A tug-of-war within the hydrologic cycle of a continental freshwater basin
The past decade was the wettest on record for much of central and eastern North America. Near the beginning of this period of regional water abundance, however, drought conditions reinforced concerns that high temperatures and evapotranspiration foreshadowed a persistent imbalance in the hydrologic cycle characterized by water loss. These fluctuating hydrologic conditions were manifest by water level variability on the Laurentian Great Lakes, the largest system of lakes on Earth. We show that, during this period, the two dominant hydrologic forces acting directly on the vast surfaces of the lakes, overlake precipitation and overlake evaporation, have evolved differently. More specifically, we find that overlake precipitation has risen to extraordinary levels, while overlake evaporation diminished rapidly in 2014 (coinciding with a strong Arctic polar vortex deformation). Our findings offer a new perspective on the impacts of competing hydrologic forces on large freshwater systems in an era of climate change.