eCite Digital Repository

Detecting and characterizing Ekman currents in the Southern Ocean


Roach, CJ and Phillips, HE and Bindoff, NL and Rintoul, SR, Detecting and characterizing Ekman currents in the Southern Ocean, Journal of Physical Oceanography, 45, (5) pp. 1205-1223. ISSN 0022-3670 (2015) [Refereed Article]


Copyright Statement

© Copyright 2015 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be ďfair useĒ under Section 107 of the U.S. Copyright Act September 2010 Page 2 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC ß108, as revised by P.L. 94-553) does not require the AMSís permission. Republication, systematic reproduction, posting in electronic form, such as on a web site or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. Additional details are provided in the AMS Copyright Policy, available on the AMS Web site located at ( or from the AMS at 617-227-2425 or

DOI: doi:10.1175/JPO-D-14-0115.1


This study presents a unique array of velocity profiles from Electromagnetic Autonomous Profiling Explorer (EM-APEX) profiling floats in the Antarctic Circumpolar Current (ACC) north of Kerguelen. The authors use these profiles to examine the nature of Ekman spirals, formed by the action of thewind on the oceanís surface, in light of Ekmanís classical linear theory and more recent enhancements. Vertical decay scales of the Ekman spirals were estimated independently from current amplitude and rotation. Assuming a vertically uniform geostrophic current, decay scales from the Ekman current heading were twice as large as those from the current speed decay, indicating a compressed spiral, consistent with prior observations and violating the classical theory. However, if geostrophic shear is accurately removed, the observed Ekman spiral is as predicted by classical theory and decay scales estimated from amplitude decay and rotation converge toward a common value. No statistically robust relationship is found between stratification and Ekman decay scales. The results indicate that compressed spirals observed in the Southern Ocean arise from aliasing of depth-varying geostrophic currents into the Ekman spiral, as opposed to surface trapping of Ekman currents associated with stratification, and extends the geographical area of similar results from Drake Passage (Polton et al. 2013). Accounting for this effect, the authors find that constant viscosity Ekman models offer a reasonable description of momentum mixing into the upper ocean in the ACC north of Kerguelen. These results demonstrate the effectiveness of a new method and provide additional evidence that the same processes are active for the entire Southern Ocean.

Item Details

Item Type:Refereed Article
Keywords:Southern Ocean, air-sea interaction, Ekman spiral, EM-APEX, SOFINE, Kerguelen, Antarctic Circumpolar Current, ACC
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Physical oceanography
Objective Division:Environmental Policy, Climate Change and Natural Hazards
Objective Group:Understanding climate change
Objective Field:Climate variability (excl. social impacts)
UTAS Author:Roach, CJ (Dr Christopher Roach)
UTAS Author:Phillips, HE (Associate Professor Helen Phillips)
UTAS Author:Bindoff, NL (Professor Nathan Bindoff)
UTAS Author:Rintoul, SR (Dr Steve Rintoul)
ID Code:99058
Year Published:2015
Funding Support:Australian Research Council (DP0877098)
Web of Science® Times Cited:10
Deposited By:IMAS Research and Education Centre
Deposited On:2015-03-12
Last Modified:2019-05-02
Downloads:253 View Download Statistics

Repository Staff Only: item control page