Resolving Key Outstanding Questions in Arctic Surface Water Dynamics Using SWOT

Principle Investigator: Sarah Cooley (Duke University)

Co-Investigator(s): Elizabeth Webb

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The northern high latitudes are home to the highest density of lakes on Earth. These water bodies sustain ecosystems and integrate diverse climatic and physiographic processes, including regional water balance, fluvial inundation, permafrost thaw, and groundwater interactions. Their seasonal and long-term dynamics affect local communities who rely on lakes for water sources and subsistence activities, wildlife that depend on lakes for habitat and breeding, and industries that rely on surface water for resource extraction. As Arctic-Boreal lakes are net sources of carbon dioxide and methane, their fluctuations influence trace gas emissions to the atmosphere and can feedback into global climate.

Numerous studies have investigated changes in Arctic lake surface area at a range of timescales, finding evidence of both drying and wetting with little agreement on the direction of long-term trends. This discrepancy is not well understood but is likely due to a combination of differences in methodological approaches and environmental factors such as the fact that observed declines in lake area may be due to changes in vegetation rather than a true loss of water storage. Notably, almost no research has examined patterns in lake water storage, even though such work could lead to valuable new insights into surface water variability and drivers of this disagreement, as well as the hydrologic implications of observed trends.

In this project, we aim to leverage the unique capabilities of SWOT to improve understanding of surface water storage variability around the pan-Arctic region. Specifically, we have identified three outstanding questions in Arctic surface water variability research that SWOT will uniquely allow us to address:

1. How do trends in surface water area compare to trends in water level and storage, and how does this affect analyses of climatic and geomorphic drivers of surface water variability?
2. How important is the contribution of small lakes to landscape-scale trends in lake water storage?
3. To what extent is Arctic surface water area change driven by changes to emergent/riparian vegetation rather than changes in water storage?

To address these questions, we will develop a workflow for quantifying lake water storage change using both SWOT and Sentinel-2 satellite data. We will start by focusing on specific areas within Alaska that coincide with existing field data, and will later expand our analysis across the pan-Arctic, estimating both lake water area and lake water storage change over 2023-2027. This novel dataset will allow us to test multiple hypotheses about climatic and geomorphic drivers of surface water storage variability, including novel identification of emergent vegetation presence in lakes. Through this work, we aim to assess SWOT’s utility for Arctic surface water observation and provide new clarity into Arctic surface water storage patterns, with implications for our understanding of permafrost-surface water feedbacks and methane emissions from northern water bodies.