Precipitation in the Alaska central Arctic

Abstract

Environmental change currently stimulates much of the interest in high-latitude hydrologic studies, as northern areas are expected to be strongly impacted by warming. This thesis consists of a comprehensive assessment of solid and liquid precipitation throughout the Alaska Central Arctic. The founding hypothesis are: (1) the spatial distribution of snow and warm season precipitation are linearly related to elevation, (2) annual precipitation inputs are dominated by warm season precipitation when potential moisture sources are ice free, and (3) moisture responsible for snow-producing storms is primarily advected through atmospheric circulation. To verify the validity of the hypothesis, the temporal variability and spatial distribution of snow and warm season precipitation were extensively measured. Snowpack patterns were established using over 1000 snow surveys from end-of-winter field campaigns. The snowpack distribution patterns were similar from year to year and relatively independent of elevation, with roughly an average of 100 mm of snow water equivalent (SWE) from the Arctic Coast to the Brooks Range divide. For the same 1500 m change in elevation, warm season precipitation has a large orographic change, which increases more than 240 mm. Warm season precipitation was evaluated using 31 meteorological stations and although a strong spatial distribution was found, no discernible long-term trends were identified in the somewhat limited 29 year data set. The accumulation of end-of-winter SWE and warm season precipitation measurements were combined to evaluate the distribution of annual precipitation. Annual precipitation varies temporally and spatially over the Alaska Central Arctic. At high elevations, 70% of the annual precipitation is liquid, while at low elevations, liquid precipitation only represents 40% of the annual budget and end-of winter SWE becomes the dominate precipitation contributor. Moisture responsible for snow-producing storms was found to originate from different sources depending on the time of year and ice cover conditions. North originating moisture is three times more likely to occur during the fall when sea ice is thin, or nonexistent. Mid-winter moisture was found to advect into the Arctic from the south. The timing and travel pathways of snowfall events were determined using an atmospheric model (HYSPLIT) and supplemental surface analysis charts.