摘要：Space-borne remotely sensed data can provide valuable insight into cryospheric processes in remote high-latitude regions for which direct observations are limited. In this study we use synthetic aperture radar (SAR) and Landsat imagery to evaluate recent changes in the ice cover of Upper and Lower Murray Lakes (81°20′N, 69°30′W) on Ellesmere Island, Nunavut, Canada. These data highlight changes in ice conditions that have occurred over the past decade and provide a means for assessing the likely impacts of rising temperatures on future lake-ice conditions. Under current (1997–2007) climatic conditions the Murray Lakes average several weeks of ice-free conditions in August and early September, although in some years a partial ice cover persists throughout the year. The observed relationship between summer temperature and ice melt at Upper and Lower Murray Lakes suggests that recent warming in the High Arctic has forced the lakes near a threshold from a state characterized by perennial ice cover to the current state that includes seasonal melting of lake ice. Projected future warming will significantly increase the duration of ice free conditions on Upper and Lower Murray Lakes, with ice-out predicted to occur 13.5 ± 4.0 and 17.6 ± 5.6 days earlier, respectively, for every 1 °C increase in mean June–July temperature.
