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The Effort to Measure Black Carbon in Antarctica

Brazilian scientists travelled more than 1400 km in West Antarctica to collect snow cores for black carbon measurements.

Black carbon measurements in Antarctica are still scarce, but necessary to understand the particle’s effect in our climate, says Luciano Marquetto, a Ph.D. student from the Polar and Climatic Center, Federal University of Rio Grande do Sul, Brazil.

“Black carbon, or BC, commonly known as soot, is a particle originated from the incomplete combustion of fossil fuels and biomass burning that warms the atmosphere. When deposited in snow and ice, BC increases surface radiation absorption and can cause melt,” explains Marquetto.

“Some scientists say that BC is second only to CO2 in its warming effects on the climate, and studies have shown that BC concentrations have risen since the industrial revolution in several places of the world, including Greenland, the Himalayas, the Alps and even Antarctica.”

But studying BC in Antarctica is logistically challenging, and only in the last decade the topic has gained more attention. “Antarctica is a vast continent, and there are regions with no BC data yet. As climatic and atmospheric models rely on field data, studying BC concentrations in Antarctic snow is essential to improve these models”, adds Marquetto.

Marquetto was part of a team of Brazilian researchers led by Dr. Jefferson Cardia Simões who carried out a traverse in West Antarctica during the 2014/2015 austral summer. They travelled more than 1400 km, collecting several shallow snow cores and samples along the way to investigate the snow chemistry in the last 50 years. One of these shallow cores was analyzed for BC in cooperation with Dr. Susan Kaspari of Central Washington University, USA.

Dating was carried out using mainly the BC variation and sulfur, sodium and strontium as secondary parameters, giving the core 17 years (1998−2014). The data showed a well-defined seasonality of BC concentrations for the first 8 m, with low concentrations of 0.016 μg/L during the wet season (austral summer/fall) and high concentrations of 0.063 μg/L during the dry season (austral winter/spring).

The annual BC concentration of 0.029 μg/L was noted by the authors to be the lowest of all BC cores in Antarctica referenced in their work published in Advances in Atmospheric Science, while the annual BC flux was 6.1 μg/m2yr, the lowest flux in West Antarctica records so far.

“We observed very low BC concentrations in snow, lower than in other works in the continent. Due to that, in the article we decided to focus on instrumental and methodological questions raised during the research that needed to be answered before going deeper into the environmental interpretation,” said Marquetto.

“However, our ultimate goal is to better understand BC seasonal variability and overall concentrations to see what impact the particle has in Antarctic snow, as well as try to identify BC geographical sources. We are also interested in the BC size distribution in snow, as particle size affects the amount of solar radiation BC can absorb. Impacts in the atmosphere and in the cryosphere are possibly being under or overestimated due to simplified representations of BC particle size in climatic models,” Marquetto believes.

“As for sectorial sources, we know biomass burning represents around 80% of all BC emitted to the atmosphere in the Southern Hemisphere, which means that the fires happening in Australia, New Zealand and South America ultimately leave a mark in Antarctic snow.” [APBN]

Source: Marquetto, L. et al. (2020). Refractory Black Carbon results and a method comparison between solid-state cutting and continuous melting sampling of a West Antarctic snow and firn core. Advances in Atmospheric Sciences37(5), 545-554.