[A-CG42] Science in the Arctic Region

[ACG42-P07] Turbulent mixing enhanced by the lee wave over the Chukchi Plateau, Arctic

*EunYae Son¹, Yusuke Kawaguchi ¹ (1.Atmosphere and Ocean Research Institute, University of Tokyo)

Keywords:Lee wave, Turbulent mixing, Arctic Ocean

The Arctic Ocean is known for the modest turbulent energy in the ocean due to a lack of energy input from the atmosphere by the insulation effects of the sea ice. Instead, the bottom topography could encourage the local enhancement in turbulence. This study aims to reveal the possible processes for the enhanced turbulent mixing due to topographic effects responding to barotropic currents in the Arctic Ocean. For the aim, we conducted field observations during summer of 2019 and 2020 using R/V “Mirai”. Vertical profiles of temperature and salinity of seawater, obtained in the southern Chukchi Plateau, showed strong spatial differences in turbulent mixing. Turbulence dissipation rate, that is estimated from microscale shear of TurboMAP observations, varying by 10 to 100 times stronger over the Chukchi Plateau compared to that in the rest of the Canada Basin. From the shipboard ADCP observation, we had a clear signal of lee waves along the lower pycnocline at depth of 150 m, where the cross-ridge barotropic current was typically 0.4 m s^-1or greater in magnitude. Regarding the barotropic flow regime near the study area, we analyzed the moored ADCP velocity from 2010 to 2012 that is deployed in the vicinity of Chukchi Plateau. The velocity data showed cross-ridge (eastward current) dominates summer to early autumn with the speed at 0.2 m s^-1. On the other hand, the cross-ridge current disappears in other seasons. We anticipate that the lee wave feature could dominate during summer to early autumn.