Physical drivers of lake evaporation across a gradient of climate and lake types

Tuesday, 16 December 2014: 1:55 PM
John D Lenters1, Peter Blanken2, Nathan C Healey3, Kenneth M Hinkel4, John Ong5, Colin Peake6, Brittany L Potter6, Diego A Riveros-Iregui7, Christopher Spence8, Katherine Van Cleave6 and Vitaly A Zlotnik9, (1)LimnoTech, Ann Arbor, MI, United States, (2)University of Colorado, Boulder, Boulder, CO, United States, (3)Florida International University, Miami, FL, United States, (4)University of Cincinnati, Cincinnati, OH, United States, (5)U.S. Geological Survey / U.S. Environmental Protection Agency, Storrs Mansfield, CT, United States, (6)University of Nebraska Lincoln, School of Natural Resources, Lincoln, NE, United States, (7)University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, (8)Environment Canada Saskatoon, Saskatoon, SK, Canada, (9)Univ. Nebraska-Lincoln, Lincoln, NE, United States
Inland waters exchange sensible and latent heat with the overlying atmosphere in ways that are very different from the surrounding terrestrial landscape. Depending on the regional climate and lake characteristics, open-water evaporation from lakes can vary out of phase with terrestrial evapotranspiration within the watershed, and key atmospheric drivers are often different as well. Lake evaporation is a complex process that interacts with many aspects of a lake ecosystem, including water temperature, vertical mixing, lake chemistry, stratification, ice cover, and water levels. Although driven primarily by vapor pressure gradient and wind speed, evaporation is also an energy-consuming process. This leads not only to significant roles from net radiation, sensible heat flux, and other components of the surface energy budget, but it also results in important feedbacks on lake temperature, ice cover, and other evaporation-mediating processes. As such, defining the climatic variables that “drive” lake evaporation is far from straightforward and often depends on timescale, lake depth, and characteristics of the regional climate. In this study, we provide some insight into the problem by examining the energy budget of a variety of lakes across a range of climatic gradients and lake types. This includes shallow Arctic lakes, deep temperate lakes, and a hypersaline lake in a semi-arid climate. Our results reveal a wide range of evaporative response to climatic forcing, including some lakes that show counterintuitive effects or even opposite responses to those of other lakes. Although process-based, mechanistic models should be able to account for such complexities, these findings highlight the need for caution when interpreting climatic drivers of lake evaporation. It is not likely, for example, that models of a solely empirical or statistical nature would be sufficient to fully capture the physics and dynamics of evaporation, particularly in an ever-changing climate.