Abstract
Abstract. Black carbon (BC) is a significant forcing agent in the Arctic, but substantial uncertainty remains to quantify its climate effects due to the complexity of the different mechanisms involved, in particular related to processes in the snowpack after deposition. In this study, we provide detailed and unique information on the evolution and variability in BC content in the upper surface snow layer during the spring period in Svalbard (Ny-Ålesund). A total of two different snow-sampling strategies were adopted during spring 2014 (from 1 April to 24 June) and during a specific period in 2015 (28 April to 1 May), providing the refractory BC (rBC) mass concentration variability on a seasonal variability with a daily resolution (hereafter seasonal/daily) and daily variability with an hourly sampling resolution (hereafter daily/hourly) timescales. The present work aims to identify which atmospheric variables could interact with and modify the mass concentration of BC in the upper snowpack, which is the snow layer where BC particles affects the snow albedo. Atmospheric, meteorological and snow-related physico-chemical parameters were considered in a multiple linear regression model to identify the factors that could explain the variations in BC mass concentrations during the observation period. Precipitation events were the main drivers of the BC variability during the seasonal experiment; however, in the high-resolution sampling, a negative association has been found. Snow metamorphism and the activation of local sources (Ny-Ålesund was a coal mine settlement) during the snowmelt periods appeared to play a non-negligible role. The statistical analysis suggests that the BC content in the snow is not directly associated to the atmospheric BC load.
Highlights
In the last 2 decades, the Arctic region has been exposed to dramatic changes in terms of atmospheric temperature rise, sea ice decrease and increase in air mass transport from lower latitudes, bringing warmer and humid air masses containing pollutants and anthropogenic-derived compounds (Law and Stohl, 2007; Comiso et al, 2008; Screen and Simmonds, 2010; Eckhardt et al, 2013; Schmale et al, 2018; Maturilli et al, 2019)
No associations were found on refractory BC (rBC) with the incoming solar radiation and the snow temperature during the sampling period. These results indicate that the rBC mass concentration in the surface snow does not undergo to diurnal changes, and this process is negligible in controlling the rBC snow surface concentration
Our results, based on a multiple linear regression model, suggest that the amount of Black carbon (BC) in the surface snow is not associated to the BC atmospheric load
Summary
In the last 2 decades, the Arctic region has been exposed to dramatic changes in terms of atmospheric temperature rise, sea ice decrease and increase in air mass transport from lower latitudes, bringing warmer and humid air masses containing pollutants and anthropogenic-derived compounds (Law and Stohl, 2007; Comiso et al, 2008; Screen and Simmonds, 2010; Eckhardt et al, 2013; Schmale et al, 2018; Maturilli et al, 2019). Numerous aerosol species directly increase the quantity of solar radiation absorbed by the snowpack, favoring snow-aging processes and the decrease in the snow albedo (Hansen and Nazarenko, 2004; Flanner et al, 2007; Hadley and Kirchstetter, 2012; Skiles et al, 2018; Skiles and Painter, 2019). Among these light-absorbing aerosols, black carbon (BC) particles are the most effective in absorbing the visible and near-infrared solar radiation. Intercomparison of different techniques agree within an uncertainty factor of 2 at Alert (Sharma et al, 2017), Ny-Ålesund and Barrow (Sinha et al, 2017)
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