We examine the net winter, summer and annual mass balance of six glaciers along the northwest coast of North America, extending from Washington State to Alaska. The net winter (NWB) and net annual (NAB) mass balance anomalies for the maritime glaciers in the southern group, located in Washington and British Columbia, are shown to be positively correlated with local precipitation anomalies and storminess (defined as the rms of highpassed 500 mb geopotential anomalies) and weakly and negatively correlated with local temperature anomalies. The NWB and NAB of the maritime Wolverine Glacier in Alaska are also positively correlated with local precipitation, but they are positively correlated with local winter temperature and negatively correlated to local storminess. Hence, anomalies in mass balance at Wolverine result mainly from the change in moisture that is being advected into the region by anomalies in the averaged wintertime circulation, rather than a change in storminess. The patterns of the wintertime 500-mb circulation and storminess anomalies associated with years of high NWB in the southern glacier group are similar to those associated with low NWB years at the Wolverine Glacier, and vice versa.
We show that the decadal ENSO-like climate phenomenon discussed by zhang et al. (1997) has a large impact on the NWB and NAB of these maritime glaciers, accounting for up to 35% of the variance in NWB. The 500 mb circulation and storminess anomalies associated with this decadal ENSO-like mode resemble the Pacific North American pattern, as do 500-mb composites of years of extreme NWB of South Cascade Glacier in Washington and Wolverine Glacier in Alaska. Hence, the decadal ENSO-like mode affects precipitation in a crucial way for the NWB of these glaciers. Specifically, the decadal ENSO-like phenomenon strongly affects the storminess over British Columbia and Washington and moisture transported by the seasonally averaged circulation into maritime Alaska. In contrast, ENSO is only weakly related to NWB of these glaciers because (i) the large scale circulation anomalies associated with ENSO do not produce substantial anomalies in moisture advection into Alaska and (ii) the storminess and precipitation anomalies associated with ENSO are far to the south of southern glacier group.
Finally, we discuss the potential for short term climate forecasts of the mass balance for the maritime glaciers in the northwest of North America.
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