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Aerosol Flux in Arctic (ALFA)
Call year: 2021
Status: active
IADC_id: 161
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One of the most obvious consequences of Arctic warming is the rapidly diminishing sea-ice extent. This is expected to change the chemical composition and radiative properties of the overlying atmosphere, affecting the Arctic environment including humans. A fundamental understanding of Arctic feedbacks, between polar changing ocean and atmosphere, is necessary for the prediction of both Arctic and Global Climate. Recently, evidence of a strong connection between sea-ice melting and new particle formation, through the release of nitrogen-rich organic precursors originating from biogenic (Dall’Osto et al., 2017; 2018) and anthropogenic sources, mainly biomass burning (Paglione et al., 2014). Furthermore, lack of fundamental understanding of processes controlling the source of aerosols and of their interaction with the hydrological cycle is isolated by the IPCC as the main reason for model discrepancies in predicting how emissions, properties and concentrations of aerosols respond to climate change (IPCC 2013). Transport and deposition of particles, first of all black carbon, i.e. light absorbing aerosol and particles, may impact on the Arctic cryosphere. Black carbon influences climate through direct absorption of solar radiation, semi-direct and indirect clouds and snow-albedo effects. The latter consisting in the deposition on surfaces with high albedo, such as snow and ice, that reduces surface albedo and increases surface solar heating, accelerating melting (Abbatt et al., 2019). Estimates of black carbon concentration in the Arctic atmosphere are associated with large uncertainties. To better constrain the radiative forcing and the associated uncertainties of the BC/particles snow-albedo effect in the Arctic, it is crucial to improve our knowledge on the depositional mechanism/efficiency and their effects on snow spectral albedo. Measurement of particles exchange fluxes and velocities over icy and snowy surfaces are relatively few despite the wide variability of process modelling (Contini et al., 2010; Petroff and Zhang, 2010). At our best knowledge, no direct aerosol deposition/emission observations, with eddy covariance technique, have been performed before at Svalbard. The objective is to evaluate aerosol dry deposition/emission in the Arctic on icy/snowy surface and its dependence on particle size and micrometeorological parameters (atmospheric stability, friction velocity and turbulence intensity). The observed data-set of a size-segregated deposition velocity could be used for the development/validation of numerical models of deposition on surfaces of low roughness. The measures of the particles exchange rate will be carried out with the technique of eddy-correlation at Ny Alesund in size-segregated mode (2-3000 nm) coupling a sonic anemometer, a CPC and an optical particle counter (OPC) that are able to detect fluctuations of the particles concentration at high frequency (1Hz). The campaign activities are planned from the early May to the end of September (approximately 5 months), covering the late spring and summer season with various conditions of thermal stratification. Collected data will be used to characterize the dynamics of aerosols at Arctic boundary layer and they will be the basis of specific parameterizations of the mass exchanges between atmosphere/surface/water. Further, aerosol size distribution (from submicron to supermicron diameter), scattering and absorption coefficients, aerosol chemical and physical characterization will be analyzed, by means of regular measurements at Gruvebadet Observatory
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Norsk Institutt for luftforskning (NILU)
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