Thermokarst Lakes on the Arctic Coastal Plain of Alaska: Spatial and Temporal Variability in Summer Water Temperature

摘要

In summer 2010, water temperature profile measurements were made in 12 thermokarst lakes along a 150-km long north-south transect across the Arctic Coastal Plain of northern Alaska. In shallow lakes, gradual warming of the water column to 1-4℃ begins at the lake bed during decay of the ice cover in spring. Rapid warming follows ice-off, with water temperature responding synchronously to synoptic weather variations across the area. Regionally, ice-off occurs 2-4 weeks later on lakes near the coast. Inland lakes are warmer (13℃) in mid-summer than those near the coast (7℃), reflecting the regional climate gradient and the maritime effect. All lakes are well mixed and largely isothermal, with some thermal stratification (< 2℃) occurring during calm, sunny periods in deeper lakes. In deep (6-9 m) lake-bed depressions that are likely ice-wedge troughs, water cools by conduction to the colder sediments below, while concurrent warming occurs in the upper water column. A spatially dense sample of near-surface temperature measurements was collected from one lake over a short period and shows warmer (2-3℃) temperatures on the upwind, sheltered end of the lake. This study demonstrates that climatic gradients, meteorological conditions and basin characteristics impact lake temperature dynamics.