A recent paper published in Geophysical Research Letters reports on the concentrations and sources of dissolved black carbon in our perennially ice covered lakes in the McMurdo Dry Valleys. These valleys are persistent integrators of landscape processes and deposition of materials in the region. In particular, the study finds 1. that upper water column black carbon has a petroleum-derived origin and the deep water black carbon has more of a wildfire signature. 2. the concentration of fossil fuel derived black carbon in the surface waters are very low and dilution from the increased glacial melting will likely continue to limit concentrations in the future.
The perennially ice-covered, closed-basin lakes in the McMurdo Dry Valleys, Antarctica, serve as unique case studies for understanding the fate of dissolved black carbon from glacial sources in aquatic ecosystems. Dissolved black carbon comes from the incomplete combustion of biomass in wildfires, as well as fossil fuels. Here we show that dissolved black carbon can persist in freshwater and saline surface waters for thousands of years, while preserving the signature of the original source materials. The ancient brines of the lake bottom waters have retained dissolved black carbon with a woody signature, representing long-range transport of black carbon from wildfires. In contrast, the surface waters are enriched in modern day black carbon from fossil fuel combustion. Comparison of samples collected 25 years apart from the same lake suggests the increase in anthropogenic black carbon is recent. This fossil fuel signature could serve as an indicator of anthropogenic influences in Antarctic environments, which may continue to expand in the future.
The study, Dissolved black carbon in Antarctic lakes: chemical signatures of past and present sources, was led by CU Boulder and McMurdo Dry Valleys LTER graduate student Alia Khan. Congratulations Alia! The photo above depicts Lake Hore in Antarctica. Read more about the study in a CU Boulder press release, in a NSF press release and read the actual publication, doi:10.1002/2016GL068609, for more information.