Spatial distribution of atmospheric black carbon in the Eurasian sector of the Arctic Ocean from 28 marine expeditions (2007–2022)

Abstract

Outflows of absorbing aerosol (black carbon) from continental regions of midlatitudes affect appreciably the climate and ecological state of the Arctic Ocean. We present a statistical generalization of the absorbing substance concentrations was measured in the equivalent of black carbon (eBC) in the atmosphere of the Eurasian sector of the Arctic Ocean (from the Greenland to Chukchi Seas), which is based on the largest amount of in-situ measurements in 28 marine expeditions. Our research results show a common regularity for all investigated regions of the Arctic Ocean with eBC decreasing with latitude rising (increasing distance from continent). The average decreasing gradient of the eBC concentrations per 1° latitude is 3.2 ng/m3 over the Barents Sea and 1.3 ng/m3 over the Kara Sea. The atmosphere of the Barents Sea stands out in the largest black carbon content: the average and modal eBC values are 56 and 15 ng/m3 respectively. Relative to the maximum over the Barents Sea, the eBC concentrations decrease to 20 ng/m3, in both the western (the Greenland Sea) and eastern directions (the East Siberian and Chukchi Seas). More than a factor of two decrease in the eBC concentrations from the Barents sea to Far East seas indicates that the total contribution of outflows of absorbing aerosol from Asian part is smaller than from the north of Europe. Episodic outflows of the strongest pollution (more than 150 ng/m3) are noted to have a significant effect on the statistical characteristics of black carbon. These situations are observed most often in the atmosphere of the Barents and Kara Seas. Under the influence of these anomalies, the average eBC concentrations increase by a factor of 1.5, and the coefficients of variations by a factor of 1.7–2.4. The maps of the average spatial distribution of the eBC concentrations, measured in marine expeditions, qualitatively agree with multiyear data from model calculations (MERRA-2 reanalysis). The main difference is the higher model eBC values in the southern part of the Laptev Sea and the East Siberian Sea. A comparison of the two data types in these regions, matched to be coincident in time and collocated in space, confirmed that the model eBC concentrations overestimate measurements by 5.68 ng/m3 on the average. Of two reasons for this difference, more probable (as the authors think) is that the model calculations overestimate the outflows of absorbing aerosol to the eastern sector of the Arctic Ocean.