How might Arctic lakes in Canada respond to continued climate change? What does this mean for the fish communities that these systems support? When we look at all lakes, which ones may open up new habitats for fishes, and which ones may become inhospitable? 

These questions were the focus of conversations I had with my graduate studies supervisors, Brian Shuter and Ken Minns, as I wrapped up my thesis on creating predictive models for lake temperature dynamics. We had these newly calibrated lake temperature models at the ready, and Brian had recently provided input on an exciting new Arctic lake climate change paper from Steve Campana and others. That paper found varied projected outcomes for coldwater fish species: new opportunities in the north, and a temperature squeeze in the south. The authors also used geospatial techniques to determine not only average lake depth, which existing databases have, but also maximum lake depth for all the lakes in the Canadian Arctic. We recognized that this extended information on the depth makeup of Arctic lakes would provide the basis for estimating seasonal thermal habitat supply across the whole water column, for all of the lakes in the Canadian Arctic.

In our paper, we took the lake temperature modelling a step further and used our updated models to project how climate change would alter the mixing of lake waters to determine the full seasonal cycle in water temperatures, from the surface of the lake to its greatest depth. This helped us estimate not just how warm the lake surface waters were going to get, but project each lake’s deep water temperatures, and whether those temperatures were similar to those at the surface, or if the lake would thermally stratify.

The backbone of our project was the aforementioned comprehensive dataset on the physical properties of Arctic lakes that Gerald Black assembled for Steve’s paper published in 2020. It was critical to our research that many of the lakes were sampled in person, including lake depth, size information, and fish presence sampling. Steve travelled to the Canadian Arctic to sample lakes for his 2020 paper, and shared some photos that capture the landscape in all of its severe beauty. You can read about those adventures in his blog post on that paper here. Brian and Ken also worked in the Arctic on other research projects earlier in their careers. Everyone’s insights on this unique landscape were vital to the completion of our project.

Our study focused on the 447,077 lakes in the Canadian Arctic that were at least ten hectares in area. Alongside this, we had data for 167 Canadian Arctic lakes to ground-truth our methods. Though just a fraction of the overall dataset, the remote and rugged nature of the Arctic landscape is not conducive to intensive study. Therefore, we were grateful to have a number as high as 167, and we found it to be sufficient to test our models.

As we worked through this project, we collaborated effectively and problem-solved over several time zones: me in Vancouver, Brian in Thunder Bay, Ken in Toronto, and Steve in Reykjavik. The shift to more remote work during the COVID-19 pandemic accelerated our ability to collaborate together from across the globe. The work for this project took place essentially all on our computers: no adventurous fieldwork or sampling giant lake trout (which you can read above in Steve’s blog post for his paper published in 2020, linked above!). Because of this, it was important to keep in mind the vast, diverse landscape that was at the heart of our study.

What does the future have in store for Arctic lakes? Our study provides a first-principles estimate, and we point to the need to continue understanding the ecological implications of climate change for this region. Polar regions are expected to continue undergoing dramatic climatic change. We project a varied response to climate change across the lake-scape, including increases in stratification of lakes, longer ice-free seasons, and potential for establishment of new fish communities. These could include new coldwater fish communities in the far north where lakes were previously frozen to the bottom in winter, and new warmwater and coolwater fish communities in the south. There is a varied response expected across a varied region.