Organic carbon and oxidation in waters of the Norwegian Sea and Northeast Atlantic

Average total organic carbon concentration in the Norwegian Sea waters varies from 1.93 mg C/liter at depth of 10 m to 1.25 mg C/liter at depth of 2000 m, which is close to average values previously calculated from determinations made by the Marine Hydrophysical Institute at 19 stations in the Atlantic Ocean. The average carbon concentration in waters of the Northeast Atlantic adjacent to the Norwegian Sea is somewhat lower. Particulate carbon concentration, as determined by precipitation with aluminum hydroxide, is measured in tens of µg C/liter, that is few percent of total carbon concentration.

Stable oxygen isotope record of epibenthic foraminifera and water samples of the Arctic Ocean

We determined d18OCib values of live (Rose Bengal stained) and dead epibenthic foraminifera Cibicidoides wuellerstorfi, Cibicides lobatulus, and Cibicides refulgens in surface sediment samples from the Arctic Ocean and the Greenland, Iceland, and Norwegian seas (Nordic Sea). This is the first time that a comprehensive d18OCib data set is generated and compiled from the Arctic Ocean. For comparison, we defined Atlantic Water (AW), upper Arctic Bottom Water (uABW), and Arctic Bottom Water (ABW) by their temperature/salinity characteristics and calculated mean equilibrium calcite d18Oequ from summer sea-water d18Ow and in situ temperatures. As a result, in the Arctic environment we compensate for Cibicidoides- and Cibicides-specific offsets from equilibrium calcite of -0.35 and -0.55 per mil, respectively. After this taxon-specific adjustment, mean d18OCib values plausibly reflect the density stratification of principle water masses in the Nordic Sea and Arctic Ocean. In addition, mean d18OCib from AW not only significantly differs from mean d18OCib from ABW, but also d18OCib from within AW differentiates in function of provenience and water mass age. Furthermore, in shallow waters brine-derived low d18Ow can significantly lower the d18OCib of Cibicides spp. and thus d18OCib may serve as a paleobrine indicator. There is no statistically significant difference, however, between deeper water masses mean d18OCib of the Nordic Sea, and of the Eurasian and Amerasian basins, and no influence of low-d18Ow brines is recorded in Recent uABW and ABW d18OCib of C. wuellerstorfi. This may be due to dilution of a low-d18Ow brine signal in the deep sea, and/or to preferential incorporation of relatively high-d18Ow brines from high-salinity shelves. Although our data encompass environments with seasonal sea-ice and brine formation supposed to ultimately ventilate the deep Arctic Ocean, d18OCib from uABW and ABW do not indicate negative excursions. This may challenge hypotheses that call for enhanced Arctic brine release to explain negative benthic d18O spikes in deep-sea sediments from the late Pleistocene North Atlantic Ocean.

Nutrition of species of the genus Amphiophiura in the Pacific and Indian Oceans

Nutrition of 6 deep-sea ophiuroid species of the genus Amphiophiura in the Pacific and Indian Oceans has been studied. One species is a detritus-feeder while the others are carnivorous. All 6 are widespread in deep-sea eutrophic regions of both oceans. Carnivorous species are also necrophagous, feeding on dead fish, surface pteropods, and crustaceans. Fishes are consumed mainly in the Indian Ocean, pteropods in the Pacific. Thus, as shown by carnivorous Amphtophiura, the rain of dead surface pelagic organisms is one of the most important sources of food for a number of deep-sea bottom-dwelling invertebrates.

(Table 1) Snow and ice thickness and layering at observation points of the North Pole 34 drifting station

Variability of total alkalinity in sea ice of the high-latitudinal Arctic from November 2005 to May 2006 is considered. For the bulk of one- and two-year sea ice, alkalinity dependence on salinity is described as TA = k x Sal, where k is salinity/alkalinity ratio in under-ice water. The given relationship is valid within a wide range of salinity from 0.1 psu in desalinated fraction of two-year ice to 36 psu in snow on the young ice surface. Geochemically significant deviations from the relationship noted were observed exclusively in snow and the upper layer of one-year ice. In the upper layer of one-year ice, deficiency of alkalinity is observed ( delta TA ~= -0.07 mEq/kg, or -15%). In snow on the surface of the one-year ice, alkalinity excess is formed under desalination ( delta TA is as high as 1.3 mEq/kg, or 380%). Deviations registered are caused by possibility of carbonate precipitation in form of CaCO3 x 6H2O under seawater freezing. It is shown that ice formation and the following melting might cause losses of atmospheric CO2 of up to 3 x 10**12 gC/year.

(Table 1) Positions of the Mesocena elliptica zone in sediment cores from the Pacific and Indian Oceans

The Mesocena elliptica Ehr. zone in deep-sea sediments of the Pacific Ocean is characterized by a short vertical range at the base of the Pleistocene section. Depending on sedimentation rate this zone lies at various depths below the ocean bottom. M. elliptica is unknown in recent oceanic plankton. In fossil state known species indicate that sediments containing them are of Oligocene-Miocene age. New data obtained in early 1960's show that within a short interval, evidently in Early Pleistocene, M. elliptica was abundant in plankton, primarily in tropical regions. Correlation of paleomagnetic data with results of diatom analysis shows that the Mesocena elliptica zone always lies above the Pliocene-Pleistocene boundary, and that maximum contents of M. elliptica coincide with the Jaramillo event (0.85-0.95 million years ago).

(Table 1) Positions of the Mesocena elliptica zone in sediment cores from the Pacific and Indian Oceans

The Mesocena elliptica Ehr. zone in deep-sea sediments of the Pacific Ocean is characterized by a short vertical range at the base of the Pleistocene section. Depending on sedimentation rate this zone lies at various depths below the ocean bottom. M. elliptica is unknown in recent oceanic plankton. In fossil state known species indicate that sediments containing them are of Oligocene-Miocene age. New data obtained in early 1960's show that within a short interval, evidently in Early Pleistocene, M. elliptica was abundant in plankton, primarily in tropical regions. Correlation of paleomagnetic data with results of diatom analysis shows that the Mesocena elliptica zone always lies above the Pliocene-Pleistocene boundary, and that maximum contents of M. elliptica coincide with the Jaramillo event (0.85-0.95 million years ago).