MIDTROPOSPHERIC CIRCULATION AND SURFACE MELT ON THE GREENLAND ICE-SHEET - PART I - ATMOSPHERIC TELECONNECTIONS

Daily values of the spatial extent of melting on the Greenland ice she et-measured from satellite passive microwave sensors-are compared with several mid-tropospheric teleconnection indices during May 1979 to Ju ne 1989. The teleconnection indices are derived by performing a rotate d principal components analysis on a 100-point subset of the 700 hPa h eights from the National Meteorological Center (NMC, now National Cent er for Environmental Prediction) octagonal grid. Loading patterns from the principal components are mapped and compared with teleconnection patterns identified in the climatological literature. Several teleconn ections are apparent in the loading patterns, the most significant bei ng the North Atlantic Oscillation (NAG). The component scores are used as predictor variables in a multiple regression analysis of surface m elt extent for the entire ice sheet and for eight topographically defi ned regions of the ice sheet. The results from the regression analysis show that the first five principal components account for more than h alf of a trend in the microwave-derived melt extent between 1979 and 1 989. The NAO is shown as the teleconnection most highly related to sur face melt extent on the Greenland ice sheet. (C) 1998 Royal Meteroiogi cal Society.