1 degree C was recorded repeatedly in the 1-minute averages during this period. NOAA’s data also indicated brief periods at or above zero on July 12th and 29th as well. These anomalously warm air-temperature periods can now be compared and contrasted with equivalent-quality data from earlier records (automatic weather stations began operating in May 1987 during the GISP2 project) and used to calibrate indications of warm surface temperatures derived from satellite sensors.

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