Cyclone Occurrence in the Arctic: Coupling With Teleconnections and the Impacts on Ice Sheet Melt Cycles

Evidence assembled over the past several decades shows the Arctic system as in the midst of significant environmental change. This includes pronounced warming over most land areas, reductions in sea ice extent, alterations in precipitation, melt-water discharge and sea ice circulation, and warming and increased aerial extent of the Arctic Ocean's Atlantic section [Serreze et al., 2000; SEARCH SSC, 2001]. The accepted paradigm is that these changes are related to the general dominance of the positive phase of the Arctic Oscillation (AO) in recent decades [Thompson and Wallace, 1998; 2000]. While the AO/NAO (North Atlantic Oscillation) has proven to be a valuable integrating framework, many aspects of climatic variability and change are fundamentally driven by events at synoptic space and time scales, in particular, by the individual or aggregate effect of extratropical cyclones. The polar basin is considered a transit area or a sink for cyclones that develop elsewhere [Putnins, 1970]. In the Northern Hemisphere, warming and cooling trends are associated, respectively, with increases and decreases in cyclone occurrence [McCabe et al., 2001]. As presented by McCabe et al. [2001], differences in extratropical cyclone frequency and strength have a direct influence on surface climate through effects on cloud cover, winds, and precipitation frequency, duration, and magnitude. Melt cycles and precipitation over the terrestrial Arctic drainage are predominantly determined by the frequency and strength of cyclones [Mote, 1998a, 1998b; Serreze et al., 2002]. Cyclone activity also has pronounced effects on the circulation and concentration of sea ice cover with attendant feedbacks.

This paper uses NCEP global sea-level pressure data over the past forty years and passive microwave data of the Greenland ice sheet over the past twelve years to address the importance of cyclone processes in the moderation of melt cycles on the Greenland ice sheet. The relationship between the intensity of these processes and differences in the general synoptic environment associated with the positive and negative phases of the AO/NAO will also be addressed.