Are small lakes becoming ice free in the Great Lakes Region?

The land cover of the Great Lakes Region is dominated by numerous, small lakes. These play an important role in local and regional climate, due to large differences in albedo, surface roughness and heat capacity, compared to the vegetative surface. Lakes also react directly to climate; therefore, an assessment of their sensitivity to historic climate variability not only provides the magnitude of changes that have occurred in the past, but also gives an indication about how these are likely to change in future. Variability and trends of lake ice phenology (i.e. ice formation, ice break up and ice duration) are important indicators, and are related to both climate and lake physical characteristics. Correlation between lake ice phenology and climate variability exists at both short and long temporal scales. Short term variability is related to atmospheric and oceanic oscillations while long term trends are associated with global climate change. We study the retrospective role of historic climate variability in the ice phenology of inland lakes in the Great Lakes region. To do this, we integrated remotely sensed and observed data related to lake ice phenology with land surface modeling for the long term (1915-2008) retrospective period. AVHRR and MODIS thermal infrared data were used to construct time series of lake surface water temperature. The lake surface water temperature time series was then used to estimate the lake ice freezing and ice break-up dates. The Variable Infiltration Capacity (VIC) land surface model was calibrated using the observations of lake ice phenology. After the calibration and evaluation, we applied the VIC model to reconstruct the historic (1915-2008) time series of lake ice phenology. We used trend analysis for various time frames (i.e. early, mid and late century) to study past changes. The role of oceanic oscillations such as ENSO, NAO and AMO were also evaluated. Results indicate that freezing and break-up of lake ice is occurring later and earlier, respectively, throughout the study domain. However, changes are more prominent in lakes located at the lower latitudes.