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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2015. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 45 (2015): 2913–2932, doi:10.1175/JPO-D-14-0179.1.
    Description: The oceanic deep circulation is shared between concentrated deep western boundary currents (DWBCs) and broader interior pathways, a process that is sensitive to seafloor topography. This study investigates the spreading and deepening of Denmark Strait overflow water (DSOW) in the western subpolar North Atlantic using two ° eddy-resolving Atlantic simulations, including a passive tracer injected into the DSOW. The deepest layers of DSOW transit from a narrow DWBC in the southern Irminger Sea into widespread westward flow across the central Labrador Sea, which remerges along the Labrador coast. This abyssal circulation, in contrast to the upper levels of overflow water that remain as a boundary current, blankets the deep Labrador Sea with DSOW. Farther downstream after being steered around the abrupt topography of Orphan Knoll, DSOW again leaves the boundary, forming cyclonic recirculation cells in the deep Newfoundland basin. The deep recirculation, mostly driven by the meandering pathway of the upper North Atlantic Current, leads to accumulation of tracer offshore of Orphan Knoll, precisely where a local maximum of chlorofluorocarbon (CFC) inventory is observed. At Flemish Cap, eddy fluxes carry ~20% of the tracer transport from the boundary current into the interior. Potential vorticity is conserved as the flow of DSOW broadens at the transition from steep to less steep continental rise into the Labrador Sea, while around the abrupt topography of Orphan Knoll, potential vorticity is not conserved and the DSOW deepens significantly.
    Description: This work is supported by ONR Award N00014-09-1-0587, the NSF Physical Oceanography Program, and NASA Ocean Surface Topography Science Team Program.
    Description: 2016-06-01
    Keywords: Circulation/ Dynamics ; Abyssal circulation ; Boundary currents ; Ocean circulation ; Ocean dynamics ; Potential vorticity ; Topographic effects
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 2
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 121 (2016): 877–907, doi:10.1002/2015JC011290.
    Description: Accelerating since the early 1990s, the Greenland Ice Sheet mass loss exerts a significant impact on thermohaline processes in the sub-Arctic seas. Surplus freshwater discharge from Greenland since the 1990s, comparable in volume to the amount of freshwater present during the Great Salinity Anomaly events, could spread and accumulate in the sub-Arctic seas, influencing convective processes there. However, hydrographic observations in the Labrador Sea and the Nordic Seas, where the Greenland freshening signal might be expected to propagate, do not show a persistent freshening in the upper ocean during last two decades. This raises the question of where the surplus Greenland freshwater has propagated. In order to investigate the fate, pathways, and propagation rate of Greenland meltwater in the sub-Arctic seas, several numerical experiments using a passive tracer to track the spreading of Greenland freshwater have been conducted as a part of the Forum for Arctic Ocean Modeling and Observational Synthesis effort. The models show that Greenland freshwater propagates and accumulates in the sub-Arctic seas, although the models disagree on the amount of tracer propagation into the convective regions. Results highlight the differences in simulated physical mechanisms at play in different models and underscore the continued importance of intercomparison studies. It is estimated that surplus Greenland freshwater flux should have caused a salinity decrease by 0.06–0.08 in the sub-Arctic seas in contradiction with the recently observed salinification (by 0.15–0.2) in the region. It is surmised that the increasing salinity of Atlantic Water has obscured the freshening signal.
    Description: NSERC. Grant Numbers RGPIN 227438-09, RGPIN 04357 and RGPCC 433898; RFBR. Grant Number 13-05-00480, 14-05-00730, and 15-05-02457; NSF Grant Number: PLR-0804010, PLR-1313614, and PLR-1203720
    Description: 2016-07-25
    Keywords: Greenland Ice Sheet melting ; Greenland freshwater ; Thermohaline circulation ; Nordic Seas ; Sub-Arctic seas ; Baffin Bay ; Labrador Sea
    Repository Name: Woods Hole Open Access Server
    Type: Article
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