Potential climate warming effects on ice covers of small lakes in the contiguous U.S.

To simulate effects of projected climate change on ice covers of small lakes in the northern contiguous U.S., a process-based simulation model is applied. This winter icersnow cover model is associated with a deterministic, one-dimensional year-round water temperature model. The lake parameters required as model input are surface area, maximum depth, and Secchi depth as a measure of radiation attenuation. The model is driven by daily weather data. Weather records from 209 stations in the contiguous U.S. for the period 1961–1979 were used to represent past climate conditions. The projected climate changes due to a doubling of atmospheric CO2 were obtained from the output of the Canadian Climate Center Global Circulation Model. To illustrate the effect of projected climate change we present herein winter ice cover characteristics simulated, respectively, with inputs of past climate conditions Ž1961–1979., with inputs of a projected 2=CO2 climate scenario as well as differences of those values. The dependence of ice cover characteristics on latitude and lake characteristics has been quantified by making simulations for 27 lake types at 209 locations across the contiguous U.S. It was found that the 2=CO2 climate scenario is projected to delay ice formation on lakes by as much as 40 days and melt ice by up to 67 days earlier. Maximum ice thicknesses are projected to be reduced by up to 0.44 m ŽSault Ste. Marie, MI., and the ice cover periods will be shorter by up to 89 days ŽRock Springs, WY.. The largest changes are projected to occur east of Idaho from the Canadian border down to the states of Colorado, Nebraska, and Iowa and the northern parts of Illinois, Indiana, Ohio, and Pennsylvania. These changes would reduce fish winterkill in most shallow lakes of the northern states of the contiguous U.S. but may endanger snowmobiles and ice fishermen. Keywords: climate change effect; ice cover; United States; lakes