Snowmelt variability in Polar Bear Pass, Nunavut, Canada, from QuikSCAT: 2000–2009

Abstract

Abstract:Snowmelt onset and end date estimates are made from QuikSCAT scatterometer measurements in the Canadian High Arctic wetland of Polar Bear Pass (PBP) and the surrounding region of Bathurst Island, Nunavut. In situ data within PBP is used to validate QuikSCAT snowmelt onset/end date estimates. Results indicate that within PBP from 2000 to 2009, the mean snowmelt onset date was Year Day (YD) 162, the mean snowmelt end date was YD179, and the mean snowmelt duration was 17 days. More interannual variability was apparent in snowmelt end date and duration compared with onset, and only snowmelt end date was significantly correlated with mean June air temperature at À0.78. Cooler air temperatures in 2004 contributed to a long snowmelt duration of 24 days, and the very short snowmelt duration in 2007 of just 11 days was caused by rapid and sustained increases in air temperature. For snowmelt end date and duration the mean spatial pattern revealed two centres of later snowmelt end date/longer snowmelt duration over Bathurst Island. They were separated by early snowmelt end date/short snowmelt duration in PBP. These patterns are in agreement with the spatial distribution of mean May to July air temperature over Bathurst Island and are likely influenced by the local-scale topography of Bathurst Island. Given the correlation between air temperature and snowmelt end date, we might expect quicker snowmelt under increased warming. The latter process may have implications for the sustainability of the PBP wetland under a warmer climate. INTRODUCTIONThe Canadian High Arctic landscape during the summer is characterised by low precipitation levels and sparse vegetation growth (Edlund and Alt, 1989). In some localised areas, a surplus of water can occur, and in combination with limited drainage of a shallow active layer, wetlands can develop (e.g. Young and Woo, 2000;Woo and Young, 2006;Abnizova and Young, 2010). These wetlands are generally areas of high productivity and vegetation growth, in stark contrast to most of the surrounding region, which is barren with only limited plant cover. Most wetlands in the Canadian High Arctic are small, patchy vegetated zones, but occasionally larger wetlands occur, and all of them can be considered critical ecological environments. These ecosystems provide nutrients, encouraging plant growth that in turn provides grazing grounds and breeding habitat for migratory birds, caribou and muskox and other mammals. The sustainability of these wetlands throughout the growing season depends on an adequate water supply to ensure that a high water table is maintained. Water inflow may come from a variety of sources such as precipitation, lateral inflow from ground ice melt, meltwater from late-lying snowbeds, streamflow and/or spillage of water from other water bodies such as nearby ponds and lakes. The largest supply of water into these wetland environments, however, is from seasonal snowmelt (Woo and Guan, 2006;Woo and Young, 2006). Recently, Brown et al. (2010) reported an increasing trend tow...

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