Delayed formation of Arctic snow cover in response to wildland fires in a warming climate

Wildland fires in seasonally snow-covered areas can have lasting effects on both the snowpack and carbon stocks. Here, using long-term satellite data, we show that from 1982 to 2018, the burned area in the Arctic has significantly increased, while the duration of snow cover has significantly decreased. An XGBoost machine learning model and causal analysis confirmed the role of wildland fires in delaying snow cover formation, with this effect strongly linked to fire-induced reductions in albedo and increases in temperature. In addition, we observed a delay of more than 5 days in snow cover formation following major wildland fires. Looking ahead, our projections under a high-emissions scenario (Shared Socioeconomic Pathway, SSP 5-8.5) indicate that the burned area could increase by a factor of 2.6 and the annual mean snow cover duration could decrease by nearly 18 days between 2015 and 2100 compared with the historical average. Wildland fires are becoming more frequent in high-latitude regions. Here the authors show that these fires delay the formation of snow cover in the Arctic, which will be exacerbated under future warming due to increases in burned areas.