Study on circulation and water mass formation in the intermediate and deep layers of the Okinawa Trough

利用以Argo浮子剖面为主要数据来源的最小盐度面水体性质、2009 - 2011年系载流计测量的Kerama海沟流速数据、2011年6月和2013年6月冲绳海槽南部CTD/LADCP数据，对冲绳海槽中深层环流和水团形成进行了综合研究。冲绳海槽中水的性质由于强烈的内旋扩散（根据平流扩散方程，6.8-21.5 cm2/s）而发生了很大的改变。深水低于窗台上的深度Kerama差距(1100 ~),通风的bottom-overflow Kerama差距到最深的层(~ 2000)在冲绳海槽南部。箱形模型预测，这种底部溢出（0.18-0.35 Sv）在冲绳海槽南部引起了强烈的上升流，这种上升流必须由强烈的底涡扩散（4.8-9.5 cm2/s）引起的深水浮力增益来维持。

Circulation and water mass formation in the intermediate and deep layers of the Okinawa Trough were investigated using comprehensive datasets for 1) water properties on the minimum salinity surface mainly derived from Argo float profiles, 2) velocity data in the Kerama Gap measured by moored current-meters from 2009 to 2011, and 3) CTD/LADCP data over the southern Okinawa Trough measured in Junes 2011 and 2013.Intermediate-water properties are largely modified in the Okinawa Trough due to strong diapycnal diffusion (6.8-21.5 cm2/s based on an advection-diffusion equation). Deep water below the sill depth of the Kerama Gap (~1100 m), is ventilated by the bottom-overflow in the Kerama Gap down to the deepest layer (~2000 m) in the southern Okinawa Trough. A box model predicts that this bottom-overflow (0.18-0.35 Sv) causes strong upwelling in the southern Okinawa Trough, which must be maintained by buoyancy gain of the deep water due to strong diapycnal diffusion (4.8-9.5 cm2/s).