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| Titel |
NW European shelf under climate warming: implications for open ocean – shelf exchange, primary production, and carbon absorption |
| VerfasserIn |
M. Gröger, E. Maier-Reimer, U. Mikolajewicz, A. Moll, D. Sein |
| 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 (2013-06-12), S.3767-3792 |
| Datensatznummer |
250018283
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| Publikation (Nr.) |
 copernicus.org/bg-10-3767-2013.pdf |
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| Zusammenfassung |
Shelves have been estimated to account for more than one-fifth of
the global marine primary production. It has been also conjectured
that shelves strongly influence the oceanic absorption of
anthropogenic CO2 (carbon shelf pump). Owing to their coarse
resolution, currently applied global climate models are
inappropriate to investigate the impact of climate change on shelves
and regional models do not account for the complex interaction with
the adjacent open ocean. In this study, a global ocean general
circulation model and biogeochemistry model were set up with
a distorted grid providing a maximal resolution for the NW European
shelf and the adjacent northeast Atlantic.
Using model climate projections we found that already a~moderate
warming of about 2.0 K of the sea surface is linked with
a reduction by ~ 30% of the biological production on the NW
European shelf. If we consider the decline of anthropogenic riverine
eutrophication since the 1990s, the reduction of biological production
amounts is even larger. The relative decline of NW European shelf productivity
is twice as strong as the decline in the open ocean
(~ 15%). The underlying mechanism is a spatially well
confined stratification feedback along the continental shelf break.
This feedback reduces the nutrient supply from the deep Atlantic to
about 50%. In turn, the reduced productivity draws down CO2 absorption in the North
Sea by ~ 34% at the end
of the 21st century compared to the end of the 20th century implying
a strong weakening of shelf carbon pumping. Sensitivity experiments
with diagnostic tracers indicate that not more than 20% of the
carbon absorbed in the North Sea contributes to the long-term carbon
uptake of the world ocean. The rest remains within the ocean's mixed
layer where it is exposed to the atmosphere.
The predicted decline in biological productivity, and decrease of
phytoplankton concentration (in the North Sea by averaged 25%) due to reduced
nutrient imports from the deeper Atlantic will probably
affect the local fish stock negatively and therefore fisheries in the North
Sea. |
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