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  • Water mass transformation  (2)
  • Arctic freshwater export  (1)
  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Elsevier Ltd. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 79 (2013): 20-39, doi:10.1016/j.dsr.2013.05.007.
    Description: The circulation and water mass transports north of the Denmark Strait are investigated using recently collected and historical in-situ data along with an idealized numerical model and atmospheric reanalysis fields. Emphasis is placed on the pathways of dense water feeding theDenmark StraitOverflowWater plume as well as the upper-layer circulation of freshwater. It is found that the East Greenland Current (EGC) bifurcates at the northern end of the Blosseville Basin, some 450 km upstream of the Denmark Strait, advecting overflow water and surface freshwater away from the boundary. This “separated EGC” flows southward adjacent to the previously identified North Icelandic Jet, indicating that approximately 70% of the Denmark Strait Overflow Water approaches the sill along the Iceland continental slope. Roughly a quarter of the freshwater transport of the EGC is diverted offshore via the bifurcation. Two hypotheses are examined to explain the existence of the separated EGC. The atmospheric fields demonstrate that flow distortion due to the orography of Greenland imparts significant vorticity into the ocean in this region. The negative wind stress curl, together with the closed bathymetric contours of the Blosseville Basin, is conducive for spinning up an anti-cyclonic gyre whose offshore branch could represent the separated EGC. An idealized numerical simulation suggests instead that the current is primarily eddy-forced. In particular, baroclinic instability of the model EGC spawns large anticyclones that migrate offshore and coalesce upon reaching the Iceland continental slope, resulting in the separated EGC. Regardless of the formation mechanism, the recently obtained shipboard data and historical hydrography both indicate that the separated EGC is a permanent feature of the circulation north of the Denmark Strait.
    Description: Support for this work was provided by the Norwegian Research Council (KV), the European Union 7th Framework Programme (FP7 2007-2013) under grant agreement n.308299 NACLIM Project (KV), US National Science Foundation grants OCE-0959381 (RP, MS, DT) and OCE-0850416 (MS), and the Natural Sciences and Engineering Research Council of Canada (KM).
    Keywords: Denmark Strait ; East Greenland Current ; North Icelandic Jet ; Blosseville Basin ; Denmark Strait Overflow Water ; Arctic freshwater export
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 2
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 39 (2012): L18806, doi:10.1029/2012GL053097.
    Description: On a variety of spatial and temporal scales, the energy transferred by air-sea heat and moisture fluxes plays an important role in both atmospheric and oceanic circulations. This is particularly true in the sub-polar North Atlantic Ocean, where these fluxes drive water-mass transformations that are an integral component of the Atlantic Meridional Overturning Circulation (AMOC). Here we use the ECMWF Interim Reanalysis to provide a high-resolution view of the spatial structure of the air-sea turbulent heat fluxes over the sub-polar North Atlantic Ocean. As has been previously recognized, the Labrador and Greenland Seas are areas where these fluxes are large during the winter months. Our particular focus is on the Iceland Sea region where, despite the fact that water-mass transformation occurs, the winter-time air-sea heat fluxes are smaller than anywhere else in the sub-polar domain. We attribute this minimum to a saddle point in the sea-level pressure field, that results in a reduction in mean surface wind speed, as well as colder sea surface temperatures associated with the regional ocean circulation. The magnitude of the heat fluxes in this region are modulated by the relative strength of the Icelandic and Lofoten Lows, and this leads to periods of ocean cooling and even ocean warming when, intriguingly, the sensible and latent heat fluxes are of opposite sign. This suggests that the air-sea forcing in this area has large-scale impacts for climate, and that even modest shifts in the atmospheric circulation could potentially impact the AMOC.
    Description: GWKM was supported by the Natural Science and Engineering Research Council of Canada. IAR was funded in part by NCAS (the National Centre for Atmospheric Sciences) and by NERC grant NE/I005293/1. RSP was funded by grant OCE-0959381 fromthe US National Science Foundation.
    Description: 2013-03-27
    Keywords: Air-sea interaction ; Climate variability ; Water mass transformation
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/msword
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  • 3
    Publication Date: 2022-10-11
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Våge, K., Semper, S., Valdimarsson, H., Jónsson, S., Pickart, R., & Moore, G. Water mass transformation in the Iceland Sea: contrasting two winters separated by four decades. Deep Sea Research Part I: Oceanographic Research Papers, 186, (2022): 103824, https://doi.org/10.1016/j.dsr.2022.103824.
    Description: Dense water masses formed in the Nordic Seas flow across the Greenland–Scotland Ridge and contribute substantially to the lower limb of the Atlantic Meridional Overturning Circulation. Originally considered an important source of dense water, the Iceland Sea gained renewed interest when the North Icelandic Jet — a current transporting dense water from the Iceland Sea into Denmark Strait — was discovered in the early 2000s. Here we use recent hydrographic data to quantify water mass transformation in the Iceland Sea and contrast the present conditions with measurements from hydrographic surveys conducted four decades earlier. We demonstrate that the large-scale hydrographic structure of the central Iceland Sea has changed significantly over this period and that the locally transformed water has become less dense, in concert with a retreating sea-ice edge and diminished ocean-to-atmosphere heat fluxes. This has reduced the available supply of dense water to the North Icelandic Jet, but also permitted densification of the East Greenland Current during its transit through the presently ice-free western Iceland Sea in winter. Together, these changes have significantly altered the contribution from the Iceland Sea to the overturning in the Nordic Seas over the four decade period.
    Description: Support for this work was provided by the Trond Mohn Foundation, Norway under grant BFS2016REK01 (K.V. and S.S.), the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 101022251 (S.S.), the US National Science Foundation under grants OCE-1259618 and OCE- 1948505 (R.S.P), and the Natural Sciences and Engineering Research Council of Canada (G.W.K.M).
    Keywords: Iceland Sea ; Water mass transformation ; North Icelandic Jet ; Iceland–Faroe Slope Jet ; East Greenland Current ; Denmark Strait overflow water
    Repository Name: Woods Hole Open Access Server
    Type: Article
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