Do contemporary (1980–2015) emissions determine the elemental carbon deposition trend at Holtedahlfonna glacier, Svalbard?

Abstract

Abstract. The climate impact of black carbon (BC) is notably amplified in the Arctic by its deposition, which causes albedo decrease and subsequent earlier snow and ice spring melt. To comprehensively assess the climate impact of BC in the Arctic, information on both atmospheric BC concentrations and deposition is essential. Currently, Arctic BC deposition data are very scarce, while atmospheric BC concentrations have been shown to generally decrease since the 1990s. However, a 300-year Svalbard ice core showed a distinct increase in EC (elemental carbon, proxy for BC) deposition from 1970 to 2004 contradicting atmospheric measurements and modelling studies. Here, our objective was to decipher whether this increase has continued in the 21st century and to investigate the drivers of the observed EC deposition trends. For this, a shallow firn core was collected from the same Svalbard glacier, and a regional-to-meso-scale chemical transport model (SILAM) was run from 1980 to 2015. The ice and firn core data indicate peaking EC deposition values at the end of the 1990s and lower values thereafter. The modelled BC deposition results generally support the observed glacier EC variations. However, the ice and firn core results clearly deviate from both measured and modelled atmospheric BC concentration trends, and the modelled BC deposition trend shows variations seemingly independent from BC emission or atmospheric BC concentration trends. Furthermore, according to the model ca. 99 % BC mass is wet-deposited at this Svalbard glacier, indicating that meteorological processes such as precipitation and scavenging efficiency have most likely a stronger influence on the BC deposition trend than BC emission or atmospheric concentration trends. BC emission source sectors contribute differently to the modelled atmospheric BC concentrations and BC deposition, which further supports our conclusion that different processes affect atmospheric BC concentration and deposition trends. Consequently, Arctic BC deposition trends should not directly be inferred based on atmospheric BC measurements, and more observational BC deposition data are required to assess the climate impact of BC in Arctic snow.

An 800 year high-resolution black carbon ice-core record from Lomonosovfonna, Svalbard

“…Moore et al (2005) also confirmed that chemical stratigraphy remained preserved despite high melt ratios. More 5 recently, the impact of melting on the HDF ice core was assumed to be low compared to the EC deposition signal (Ruppel et al, 2014(Ruppel et al, , 2017. Similar findings were postulated for the Lomonosovfonna 2009 (LF-09) ice core in which melting impact was negligible on ionic species at a decadal resolution (Wendl et al, 2015).…”

“…However, EC concentrations in Svalbard snow (Aamaas et al, 2011;Doherty et al, 2010;Forsström et al, 2009Forsström et al, , 2013 as well as in the HDF and Fiescherhorn ice cores (Jenk et al, 2006;Ruppel et al, 2014Ruppel et al, , 2017 are one order of magnitude higher than rBC concentrations in the topmost part of the LF core. This can be mainly explained by the different analytical methods employed, which do not measure the same fraction of the carbonaceous compounds, as discussed by Ruppel et al (2014).…”

“…Several hypotheses have been discussed, such as increased flaring emissions from Siberia 40 (Stohl et al, 2013) or changes in BC scavenging efficiencies due to higher temperatures. However, in a more recent study on a shallow firn core from the same ice field, no comparable recent increase could be detected (Ruppel et al, 2017).…”

An 800-year high-resolution black carbon ice core record from Lomonosovfonna, Svalbard

“…The entire LF-09 core and the LF-11 core were analyzed for rBC at PSI in several campaigns between 2012 and 2016 and in April-May 2016, respectively, following the proce-dure established by Wendl et al (2014) for liquid samples and further evaluated by Lim et al (2014). Discrete rBC samples were melted at room temperature, sonicated in a ultrasonic bath for 25 min, and immediately analyzed using a SP2 (Droplet Measurement Technologies, USA) (Schwarz et al, 2006;Stephens et al, 2003) coupled with a jet nebulizer (APEX-Q, Elemental Scientific Inc., USA). External calibrations from 0.1 to 50 ng g −1 (R 2 > 0.999) were usually performed twice a week by preparing eight fresh dilutions from a rBC standard (Aquadag ® , Acheson Industries Inc., USA) (Gysel et al, 2011;Wendl et al, 2014).…”

Individual Particle Characteristics, Optical Properties and Evolution of an Extreme Long‐Range Transported Biomass Burning Event in the European Arctic (Ny‐Ålesund, Svalbard Islands)

“…Namely, in the case of atmospheric stability the BB particles can station at some height above ground where they can undergo aging effects while exerting a main action on the aerosol optical properties. At turbulent regimes, instead, the particles can more easily reach the ground and affect the albedo properties of snow and ice exposed surfaces even a long time after the BB transport event (Ruppel et al, 2017).…”