Sea Ice and Ice Temperature Variability as Observed by Microwave and Infrared Satellite Data

Recent reports of a retreating and thinning sea ice cover in the Arctic have pointed to a strong suggestion of significant warming in the polar regions. It is especially important to understand what these reports mean in light of the observed global warming and because the polar regions are expected to be most sensitive to changes in climate. To gain insight into this phenomenon, co-registered ice concentrations and surface temperatures derived from two decades of satellite microwave and infrared data have been processed and analyzed. While observations from meteorological stations indicate consistent surface warming in both regions during the last fifty years, the last 20 years of the same data set show warming in the Arctic but a slight cooling in the Antarctic. These results are consistent with the retreat in the Arctic ice cover and the advance in the Antarctic ice cover as revealed by two decades of historical satellite passive microwave data. Surface temperatures derived from satellite infrared data are shown to be consistent with the station data. Altough the former (with about 2.5 K error) is not as accurate as the latter, it provides ability to identify detailed interannual changes on a regional basis over the twenty year period. For example, the warmest year globally during the last century is 1998 but in the Arctic, much of the warming occurred in the Beaufort Sea and the North American region while a slight cooling actually happened in parts of the Laptev Sea and Northern Siberia during the same time period. Big warming anomalies are also observed during the last five years but a decadal cycle is apparent in the time series suggesting a possible influence of the North Atlantic Oscillation. In the Antarctic, large interannual and seasonal changes are also observed in the circumpolar ice cover with regional changes showing good coherence with surface temperature anomalies. Some of these spatial and temporal changes appear to be influenced by the Antarctic Circumpolar Wave (ACW) and changes in coastal polynya activities. However, a mode 3 wave is observed to be more dominant than the mode 2 wave reported in the literature. The temperature anomalies in the Bellingshausen Sea are also observed to be correlated with Southern Oscillation indices.