Temperature variations in lake ice in central Alaska, USA

In winter 2002/03 and 2003/04, thermistors were installed in the ice on two shallow ponds in central Alaska in order to obtain data on ice temperatures and their response to increasing and decreasing air temperatures, and flooding and snow-ice formation. Snow depth and density, and ice thickness were also measured in order to understand how they affected and were affected by ice temperature variability. The lowest ice temperature (–15.58C) and steepest temperature gradient (–39.88C m–1) occurred during a 9 week period in autumn when there was no snow on the ice. With snow on the ice, temperature gradients were more typically in the range –20 to –58C m–1. Average ice temperatures were lower during the warmer, first winter, and higher during the cooler, second winter because of differences in the depth and duration of the snow cover. Isothermal ice near the freezing point resulted from flooding and snow-ice formation, and brief episodes of warm weather with freezing rain. Under these circumstances, congelation-ice growth at the bottom of the ice cover was interrupted, even reversed. It is suggested that the patterns in temperatures brought about by the snow-ice formation and rain events may become more prevalent due to the increase in frequency of these events in central Alaska if temperature and precipitation change as predicted by Arctic climate models.