Evolving ice fraction in the shallow firn layer of Devon Ice Cap, Canada, between 2012 and 2022

Abstract

Firn can store glacial meltwater and delay contribution to sea level rise, but ice layers and ice slabs within the shallow firn layer can impede the downward percolation of melt. Here we report firn conditions along a transect on southwest Devon Ice Cap (DIC), Nunavut, and explore its response to air temperature variability over a decadal period. We present results from two field campaigns, during which six shallow firn cores were extracted along the same transect in spring 2012 and 2022. At all sites, the ice fraction (IF) was less in 2022 than in 2012, and the firn content increased. Between 2012 and 2022, the IF of the firn layer changed by −30% at the lowest elevation site (1400 m a.s.l.) and by −11% at the highest elevation site (1800 m a.s.l.) and by an average of −26% across all sites. Despite higher annual positive degree day sums during 2012–22 compared to 2002–12, cooler summers in 2013, 2018 and 2021 resulted in less ice content in the shallow firn layer. This demonstrates that the shallow firn layer can regenerate from several cooler years and highlights the nuanced response of the DIC shallow firn layer to climate warming.

Keywords

• Arctic firn
• Canadian Arctic
• glaciology
• ice cap