Lithogenic and biogenic particle fluxes on the Lomonosov Ridge (central Arctic Ocean) and their relevance for sediment accumulation: Vertical vs. lateral transport

Fahl, Kirsten; Nöthig, Eva‐Maria

doi:10.1016/j.dsr.2007.04.014

Cited by 108 publications

(118 citation statements)

References 51 publications

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“…These studies do not prove offshore transport to the central Arctic basin and could represent a timescale offset between pulsed export events and gradual benthic respiration, but indicates that further study specifically targeting these transport processes is warranted. Sediment trap data from the Canada and Amundsen Basins suggest that lateral transport of allochthonous matter is likely the source of most trap material and not production from the overlying waters (Fahl and Nöthig, 2007;. In addition, fluxes at 3000 m in the Canada Basin increased in months when the region was completely ice covered and productivity was limited, further supporting the dominance of lateral over vertical transport of organic matter.…”

Section: Particulate 234 Th Maxima: An Indicator Of Shelf To Basin Ofmentioning

confidence: 78%

An investigation of basin-scale controls on upper ocean export and remineralization

Black¹

2018

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The biological carbon pump (BCP) helps to moderate atmospheric carbon dioxide levels by bringing carbon to the deep ocean, where it can be sequestered on timescales of centuries to millennia. Climate change is predicted to decrease the efficiency of the global BCP, however, the magnitude and timescale of this shift is largely uncertain and will likely impact some areas of the global ocean more significantly than others. Therefore, it is imperative that we (1) accurately quantify surface export and remineralization of particulate organic carbon (POC) via the BCP over large regions of the global ocean, (2) examine the factors controlling these POC fluxes and their variability, which includes the cycling of biologically-relevant trace metals, and (3) establish if and how the BCP is changing over time.This thesis focuses on addressing various aspects of these objectives using the 234 Th-238 U method across basin-scale GEOTRACES transects. First, the export and remineralization of POC were examined across large gradients in productivity, upwelling, community structure, and dissolved oxygen in the southeastern tropical Pacific Ocean. Although low oxygen zones are traditionally thought to have decreased POC flux attenuation relative to other regions of the global ocean and the low oxygen Pacific locations followed this pattern, regions that were functionally anoxic had enhanced attenuation in the upper 400 m. Second, trace metal export and remineralization were quantified across the Pacific transect. Because many trace metals are necessary for the metabolic functions of marine organisms and can co-limit marine productivity, the controls on the cycling of trace metals in the upper ocean were examined. Lastly, POC export was determined across two transects in the Western Arctic Ocean, where light and nutrient availability drive the biological pump. Upper ocean export estimates in the central basin did not reflect a substantial change in the biological pump compared to studies from the last three decades, however, an extensive maximum in 234 Th relative to 238 U deeper in the water column indicated that rapid vertical transport had occurred, which could suggest a more efficient biological pump in the Arctic Ocean.

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Section: Particulate 234 Th Maxima: An Indicator Of Shelf To Basin Ofmentioning

confidence: 78%

An investigation of basin-scale controls on upper ocean export and remineralization

Black¹

2018

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“…Terrestrial organic carbon sources to the Laptev and East Siberian shelf and slope are riverine discharge and coastal erosion of the ice core complex (Stein and Macdonald, 2004;Vonk et al, 2012;Rachold et al, 2004;Fahl and Nöthig, 2007;Semiletov, 1999). Marine organic carbon is derived from open-water production during the ice-free months, export of ice algae, and new production in polynyas (Sakshaug et al, 2004;Nitishinsky et al 2007).…”

Section: Marine Versus Terrestrial Organic Matter Contributionmentioning

confidence: 99%

Carbon mineralization in Laptev and East Siberian sea shelf and slope sediment

et al. 2018

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Abstract. The Siberian Arctic Sea shelf and slope is a key region for the degradation of terrestrial organic material transported from the organic-carbon-rich permafrost regions of Siberia. We report on sediment carbon mineralization rates based on O 2 microelectrode profiling; intact sediment core incubations; 35 S-sulfate tracer experiments; pore-water dissolved inorganic carbon (DIC); δ 13 C DIC ; and iron, manganese, and ammonium concentrations from 20 shelf and slope stations. This data set provides a spatial overview of sediment carbon mineralization rates and pathways over large parts of the outer Laptev and East Siberian Arctic shelf and slope and allows us to assess degradation rates and efficiency of carbon burial in these sediments. Rates of oxygen uptake and iron and manganese reduction were comparable to temperate shelf and slope environments, but bacterial sulfate reduction rates were comparatively low. In the topmost 50 cm of sediment, aerobic carbon mineralization dominated degradation and comprised on average 84 % of the depthintegrated carbon mineralization. Oxygen uptake rates and anaerobic carbon mineralization rates were higher in the eastern East Siberian Sea shelf compared to the Laptev Sea shelf. DIC / NH + 4 ratios in pore waters and the stable carbon isotope composition of remineralized DIC indicated that the degraded organic matter on the Siberian shelf and slope was a mixture of marine and terrestrial organic matter. Based on dual end-member calculations, the terrestrial organic carbon contribution varied between 32 and 36 %, with a higher contribution in the Laptev Sea than in the East Siberian Sea. Extrapolation of the measured degradation rates using isotope end-member apportionment over the outer shelf of the Laptev and East Siberian seas suggests that about 16 Tg C yr −1 is respired in the outer shelf seafloor sediment. Of the organic matter buried below the oxygen penetration depth, between 0.6 and 1.3 Tg C yr −1 is degraded by anaerobic processes, with a terrestrial organic carbon contribution ranging between 0.3 and 0.5 Tg yr −1 .

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“…Finegrained sediment from the shelf edge may become suspended and transported to the center of the Lomonosov Ridge (Fahl and Nöthig, 2007), although the magnitude of this transport mechanism is uncertain. Sea ice transported by the Transpolar Drift carries material from the Siberian shelf, mostly from the Laptev Sea, over the Lomonosov Ridge towards the Fram Strait.…”

Section: Possible Circulation and Provenance Controls On Stratigraphymentioning

confidence: 99%

Spatial and temporal Arctic Ocean depositional regimes: a key to the evolution of ice drift and current patterns

Sellén

O’Regan

Jakobsson

2010

Quaternary Science Reviews

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a b s t r a c tSediment physical properties measured in cores from all the major ridges and plateaus in the central Arctic Ocean were studied in order to analyze the spatial and temporal consistency of sediment depositional regimes during the Quaternary. In total, six physiographically distinct areas are outlined. In five of these, cores can be correlated over large distances through characteristic patterns in sediment physical properties. These areas are (1) the southern Mendeleev Ridge, (2) the northern Mendeleev Ridge and Alpha Ridge, (3) the Lomonosov Ridge, (4) the Morris Jesup Rise and (5) the Yermak Plateau. Averaged downhole patterns in magnetic susceptibility, bulk density and lithostratigraphy were compiled to establish a composite stratigraphy for each area. In the sixth physiographic area, the Chukchi Borderland, repeated ice-grounding during recent glacial periods complicates the stratigraphy and prevents the compilation of a composite stratigraphy using the studied material. By utilizing published age models for the studied cores we are able to show that the northern Mendeleev Ridge and Alpha Ridge have the lowest average late Quaternary sedimentation rates, while intermediate sedimentation rates prevail on the southern Mendeleev Ridge and the Morris Jesup Rise. The second highest sedimentation rate is observed on the Lomonosov Ridge, whereas the average sedimentation rate on the Yermak Plateau is more than twice as high. The close correlation of physical properties within each area suggests uniform variations in sediment transport through time, at least throughout the later part of the Quaternary. The unique stratigraphic characteristics within each area is the product of similar past depositional regimes and are key for furthering our understanding of the evolution of ice drift and current patterns in the central Arctic Ocean.

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Lithogenic and biogenic particle fluxes on the Lomonosov Ridge (central Arctic Ocean) and their relevance for sediment accumulation: Vertical vs. lateral transport

Cited by 108 publications

References 51 publications

An investigation of basin-scale controls on upper ocean export and remineralization

An investigation of basin-scale controls on upper ocean export and remineralization

Carbon mineralization in Laptev and East Siberian sea shelf and slope sediment

Spatial and temporal Arctic Ocean depositional regimes: a key to the evolution of ice drift and current patterns

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