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| Titel |
Short- and long-term thermo-erosion of ice-rich permafrost coasts in the Laptev Sea region |
| VerfasserIn |
F. Günther, P. P. Overduin, A. V. Sandakov, G. Grosse, M. N. Grigoriev |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 6 ; Nr. 10, no. 6 (2013-06-27), S.4297-4318 |
| Datensatznummer |
250018314
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| Publikation (Nr.) |
 copernicus.org/bg-10-4297-2013.pdf |
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| Zusammenfassung |
| Permafrost coasts in the Arctic are susceptible to a variety of changing
environmental factors all
of which currently point to increasing coastal erosion rates and mass fluxes of sediment and
carbon to the shallow arctic shelf seas. Rapid erosion along high yedoma coasts composed of Ice
Complex permafrost deposits creates impressive coastal ice cliffs and inspired research for
designing and implementing change detection studies for a long time, but continuous quantitative
monitoring and a qualitative inventory of coastal thermo-erosion for large coastline segments is
still lacking. Our goal is to use observations of thermo-erosion along the mainland coast of the
Laptev Sea, in eastern Siberia, to understand how it depends on coastal geomorphology and
the relative contributions of water level and atmospheric drivers. We compared multi-temporal sets of orthorectified
satellite imagery from 1965 to 2011 for three segments of coastline ranging in length from 73 to 95 km
and analyzed thermo-denudation (TD) along the cliff top and thermo-abrasion (TA) along the cliff
bottom for two nested time periods: long-term rates (the past 39–43 yr) and short-term rates (the
past 1–4 yr). The Normalized Difference Thermo-erosion Index (NDTI) was used as a proxy to
qualitatively describe the relative proportions of TD and TA. Mean annual erosion rates at all
three sites were higher in recent years (−5.3 ± 1.3 m a−1) than over the long-term mean (−2.2 ± 0.1 m a−1). The Mamontov Klyk coast exhibits primarily spatial
variations of thermo-erosion, while intrasite-specific variations caused by local relief were strongest at the Buor Khaya
coast, where the slowest long-term rates of around −0.5 ± 0.1 m a−1 were observed. The
Oyogos Yar coast showed continuously rapid erosion up to −6.5 ± 0.2 m a−1. In
general, variable characteristics of coastal thermo-erosion were observed not only between study
sites and over time, but also within single coastal transects along the cliff profile. Varying
intensities of cliff bottom and top erosion are leading to diverse qualities of coastal erosion
that have different impacts on coastal mass fluxes. The different extents of Ice Complex
permafrost degradation within our study sites turned out to influence not only the degree of
coupling between TD and TA, and the magnitude of effectively eroded volumes, but also the quantity
of organic carbon released to the shallow Laptev Sea from coastal erosion, which ranged on
a long-term from 88 ± 21 to 800 ± 61 t per km coastline per year and will
correspond to considerably higher amounts, if recently observed more rapid coastal erosion rates
prove to be persistent. |
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