5:15 PM - 6:45 PM
[AOS14-P08] Effects of Eddies on the Formation and Subduction of North Pacific Subtropical Mode Water Based on Argo Observations
Keywords:The contributions of eddies to the total formation of NPSTMW are 21.2%., The eddy-induced buoyancy loss broadens the region of air-sea buoyancy loss near the KE, Eddy-induced subduction have similar interannual variations related to the KE variable state, The contributions of eddies to the total subduction of NPSTMW are 56%.
North Pacific subtropical mode water (NPSTMW) is formed in the winter deep mixed layer (ML), due to ocean-to-atmosphere interactions, south of the Kuroshio Extension (KE), one of the most energetic eddy activity regions. The large-scale effects of eddies on the formation and subduction of NPSTMW are investigated on updated Argo observations via kinematic and thermodynamic parameterization approaches. The climatological annual mean eddy-induced subduction of NPSTMW can reach 4.51 Sv, which accounts for nearly 56% of the total subduction. The local enhancement of the eddy-induced subduction rate can reach 90 m yr−1 in the high eddy kinetic energy (EKE) zone. Moreover, the spatial distributions of the large eddy-induced subduction are mostly generated in a zone of steep isopycnals near the KE front area via the parameterization. The diagnosis of the thermodynamic relationship indicates that the eddy-induced buoyancy flux broadens the area of ocean surface buoyancy loss and then fosters the formation of NPSTMW in winter. The eddy-induced buoyancy loss due to diapycnal mixing is likely to occur in the relatively steep isopycnals near the KE region, which accounts for 21.2% of the net NPSTMW formation. The contribution of eddy-induced subduction has the same order as that of lateral induction in each year. The eddy-induced subduction and lateral induction show similar interannual variations related to the KE variable state.