14 April 2014

An AeroCom Assessment of Black Carbon in Arctic Snow and Sea Ice


Measurements of black carbon (BC) in Arctic snow and ice provide an opportunity to evaluate model deposition of BC at high latitudes and constrain the Arctic BC-in-snow radiative effect. BC aerosols can influence climate through different ways, including direct radiative forcing, semi-direct cloud effects, indirect cloud effects, and deposition to snow and ice surfaces. A team of scientists, including DOE researchers at Pacific Northwest National Laboratory, applied BC deposition fields produced from 25 global aerosol models to two phases of the Aerosol Comparisons between Observations and Models (AeroCom) project to simulate vertically resolved BC concentrations in snow and sea ice with offline components of the Community Earth System Model. The team found that models generally underestimate BC concentrations in snow in northern Russia and Norway, while overestimating BC amounts elsewhere in the Arctic. The AeroCom project was initiated for the aerosol observation and modeling communities to synthesize results in order to improve aerosol simulation skills. This comparison has enabled researchers to explore inter-model variability in Arctic BC deposition, evaluate model BC fields against a comprehensive field survey of BC measurements in Arctic snow, and develop an observationally constrained estimate of Arctic radiative effects from BC in snow and sea ice. Model aerosol transport and removal processes are the main factors influencing model–measurement evaluations, rather than the efficiency of particle removal with snowmelt water or variability in emissions applied within the models.