Arctic Black Carbon & Aerosol Deposition Study
1 September 2021 - 30 November 2021
Lead Scientist: Delphine Farmer
Aerosols are the strongest driver of uncertainties in understanding climate, which they affect through a multitude of complex and difficult-to-constrain mechanisms. All the different ways that aerosol affects climate, however, depend on their concentrations, which itself depends strongly on wet and dry aerosol deposition rates. Presently, there are serious problems with the existing understanding of depositions rates: current parameterizations are inaccurate (Pryor et al. 2009, 2013; Vong et al. 2010); measurements are scarce; and, as expected, the rates are very important — for example they are the single largest contributor to uncertainty in cloud condensation nuclei (CCN) concentration in global models, which is critical to understanding cloud interactions (Lee et al. 2013). There is a clear need for additional observational constraints and investigation of aerosol deposition, which we propose to address by performing the first unambiguous direct eddy flux covariance measurements of aerosol dry deposition over the cryosphere. We will achieve this by making eddy covariance flux measurements of dry deposition and off-line wet deposition measurements of black carbon containing aerosol, plus eddy covariance measurements of size-resolved accumulation-mode scattering aerosol over the DOE ARM AMF3 Oliktok Point site in fall ,2020. Black carbon (BC) is a particularly important material for understanding aerosol lifetime: BC is chemically stable and non-volatile, is only formed in combustion, and can be sensitively and selectively detected, both in the air, and post-deposition in the cryosphere. The DOE ARM AMF3 Oliktok Point site is relevant to understanding anthropogenic influences on the remote Arctic. We will compare our measurements to model parameterizations to constrain uncertainties and systematic bias, and improve deposition parameterizations. We will assess the possibility for achieving full deposition budget closure using surface snow measurements of black carbon. This work will fundamentally improve understanding of aerosol removal processes from the atmosphere at a DOE ARM site, and is thus directly relevant to the funding call.