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| Titel |
Melt ponds on Arctic sea ice determined from MODIS satellite data using an artificial neural network |
| VerfasserIn |
A. Rösel, L. Kaleschke, G. Birnbaum |
| 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 ; 6, no. 2 ; Nr. 6, no. 2 (2012-04-03), S.431-446 |
| Datensatznummer |
250003489
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| Publikation (Nr.) |
 copernicus.org/tc-6-431-2012.pdf |
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| Zusammenfassung |
Melt ponds on sea ice strongly reduce the surface albedo and accelerate the decay of Arctic sea ice.
Due to different spectral properties of snow, ice, and water, the fractional coverage of these distinct surface types
can be derived from multispectral sensors like the Moderate Resolution Image Spectroradiometer (MODIS)
using a spectral unmixing algorithm.
The unmixing was implemented using a multilayer perceptron to reduce computational costs.
Arctic-wide melt pond fractions and sea ice concentrations are derived from the level 3 MODIS
surface reflectance product. The validation of the MODIS melt pond data set was conducted
with aerial photos from the
MELTEX campaign 2008 in the Beaufort Sea, data sets from the National Snow and Ice Data Center (NSIDC)
for 2000 and 2001 from four sites spread over the entire Arctic, and with ship observations
from the trans-Arctic HOTRAX cruise in 2005. The root-mean-square errors
range from 3.8 % for the comparison with HOTRAX data, over 10.7 % for the comparison with NSIDC data,
to 10.3 % and 11.4 % for the comparison with MELTEX data, with coefficient of determination
ranging from R2=0.28 to R2=0.45.
The mean annual cycle of the melt pond fraction per grid cell for the entire Arctic shows a strong increase in June,
reaching a maximum of 15 % by the end of June.
The zonal mean of melt pond fractions indicates a dependence of the temporal development of melt ponds on the geographical latitude,
and has its maximum in mid-July at latitudes between 80° and 88° N.
Furthermore, the MODIS results are used to estimate the influence of melt ponds on retrievals of
sea ice concentrations from passive microwave data. Results from a case study
comparing sea ice concentrations from ARTIST Sea Ice-, NASA Team 2-, and Bootstrap-algorithms with
MODIS sea ice concentrations indicate an underestimation of around 40 % for
sea ice concentrations retrieved with microwave algorithms. |
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