Decadal Changes in the Cryosphere as Observed by Historical Satellite Sensors

Abstract:

The earliest signals of a climate change are being observed in the Arctic where warming has been amplified primarily on account of ice-albedo feedbacks associated with the high albedo of snow and ice. It is also the region where the sea ice cover has been declining rapidly. Because of general inaccessibility, there is a paucity of in situ data and hence the need to use satellite data to observe the large-scale variability and trends in surface temperature and sea ice in the region. The sensor with the longest record on surface temperature has been the Advanced Very High Resolution Radiometer (AVHRR) that has provided continuous thermal infrared data since 1981. The primary source of error in the data is cloud masking because of similar signatures of clouds and snow/ice covered surfaces and calibration of the different AVHRR sensors that makes up the historical data. The temperatures derived from the Moderate Resolution Imaging Spectro-radiometer from 2000 have provided higher quality data and are used as the baseline for enhancing the AVHRR data. Sea ice cover parameters are derived from the Scanning Multichannel Microwave Radiometer (SMMR) and a series of Special Scanning Microwave Imager (SSM/I) data which together provide continuous data from November 1978 to the present. The results of analysis of temperature data show an average warming rate of 0.6°C per decade in the Arctic from 1981 to 2014 which is 3 times that of about 0.2°C per decade globally for the same period. The trend in the sea ice cover in the Arctic has been -3.8 % per decade but the thicker portion called multiyear ice has been declining more drastically at about -14% per decade. Other parameters like albedo and cloud cover have been changing as well but the uncertainties in the trends are greater. The strength of the relationships of the different cryospheric parameters will be discussed.