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  • 1
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    Circulation in the northwest Laptev Sea in the eastern Arctic Ocean: Crossroads between Siberian River water, Atlantic water and polynya-formed dense water (2017)
    AGU (American Geophysical Union) | Wiley
    In:  Journal of Geophysical Research: Oceans, 122 (8). pp. 6630-6647.
    Details
    Publication Date: 2020-02-06
    Description: This paper investigates new observations from the poorly understood region between the Kara and Laptev Seas in the Eastern Arctic Ocean. We discuss relevant circulation features including riverine freshwater, Atlantic-derived water, and polynya-formed dense water, emphasize Vilkitsky Strait (VS) as an important Kara Sea gateway, and analyze the role of the adjacent ∼250 km-long submarine Vilkitsky Trough (VT) for the Arctic boundary current. Expeditions in 2013 and 2014 operated closely spaced hydrographic transects and 1 year-long oceanographic mooring near VT's southern slope, and found persistent annually averaged flow of 0.2 m s−1 toward the Nansen Basin. The flow is nearly barotropic from winter through early summer and becomes surface intensified with maximum velocities of 0.35 m s−1 from August to October. Thermal wind shear is maximal above the southern flank at ∼30 m depth, in agreement with basinward flow above VT's southern slope. The subsurface features a steep front separating warm (–0.5°C) Atlantic-derived waters in central VT from cold (〈–1.5°C) shelf waters, which episodically migrates across the trough indicated by current reversals and temperature fluctuations. Shelf-transformed waters dominate above VT's slope, measuring near-freezing temperatures throughout the water column at salinities of 34–35. These dense waters are vigorously advected toward the Eurasian Basin and characterize VT as a conduit for near-freezing waters that could potentially supply the Arctic Ocean's lower halocline, cool Atlantic water, and ventilate the deeper Arctic Ocean. Our observations from the northwest Laptev Sea highlight a topographically complex region with swift currents, several water masses, narrow fronts, polynyas, and topographically channeled storms.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2017JC013159
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Correlation of river water and local sea-ice melting on the Laptev Sea shelf (Siberian Arctic) (2013)
    AGU (American Geophysical Union) | Wiley
    In:  Journal of Geophysical Research: Oceans, 118 (1). pp. 550-561.
    Details
    Publication Date: 2019-09-23
    Description: Hydrographic and stable isotope (δ18O) data from 4 summer surveys in the Laptev Sea are used to derive fractions of sea-ice meltwater and river water. Sea-ice meltwater fractions are found to be correlated to river water fractions. While initial heat of river discharge is too small to melt the observed 0-158 km3 of sea-ice meltwater, arctic rivers contain suspended particles (SPM) and colored dissolved organic material (CDOM) that preferentially absorb solar radiation. Accordingly heat content in surface waters is correlated to river water fractions. But in years when river water is largely absent within the surface layer absolute heat content values increase to considerably higher values with extended exposure time to solar radiation and sensible heat. Nevertheless no net sea-ice melting is observed on the shelf in years when river water is largely absent within the surface layer. The total freshwater volume of the central-eastern Laptev Sea (72-76°N, 122-140°E) varies between ~1000-1500 km3 (34.92 reference salinity). It is dominated by varying river water volumes (~1300-1800 km3) reduced by an about constant freshwater deficit (~350-400 km3) related to sea-ice formation. Net sea-ice melt (~109-158 km3) is only present in years with high river water budgets. Intermediate to bottom layer (〉25 salinities) contain ~60% and 30% of the river budget in years with low and high river budgets, respectively. The average mean residence time of shelf waters was ~2-3 years during 2007-2009.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1002/jgrc.20076
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    The impact of Siberian coastal polynyas on shelf-derived Arctic Ocean halocline waters (2012)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 117 (C4). C00G12.
    Details
    Publication Date: 2019-09-23
    Description: Hydrographic and stable oxygen isotope (H218O/H216O) sampling was carried out within the West New Siberian (WNS) coastal polynyas in the southern Laptev Sea in late winters 2008 and 2009. The impact of sea-ice formation on the water column was quantified by a salinity/{lower case delta}18O mass balance. Several stations had vertically homogeneous physical properties in April/May 2008 and featured polynya-formed local bottom water with elevated signals of brine released during sea-ice formation and elevated fractions of river water. The polynya-formed bottom water was fresher than surrounding bottom waters. At other stations salinity/{lower case delta}18O correlation showed well defined mixing lines for bottom and surface layers. In March/April 2009 surface waters were strongly influenced by Lena River water and local polynya activity with elevated brine signals reached to intermediate depth, but did not penetrate the bottom layer in the highly stratified water column. Inventory values of sea-ice formation were comparable in both years, but freshwater distributions from the preceding summers were different. Therefore, the observed difference in the impact of polynya activity on the water column is not primarily controlled by the amount of sea-ice formed during winter but by preconditioning from the preceding summer. Only in years when the river plume is mostly absent in the polynya region stratification is weak and allows winter sea-ice formation to reach the bottom layer. Thus summer stratification controls the influence of local polynya water on the shelf's bottom hydrography and, as bottom water is exported, impacts on the source water of shelf-derived halocline waters.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1029/2011JC007282
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Kara Sea freshwater transport through Vilkitsky Strait: Variability, forcing, and further pathways toward the western Arctic Ocean from a model and observations (2015)
    AGU (American Geophysical Union) | Wiley
    In:  Journal of Geophysical Research: Oceans, 120 (7). pp. 4925-4944.
    Details
    Publication Date: 2019-09-23
    Description: Siberian river water is a first-order contribution to the Arctic freshwater budget, with the Ob, Yenisey, and Lena supplying nearly half of the total surface freshwater flux. However, few details are known regarding where, when, and how the freshwater transverses the vast Siberian shelf seas. This paper investigates the mechanism, variability, and pathways of the fresh Kara Sea outflow through Vilkitsky Strait toward the Laptev Sea. We utilize a high-resolution ocean model and recent shipboard observations to characterize the freshwater-laden Vilkitsky Strait Current (VSC), and shed new light on the little-studied region between the Kara and Laptev Seas, characterized by harsh ice conditions, contrasting water masses, straits, and a large submarine canyon. The VSC is 10-20 km wide, surface intensified, and varies seasonally (maximum from August to March) and interannually. Average freshwater (volume) transport is 500 ± 120 km3 a-1 (0.53 ± 0.08 Sv), with a baroclinic flow contribution of 50-90%. Interannual transport variability is explained by a storage-release mechanism, where blocking-favorable summer winds hamper the outflow and cause accumulation of freshwater in the Kara Sea. The year following a blocking event is characterized by enhanced transports driven by a baroclinic flow along the coast that is set up by increased freshwater volumes. Eventually, the VSC merges with a slope current and provides a major pathway for Eurasian river water toward the western Arctic along the Eurasian continental slope. Kara (and Laptev) Sea freshwater transport is not correlated with the Arctic Oscillation, but rather driven by regional summer pressure patterns.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2014JC010635
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Observed interannual changes beneath Filchner-Ronne Ice Shelf linked to large-scale atmospheric circulation (2021)
    Springer Nature
    In:  EPIC3Nature Communications, Springer Nature, 12(1), ISSN: 2041-1723
    Details
    Publication Date: 2021-06-16
    Description: Floating ice shelves are the Achilles’ heel of the Antarctic Ice Sheet. They limit Antarctica’s contribution to global sea level rise, yet they can be rapidly melted from beneath by a warming ocean. At Filchner-Ronne Ice Shelf, a decline in sea ice formation may increase basal melt rates and accelerate marine ice sheet mass loss within this century. However, the understanding of this tipping-point behavior largely relies on numerical models. Our new multi-annual observations from five hot-water drilled boreholes through Filchner-Ronne Ice Shelf show that since 2015 there has been an intensification of the density-driven ice shelf cavity-wide circulation in response to reinforced wind-driven sea ice formation in the Ronne polynya. Enhanced southerly winds over Ronne Ice Shelf coincide with westward displacements of the Amundsen Sea Low position, connecting the cavity circulation with changes in large-scale atmospheric circulation patterns as a new aspect of the atmosphere-ocean-ice shelf system.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
    Format: application/pdf
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