https://doi.org/10.1029/2022EF002685

Aubry-Wake Caroline, Bertoncini André, Pomeroy John W. (2022). Fire and Ice: The Impact of Wildfire-Affected Albedo and Irradiance on Glacier Melt. AGU 10(4) April 2022 e2022EF002685. https://doi.org/10.1029/2022EF002685

Wildfire occurrence and severity is predicted to increase in the upcoming decades with severe negative impacts on human societies. The impacts of upwind wildfire activity on glacier melt, a critical source of freshwater for downstream environments, were investigated through analysis of field and remote sensing observations and modeling experiments for the 2015–2020 melt seasons at the well-instrumented Athabasca Glacier in the Canadian Rockies. Upwind wildfire activity influenced surface glacier melt through both a decrease in the surface albedo from deposition of soot on the glacier and through the impact of smoke on atmospheric conditions above the glacier. Athabasca Glacier on-ice weather station observations show days with dense smoke were warmer than clear, non-smoky days, and sustained a reduction in surface shortwave irradiance of 103 W m−2 during peak shortwave irradiance and an increase in longwave irradiance of 10 W m−2, producing an average 15 W m−2 decrease in net radiation. Albedo observed on-ice gradually decreased after the wildfires started, from a summer average of 0.29 in 2015 before the wildfires to as low as 0.16 in 2018 after extensive wildfires and remained low for two more melt seasons without substantial upwind wildfires. Reduced all-wave irradiance partly compensated for the increase in melt due to lowered albedo in those seasons when smoke was detected above Athabasca Glacier. In melt seasons without smoke, the suppressed albedo increased melt by slightly more than 10% compared to the simulations without fire-impacted albedo, increasing melt by 0.42 m. w.e. in 2019 and 0.37 m. w.e. in 2020.

Key Points
-The effect of wildfire smoke on the energy and mass balance of Athabasca Glacier, Canada was investigated using measurements and modeling
-Wildfire smoke reduced surface net irradiance, causing net radiation to decrease by 15 Wm−2 during smoky conditions
-In the years after record wildfires activity, the lowered albedo from antecedent soot deposition still increased ice melt by up to 10%

Wildfire activity, which is expected to increase in the upcoming decades, has wide-ranging consequences. Wildfire smoke can drift to far mountains range and change the amount of glacier melt, an important source of water for downstream environments. On the Athabasca Glacier, in the Canadian Rockies, the impacts of wildfire smoke on glacier melt were investigated using weather measurements collected on the glacier and computer simulations for the 2015–2020 melt seasons. Smoky days were found to be warmer, drier and with lower incoming solar energy than days without smoke. During heavy fire years, the wildfire smoke deposited on the glacier surface gradually darkens the ice. The glacier surface stayed dark in the following years, even when no-fire activity was detected. This darker ice surface caused ice melt to increase by up to 10% compared to simulations where the impacts of fire activity were removed. However, in years when smoke was detected, the increased melt due to the darker ice surface was partially compensated by a reduction in how much solar energy reached the ice. This works helps us understand climate change, wildfires, and glacier melt are connected, and better predict future water resources in mountain regions.

https://news.usask.ca/articles/research/2023/a-story-of-fire-and-ice-usask-research-studies-how-wildfires-impact-glacier-melt.php?utm_source=paws&utm_medium=email&utm_campaign=OCN

https://doi.org/10.1029/2022EF002685