To understand how high-altitude lakes respond to and influence climate change

To get to Nunavut, turn left at the Dakotas and drive north. You can’t miss it – the vast tundra area covers nearly a million square miles of Northern Canada. Relatively few people call this lake-scattered landscape home, but the region plays a vital role in understanding global climate change. New research from Soren Brothers, assistant professor in the Department of Watershed Sciences and Ecology Center, shows how lakes in Nunavut can have a big impact on carbon dioxide levels in the atmosphere, and it’s not all bad news – at least for now. Brothers examined 23 years of data from lakes at Rankin Inlet. He noted a peculiarity: As the lakes warmed, their carbon dioxide concentrations dropped. Most of the lakes are natural sources of carbon dioxide, but these lakes were now largely in equilibrium with the atmosphere.

This was weird. The expected pattern is that warmer temperatures should cause greater greenhouse gas emissions from lakes. In places like Alaska, centuries of collected plant matter in the permafrost releases a large amount of carbon that is consumed by microbes when thawing. Experiments have also shown that as water heats up, carbon dioxide production by microbes increases faster than plants’ uptake of carbon dioxide, causing the system to become unbalanced. Together, these processes should in any case increase the emission of greenhouse gases from the air by waterways. So why not in Nunavut? There is no doubt that the first step in this Rube Goldberg machine is: the climate is heating up. So why don’t the lakes at Rankin Inlet release carbon?

Brothers and his team put on good, thick parkas, visited the lakes, and came up with a few ideas as to why this is happening. First, they note that much of Nunavut is on the Canadian Shield – an ancient granite rock where thin soils are unlikely to contain and thus release the vast amounts of organic matter entering elsewhere in the Arctic. Second, longer ice-free seasons can change water chemistry and biology in ways that actually lower carbon dioxide concentrations, including longer growing seasons for plants (which take up carbon dioxide), and potentially better growing conditions for algae on their soils. shallow, clear lakes.

Does this mean that nature has come to the aid of the climate? Probably not – other lakes around the world can still increase carbon dioxide emissions due to warming, and the lakes in Nunavut could eventually overtake them. More likely, Brothers is suggesting that the relationship between ice cover duration and carbon dioxide concentrations may take us some time before stronger positive feedbacks are released between global warming and its ecosystems. It may be a complicated process, but by understanding this complexity, scientists can predict variations in how lakes respond to – and influence – climate change. It’s a look under the hood, making planetary feedback and tipping points a little more predictable. While the long-term trajectory of greenhouse gas emissions from lakes has not yet been determined, these results are an important puzzle piece in climate change science.