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Sensitivity of High Arctic lake-ice conditions to climate change |
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| Map showing the location of the study site and a sample Synthetic Aperture Radar (SAR) image showing the contrast between open water and lake ice. SAR imagery © Canadian Space Agency | |
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The duration of ice cover on lakes is of fundamental importance to physical, chemical and biological processes in lake systems. This study used remote sensing data to evaluate recent changes in the ice cover of Upper Murray Lake in the Canadian High Arctic, with the goal of understanding the sensitivity of lake ice cover to past and future changes in climatic conditions. Upper Murray Lake is a relatively large (7.6 km²), deep (~80m max depth) lake located on northeastern Ellesmere Island in the Canadian High Arctic (81° 20'N, 69° 30'W). The combination of a long, cold winter and a brief summer melt season leads to the development of thick ice covers (measurements in 2005 ranged from ~1.5 to 2.2 m at the start of the melt season) and limited open water conditions. Changes in lake-ice conditions were monitored using space-borne synthetic aperture radar (SAR) data from the Canadian Space Agency (CSA) Radarsat-1 satellite. Climatic controls on the rate and timing of ice melt were evaluated using the National Centers for Environmental Prediction / National Center for Atmospheric Research (NCEP/NCAR) reanalysis data. Under current climatic conditions Upper Murray Lake averages several weeks of ice-free conditions in August and early September, although in some years a continuous ice cover persists throughout the year. The relationship between summer temperature and ice melt at Upper Murray Lake indicates that recent warming in the High Arctic has forced the lake across a threshold from a state of perennial ice cover to seasonal melting. Projected future warming will continue to increase the duration of ice free conditions in High Arctic lakes. At Upper Murray Lake ice out is predicted to occur ~14 days earlier for every 1 ° C of warming. Results | |
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| (a) Recent summer temperature records from Ellesmere Island, including annual and 11 yr mean June, July, and August reanalysis data and 11 yr mean reconstructed July-September temperatures from Alexandra Fiord (Rayback and Henry, 2006). Temperature records are plotted as departures from their 1961-1990 means. (b) Plot showing percent ice cover remaining as a function of cumulative melting degree days for all years 1997 through 2007. (c) Cumulative melting degree day plots based on 1997-2007 mean daily temperatures and 0.5, 1.0, and 1.5 ° C temperature reductions. Comparison of (b) and (c) indicates that complete melting of the Upper Murray Lake ice cover is unlikely if temperatures are reduced by 1.0 ° C, an amount similar in magnitude to recent 20th century warming on Ellesmere Island as shown in (a). | |
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Plot showing the relationship between the timing of ice out and mean June and July temperatures. Linear regression indicates that ice out occurs ~14 days earlier for each 1.0 ° C temperature increase
References
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Last Update: September 16, 2008 | |