Refractory black carbon (rBC) variability in a 47-year West Antarctic snow and firn core

Abstract

Abstract. Black carbon (BC) is an important climate-forcing agent that affects snow albedo. In this work, we present a record of refractory black carbon (rBC) variability, measured from a 20 m deep snow and firn core drilled in West Antarctica (79∘55′34.6′′ S, 94∘21′13.3′′ W, 2122 m above sea level) during the 2014–2015 austral summer. This is the highest elevation rBC record from West Antarctica. The core was analyzed using the Single Particle Soot Photometer (SP2) coupled to a CETAC Marin-5 nebulizer. Results show a well-defined seasonality with geometric mean concentrations of 0.015 µg L−1 for the wet season (austral summer–fall) and 0.057 µg L−1 for the dry season (austral winter–spring). The core was dated to 47 years (1968–2015) using rBC seasonality as the main parameter, along with sodium (Na), sulfur (S) and strontium (Sr) variations. The annual rBC concentration geometric mean was 0.03 µg L−1, the lowest of all rBC cores in Antarctica referenced in this work, while the annual rBC flux was 6.25 µg m−2 a−1, the lowest flux in West Antarctica rBC records. No long-term trend was observed. Snow albedo reductions at the site due to BC were simulated using SNICAR online and found to be insignificant (−0.48 %) compared to clean snow. Fire spot inventory and BC emission estimates from the Southern Hemisphere suggest Australia and Southern Hemisphere South America as the most probable emission sources of BC to the drilling site, whereas HYSPLIT model particle transport simulations from 1968 to 2015 support Australia and New Zealand as rBC sources, with limited contributions from South America. Spectral analysis (REDFIT method) of the BC record showed cycles related to the Antarctic Oscillation (AAO) and to El Niño–Southern Oscillation (ENSO), but cycles in common with the Amundsen Sea Low (ASL) were not detected. Correlation of rBC records in Antarctica with snow accumulation, elevation and distance to the sea suggests rBC transport to East Antarctica is different from transport to West Antarctica.

Spatial Variability of the Snowmelt‐Albedo Feedback in Antarctica

“…The impact of snow impurities is assumed negligible for Antarctica and thus we set d α c = 0 (Bisiaux et al., 2012; Grenfell et al., 1994; Marquetto et al., 2020; Warren & Clarke, 1990). Jakobs et al.…”

Mass and Number Size Distributions of rBC in Snow and Firn Samples From Pine Island Glacier, West Antarctica

“…Considering the low BC concentration in the samples, especially in the wet season (as low as 200 detected particles/sample), we present our results as a grouping of individual samples in 94 seasonally resolved clusters (wet season subset = summer/fall, 474 samples and 47 clusters; dry season subset = winter/spring, 530 samples and 47 clusters). The number of clusters is due to the estimated dating of the core (47 years, Marquetto, Kaspari, & Simões, 2020). Although the dry season subset presented considerably more particles ( n = 8.28 × 10 5 ) than the wet season subset ( n = 2.03 × 10 5 ), both have a robust number of collected particles.…”

“…Seasonal sample discrimination was based on the core dating presented in Marquetto, Kaspari, and Simões (2020). Antarctic ice core BC records show a well‐defined seasonality, with peak concentrations in the dry season due to increased biomass burning activity in the Southern Hemisphere (SH) during this time of the year (Bisiaux, Edwards, McConnell, Curran, et al, 2012; Sand et al, 2017; Winstrup et al, 2019); more efficient transport to the ice core site (Marquetto, Kaspari, & Simões, 2020; Neff & Bertler, 2015; Schwanck et al, 2017; Stohl & Sodemann, 2010); and weaker precipitation (Legrand & Mayewski, 1997; Sinclair et al, 2010). The wet season is identified by much lower BC concentrations.…”

“…rBC size distribution data have been published online on PANGAEA repository as Marquetto, Kaspari, & Simões (2020): Refractory black carbon mass and number size distributions in West Antarctica snow and firn samples, PANGAEA (https://doi.org/10.1594/PANGAEA.920981).…”

“…In this work we present the rBC number and mass size distributions of 1,004 snow samples from a 20 m snow/firn core (TT07) drilled in West Antarctica during the 2014/2015 austral summer that spans 1968–2015 (Marquetto, Kaspari, & Simões, 2020). The rBC present in the core likely reflects long‐range transport from sources in South America and Australia/New Zealand and is associated mostly with biomass burning emissions (Arienzo et al, 2017; Bisiaux, Edwards, McConnell, Albert, et al, 2012; Koch et al, 2007; Stohl & Sodemann, 2010).…”