Climate drivers of summer warming in Emerald Lake, Sierra Nevada, California

Mountain lakes experience extreme inter-annual climate variation as well as rapidly warming air temperatures, making them ideal systems to understand lake-climate responses. Snowpack and water temperature are highly correlated in mountain lakes, but we lack a complete understanding of underlying mechanisms. Motivated by predicted declines in snowfall with future temperature increases, we investigated how surface heat fluxes and lake temperature responded to variation in snowpack, ice-duration, and weather in a typical high elevation lake in the Sierra Nevada, California. Ice duration determined the phenology of lake exposure to solar radiation, and was the dominant mechanism linking snowpack to lake temperature. The relative importance of heat loss fluxes (longwave radiation, latent and sensible heat exchange) varied among wet and dry years. Declines in snowpack and ice cover in mountain systems will reduce the scale of variation in lake thermal responses and increase the responsiveness of lake warming to atmospheric forcing.