[A-AS03] [EE] International Field Campaign - Years of the Maritime Continent (YMC)

[AAS03-P02] Drastic deepening of the barrier layer off the western coast of Sumatra
due to the MJO passage during the Pre-YMC

*Qoosaku Moteki¹, Kunio Yoneyama¹, Masaki Katsumata¹, Kentaro ANDO¹, Takuya Hasegawa¹ (1.Department of Coupled Ocean-Atmosphere-Land Processes Research, Japan Agency for Marine-Earth Science and Technology)

Keywords:barrier layer, MJO

Drastic deepening of the barrier layer off the western coast of Sumatra
(4°S, 102°E, 800 m depth) due to the MJO passage observed during
December 2015 is investigated. The Research Vessel Mirai observation
captured the drastic increase of isothermal depth from 20 m to 100 m
for only 4 days due to the westerly burst (5-9 m/s) associated with
the MJO. While, the mixed layer was deepened from 10 m to 40 m because
of the strong stratification of the salinity in the ocean surface
layer. As a result, the barrier layer depth was deepened from 10 m to
80 m. This drastic deepening of the barrier layer was associated with
the increase of turbulent energy dissipation rate. Because the current
speed in the surface layer off the western coast of Sumatra was very
slower (less than 20 cm/s) than that over the open ocean (more than 50
cm/s), the vertical mixing due to the westerly burst could be a main
factor for the barrier layer deepening.