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Net Modulation of Upper Ocean Thermal Structure by Typhoon Kalmaegi (2014)

2018-10-08

Zhang, H., R. Wu, D. Chen, X. Liu, H. He, Y. Tang, D. Ke, Z. Shen, J. Li, J. Xie, D. Tian, J. Ming, F. Liu, D. Zhang and W. Zhang. Net Modulation of Upper Ocean Thermal Structure by Typhoon Kalmaegi (2014). Journal of Geophysical Research: Oceans, 2018, 123(10): 7154-7171.


In situ observation of a buoys/moorings array and a model simulation were used to study the modulation of upper ocean thermal structure by Typhoon Kalmaegi in September 2014. The inertial period signals were significant after forcing of Kalmaegi, but they did not account for the net heat change. Removing the inertial period signals showed that the net thermal response biased to the right of Kalmaegi’s track. Vertical mixing caused surface cooling with an inverted-cone structure and subsurface warming with a double-wing structure. Net upwelling converted the left wing of the subsurface warming to cooling, while net downwelling warmed the upper ocean in front and on both sides of the net upwelling zone. Horizontal advection was not as important as vertical mixing and vertical advection in modulating the thermal structure but contributed to the net outward advection of thermal anomaly in the mixed layer during the forced stage and also in the net along-track recovery of subsurface anomaly during the relaxation stage. In general, horizontal and vertical advection modulated thermal anomalies in the upper ocean across a broader horizontal range and into the deeper ocean compared with the effect of vertical mixing. Our results indicate the need to consider both mixing and advection (rather than only mixing) when studying the effects of tropical cyclones on local ocean heat uptake and global ocean heat transport.

 

Figure 1. Average temperature change after Kalmaegi caused by (a) mixing, (c) vertical advection, and (e) horizontal advection, and (b, d, f) the corresponding heat change above 160 m. Black dashed lines are positions of different stations.