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Impact of dust deposition on the albedo of Vatnajökull ice cap, Iceland

Impact of dust deposition on the albedo of Vatnajökull ice cap, Iceland


Titill: Impact of dust deposition on the albedo of Vatnajökull ice cap, Iceland
Höfundur: Wittmann, Monika
Groot Zwaaftink, Christine   orcid.org/0000-0002-4286-5438
Steffensen Schmidt, Louise
Guðmundsson, Sverrir
Pálsson, Finnur   orcid.org/0000-0002-0874-6443
Arnalds, Olafur   orcid.org/0000-0002-9005-7347
Björnsson, Helgi
Thorsteinsson, Throstur   orcid.org/0000-0001-5964-866X
Stohl, Andreas   orcid.org/0000-0002-2524-5755
Útgáfa: 2017-03-23
Tungumál: Enska
Umfang: 741-754
Háskóli/Stofnun: Háskóli Íslands
University of Iceland
Landbúnaðarháskóli Íslands
Agricultural University of Iceland
Svið: Verkfræði- og náttúruvísindasvið (HÍ)
School of Engineering and Natural Sciences (UI)
Deild: Jarðvísindastofnun (HÍ)
Institute of Earth Sciences (UI)
Auðlinda- og umhverfisdeild (LBHÍ)
Faculty of Natural Resources and Environmental Sciences (AUI)
Birtist í: The Cryosphere;11(2)
ISSN: 1994-0416
1994-0424 (eISSN)
DOI: 10.5194/tc-11-741-2017
Efnisorð: Vatnajökull; Bráðnun (jöklafræði); Svifryk; Jöklarannsóknir
URI: https://hdl.handle.net/20.500.11815/274

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Tilvitnun:

Wittmann, M., Groot Zwaaftink, C. D., Steffensen Schmidt, L., Guðmundsson, S., Pálsson, F., Arnalds, O., Björnsson, H., Thorsteinsson, T., and Stohl, A.: Impact of dust deposition on the albedo of Vatnajökull ice cap, Iceland, The Cryosphere, 11, 741-754, doi:10.5194/tc-11-741-2017, 2017.

Útdráttur:

Deposition of small amounts of airborne dust on glaciers causes positive radiative forcing and enhanced melting due to the reduction of surface albedo. To study the effects of dust deposition on the mass balance of Brúarjökull, an outlet glacier of the largest ice cap in Iceland, Vatnajökull, a study of dust deposition events in the year 2012 was carried out. The dust-mobilisation module FLEXDUST was used to calculate spatio-temporally resolved dust emissions from Iceland and the dispersion model FLEXPART was used to simulate atmospheric dust dispersion and deposition. We used albedo measurements at two automatic weather stations on Brúarjökull to evaluate the dust impacts. Both stations are situated in the accumulation area of the glacier, but the lower station is close to the equilibrium line. For this site ( ∼  1210 m a.s.l.), the dispersion model produced 10 major dust deposition events and a total annual deposition of 20.5 g m−2. At the station located higher on the glacier ( ∼  1525 m a.s.l.), the model produced nine dust events, with one single event causing  ∼  5 g m−2 of dust deposition and a total deposition of  ∼  10 g m−2 yr−1. The main dust source was found to be the Dyngjusandur floodplain north of Vatnajökull; northerly winds prevailed 80 % of the time at the lower station when dust events occurred. In all of the simulated dust events, a corresponding albedo drop was observed at the weather stations. The influence of the dust on the albedo was estimated using the regional climate model HIRHAM5 to simulate the albedo of a clean glacier surface without dust. By comparing the measured albedo to the modelled albedo, we determine the influence of dust events on the snow albedo and the surface energy balance. We estimate that the dust deposition caused an additional 1.1 m w.e. (water equivalent) of snowmelt (or 42 % of the 2.8 m w.e. total melt) compared to a hypothetical clean glacier surface at the lower station, and 0.6 m w.e. more melt (or 38 % of the 1.6 m w.e. melt in total) at the station located further upglacier. Our findings show that dust has a strong influence on the mass balance of glaciers in Iceland.

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This work is distributed under the Creative Commons Attribution 3.0 License.

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