Atlantic Water properties and circulation north of Svalbard in a changing Arctic

Abstract : The Atlantic Water (AW) inflow is crucial for the heat and salt budget of the Arctic. This PhD thesis brings new insights to the inflow of AW in the area north of Svalbard.The IAOOS (Ice Atmosphere Ocean Observing System) platforms were deployed during the N-ICE2015 expedition which gathered the first winter hydrographic data in the area. They document shallow warm water over the Svalbard continental slope that melts sea ice with ice-ocean heat fluxes reaching up to 400W.m-2. Heat is brought from the AW layer up to the surface through near-inertial waves generated by winter storms, large barotropic tides over steep topography and/or geostrophic adjustments. Sea ice extent largely differs between winters 2015 and 2016. 1/12° operational model outputs from Mercator-Ocean suggest that convection-induced upward heat fluxes explain the differences. Model outputs are also used to examine the AW inflow pathways : besides the Svalbard Branch and the Yermak Branch, the model shows an AW winter pathway not much documented before : the Yermak Pass Branch across the Yermak Plateau. Finally, the model suggests an important mesoscale activity throughout the AW flow. The Yermak Pass Branch properties are examined using one-year (2007-2008) of moored ADCP data in the Yermak Pass. The flow is largely dominated by tides. In winter, baroclinic eddies of AW with a periodicity of 5 to 10 days and pulses of AW monthly/bimonthly are found, carrying AW eastward through the Pass. Model outputs suggest that the Yermak Pass Branch is a robust winter pattern over the last 10 years, carrying on average 31% of the volume transport of the West Spitsbergen Current.
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Zoé Koenig. Atlantic Water properties and circulation north of Svalbard in a changing Arctic. Oceanography. Université Pierre et Marie Curie - Paris VI, 2017. English. ⟨NNT : 2017PA066306⟩. ⟨tel-01721467v1⟩

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