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Critical Role of Continental Slopes in Halocline and Eddy Dynamics of the Ekman-Driven Beaufort Gyre

Manucharyan, G. E. and Isachsen, P. E. (2019) Critical Role of Continental Slopes in Halocline and Eddy Dynamics of the Ekman-Driven Beaufort Gyre. Journal of Geophysical Research. Oceans, 124 (4). pp. 2679-2696. ISSN 2169-9275. https://resolver.caltech.edu/CaltechAUTHORS:20190606-084354650

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Abstract

The Beaufort Gyre (BG) is a large‐scale bathymetrically constrained circulation driven by a surface Ekman convergence that creates a bowl‐shaped halocline and stores a significant portion of the Arctic Ocean's freshwater. Theoretical studies suggest that in the gyre interior, the halocline is equilibrated by a balance between Ekman pumping and counteracting mesoscale eddy transport energized by baroclinic instability. However, the strongest anticyclonic flows occur over steep continental slopes, and, despite bathymetric slopes being known to influence baroclinic instability, their large‐scale impacts on BG halocline remain unexplored. Here we use an idealized eddy‐resolving BG model to demonstrate that the existence of continental slopes dramatically affects key gyre characteristics leading to deeper halocline, stronger anticyclonic circulation, and prolonged equilibration. Over continental slopes, the magnitude of the Eulerian mean circulation is dramatically reduced due to the Ekman overturning being compensated by the eddy momentum‐driven overturning. The eddy thickness flux overturning associated with lateral salt transport is also weakened over the slopes, indicating a reduction of eddy thickness diffusivity despite the isopycnal slopes being largest there. Using a theoretical halocline model, we demonstrate that it is the localized reduction in eddy diffusivity over continental slopes that is critical in explaining the halocline deepening and prolonged equilibration time. Our results emphasize the need for observational studies of eddy overturning dynamics over continental slopes and the development of slope‐aware mesoscale eddy parameterizations for low‐resolution climate models.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1029/2018JC014624DOIArticle
ORCID:
AuthorORCID
Manucharyan, G. E.0000-0001-7959-2675
Isachsen, P. E.0000-0003-1249-3052
Additional Information:© 2019 American Geophysical Union. Received 1 OCT 2018; Accepted 26 FEB 2019; Accepted article online 12MAR 2019; Published online 16 APR 2019. All information necessary to reproduce the numerical experiments and data analysis is present in the paper and requires the use of publicly available software. G. E. M. acknowledges support from the Stanback Postdoctoral Fellowship at Caltech. P. E. I. was partially funded by grant 221780 (NorSEE) from the Research Council of Norway. This work used the Extreme Science and Engineering Discovery Environment (XSEDE; Towns et al., 2014), which is supported by NSF grant ACI‐1053575. The manuscript benefited from discussions at the annual Forum for Arctic Modeling and Observing Synthesis (FAMOS) funded by the NSF OPP award PLR‐1313614 and PLR‐1203720. The authors thank John Marshall and an anonymous reviewer for their insightful comments.
Funders:
Funding AgencyGrant Number
Coco and Foster Stanback Postdoctoral Fellowship in Global Environmental ScienceUNSPECIFIED
Research Council of Norway221780
NSFACI‐1053575
NSFPLR‐1313614
NSFPLR‐1203720
Subject Keywords:Beaufort Gyre; mesoscale eddies; freshwater content; halocline; eddy‐mean flow interactions; continental slopes
Issue or Number:4
Record Number:CaltechAUTHORS:20190606-084354650
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190606-084354650
Official Citation:Manucharyan, G. E., & Isachsen, P. E. ( 2019). Critical role of continental slopes in halocline and eddy dynamics of the Ekman‐driven Beaufort Gyre. Journal of Geophysical Research: Oceans, 124, 2679– 2696. https://doi.org/10.1029/2018JC014624
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96184
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:06 Jun 2019 22:30
Last Modified:04 Oct 2019 21:35

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