Trends in the sea ice cover using enhanced and compatible AMSR‐E, SSM/I, and SMMR data

Abstract

Arguably, the most remarkable manifestation of change in the polar regions is the rapid decline in the Arctic perennial ice cover. Changes in the global sea ice cover, however, have been more modest, being only slightly negative in the Northern Hemisphere and even slightly positive in the Southern Hemisphere, the significance of which has not been adequately assessed because of unknown errors in the satellite historical data. Recent Advanced Microwave Scanning Radiometer (AMSR‐E) high‐resolution data are used as the baseline for generating an enhanced sea ice data set used in this study. Brightness temperature data from historical Special Scanning Microwave Imager (SSM/I) and Scanning Multichannel Microwave Radiometer (SMMR) sensors were normalized to be consistent with those from AMSR‐E, and sea ice parameters were derived from all three data sets using the same algorithm for optimum consistency and accuracy. A small bias in sea ice extent is observed between AMSR‐E and SSM/I data which, if uncorrected, causes an error of 0.62%/decade in the Arctic and 0.26%/decade in the Antarctic. Similar corrections are not needed in trend estimates of sea ice area. Biases due to seasonal changes in the accuracy of ice edge determinations, especially during melt periods, were also evaluated, and impacts on the trend results appear to be small. When updated to 2006, the trends in ice extent and area in the Arctic are now slightly more negative at −3.4 ± 0.2 and −4.0 ± 0.2% per decade, respectively, while the corresponding trends in the Antarctic remains slight but positive at 0.9 ± 0.2 and 1.7 ± 0.3% per decade.