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    Bottom Friction in a Baroclinic Ocean: Influences on Sea Level and Slope Currents


    Diabaté, Sam Tiéfolo, Fraser, Neil J. and McCarthy, Gerard D. (2026) Bottom Friction in a Baroclinic Ocean: Influences on Sea Level and Slope Currents. Journal of Physical Oceanography, 56 (5). pp. 1125-1145. ISSN 0022-3670

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    Abstract

    In the flat-bottomed open ocean, the seawater density distribution yields alone the existence of geostrophic baroclinic currents and steric sea-level spatial changes. However, at basin margins, the bathymetry exerts a considerable control on both these quantities. Indeed, the steric sea level vanishes at the coast where depth is zero. Also, continental slopes are vorticity barriers hindering convergence (divergence) of baroclinic transport toward the coast and accumulation (removal) of water there. In the limit of no temporal development, how the coastal sea level is impacted by open-ocean density changes is hence nontrivial and must involve ageostrophic mechanisms. Here, we focus on bottom friction as one such process, provide derivations extending the arrested topographic wave theories to a fully baroclinic ocean, and discuss an application for an eastern boundary margin (representative of the Rockall Slope Current region, for example). We demonstrate that open-ocean density changes yield important joint effect of baroclinicity and relief (JEBAR) along-slope currents, which generate cross-slope Ekman currents due to friction with the seabed. The latter are associated with divergence and convergence leading to sea-level changes above the slope, mediated to the coast via coastally trapped waves. Through this process, not only the coastal sea level is modified but also the along-slope currents are slowed down to well-known asymptotical solutions. Hence, our results link modern theoretical developments in sea-level research and past analytical studies of slope currents. Our effort describes the fundamental notions, and we anticipate it paves the way for more sophisticated works.
    Item Type: Article
    Additional Information: The authors thank the two anonymous reviewers, who helped improve the manuscript. The authors express their thanks to Dr. Sam Jones for providing his reconstruction of the density field along the 1000-m isobath in the subpolar North Atlantic. S. T. Diabaté wishes to express his thanks to Louis Marié, Robert Marsh, Jamie Pringle, Steven Lentz, Robin Waldman, and Christopher Piecuch for the interesting discussions on JEBAR and ATW theories. N. J. Fraser and S. T. Diabaté were supported by the U.K. Natural Environment Research Council (NERC) Grants U.K.-OSNAP (NE/K010700/1) and ODISSEA (NE/Y005236/1). N. J. Fraser was further supported by SNAP-DRAGON (NE/T013494/1) and NERC program AtlantiS (NE/Y005589/1). S. T. Diabaté and G. D. McCarthy were supported by the A4 project (Grant-Aid Agreement PBA/CC/18/01), which is carried out with the support of the Marine Institute under the Marine Research Programme funded by the Irish Government. Furthermore, the research of S. T. Diabaté was in part supported by the U.K. Natural Environment Research Council National Capability funding (NE/R015953/1), and this study is a contribution to the Climate Linked Atlantic Sector Science (CLASS) program.
    Keywords: Sea level; Boundary currents; Continental shelf/slope; Ageostrophic circulations; Baroclinic flows; Barotropic flows;
    Academic Unit: Faculty of Social Sciences > Geography
    Faculty of Social Sciences > Research Institutes > Irish Climate Analysis and Research Units, ICARUS
    Item ID: 21909
    Identification Number: 10.1175/JPO-D-24-0163.1
    Depositing User: ICARUS Geography
    Date Deposited: 06 Oct 2026 14:31
    Journal or Publication Title: Journal of Physical Oceanography
    Publisher: American Meteorological Society
    Refereed: Yes
    Use Licence: This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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