The Scale and Activity of Symmetric Instability Estimated from a Global Submesoscale-Permitting Ocean Model

Journal Article · 30 April 2021 · Journal of Physical Oceanography

DOI: https://doi.org/10.1175/JPO-D-20-0159.1 · OSTI ID:2375543

Dong, Jihai  ^[1]; Fox-Kemper, Baylor ^[2]; Zhang, Hong ^[3]; Dong, Changming ^[1]

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1. a School of Marine Sciences, Nanjing University of Information Science and Technology, Nanjing, Jiangsu, China, b Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, Guangdong, China
2. c Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, Rhode Island
3. d Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California

Abstract Symmetric instability (SI) extracts kinetic energy from fronts in the surface mixed layer (SML), potentially affecting the SML structure and dynamics. Here, a global submesoscale-permitting ocean model named MITgcm LLC4320 simulation is used to examine the Stone linear prediction of the maximum SI scale to estimate grid spacings needed to begin resolving SI. Furthermore, potential effects of SI on the usable wind work are estimated roughly: this estimate of SI “activity” is useful for assessing if these modes should be resolved or parameterized. The maximum SI scale varies by latitude with median values from 568 to 23 m. Strong seasonality is observed in the SI scale and activity. The median scale in winter is 188 m globally, 2.5 times of that of summer (75 m). SI is more active in winter: 15% of the time compared with 6% in summer. The strongest SI activity is found in the western Pacific, western Atlantic, and Southern Oceans. The required grid spacings for a global model to begin resolving SI eddies in the SML are 24 m (50% of regions resolved) and 7.9 m (90%) in winter, decreasing to 9.4 m (50%) and 3.6 m (90%) in summer. It is also estimated that SI may reduce usable wind work by an upper bound of 0.83 mW m ⁻² globally, or 5% of the global magnitude. The sensitivity of these estimates to empirical thresholds is provided in the text.

• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Office of Naval Reactors
• OSTI ID: 2375543
• Journal Information: Journal of Physical Oceanography, Journal Name: Journal of Physical Oceanography Journal Issue: 5 Vol. 51; ISSN 0022-3670
• Publisher: American Meteorological SocietyCopyright Statement
• Country of Publication: United States
• Language: English