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| Titel |
Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems |
| VerfasserIn |
J. E. Vonk, S. E. Tank, W. B. Bowden, I. Laurion, W. F. Vincent, P. Alekseychik, M. Amyot, M. F. Billet, J. Canário, R. M. Cory, B. N. Deshpande, M. Helbig, M. Jammet, J. Karlsson, J. Larouche, G. MacMillan, M. Rautio, K. M. Walter Anthony, K. P. Wickland |
| 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. 23 ; Nr. 12, no. 23 (2015-12-08), S.7129-7167 |
| Datensatznummer |
250118204
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| Publikation (Nr.) |
 copernicus.org/bg-12-7129-2015.pdf |
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| Zusammenfassung |
| The Arctic is a water-rich region, with freshwater systems covering about
16 % of the northern permafrost landscape. Permafrost thaw creates new
freshwater ecosystems, while at the same time modifying the existing lakes,
streams, and rivers that are impacted by thaw. Here, we describe the current
state of knowledge regarding how permafrost thaw affects lentic (still) and
lotic (moving) systems, exploring the effects of both thermokarst (thawing
and collapse of ice-rich permafrost) and deepening of the active layer (the
surface soil layer that thaws and refreezes each year). Within thermokarst,
we further differentiate between the effects of thermokarst in lowland
areas vs. that on hillslopes. For almost all of the processes that we
explore, the effects of thaw vary regionally, and between lake and stream
systems. Much of this regional variation is caused by differences in ground
ice content, topography, soil type, and permafrost coverage. Together, these
modifying factors determine (i) the degree to which permafrost thaw
manifests as thermokarst, (ii) whether thermokarst leads to slumping or the
formation of thermokarst lakes, and (iii) the manner in which constituent
delivery to freshwater systems is altered by thaw. Differences in
thaw-enabled constituent delivery can be considerable, with these modifying
factors determining, for example, the balance between delivery of
particulate vs. dissolved constituents, and inorganic vs. organic
materials. Changes in the composition of thaw-impacted waters, coupled with
changes in lake morphology, can strongly affect the physical and optical
properties of thermokarst lakes. The ecology of thaw-impacted lakes and
streams is also likely to change; these systems have unique microbiological
communities, and show differences in respiration, primary production, and
food web structure that are largely driven by differences in sediment,
dissolved organic matter, and nutrient delivery. The degree to which thaw
enables the delivery of dissolved vs. particulate organic matter, coupled
with the composition of that organic matter and the morphology and
stratification characteristics of recipient systems will play an important
role in determining the balance between the release of organic matter as
greenhouse gases (CO2 and CH4), its burial in sediments, and its
loss downstream. The magnitude of thaw impacts on northern aquatic
ecosystems is increasing, as is the prevalence of thaw-impacted lakes and
streams. There is therefore an urgent need to quantify how permafrost thaw
is affecting aquatic ecosystems across diverse Arctic landscapes, and the
implications of this change for further climate warming. |
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