Colorado mountains
From Long-Term Data to Understanding: Toward a Predictive Ecology
2015 LTER ASM Estes Park, CO - August 30 - September 2, 2015

Solar radiation and temperature trends in McMurdo Dry Valleys explained: exploring the role of sulfur dioxide emissions

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Maciek Obryk
A. Fountain
P. Doran
B. Lyons

The last published solar radiation record from the McMurdo Dry Valleys (MDVs), Antarctica between 1987 and 1999 showed an increase of 8.1 W m-2 per decade, while surface air temperature decreased by 0.7°C per decade; however, the driving mechanisms behind either trend have not been explained. Here, we provide an up-to-date meteorological record from the McMurdo Dry Valleys and attribute changes in solar radiation trends to anthropogenic sulfur dioxide emissions (r = -0.94, p < 0.001). We found solar radiation is mainly controlled by anthropogenic sulfur dioxide emissions, which explains 88% of variance. Other influences noted include major natural pulses (influences) such as volcanic eruption and wildfires, and indirectly inferred dimethylsulfide production (a biogenic precursor to sulfate aerosols). Sulfate aerosols are effective cloud condensation nuclei and are extremely efficient at scattering downwelling solar radiation. The pristine nature of the Antarctic continent, due to its isolation from human disturbance and the effect of polar amplification, establishes the McMurdo Dry Valleys as a proxy for a true global monitoring site of anthropogenic and natural sulfur dioxide emissions. Annually averaged solar radiation increased by more than 20 W m-2 in the MDVs since 1989 as a direct consequence of decreasing anthropogenic sulfur dioxide emissions. Solar radiation is the main driver of surface air temperatures on the Antarctic Plateau, explaining 99% of variance. However, solar radiation in MDVs only explains 86% of variance, suggesting that other minor drivers control surface air temperatures in this region. We postulate that reradiated heat (upwelling longwave radiation) from the exposed bare soils in MDVs explains the remaining variance.