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Global observations of horizontal mixing from Argo float and surface drifter trajectories

Citation

Roach, CJ and Balwada, D and Speer, K, Global observations of horizontal mixing from Argo float and surface drifter trajectories, Journal of Geophysical Research: Oceans, 123, (7) pp. 4560-4575. ISSN 2169-9275 (2018) [Refereed Article]


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Copyright Statement

2018. American Geophysical Union. All Rights Reserved.

DOI: doi:10.1029/2018JC013750

Abstract

Mixing by mesoscale eddies in the ocean plays a major role in setting the distribution of oceanic tracers, with important implications for physical and biochemical systems at local to global scales. Roach et al. (2016; https://doi.org/10.1002/2015JC011440) demonstrated that a two‐particle analysis of Argo trajectories produces robust estimates of horizontal mixing in the Southern Ocean. Here we extend this analysis to produce global 1נ1 maps of eddy diffusivity at the nominal Argo parking depth of 1,000m. We also applied this methodology to estimate surface eddy diffusivities from Global Drifter Program (GDP) surface drifters. The global mean eddy diffusivity was 543155m2/s at 1,000m and 2637311m2/s at the surface, with elevated diffusivities in regions of enhanced eddy kinetic energy, such as western boundary currents and along the Antarctic Circumpolar Current. The eddy kinetic energy at the equator is high at both the surface and depth, but the eddy diffusivity is only enhanced near the surface. At depth the eddy diffusivity is strongly suppressed due to the presence of mean flow. We used our observational estimates to test the validity of an eddy diffusivity parameterization that accounts for mixing suppression in the presence of zonal mean flows. Our results indicated that this parameterization generally agrees with the directly observed eddy diffusivities in the midlatitude and high‐latitude oceans.

Item Details

Item Type:Refereed Article
Keywords:eddy, mixing, eddy diffusivity, Argo
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Physical oceanography
Objective Division:Environmental Management
Objective Group:Marine systems and management
Objective Field:Oceanic processes (excl. in the Antarctic and Southern Ocean)
UTAS Author:Roach, CJ (Dr Christopher Roach)
ID Code:126945
Year Published:2018
Web of Science® Times Cited:15
Deposited By:Oceans and Cryosphere
Deposited On:2018-07-04
Last Modified:2018-11-27
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