Improving Estimates of Evaporation from Earth's Largest Lake System

The North American Great Lakes constitute the largest surface of fresh water on Earth (Lake Superior and Lake Michigan-Huron, the largest of the two Great Lakes, are also the Earth's two largest lakes by surface area). Beginning in the late 1990s (a period that coincided with a very strong winter El Niņo) evaporation rates over the Great Lakes accelerated rapidly, leading to a dramatic decline in water levels. Recent research suggests that evaporation rates over the lakes have remained high since then, but the mechanisms driving the sustained high rates are not entirely known. A growing ensemble of in situ measurements, including off-shore eddy flux towers (the first of which was installed in 2007), buoy-based sensors, and vessel-based platforms, are being deployed through an ongoing regional binational collaborative effort to reduce uncertainties in Great Lakes evaporation estimates, and provide a more robust basis for short-term projections. Here, we provide an overview of this initiative, currently referred to as the Great Lakes Evaporation Network (GLEN), along with an overview of the latest data collection efforts, and intercomparison studies between conventional thermodynamics models (some of which are currently employed in regional operational water budget and water level forecasting) and monitoring results. Finally, we discuss how data from this network is being processed, stored, and assimilated into model projections and regional water resource management decisions.