Decadal variability of Lake Superior ice cover and water temperature: An ecosystem in transition?

Session: 52. - Climate Interactions with Large Lakes? Physical Systems

Peter Blanken, University of Colorado, blanken@colorado.edu
John Lenters, University of Wisconsin-Madison, Center for Limnology, jlenters@wisc.edu
Christopher Spence, Environment and Climate Change Canada, chris.spence@canada.ca
Yafang Zhong, University of Wisconsin-Madison, yafangzhong@wisc.edu
Steve Vavrus, University of Wisconsin-Madison, sjvavrus@wisc.edu
Michael Notaro, University of Wisconsin-Madison, mnotaro@wisc.edu

Abstract

Lake Superior is one of the most rapidly warming lakes on the planet. Warmer winters, declining ice cover, increased solar radiation, and earlier stratification have all combined to create a “perfect storm” of factors leading to rapid warming of Lake Superior’s surface waters. This is particularly true for deeper, offshore regions of the lake, where changes in the onset of stratification are much more sensitive to antecedent spring conditions than in shallow, nearshore regions. Somewhat perplexingly, much of this decadal-scale variability in Lake Superior ice cover and summer water temperature has been characterized as a step change, or “regime shift,” which occurred following the warm, El Niño winter of 1997-98 and lasted through at least 2010. Here, we reexamine the 1998 regime shift in the context of more recent data, which shows that the transition has persisted through 2017 for annual maximum ice cover and stratification onset, but with some "recovery" in summer water temperature. Interannual variability has also increased, and recent model results suggest that our ability to predict Lake Superior’s transitioning state is extremely limited. This argues for renewed investment in Great Lakes observations and modeling to improve our understanding of large-lake ecosystems and our ability to anticipate future change.

1. Keyword
climate change

2. Keyword
ice

3. Keyword
atmosphere-lake interaction

4. Additional Keyword
water temperature

5. Additional Keyword
stratification