The Great Lakes Evaporation Network (GLEN): Building an Integrated Observing System for Great Lakes Flux Measurements

Around 1998, the Laurentian Great Lakes underwent a regime shift toward higher summer evaporation rates and lower water levels, in conjunction with warmer summer water temperatures and reduced winter ice cover. More recently, cold, high-ice winters such as 2013-14 remind us of the large interannual variability in the Great Lakes system and the continued need for long-term observations. A growing ensemble of observations, including offshore eddy flux towers, buoy-based sensors, and vessel-based platforms, are being deployed through a bi-national collaboration to reduce uncertainties in the Great Lakes water balance, provide a more robust basis for short- and long-term projections, and fill a significant gap in over-lake flux measurements and related meteorological data. Here, we provide an overview of this initiative, known as the Great Lakes Evaporation Network (GLEN). Although the network was initiated to provide improved estimates of evaporation, it is intended to be of utility for a wide range of applied and basic research needs. We provide an overview of the data collection efforts, the array of instrumentation and platforms, and the network of heat, moisture, and CO2 flux measurements and associated meteorological observations that are available to research scientists, operational forecasters, the commercial shipping industry, recreational boaters, and other Great Lakes stakeholders.