LAKE RESPONSE TO METEOROLOGICAL FORCING ALONG A CLIMATE GRADIENT IN THE LOW ARCTIC OF WEST GREENLAND.
ANDERSON, JOHN . Geological Survey of Denmark & Greenland.
Brodersen, Klaus P. Freshwater Biological Lab., University of Copenhagen.
Lakes respond to climate forcing at a variety of timescales. Long-term (i.e. Holocene) changes in lake response to climatic variability can be modeled by understanding contemporary response, such as high-frequency breakdowns in thermal stratification driven by cooling and increased wind speed. However, direct meteorological forcing is tempered by lake size and morphometric setting. West Greenland contains thousands of lakes along a climatic gradient of low effective precipitation and continentality at the ice sheet margin to the more maritime (cooler and wetter) conditions at the coast (~150 km).
We used temperature thermistors in 40 lakes and two automated weather stations to monitor changing thermal response (including date of ice melt) to climatic variability since 1998. Thermistors were placed in the littoral zone of lakes immediately prior to ice melt in 1998 and 1999. In 1999 we also placed strings of thermistors (4-8 per lake) in the deepest part of the basin so we could monitor the development of thermal stratification. From May 2000, however, the thermistors have been recording continuously at a number of sites. To confirm the date of ice melt as recorded by the thermistors we have also used remote control digital cameras which take one photograph everyday, thereby recording the rate of ice melt.
The response of individual lakes to a meteorological event is related to their size, catchment characteristics and chemistry. The range in date of ice melt reflects interannual differences in air temperature and lake location. There is, however, considerable synchroneity in the timing of lake stratification response to changing weather patterns. The implications of these results for interpreting high-resolution stratigraphic records are discussed.
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