Impact of changing Arctic sea ice extent, sea ice age, and snow depth on
sea salt aerosol from blowing snow and the open ocean for 1980-2017
Abstract
We evaluate the effects of rapidly changing Arctic sea ice conditions on
sea salt aerosol (SSA) produced by oceanic wave-breaking and the
sublimation of wind-lofted salty blowing snow on sea ice. We use the
GEOS-Chem chemical transport model to assess the influence of changing
extent of the open ocean, multi-year sea ice, first-year sea ice (FYI),
and snow depths on SSA emissions for 1980-2017. We combine snow depths
from the Lagrangian snow-evolution model (SnowModel-LG) together with an
empirically-derived snow salinity function of snow depth to derive
spatially and temporally varying snow surface salinity over Arctic FYI.
We find that snow surface salinity on Arctic sea ice is increasing at a
rate of ~30% decade-1 and SSA
emissions are increasing at a rate of 7-9% decade-1
during the cold season (November – April). As a result, simulated SSA
mass concentrations over the Arctic increased by 8-12%
decade-1 in the cold season for 1980-2017. Blowing
snow SSA accounts for more than 75% of this increase. During the warm
season (May – October), sea ice loss results in a 12-14%
decade-1 increase in SSA emissions due to increasing
open ocean emissions. Observations of SSA mass concentrations at Alert,
Canada display positive trends during the cold season (10-12%
decade-1), consistent with our pan-Arctic simulations.
During fall, Alert observations show a negative trend (-18%
decade-1), due to locally decreasing wind speeds and
thus lower open ocean emissions. These significant changes in SSA
concentrations could potentially affect past and future bromine
explosions and Arctic climate feedbacks.