Seasonality of Four Types of Baroclinic Instability in the Global Oceans

Distinct geographical distributions of four types of mesoscale baroclinic instabilities (BCIs) exist in the global oceans, implying preferences of surface or subsurface mesoscale eddies to specific regions. This study explores seasonal variations of global BCI types and their dependence on varying b...

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Bibliographic Details
Published in:Journal of Geophysical Research: Oceans
Main Authors: Feng, Ling, Liu, Chuanyu, Koehl, Armin, Wang, Fan
Format: Report
Language:English
Published: AMER GEOPHYSICAL UNION 2022
Subjects:
seasonal variability
baroclinic instability types
baroclinic energy conversion rate
mesoscale eddies
Oceanography
Antarctic
The Antarctic
Pacific
Antarc*
Online Access:http://ir.qdio.ac.cn/handle/337002/179368
http://ir.qdio.ac.cn/handle/337002/179369
https://doi.org/10.1029/2022JC018572
Description
Summary:Distinct geographical distributions of four types of mesoscale baroclinic instabilities (BCIs) exist in the global oceans, implying preferences of surface or subsurface mesoscale eddies to specific regions. This study explores seasonal variations of global BCI types and their dependence on varying background ocean states with a focus on three representative regions. First, the regions of the Kuroshio Extension and Gulf Stream are representative for distinctive seasonal transition of BCI types: the Charney surface BCIs prevail in winter, while the Phillips BCIs prevail in summer, which is controlled by weak (strong) upper-layer stratification in winter (summer) but is less impacted by the seasonal changes in the mean flow-induced shear. Second, the region covering both the tropics and subtropics of the North Pacific (10 degrees N-35 degrees N) is representative for seasonal meridional migration of the border between the domains of the Phillips and the Charney surface BCIs; their border migrates equatorward (poleward) in spring and summer (autumn and winter), which is primarily caused by the equatorward (poleward) shift of both the North Equatorial Current and the Subtropical Countercurrent in spring and summer (autumn and winter), and is secondarily modulated by the variation in the upper-layer stratification. Third, the Antarctic Circumpolar Current region is chosen to represent a weak seasonal variation of BCIs. Those seasonal variations in BCI types are further demonstrated as being associated with seasonal variations of baroclinic conversion rate, implying possible generation of corresponding eddies.

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