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| Titel |
Distribution and biophysical processes of beaded streams in Arctic permafrost landscapes |
| VerfasserIn |
C. D. Arp, M. S. Whitman, B. M. Jones, G. Grosse, B. V. Gaglioti, K. C. Heim |
| 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 ; 12, no. 1 ; Nr. 12, no. 1 (2015-01-06), S.29-47 |
| Datensatznummer |
250117757
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| Publikation (Nr.) |
 copernicus.org/bg-12-29-2015.pdf |
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| Zusammenfassung |
| Beaded streams are widespread in permafrost regions and are considered a
common thermokarst landform. However, little is known about their
distribution, how and under what conditions they form, and how their
intriguing morphology translates to ecosystem functions and habitat. Here we
report on a circum-Arctic survey of beaded streams and a watershed-scale
analysis in northern Alaska using remote sensing and field studies. We
mapped over 400 channel networks with beaded morphology throughout the
continuous permafrost zone of northern Alaska, Canada, and Russia and found
the highest abundance associated with medium to high ground-ice content
permafrost in moderately sloping terrain. In one Arctic coastal plain
watershed, beaded streams accounted for half of the drainage density,
occurring primarily as low-order channels initiating from lakes and drained
lake basins. Beaded streams predictably transition to alluvial channels with
increasing drainage area and decreasing channel slope, although this
transition is modified by local controls on water and sediment delivery.
The comparisons of one beaded channel using repeat photography between 1948 and
2013 indicate a relatively stable landform, and 14C dating of basal
sediments suggest channel formation may be as early as the
Pleistocene–Holocene transition. Contemporary processes, such as deep snow
accumulation in riparian zones, effectively insulate channel ice and allows
for perennial liquid water below most beaded stream pools. Because of this,
mean annual temperatures in pool beds are greater than 2 °C,
leading to the development of perennial thaw bulbs or taliks underlying
these thermokarst features that range from 0.7 to 1.6 m. In the summer, some
pools thermally stratify, which reduces permafrost thaw and maintains
cold-water habitats. Snowmelt-generated peak flows decrease rapidly by two or
more orders of magnitude to summer low flows with slow reach-scale velocity
distributions ranging from 0.01 to 0.1 m s−1, yet channel runs still move
water rapidly between pools. The repeating spatial pattern associated with
beaded stream morphology and hydrological dynamics may provide abundant and
optimal foraging habitat for fish. Beaded streams may create important
ecosystem functions and habitat in many permafrost landscapes and their
distribution and dynamics are only beginning to be recognized in Arctic
research. |
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