Monitoring the melt season length of the Barnes Ice Cap over the 1979-2010 period using active and passive microwave remote sensing data

The Barnes Ice Cap (BIC) located on Baffin Island (Nunavut, Canada) is one of the most southern ice caps of the Canadian Arctic Archipelago. Observational data provide evidence of increased melting, thinning and contour recession due to recent climate warming in the Arctic. The duration of the summer melt season for the BIC, over the period 1979-2010, was derived using a threshold algorithm for 19?GHz horizontal polarization brightness temperature data; the passive microwave satellite measurements included data from the quasi-daily Scanning Multichannel Microwave Radiometer and the Special Sensor Microwave Imager. Our results show the melt season lengthened by 33% from 65.6 +/- 6?days at the beginning of the period (1979-1987) to 87.1?+/-?7.8?days towards the end (2002-2010). The interannual variations of the number of melt days were in agreement with those derived from active microwave backscatter data from the QuikSCAT scatterometer for the overlapping 2000-2009 period. In addition, elevation change data from the ICESat altimeter confirmed the thinning of the BIC at a mean rate of -0.75?m/year for the 2003-2009 period. For the 32-year period that we analysed, correlations with summer and annual air temperature and annual sum of positive days were examined for both the North American Regional Reanalysis and the Clyde River Automatic Weather Station data. Correlations with land surface temperature data from MODIS were also examined over the last decade. The results of these investigations showed that these climate indicators did not adequately explain the observed melt variations for the BIC. Ground-based snow and ice measurements collected near the BIC summit during a 10-day field campaign in March 2011 provided insights onto the surface properties and confirm the relevance of the remote sensing invariant threshold algorithm used for melt detection. Copyright (c) 2012 John Wiley & Sons, Ltd.