The effects of mid-winter rain on lake ice in the mid-latitudes

Abstract:

Lake Ice growth and decay are closely linked with regional climate variability and are strongly affected by temperature and precipitation. Most of the research on lake ice focuses on high latitude lakes which are characterized by thick cold ice and low precipitation amounts (especially rain) compared to the mid-latitudes. Lake ice models are a useful tool for examining climate effects on lake ice however, most existing models do not adequately incorporate the effects of mid-winter rain. This makes many lake ice models ill-suited for mid-latitude lakes since some of the ice development in these regions is due to temperature fluctuations or mid-winter rain causing surface melt and later refreezing of the top layer. This is unlike the typical process of what is called snow-ice formation, where water floods the snow above the ice due to the magnitude of the snow’s mass depressing the ice. In Ontario, rainfall amounts have been slightly decreasing over the years and are projected to continue to decline for most areas of the province. In addition, the frequency of extreme events, such as heavy precipitation days, is projected to increase. On the other hand, air temperature projections show a significant warming trend throughout the century. Despite the declining precipitation trends, the warming trends may suggest that more precipitation will fall as rain during the winter months. Initial examination of winter rain trends suggest that winter rainfall amounts are increasing. As a result, mid-winter rain may have a more prevalent role over time in determining ice break-up and ice composition in the region; and adequately representing the effects of rain in lake ice models will become more essential. This research i) incorporates the effects of rain into the Canadian Lake Ice Model to examine the effects of mid-winter rain on freeze-up and break-up dates, ice thickness and ice composition of small/medium lakes in Central Ontario and ii) analyzes winter precipitation trends and projections in Central Ontario to determine mid-winter rainfall amounts and their effects on lake ice characteristics. Incorporating the effects of mid-winter rain into lake ice models will facilitate the study of lakes across the mid-latitudes, where lake abundance is high and many of the lakes are important for recreational and economic purposes.