Melting Trends (1979 - 2009) Over the Arctic and Links to Climate Variability

In this presentation I summarize results regarding melting over Greenland and and discuss pan-arctic terrestrial snowmelt trends for the period 1979 - 2009 derived from spaceborne microwave brightness temperature (Tb). In the case of Greenland, I report on 2009 updated melting trends and melting anomalies and discuss the potential combination of satellites observations with the results of a regional surface energy balance model via an assimilation framework. Pan-arctic snowmelt trends are discussed in the context of the Arctic Oscillation (AO). In this case, differently from Greenland, melting is detected using a spatially and temporally dynamic algorithm using the difference between daytime and nighttime Tb values (Diurnal Amplitude Variations, DAV). Results indicate statistically significant positive trends for melting over Greenland and negative trends for melt onset and end dates over the Arctic region as well as for the length of the melt season. On the average, over the past 30 years melt has been starting (finishing) ~ 0.5 days/year (~ 1 days/year) earlier and the length of the melting season is shortening by ~ 0.6 days/year. Results indicate that the AO index variability can explain up to 50 % of the melt onset variability over Eurasia and only 10 % of that over North America, consistent with spatial patterns of surface temperature changes related to the AO.