Thermal stratification in small arctic lakes of southwest Greenland affected by water transparency and epilimnetic temperatures

• Published in: Limnology and Oceanography
• Main Authors: Saros, Jasmine E., Northington, Robert M., Osburn, Christopher L., Burpee, Benjamin T., John Anderson, Nicholas
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2016
• Subjects: Arctic; Greenland
• Online Access: http://dx.doi.org/10.1002/lno.10314; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Flno.10314; https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.1002/lno.10314

Abstract We assessed which factors control summer epilimnion thickness in arctic lakes of southwest Greenland. A suite of 22 lakes that thermally stratify was measured in the summer of 2013; a sub‐set of eight of the lakes was measured again in 2014, which was a warmer summer than 2013. Regression analysis of the 22 lakes indicated that the 1% attenuation depth for photosynthetically active radiation (PAR) was the strongest single predictor ( R 2 = 0.75) of epilimnion thickness across lakes; the addition of epilimnion temperature to the PAR model explained additional variability ( R 2 = 0.79). The importance of including temperature in the model was apparent in the results of model validation as well as when comparing across years: while the 1% PAR was 0.4–2 m deeper in 2014 compared with 2013, water temperatures were 2–3°C higher, resulting in July epilimnion thicknesses that were equal to or shallower than in 2013. In these lakes with low color dissolved organic carbon (DOC), multiple factors control the 1% PAR, including absorbance at 440 nm ( a 440 ), 380 nm ( a 380 ), and 320 ( a 320 ), chlorophyll a (Chl a ) and DOC concentration. In 2014, when 1% PAR was deeper than in 2013, a 380, Chl a and DOC were lower in six of the eight lakes. Our results reveal that the thermal structure of these arctic lakes is under complex control by air temperatures and factors that affect PAR attenuation, particularly Chl a and DOC quality, suggesting that continued warming in the Arctic will have strong effects on lake stratification.