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4. Sediment accumulation rates at the edge of the Atlantic: relationships among sea ice, water current and sea floor relief

Author

Isla, Enrique, DeMaster, D.J., and Taylor, Richard

Subjects
fungi
Abstract

Scientific Committee on Antarctic Research Open Science Conference (SCAR 2020), 3-7 August 2020, Sediment accumulation rates were studied at the southernmost Atlantic Ocean in the vicinities of the Filchner Trough. This is an important region for water mass formation and a marine mammal feeding spot, presumably following high primary production. The region also experiences contrasting sea ice patterns. In spring and summer there are open water conditions at the east of the trough, whereas at the west, the sea surface usually remains covered by multiyear sea ice. Earlier studies showed that sedimentary organic carbon and biogenic silica were more concentrated on the eastern flank of the trough. We attempted to study whether sediment accumulation follow this pattern and its implication for the long-term (hundreds of years) carbon storage in the sediment column. We analyzed 16, 20-cm sediment cores along the axis of the Filchner Trough and the adjacent continental shelf and slope. Sediment accumulation rates (SAR) varied from 8 to 128 cm ky-1. The highest SAR were found on the deepest parts of the axis of the trough and the shelf and slope of its eastern flank, whereas the smallest SAR were found in the shelf and slope of the western flank and at the mouth of the trough. Preliminarily, SAR values matched with the sea-ice pattern and the water current system, showing high values in areas with seasonal open water conditions and the inflow of deep water onto the shelf and low values in areas where multiyear sea ice persists and the outflow of dense cold water towards the deep Weddell Sea

Published
2020

15. Bioturbation and particle transport in Carolina slope sediments: a radiochemical approach

Author

Fornes, W.L., DeMaster, D.J., Levin, L.A., and Blair, N.E.

Subjects
Sediments (Geology) -- Research, Continental margins -- Research, Sediment transport -- Research, Biological sciences, Earth sciences
Abstract

Short-term sediment mixing processes at two continental margin sites in North Carolina with different organic C fluxes were examined. The study sought to demonstrate that bioturbation, over short time scales, is determined by the nature of the sedimentary particles as well as the assemblages of animals in the sediment. The findings vary significantly from earlier studies describing biological mixing as events integrated over time ranging from weeks to centuries.

Published
1999

28. Deposition of bomb 14C in continental slope sediments of the Mid-Atlantic Bight: assessing organic matter sources and burial rates

Author

DeMaster, D.J., Thomas, C.J., Blair, N.E., Fornes, W.L., Plaia, G., and Levin, L.A.

Subjects
*BENTHIC animals, *MARINE sediments, *CONTINENTAL slopes
Abstract

As part of the Ocean Margins Program (OMP), organic carbon 14C measurements have been made on benthic fauna and kasten core sediments from the North Carolina continental slope. These analyses are used to evaluate the nature and burial flux of organic matter in the OMP study area off Cape Hatteras. Despite the fact that surface sediment 14C contents ranged from −41 to −215 per mil, the benthic fauna (primarily polychaetes) all contained significant amounts of bomb-14C (body tissue 14C contents ranging from +20 to +82 per mil). Bomb-14C clearly is reaching the seabed on the North Carolina slope, and the labile planktonic material carrying this signal is a primary source of nutrition to the benthic ecosystem. The enrichment of 14C in benthic faunal tissue relative to the 14C content of bulk surface-sediment organic matter (a difference of ∼150 per mil) is attributed to a combination of particle selection and selective digestive processes. Organic carbon burial rates from 12 stations on the North Carolina slope varied from 0.02 to 1.7 mol of C m−2 yr−1, with a mean value of 0.7 mol of C m−2 yr−1. The accumulation of organic matter on the upper slope accounts for <1% of the primary production in the entire continental margin system. The North Carolina margin was deliberately selected because of its potential for offshore transport and high sediment deposition rates, and even in this environment, burial of organic carbon accounts for a very small fraction of the primary production occurring in surface waters. [Copyright &y& Elsevier]

Published
2002
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