As the Arctic warms, sea ice melts faster and more water evaporates, leading to more frequent and intense summer rainstorms. These heavy rains can thaw permafrost and release contaminants into rivers and lakes, damaging infrastructure, triggering landslides, and polluting water.

In July 2025, a six-day rainstorm (July 11–17) occured in Qaanaaq, Greenland. Water levels rose significantly at three river sites: two glacier-fed rivers (West and East Qaanaaq Rivers) and one non-glacial river (Qaanaaq River), with flows much higher than during the same period in 2024.

Researchers collected rain and river water samples throughout the storm to study how water moved through the landscape. They measured river levels, flow rates, and water properties such as salts, minerals, and organic matter. River levels rose steadily with rainfall, peaking near the storm’s end. This suggests the soil’s active layer (the top layer above permafrost) gradually became saturated.

Water tests showed increased soil and organic material in the rivers, consistent with local geology and vegetation. No harmful pollutants were detected. Ongoing analysis of water isotope data will reveal the sources of water—rain, groundwater, or glacier melt. These findings will improve our understanding of how Arctic rivers respond to extreme rain as the region warms.