Eintrag, Akkumulation und Überlieferung von organischem Kohlenstoff in Oberflächensedimenten des Europäischen Nordmeeres (engl. titel: Input, accumulation, and preservation of organic carbon in surface sediments of the European Nordic seas)


Contact
esauter [ at ] awi-bremerhaven.de

Abstract

AbstractA new driven measuring and sampling device was developed, capable to performe in situ measurements of porewater oxygen and formationfactor depth distributions within the upper sediment layers. The wire driven system was designed for the use even in ice covered regions as the East Greenland Sea and successfully employed at nine stations. Out of sediment cores taken by the implemented corer unit from the immediate vicinity of the measurement location other geochemical parameters were determined in laboratory.The production of oxygen microsensors for in situ and shipboard use was established at GEOMAR. In order to calculate the diffusive oxygen flux through the water/sediment interface the oxygen depth profiles measured with microsensors were fit by an exponential function. Out of that the Corg-flux onto the sediment surface was calculated, assuming oxic respiration in these well oxygenated sediments to be the main process of carbon degradation. Compared with fluxes obtained out of in situ oxygen measurements laboratory measured profiles lead to an overestimation of diffusive fluxes through the water/sediment-surface, dependending on waterdepth whereas oxygen penetration depth is much less affected.The Corg-flux onto the sediment surface was found to be relatively low in the region offshore East Greenland. Typical values reach from 3 to 8 gCm-2a-1 on the shelf and from 0.5 to 1 gCm-2a-1 at the deeper locations of the Greenland and Norwegian Sea respectively. Fluxes are found to be higher in summer than in fall by a factor of about 1.4. For some stations organic carbon akkumulation rates were calculated, considering published sedimentation rates of the respect location. In shelf sediments 0.2 to 0.3 gm-2a-1 of organic carbon akkumulates whereas in deep-sea sediments of the Nordic Seas akkumulation rates lie between 0.02 and 0.08 gCm-2a-1. In relation to the influx onto the sediment surface less than 5% of organic carbon are buried within surface sediments on the shelf an 7 to 21% at deep locations respectively. Organic matter degradation rates, obtained out of the second derivative of the oxygen profiles, rapidly decrease underneath the sediment surface. Maximum rates were found at the surface of shelf sediments with values of 0.5 mgCcm-3a-1 whereas only 0.04 mgcm-3a-1 of organic carbon degrades in deep-sea surface sediments of the Nordic Seas.Many of the measured parameters don't show a distinct dependence on waterdepth due to complex interaction of different processes. The conditions for primary production and sedimentation of the investigated area are strongly influenced by the seasonal variations in ice covering. In addition to that the region is ruled by a complex system of current like East Greenland, Westspitzbergen and Jan Mayen current.Over an area of 2.6x1012 m2 about 5.5 Mt (1 Mt = 106 tons) of organic carbon reaches the seafloor of the European Nordic Seas per year. This makes roughly 5% of the anual organic carbon sedimentation of the Atlantic and 1.8% of the Corg falling onto the world oceans sea-bottom respectively. With a rate of 3.21 MtCa-1 more than half of the Corg-input is degraded within the uppermost 3 cm of sediment column of organic carbon is degraded by oxic respiration. In the deep basins about 80% of Corg is remineralysed by oxygen within this surface layer.



Item Type
Thesis (PhD)
Authors
Divisions
Programs
Peer revision
Not peer-reviewed
Publication Status
Published
Eprint ID
5132
Cite as
Sauter, E. (1997): Eintrag, Akkumulation und Überlieferung von organischem Kohlenstoff in Oberflächensedimenten des Europäischen Nordmeeres (engl. titel: Input, accumulation, and preservation of organic carbon in surface sediments of the European Nordic seas) , PhD thesis, Christian Albrechts University Kiel, Germany.


Share

Research Platforms
N/A

Campaigns


Actions
Edit Item Edit Item