EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Symmetric Instability and Ageostrophic Secondary Circulation in the East Korea Warm Current

Seongjung Kim1, Young-Tae Son2, and SungHyun Nam1,3
Seongjung Kim et al.
  • 1Seoul National University, Collage of Natural Science , Earth and Environmental Science , Republic of Korea (
  • 2Geosystem Research Cooperation, Republic of Korea
  • 3Seoul National University, Collage of Natural Science , Research Institute of Oceanography,

Submesoscale dynamics and ocean-atmosphere exchange process in frontal regions play an important role in regulating ocean overturning circulation and cycles of materials (including carbon) and energy, yet our understanding on the dynamics is limited primarily due to lack of relevant observation. To investigate frontal processes such as symmetric instability (SI) and ageostrophic secondary circulation (ASC), multiple comprehensive hydrographic and current observations were made with marine meteorological measurements across a sharp front of the East Korea Warm Current (EKWC) over spring 2017, summer 2017 and fall 2018. Submesoscale features were identified from the observations, estimating diagnostic variables that are the Ertel’s potential vorticity (fq), balanced Richardson number angle ( ), and Ekman buoyancy flux (EBF). The results with fq < 0 along the front,  corresponding to SI regime, and enhanced EBF along the surface of front support that submesoscale overturning circulation induced by down-front wind is due to the SI and ASC. The ASCs with ageostrophic current estimated using the Omega equations further provide vertical motions in the vicinity of the front. Our results suggest that the western boundary currents like EKWC within the North Pacific marginal sea strongly interact with local wind to impact submesoscale overturning circulation and (re-)distribution of materials via SI and ASC.

How to cite: Kim, S., Son, Y.-T., and Nam, S.: Symmetric Instability and Ageostrophic Secondary Circulation in the East Korea Warm Current, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3192,, 2020