Aerial photo of Arctic ponds.
Ponds on the Arctic Coastal Plain. Credit: Josh Koch, USGS
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Geophysical Research Letters

Arctic ponds play a key role in permafrost thaw and greenhouse gas emissions; however, their physical mixing processes remain poorly characterized. Most conceptual models assume that vertical, one-dimensional mixing—driven by surface cooling due to which water becomes denser, and sinks vertically, mixing the water mass from the top down—is the primary mechanism for deep water renewal.

Henderson and MacIntyre [2025] challenges that model by showing that two-dimensional thermal overturning circulation dominates in a shallow permafrost pond. Specifically, nighttime surface cooling in shallow areas generates cold, dense water that flows downslope along the pond bed, displacing and renewing deeper waters. Using high-resolution velocity, temperature, and other related measurements, the authors demonstrate that these gravity currents ventilate the bottom despite persistent stable stratification during nighttime. These findings reveal that lateral thermal flows can drive vertical exchange in small water bodies. The results have important implications for biogeochemical modeling and upscaling greenhouse gas fluxes across Arctic landscapes.

This is a diagram of how cold water moves at night in a pond. At night, the shallow parts of the pond (near the right edge) cool down faster than the deeper parts. This creates thin layers of cold, dense water near the shore. Because this water is denser (heavier), it sinks and flows sideways along the sloped pond bottom toward the deepest part of the pond—like a slow, underwater landslide of cold water. As this cold water flows downhill, it pushes the existing bottom water upward, creating a gentle circulation loop: surface water cools and sinks at the edges, flows along the bottom, and pushes older deep water upward toward the middle. Credit: Henderson and MacIntyre, Figure 3a

Citation: Henderson, S. M., & MacIntyre, S. (2025). Thermal overturning circulation in an Arctic pond. Geophysical Research Letters, 52, e2024GL114541. https://doi.org/10.1029/2024GL114541

—Valeriy Ivanov, Editor, Geophysical Research Letters

Text © 2025. The authors. CC BY-NC-ND 3.0
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