Sensitivity study of Greenland topography and its potential impact on the North Atlantic Oscillation (NAO)

The climatic significance of Greenland is determined by two main facts: the thermal forcing of the Ice Sheet and its topographic forcing in the middle of the North Atlantic storm track. The impact of Greenland on the Icelandic Low is investigated using Polar MM5 with the Greenland Ice Sheet reduced to one tenth of its current elevation for a positive and a negative NAO January. The leveling of the Ice Sheet causes air over the surrounding ocean to fill the void left by the former ice mass. Cyclones can cross the reduced ice sheet more frequently. The monthly mean sea level pressure center both for positive and negative NAO Januarys with reduced Greenland is located to the south of Iceland; this contrasts with a center near southeast Greenland for the present ice sheet configuration during positive NAO January. This shows that the number of cyclogensis events in the lee of the southern part of reduced Greenland decreases greatly. The upper level heights fall due to removal of the ice sheet and the upper level jets disappear. The sensitivity study also shows that leveling of the Greenland Ice Sheet could change the NAO because the strength and position of the Icelandic Low change, indicating that the NAO is highly related to the existence of the current Greenland Ice Sheet.