In January 2001, the National Snow and Ice Data Center (NSIDC) released
a compilation of yearly snow melt onset dates over arctic sea ice,
derived from Nimbus-7 SMMR and DMSP SSM/I brightness temperatures.
Sheldon Drobot (University of Colorado) and Mark Anderson (University of
Nebraska) developed the data set, which provides a new proxy for climate
in arctic sea ice zones.
Snow melt onset is defined as the point in time when microwave
brightness temperature increases sharply due to the presence of liquid
water in the snowpack. The snow melt onset data currently span the years
1979 through 1998, and are available in a polar stereographic grid at 25
km resolution. Tab-delimited ASCII files and GIF images are available
from NSIDC (http://nsidc.org/data/nsidc-0105.html). Several value-added
products, including mean melt onset date and standard deviation of melt
onset date, are also available.