The vertical heat transport of internal solitary waves over the continental slope in the northern South China Sea

Abstract

An integrated analysis of internal solitary wave (ISW) observations obtained from two moorings over the continental slope in the northern South China Sea (SCS) leads to an assessment of the vertical heat transport of the ISWs. The clusters of ISW packets are phase-locked to the fortnightly cycle of the semidiurnal tide. The ISWs appear during large semidiurnal tides, and there is a period of 5–6 d when no ISWs are observed. The effect of the ISWs on the continental slope heat budget is observed. The ISWs can modify a local temperature field in which the temperature in the upper layer can be changed by O (100) °C after the ISWs passed the mooring. Both ISWinduced diffusion and ISW-induced advection contribute to the temperature variation. The estimates imply an average vertical heat flux of 0.01 to 0.1 MW/m2 in the ISWs in the upper 500 m of the water column. The vertical heat transport ranges from 0.56 to 2.83 GJ/m2 with a mean value of 1.63 GJ/m2. The observations suggest that the vertical heat transport is proportional to the maximum vertical displacement.