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| Titel |
Regional melt-pond fraction and albedo of thin Arctic first-year drift ice in late summer |
| VerfasserIn |
D. V. Divine, M. A. Granskog, S. R. Hudson, C. A. Pedersen, T. I. Karlsen, S. A. Divina, A. H. H. Renner, S. Gerland |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 9, no. 1 ; Nr. 9, no. 1 (2015-02-09), S.255-268 |
| Datensatznummer |
250116749
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| Publikation (Nr.) |
 copernicus.org/tc-9-255-2015.pdf |
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| Zusammenfassung |
| The paper presents a case study of the regional (≈150 km)
morphological and optical properties of a relatively thin, 70–90 cm modal
thickness, first-year Arctic sea ice pack in an advanced stage of melt. The
study combines in situ broadband albedo measurements representative of the
four main surface types (bare ice, dark melt ponds, bright melt ponds and
open water) and images acquired by a helicopter-borne camera system during
ice-survey flights. The data were collected during the 8-day ICE12 drift
experiment carried out by the Norwegian Polar Institute in the Arctic, north
of Svalbard at 82.3° N, from 26 July to 3 August 2012. A set of > 10 000
classified images covering about 28 km2 revealed a homogeneous
melt across the study area with melt-pond coverage of ≈ 0.29 and open-water fraction of ≈ 0.11. A decrease in pond fractions observed in the
30 km marginal ice zone (MIZ) occurred in parallel with an increase in open-water coverage. The moving block bootstrap technique applied to sequences of
classified sea-ice images and albedo of the four surface types yielded a
regional albedo estimate of 0.37 (0.35; 0.40) and regional sea-ice albedo
of 0.44 (0.42; 0.46). Random sampling from the set of classified images
allowed assessment of the aggregate scale of at least 0.7 km2 for the
study area. For the current setup configuration it implies a minimum set of
300 images to process in order to gain adequate statistics on the state of the ice
cover. Variance analysis also emphasized the importance of longer series of
in situ albedo measurements conducted for each surface type when performing
regional upscaling. The uncertainty in the mean estimates of surface type
albedo from in situ measurements contributed up to 95% of the variance of
the estimated regional albedo, with the remaining variance resulting from the
spatial inhomogeneity of sea-ice cover. |
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