Fig. 3: Black Carbon (BC) concentration is above background levels even around deep-field tourist destinations.

a C-130 aircraft about to land on the blue-ice runway at Union Glacier (79°S, Ellsworth Mountains), an increasingly popular deep-field destination (a private four-engine turbofan Ilyushin Il-76 landed on the runway 30 times in the 2019–2020 season only³⁴). b, c Snowpit for snow sampling (6 km east of the blue-ice runway and about 1 km west of the designed landing sites for ski-equipped airplanes). d BC concentrations measured at different snow layers. BC concentration peaked at about 3 ng/g during the 2013–2014 season. Although private activities began years earlier, the Chilean Union Glacier Camp became operational during the 2013–2014 season. In each box, the central mark (red stripe) indicates the median, and the edges indicate the 25th and 75th percentiles. The whiskers extend to the maximum and minimum data excluding outliers. e Mean of the absorption Ångström exponent of light-absorbing impurities in snow from different layers. Photographs taken by the authors. Plots were generated by using Python’s Matplotlib Library⁵⁸.