Preprints
https://doi.org/10.5194/tc-2022-11
https://doi.org/10.5194/tc-2022-11
 
03 Feb 2022
03 Feb 2022
Status: this preprint is currently under review for the journal TC.

Megadunes in Antarctica: migration and evolution from remote and in situ observations

Giacomo Traversa1,2, Davide Fugazza2, and Massimo Frezzotti3 Giacomo Traversa et al.
  • 1Department of Physical Sciences, Earth and Environment (DSFTA), Università degli Studi di Siena, 53100 Siena, Italy
  • 2Department of Environmental Science and Policy (ESP), Università degli Studi di Milano, 20133 Milan, Italy
  • 3Department of Science, Università degli Studi Roma Tre, 00146 Rome, Italy

Abstract. Megadunes are peculiar snow dune fields known to be present only on the East Antarctic plateau and other planets (Mars and Pluto). Antarctic megadunes are climatically important because their leeward flanks are characterized by glazed surfaces, a particular morphogenetic state of snow which makes these zones ablation areas, as their surface mass balance is near-zero or negative, on a continental ice sheet where surface mass balance is on average positive. This work builds on previous efforts in this field and by taking advantage from the most recent remote-sensing products and techniques coupled with field data, aims to provide new information and confirm previous hypotheses about megadunes. Focusing on two sample areas of the East Antarctic plateau where in the past international field activities were carried out (EAIIST and It-ITASE), we analysed the dynamic parameters of megadunes, their albedo and morphology. For the first time we provide a detailed analysis of their upwind migration, in all its components (absolute, sedimentological and ice flow) from remote and field observations, finding absolute values of approximately 10 m a−1 and demonstrating the upwind migration of dune windward flanks, with a relative stability of the leeward faces. Using remote sensing, we analysed their optical characteristics, i.e., albedo (broadband and NIR), brightness temperature and topographic parameters, including slope, aspect and slope along the prevailing wind direction (SPWD). First numerical results about glazed-surface albedo are thus provided, which is found to be lower than the surrounding snow, especially in NIR wavelengths. This detailed information allowed us to perform a precise mapping of glazed surfaces and their evolution and trends over time, demonstrating a general overall intra-annual areal decrease in summer (−16 %) and an inter-annual increase over recent years (at maximum almost +0.2 % per year in January).

Giacomo Traversa et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2022-11', Ted Scambos, 22 Feb 2022
    • AC2: 'Reply on RC1', Giacomo Traversa, 02 Jun 2022
  • RC2: 'Comment on tc-2022-11', Stef Lhermitte, 29 Mar 2022
    • AC3: 'Reply on RC2', Giacomo Traversa, 02 Jun 2022
  • EC1: 'Editor Comment on tc-2022-11', Olaf Eisen, 11 Apr 2022
    • AC1: 'Reply on EC1', Giacomo Traversa, 01 Jun 2022

Giacomo Traversa et al.

Giacomo Traversa et al.

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Short summary
Megadunes are fields of huge snow dunes present in Antarctica and other planets, important as they present mass loss on the leeward side (glazed surfaces), in a continent characterised by mass gain. Here, we studied megadunes using remote data and measurements acquired during past field expeditions. For the first time, we quantified their physical properties and demonstrated that they migrate against slope and wind. We further discovered an expansion of glazed surfaces over recent years.