Determining a sub-mesoscale diffusivity using a roughness measure applied to a tracer release experiment in the Southern Ocean.

• Published in: Journal of Physical Oceanography
• Main Authors: Watson, Andrew J., Boland, EJD, Shuckburgh, E, Haynes, PH, Ledwell, JR, Messias, MJ
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Meteorological Society 2015
• Subjects: Geographic location/entity; Southern Ocean; Circulation/ Dynamics; Diffusion; Physical Meteorology and Climatology; Isopycnal mixing; Observational techniques and algorithms; Tracers; Models and modeling; Model comparison; Antarctic; Drake Passage; Pacific; The Antarctic; Antarc*
• Online Access: http://hdl.handle.net/10871/17645; https://doi.org/10.1175/JPO-D-14-0047.1

Article © 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 “fair use” 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 §108, as revised by P.L. 94-553) does not require the AMS’s 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 (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or [e-mail]. The use of a measure to diagnose submesoscale isopycnal diffusivity by determining the best match between observations of a tracer and simulations with varying small-scale diffusivities is tested. Specifically, the robustness of a “roughness” measure to discriminate between tracer fields experiencing different submesoscale isopycnal diffusivities and advected by scaled altimetric velocity fields is investigated. This measure is used to compare numerical simulations of the tracer released at a depth of about 1.5 km in the Pacific sector of the Southern Ocean during the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) field campaign with observations of the tracer taken on DIMES cruises. The authors find that simulations with an isopycnal diffusivity of ~20 m2 s−1 best match observations in the Pacific sector of the Antarctic Circumpolar Current (ACC), rising to ~20–50 m2 s−1 through Drake Passage, representing submesoscale processes and any mesoscale processes unresolved by the advecting altimetry fields. The roughness measure is ...