In August 2021, an unusual event occurred at the summit of Greenland’s ice cap: rain fell, causing a significant meltdown and retreat of the snowline. This occurrence highlighted an increasing trend of Arctic rainfall anomalies, a shift from the region’s typical cold, dry conditions that rarely produce precipitation.
Joel Harper, a glaciologist at the University of Montana, noted a similar anomaly in 2008, suggesting late-season rainfall during times of near-constant darkness and freeze. This trend of Arctic rainfall anomalies is particularly alarming given the role of the Greenland ice sheet in global sea level rise.
The 2021 rainfall event lasted four days with a 30-degree Celsius temperature increase, significantly warming the firn layer, a transitional stage between snow and ice. The rainwater and subsequent surface melt penetrated the firn up to 20 feet, refreezing and altering the layer’s structure. This change is significant because each Arctic rainfall anomaly event makes the firn more vulnerable to future melting. Harper’s observation aligns with predictions that even slight increases in these events’ frequency and intensity could have disproportionate impacts on the Arctic environment.
Historically, rainfall in the Arctic was rare, with the region being too cold and dry for cloud formation and moisture absorption. However, as Arctic rainfall anomalies become more common due to warming temperatures – the Arctic is warming three times faster than the global average – the impacts are profound. These include more frequent flooding, landslides, avalanches, and distress for Arctic wildlife. For instance, increased rainfall has been linked to significant wildlife deaths, like the starvation of 20,000 muskoxen on Canada’s Banks Island and the demise of tens of thousands of reindeer on Siberia’s Yamal Peninsula due to rain-hardened snow.
Researchers like Rick Thoman from the University of Alaska Fairbanks have observed a 17% increase in annual rainfall in Alaska over the past fifty years. These rain events, particularly during winter, pose hazards such as persistent ice on roads and contribute to large-scale environmental disasters, like tsunamis triggered by landslides. The science of rain and rain-on-snow events in the Arctic is still developing, with satellite and weather station data often unable to accurately distinguish between snow and rain.
The ecological and cultural impacts of these Arctic rainfall anomalies are extensive. Indigenous peoples, who depend on Arctic wildlife, face significant challenges due to changing weather patterns affecting animal populations. Caribou herds, a vital source of sustenance for many Indigenous communities, have declined dramatically, partly due to the increase in rain-on-snow events. Scientists and Indigenous peoples are collaborating to better understand and adapt to these changes, but the closure of many weather stations in Canada, and the challenges in differentiating between rain and snow, complicate this task.
This trend of increasing Arctic rainfall anomalies suggests that the region might have reached a climate-change tipping point, with more unexpected changes likely to occur. Understanding and adapting to these changes requires more on-ground research and collaboration with Indigenous communities, who are directly experiencing the effects of these climatic shifts.
https://e360.yale.edu/features/arctic-rainfall-climate-change