Enhanced simulated early 21st century Arctic sea ice loss due to CMIP6 biomass burning emissions

Patricia DeRepentigny; Alexandra Jahn; Marika M Holland; Jennifer E Kay; John Fasullo; Jean-François Lamarque; Simone Tilmes; Cécile Hannay; Michael J Mills; David A Bailey; Andrew P Barrett

doi:10.1126/sciadv.abo2405

Enhanced simulated early 21st century Arctic sea ice loss due to CMIP6 biomass burning emissions

Sci Adv. 2022 Jul 29;8(30):eabo2405. doi: 10.1126/sciadv.abo2405. Epub 2022 Jul 27.

Authors

Patricia DeRepentigny^{1

2}, Alexandra Jahn^{1

2}, Marika M Holland³, Jennifer E Kay^{1

4}, John Fasullo^{1

3}, Jean-François Lamarque³, Simone Tilmes⁵, Cécile Hannay³, Michael J Mills⁵, David A Bailey³, Andrew P Barrett⁶

Affiliations

¹ Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, CO, USA.
² Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO, USA.
³ Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO, USA.
⁴ Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA.
⁵ Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder, CO, USA.
⁶ National Snow and Ice Data Center, University of Colorado Boulder, Boulder, CO, USA.

Abstract

The mechanisms underlying decadal variability in Arctic sea ice remain actively debated. Here, we show that variability in boreal biomass burning (BB) emissions strongly influences simulated Arctic sea ice on multidecadal time scales. In particular, we find that a strong acceleration in sea ice decline in the early 21st century in the Community Earth System Model version 2 (CESM2) is related to increased variability in prescribed BB emissions in the sixth phase of the Coupled Model Intercomparison Project (CMIP6) through summertime aerosol-cloud interactions. Furthermore, we find that more than half of the reported improvement in sea ice sensitivity to CO₂ emissions and global warming from CMIP5 to CMIP6 can be attributed to the increased BB variability, at least in the CESM. These results highlight a new kind of uncertainty that needs to be considered when incorporating new observational data into model forcing while also raising questions about the role of BB emissions on the observed Arctic sea ice loss.