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High latitude extreme poleward aerosol transport events (Aerosol Atmospheric Rivers) in E3SM and their impacts on the Arctic climate system during the MOSAiC campaign.

Presentation Date
Wednesday, December 13, 2023 at 9:40am - Wednesday, December 13, 2023 at 9:50am
MC - 2003 - West



The role of atmospheric aerosols is a key uncertainty in the response of the polar regions to continued anthropogenic warming as aerosols can modulate radiative fluxes directly through absorption and scattering as well as indirectly through their interactions with clouds and surface albedo. In recent years, model development and analysis has highlighted an increasing importance of aerosols in determining simulated trends in Arctic climate change over the historical period. However, despite a strong sensitivity to aerosol forcing, global climate models such as the Energy Exascale Earth System Model (E3SMv2) and Community Earth System Model (CESM2), underestimate meridional transport and concentrations of aerosols at high latitudes relative to observations and reanalysis, degrading confidence in their ability to simulate historical and future changes in polar climate. To understand the causes and implications of this underestimation, we conduct E3SMv2 simulations with winds nudged to those from the Modern Era Retrospective Reanalysis version 2 (MERRA-2) and aerosol source-region tagging. Our analysis focuses on the 2019-2020 Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition period to utilize in situ measurements from the central Arctic. We find good agreement between MOSAiC black carbon measurements and simulated transport events when the model captures specific large-scale circulation patterns determining key transport pathways. Extending the concept of atmospheric rivers to extreme aerosol transport events, we also find a dominant role of aerosol atmospheric rivers (AARs) in contributing to extremely high concentrations during MOSAiC and modifying radiative fluxes across the Arctic both directly and indirectly, which we quantify by perturbing aerosol emissions. We also compare AARs in the E3SMv2 to similar events simulated in E3SM-Arctic, which has regionally refined ocean and atmospheric horizontal grids poleward 45°N, to identify resolution sensitivity of the filamentary structures in extreme aerosol transport events.

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