Modulation of Mode-Water Eddies on Upper Ocean Responses to Tropical Cyclones

The modulation of anticyclonic subsurface-intensified mode-water eddies (MWEs) on the oceanic physical and biological responses to tropical cyclones (TCs) is investigated using satellite measurements, in situ observations and numerical model outputs. Extreme cooling of the surface (4.2°C) and mixed-layer (2.3°C) is observed in a MWE, which can be remarkably stronger than those in adjacent cyclonic eddy and non-eddy environments. The special thermodynamic structure above the lens of MWEs, which would favor the TC-induced entrainment more efficiently, facilitates the elevation of substantial subsurface cold water. It also leads to increased mixed-layer salinity and deepening of the mixed-layer. Additionally, variations in nitrate and chlorophyll-a concentrations appear to be depressed and exhibit intricate multi-layer patterns due to TC-induced and MWE-influenced vertical processes. This study provides novel insights into the interactions between TCs and subsurface-intensified eddies.