Coupled atmosphere-ocean observations of a cold air outbreak and its impact on the Iceland Sea

Renfrew, Ian A. ORCID:, Huang, Jie, Semper, Stefanie, Barrell, Christopher, Terpstra, Annick, Pickard, Robert S., Våge, Kjetil, Elvidge, Andrew D. ORCID:, Spengler, Thomas, Strehl, Anna-Marie and Weiss, Alexandra (2022) Coupled atmosphere-ocean observations of a cold air outbreak and its impact on the Iceland Sea. Quarterly Journal of the Royal Meteorological Society. ISSN 0035-9009

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Marine cold air outbreaks are vigorous equatorward excursions of cold air over the ocean, responsible for the majority of wintertime oceanic heat loss from the subpolar seas of the North Atlantic. However, the impact of individual cold air outbreak (CAO) events on the ocean is poorly understood. Here we present the first coupled observations of the atmosphere and ocean during a wintertime CAO event, between 28 February and 13 March 2018, in the subpolar North Atlantic region. Comprehensive observations are presented from five aircraft flights, a research vessel, a meteorological buoy, a subsurface mooring, an ocean glider, and an Argo float. The CAO event starts abruptly with substantial changes in temperature, humidity, and wind throughout the atmospheric boundary layer. The CAO is well-mixed vertically and, away from the sea-ice edge, relatively homogeneous spatially. During the CAO peak, higher sensible heat fluxes occupy at least the lowest 200 m of the atmospheric boundary layer, while higher latent heat fluxes are confined to the surface layer. The response of the ocean to the CAO is spatially dependent. In the interior of the Iceland Sea the mixed layer cools, while in the boundary current region it warms. In both locations, the mixed layer deepens and becomes more saline. Combining our observations with one-dimensional mixed-layer modelling, we show that in the interior of the Iceland Sea, atmospheric forcing dominates the ocean response. In contrast, in the boundary current region lateral advection and mixing counteract the short-term impact of the atmospheric forcing. Time series observations of the late-winter period illustrate a highly variable ocean mixed layer, with lateral advection and mixing often masking the ocean's general cooling and deepening response to individual CAO events.

Item Type: Article
Additional Information: Funding information: Norges Forskningsråd (GrantNumber(s): 280573 and 227777); Trond Mohn Foundation (GrantNumber(s): BFS2016REK01); Natural Environment Research Council (GrantNumber(s): NE/N009754/1); Sixth Framework Programme (GrantNumber(s): 608695 and 101022251)
Uncontrolled Keywords: sdg 14 - life below water ,/dk/atira/pure/sustainabledevelopmentgoals/life_below_water
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: LivePure Connector
Date Deposited: 09 Jan 2023 13:32
Last Modified: 16 Jan 2023 01:52
DOI: 10.1002/qj.4418

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