10:15 AM - 10:30 AM
[AOS16-06] The vertical structure of near inertial internal waves in the Japan Sea
Keywords:internal wave, the Japan Sea
The Japan Sea has a unique thermohaline circulation system, isolated from the North Pacific. The dense water sunken in the northwestern area spreads into the abyssal Japan Sea forming the Japan Sea Proper Water (JSPW). The JSPW is water mass with very narrow temperature and salinity ranges below the thermocline. The upwelling process of the JSPW is unclear, although vertical mixing in the deep sea is believed to be an important factor.
In the Yamato Basin, the southeastern area of the sea, a significant vertical diffusivity has been estimated from a box model analysis (4.03 ×10–3 m2s–1 (Senjyu et al., 2005)). In addition, dominant near-inertial internal waves (NIWs) have been observed in the abyssal Japan Sea using moored current meters. Recently, Senjyu and Shin (2021) revealed a bottom intensified structure of NIWs in the southern basins. They tried to explain the flow intensification by the superposition of upward and downward propagating NIWs. However, they could not observe the node and loop structures in the flow field. Therefore, to validate and confirm Senjyu and Shin (2021)'s hypothesis, we conducted mooring observations in the Yamato Basin with six current meters from October 3, 2019 to November 15, 2020.
The bottom intensified NIWs were observed through the observation layers, especially in the winter season. Since this vertical structure has been suggested to be the superposition of upward- and downward- propagating NIWs, we formally decomposed eastward and northward current into upward- and downward- phase propagating NIWs. The current of borh directions of propagation had no intensification nor weakening. This result supported the Senjyu and Shin (2021)'s hypothesis.
In the Yamato Basin, the southeastern area of the sea, a significant vertical diffusivity has been estimated from a box model analysis (4.03 ×10–3 m2s–1 (Senjyu et al., 2005)). In addition, dominant near-inertial internal waves (NIWs) have been observed in the abyssal Japan Sea using moored current meters. Recently, Senjyu and Shin (2021) revealed a bottom intensified structure of NIWs in the southern basins. They tried to explain the flow intensification by the superposition of upward and downward propagating NIWs. However, they could not observe the node and loop structures in the flow field. Therefore, to validate and confirm Senjyu and Shin (2021)'s hypothesis, we conducted mooring observations in the Yamato Basin with six current meters from October 3, 2019 to November 15, 2020.
The bottom intensified NIWs were observed through the observation layers, especially in the winter season. Since this vertical structure has been suggested to be the superposition of upward- and downward- propagating NIWs, we formally decomposed eastward and northward current into upward- and downward- phase propagating NIWs. The current of borh directions of propagation had no intensification nor weakening. This result supported the Senjyu and Shin (2021)'s hypothesis.