Collaborative Research: Type 1: LOI: L02170303: Arctic Climate Response to Decadal Changes in Radiative Forcing from Aerosols and Ozone

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Current general circulation models (GCMs) have difficulty reproducing the rapid Arctic warming and sea ice loss observed over the past decades. One possible factor is that they do not properly represent the radiative forcings from aerosols and tropospheric ozone that could be particularly important in the Arctic. This EaSM Type 1 project will develop an improved understanding of the distributions and decadal trends of aerosols and ozone in the Arctic, including black carbon (BC) deposition fluxes and albedo effects for snow and sea ice, and will study the implications for Arctic climate change over the 1980-2010 period. It will build an interdisciplinary partnership between atmospheric chemists using the GEOS-Chem CTM and cryosphere scientists using CCSM4, to better describe aerosol-chemistry-climate interactions in the Community Earth System Model (CESM). The project will take advantage of intensive observations during the International Polar Year (IPY) to test and improve the GEOS-Chem representation of aerosols, ozone, and BC deposition fluxes in the Arctic. A 30-year GEOS-Chem simulation (1980-2010) with evolving sources from human activity and fires will be conducted and evaluated against long-term records. Aerosols, ozone, and BC deposition fluxes from GEOS-Chem will be input to CCSM4 to simulate Arctic radiative forcing and climate response over the 30-year period. Ensemble sensitivity simulations conducted with CCSM4 will diagnose the perturbations to temperature, sea ice, and atmospheric circulation associated with these radiative forcings. Knowledge gained from this project will be used to evaluate the simulation of Arctic aerosols, tropospheric ozone, and BC deposition fluxes within CESM. Fully coupled aerosol-chemistry-climate simulations of the 1980-2010 period will be conducted in CESM to assess Arctic climate response from aerosols and ozone and to investigate climate feedbacks. This project will also provide policy analysts with information on the role of aerosols and tropospheric ozone in driving Arctic climate change. Two graduate students will be trained in interdisciplinary environmental modeling.