Estimating the freshwater budget of high-latitude land areas

Abstract

As the most land-locked of the world's oceans, freshwater input from the land surface strongly controls the salinity of the Arctic Ocean, and subsequently the thermohaline circulation of the North Atlantic. There is mounting evidence of recent warming in the arctic, including thinning of sea ice, permafrost warming and increases in fall and winter streamflow in Siberia and Alaska. Such changes have the potential to feedback and further influence global climate through the modulation of fresh water inputs to the Arctic Ocean, and subsequently, the rate of deep water formation in the Greenland Sea. Based on observations alone we do not have the ability to close the water budget of the Arctic drainage basin, or make predictions regarding its response to warmer temperatures. This dissertation describes a course of research aimed at better estimating the arctic regional water budget, with a focus on the influence of lakes and wetlands and sublimation from blowing snow. In low-gradient arctic watersheds, permafrost contributes to the generation of extensive wetlands, ponds and lakes in a semi-arid region of precipitation. In the Putuligayuk catchment in northern Alaska, water balance calculations indicate that between 24 and 42 percent of snow melt water is not immediately available for runoff. This observed storage effect can be explained in large part by the excess of evapotranspiration over summer precipitation from open water areas which results in a seasonal reduction in the extent of surface water of 58 to 73 percent. A lake and wetland algorithm added to the Variable Infiltration Capacity (VIC) macroscale hydrology model is able to simulate this seasonal reduction in wetland extent. An algorithm to represent topographically induced sub-grid variability in wind speed and blowing snow sublimation was designed for use within the VIC model. Annual average sublimation from blowing snow predicted by this model for a region on the Alaskan north slope varies from 55 mm in the foothills of the Brooks Range to approximately 25 mm on the Arctic coastal plain.