Enhanced simulated early 21st century Arctic sea ice loss due to CMIP6
biomass burning emissions
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
multi-decadal timescales. 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 CMIP6 BB emissions 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.