Preprints
https://doi.org/10.5194/bg-2020-461
https://doi.org/10.5194/bg-2020-461

  19 Jan 2021

19 Jan 2021

Review status: a revised version of this preprint was accepted for the journal BG and is expected to appear here in due course.

On the influence of erect shrubs on the irradiance profile in snow

Maria Belke-Brea1,2,3, Florent Domine1,2,4, Ghislain Picard5, Mathieu Barrere1,2,3,6, and Laurent Arnaud5 Maria Belke-Brea et al.
  • 1Takuvik Joint International Laboratory, Université Laval (Canada) and CNRS-INSU (France), Québec City, QC, G1V 0A6, Canada
  • 2Centre d’Études Nordiques, Université Laval, Québec City, QC, Canada
  • 3Department of Geography, Université Laval, Québec City, QC, Canada
  • 4Department of Chemistry, Université Laval, Québec City, QC, Canada
  • 5Univ. Grenoble Alpes, CNRS, IRD, Grenoble INP, IGE, Grenoble, France
  • 6Météo-France – CNRS, CNRM UMR 3589, CEN, Grenoble, France

Abstract. The warming-induced expansion of shrubs in the Arctic is transforming snowpacks into a mixture of snow, impurities and buried branches. Because snow is a translucent medium into which light penetrates up to tens of centimeters, buried branches may alter the snowpack radiation budget with important consequences for the snow thermal regime and microstructure. To characterize the influence of buried branches on radiative transfer in snow, irradiance profiles were measured in snowpacks with and without shrubs near Umiujaq in the Canadian Low Arctic (56.5° N, 76.5° W) in November and December 2015. Using the irradiance profiles measured in shrub-free snowpacks in combination with a Monte Carlo radiative transfer model revealed that the dominant impurity type was black carbon (BC) in variable concentrations up to 185 ng g−1. This allowed the separation of the radiative effects of impurities and buried branches. Irradiance profiles measured in snowpacks with shrubs showed that the impact of buried branches was generally weak, except for layers where branches were also visible in snowpit photographs, suggesting that branches influence snow locally (i.e. a few centimeters around branches). The local-effect hypothesis was further supported by observations of localized melting and depth hoar pockets that formed in the vicinity of branches. Buried branches therefore affect snowpack properties, with possible impacts on Arctic flora and fauna and on the thermal regime of permafrost. Lastly, the unexpectedly high BC concentrations in snow are likely caused by nearby open-air waste burning, suggesting that cleaner waste management plans are required for northern community and ecosystem protection.

Maria Belke-Brea et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2020-461', Anonymous Referee #1, 11 Feb 2021
    • AC1: 'Reply on RC1', Maria Belke-Brea, 06 Apr 2021
  • RC2: 'Comment on bg-2020-461', Inge Grünberg, 23 Feb 2021
    • AC2: 'Reply on RC2', Maria Belke-Brea, 06 Apr 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2020-461', Anonymous Referee #1, 11 Feb 2021
    • AC1: 'Reply on RC1', Maria Belke-Brea, 06 Apr 2021
  • RC2: 'Comment on bg-2020-461', Inge Grünberg, 23 Feb 2021
    • AC2: 'Reply on RC2', Maria Belke-Brea, 06 Apr 2021

Maria Belke-Brea et al.

Maria Belke-Brea et al.

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Short summary
Expanding shrubs in the Arctic are changing snowpacks into a mixture of snow, impurities and buried branches. Snow is a translucent medium into which light penetrates and gets partly absorbed by branches. Thus, branches heat up and modify snow properties. Measurements taken in snowpacks with shrubs showed that buried branches increase light absorption, but only locally. This is supported by observations of localized melting and pockets of large crystals forming a few centimeters around branches.
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