23-Year Data Reveals How High-Latitude Lakes Respond To Climate Change

A new study based on 23 years of lake data near Rankin Inlet in Nunavut, Canada, reveals an unusual behavior on how these lakes respond to climate change.

Nunavut is the youngest and among Canada's northernmost territories, with a large tundra covering the 780,000 square mile area. While it only has a small population, the location has become an important clue on further understanding climate change.

The new research led by Soren Brothers, an assistant professor from the Department of Watershed Sciences and Ecology Center at the Utah State University, details how Nunavut lakes are affected and respond to climate change. Details of their study are published in the journal Global Biogeochemical Cycles.

Going Against Expected Patterns

Brothers found that as the observed lakes became warmer, their carbon dioxide concentrations started declining. While most lakes are natural carbon dioxide sources for their respective environment, the Nunavut lakes now have CO2 levels almost the same as their surroundings.

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These observations are considered odd since the expected behavior is that increasing temperatures should lead to larger releases of greenhouse gases, like carbon dioxide, from bodies of water. For similar environments such as in Alaska, plant material preserved in the cold and accumulated in lakebeds release large amounts of carbon after being thawed from its permafrost casing. Additionally, previous studies have already illustrated how increasingly warmer waters due to global warming also increase the rate at how microorganisms produce more carbon dioxide, surpassing the rate at how plants absorb CO2 and cause an upset in the local environment.

With these established patterns, the question is, why doesn't Nunavut exhibit the same behavior despite clear indications that it is also affected by global warming.

Possible Explanations for the Nunavut Lakes

It led the USU team to visit the lakes and propose possible explanations for this seemingly erratic behavior. First, they reported that a major part of the Nunavut territory rests on the so-called Canadian shield. It is one of the world's largest continental shields and is a large expanse of bedrock whose soils do not have much storage capacity and release organic matter.

Another possible explanation is that longer seasons with no ice might be affecting water chemistry and biology, leading to surprisingly lower carbon dioxide levels. This includes longer growth periods for plants, thus consuming carbon dioxide in the process, and conditions that further encourage algae growth on the beds of these lakes.

While it appears that the Nunavut lakes have their own mechanisms for keeping global warming in check, other lakes in the world continue to behave as predicted, and the chances are that these lakes in Northern Canada would also start displaying the same behavior after crossing a threshold. A press release from USU reported that Brothers believes that a connection between ice cover duration and carbon dioxide levels might be "buying us some time" before stronger feedback between global warming and the ecosystem appears.