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The Cryosphere An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/tc-2020-170
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/tc-2020-170
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  10 Aug 2020

10 Aug 2020

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This preprint is currently under review for the journal TC.

Spectral Characterization, Radiative Forcing, and Pigment Content of Coastal Antarctic Snow Algae: Approaches to Spectrally Discriminate Red and Green Communities and Their Impact on Snowmelt

Alia L. Khan1,2, Heidi Dierssen3, Ted Scambos4, Juan Höfer5,6, and Raul R. Cordero7 Alia L. Khan et al.
  • 1Department of Environmental Sciences, Huxley College of the Environment, Western Washington University, Bellingham, WA, USA
  • 2National Snow and Ice Data Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado – Boulder, Boulder, CO, USA
  • 3Department of Marine Sciences and Geography, University of Connecticut, Groton, CT, USA
  • 4Earth Science and Observation Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado – Boulder, Boulder, CO, USA
  • 5Escuela de Ciencias del Mar, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
  • 6Centro FONDAP de Investigación en Dinámica de Ecosistemas Marinos de Altas Latitudes (IDEAL), Valdivia, Chile
  • 7Department of Physics, University of Santiago, Av. Bernardo O’Higgins 3363, Santiago, Chile

Abstract. Here, we present radiative forcing (RF) estimates by snow algae in the Antarctic Peninsula (AP) region from multi-year measurements of solar radiation and ground-based hyperspectral characterization of red and green snow algae collected during a brief field expedition in austral summer 2018. Our analysis includes pigment content from samples at three bloom sites. Algal biomass in the snow and albedo reduction are well-correlated across the visible spectrum. Relative to clean snow, visibly green-patches reduce snow albedo by ~ 40 % and red-patches by ~ 20 %. However, red communities absorb considerably more light per mg of pigment compared to green communities, particularly in green wavelengths. Based on our study results, it should be possible to differentiate red and green algae using Sentinel-2 bands in blue, green and red wavelengths. Instantaneous RF averages were double for green (180 W m−2) vs. red communities (88 W m−2), with a maximum of 228 W m−2. Based on multi-year solar radiation measurements at Palmer Station, this translated to a mean daily RF of ~ 26 W m−2 (green) and ~ 13 W m−2 (red) during peak growing season – on par with mid-latitude dust attributions capable of advancing snowmelt. This results in ~ 2522 m3 of snow melted by green-colored-algae and ~ 1218 m3 of snow melted by red-colored-algae annually over the summer, suggesting snow algae play a significant role in snowmelt in the AP regions where they occur. We suggest impacts of RF by snow algae on snowmelt be accounted for in future estimates of Antarctic ice-free expansion in the AP region.

Alia L. Khan et al.

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Alia L. Khan et al.

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Short summary
We present radiative forcing (RF) estimates by snow algae in the Antarctic Peninsula (AP) region from multi-year measurements of solar radiation and ground-based hyperspectral characterization of red and green snow algae collected during a brief field expedition in austral summer 2018. Mean daily RF was double for green (~ 26 W m−2) vs. red (~ 13 W m−2) colored snow algae during the peak growing season, which is on par with mid-latitude dust attributions capable of advancing snowmelt.
We present radiative forcing (RF) estimates by snow algae in the Antarctic Peninsula (AP) region...
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