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| Titel |
The impacts of eutrophication and biological feedbacks on the variability of the carbon shelf pump in the North Sea from 1970 to 2006 |
| VerfasserIn |
Ina Lorkowski, Johannes Pätsch, Andreas Moll, Wilfried Kühn |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042364
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| Zusammenfassung |
| ECOHAM4, a 3D coupled biogeochemical-physical ecosystem model for the North Sea
(511,725 km2), was used to generate a hindcast from 1970-2006 for the Northwest European
Shelf (47Ë 41‘ – 63Ë 53’ N, 15Ë 5’ W – 13Ë 55’ E) to analyze the carbon budgets and the
variability of the transport of atmospheric carbon via biological fixation into the North
Atlantic. Together with the lateral advection and the vertical export of carbon, this process is
often referred to as the carbon shelf pump. The model treats, partly decoupled, the marine
carbon cycle, the nutrient cycles for N, P and Si, oxygen, two phytoplankton and two
zooplankton groups as well as marine bacteria and detritus. A set of forcings is
included, among others 6-hourly meteorological fields by NCEP reanalysis, annual
atmospheric nitrogen deposition (EMEP) and daily riverine input of nutrients and
carbon.
The simulated primary production for diatoms varied between 2900 Gmol C yr-1 in 1996
and 3650 Gmol C yr-1 in 1988 while the primary production of non-diatoms ranged between
5500 Gmol C yr-1 and 6000 Gmol C yr-1. Both phytoplankton groups exhibited high
production rates in the mid-80s. This corresponds with riverine nutrient input peaking also in
the mid-80s. The simulated Net Ecosystem Production (NEP) varied from an unusually
low value of 25 Gmol C yr-1 in 1996 up to 673 Gmol C yr-1 in 2000. A very
low winter NAOI and low riverine inputs of nitrogen and DIC coincided with the
low NEP in 1996. For the total water column the Northern North Sea could be
characterized by a changing positive and negative NEP with strictly positive near-surface
values while the Southern North Sea exhibited a positive NEP during the whole
period.
In our simulation, the whole North Sea is characterized by an uptake of atmospheric CO2
ranging from about 430 to 743 Gmol C yr-1 during the years. While the Northern North Sea
was a sink for atmospheric CO2 during the whole period, taking up between 470 Gmol C
yr-1 in 1997 and 715 Gmol C yr-1 in 1981, the Southern North Sea showed a higher
variability and changed between being a source (e.g. 1976) or a sink (e.g. 1990) for
atmospheric CO2. |
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