Latitude-for-Time Proxy for Climate Change in Lakes

Abstract:

While the full interpretation of climate signals in lake systems requires an understanding of lake-specific physical forcing and response mechanisms, we propose that insight into the response of a lake at a specific latitude to climate change can be acquired by comparing the present conditions of a morphologically and dynamically similar lake at lower latitude. The latitude-for-time shift comes from swapping current latitudinal gradients of air temperature with predicted air temperature trends due to climate change. Of interest is the potential transition of a lake from one mictic state to another, with consequences to the resupply of nutrients to the euphotic zone, and to the phenology of spring and fall phytoplankton blooms. Here we compare the annual thermal histories in seven deep, intermontane lakes in western Canada along a north-south transect from 49^o to 61^o N, and use predicted trends in air temperature to estimate commensurate changes in duration of summer stratification period. While the actual response of lakes to climate change is likely to be much more complex, this simple model offers support that field observations in large lakes spanning the full range of present day climatic conditions offers a valuable tool for assessing the response of lake dynamics to climate warming.