In a new study, researchers found a temporary decrease in meltwater on the Devon Ice Cap, one of the largest ice caps in the Canadian Arctic. This was caused by a cooler-than-average summer in 2021. The findings highlight the complex, non-linear way glaciers respond to climate change, where a single cooler season can temporarily slow melt, but does not reverse the overall trend of glacial loss.
The Role of Firn
The study focused on firn, a layer of dense, porous snow that sits atop glaciers. This layer acts like a sponge, absorbing and refreezing meltwater. This process is crucial because it temporarily prevents meltwater from running off into the ocean and contributing to sea-level rise. The ability of firn to store meltwater is influenced by temperature, firn grain size, and the presence of refrozen ice layers. The more ice layers present, the less “spongy” the firn becomes, forcing meltwater to flow off the glacier instead of being stored.
Key Findings at the Devon Ice Cap
By comparing firn cores collected in 2022 to those from 2012, researchers found a decrease in the amount of refrozen meltwater content. This decrease was more pronounced at lower elevations (20-30% reduction) than at higher elevations (11% reduction), where temperatures are colder. This decrease was a direct result of the cooler summer in 2021, and shows that a reduction in refrozen meltwater increases the firn layer’s capacity to absorb more meltwater in the future.
Global Implications
This phenomenon isn’t unique to the Devon Ice Cap. A similar pattern was observed on the Greenland Ice Sheet in 2019, where less surface melt in one year led to an increase in meltwater storage capacity in the firn layer the following year. However, the study also notes that in the long term, the Greenland Ice Sheet is more sensitive to warming than to cooling. A single year of extreme heat can have a greater impact on meltwater runoff than several cooler years combined. Eventually, glaciers will reach a “peak refreezing point” where the firn layer becomes too saturated with ice to store any more meltwater, causing all subsequent melt to run off into the ocean.
With the Canadian Arctic containing 14% of the world’s glaciers and ice caps, understanding firn processes is crucial for accurately predicting future sea-level rise.