While trends toward earlier ice-out have been documented globally, the links between ice-out timing and lake thermal and biogeochemical structure remain unclear, especially in high-latitude lakes where ice-out occurs close to summer solstice and spring mixing tends to be very short. Using a unique, long-term dataset of vertical profiles and high-frequency data collected intermittently over the past 20 years from 15 oligotrophic lakes located near Kangerlussuaq in West Greenland, we investigate how changing ice-out and weather conditions affect lake thermal structure and hypolimnetic oxygen concentrations. Ice-out timing and weather conditions immediately following ice-out have a decisive impact on temperatures in hypolimnion, with the highest hypolimnetic temperatures (~13ºC) occurring during years when early ice-out is coupled with cooler air temperatures, and the lowest (~4ºC) in years when late ice-out and higher air temperatures prevent full spring mixing in some lakes. We also found that warmer hypolimnion is associated with less hypoxia. This unexpected correlation is a result of higher potential for a substantive spring mixing in years with early ice-out. By affecting the variability of spring mixing occurrence and duration, shifts in ice phenology can have unexpected consequences for lakes at high latitudes that differ from expectations based on temperate regions. 

Primary Presenter: Vaclava Hazukova, University of Maine (vaclava.hazukova@maine.edu)

Authors:

Vaclava Hazukova, University of Maine  (vaclava.hazukova@maine.edu)

Benjamin Burpee,   (benjaminburpee@gmail.com)

Robert Northington, Husson University  (northingtonr@husson.edu)

Nicholas Anderson, Loughborough University  (N.J.Anderson@lboro.ac.uk)

Jasmine Saros, University of Maine  (jasmine.saros@maine.edu)