Deep water in the South China Sea is renewed by the cold and dense Luzon Strait overflow.However,from where and how the deep water upwells is poorly understood yet.Based on the Hybrid Coordinate Ocean Model reanalysis...Deep water in the South China Sea is renewed by the cold and dense Luzon Strait overflow.However,from where and how the deep water upwells is poorly understood yet.Based on the Hybrid Coordinate Ocean Model reanalysis data,vertical velocity is derived to answer these questions.Domain-integrated vertical velocity is of two maxima,one in the shallow water and the other at depth,and separated by a layer of minimum at the bottom of the thermocline.Further analysis shows that this two-segmented vertical transport is attributed to the vertical compensation of subsurface water to the excessive outflow of shallow water and upward push of the dense Luzon Strait overflow,respectively.In the abyssal basin,the vertical transport increases upward from zero at the depth of 3500–4000 m and reaches a maximum of 1.5×10^(6) m^(3)/s at about 1500 m.Deep water upwells mainly from the northeastern and southwestern ends of the abyssal basin and off the continental slopes.To explain the upward velocity arising from slope breaks,a possible mechanism is proposed that an onshore velocity component can be derived from the deep western boundary current above steep slopes under bottom friction.展开更多
This study aims to investigate variability of the deep South China Sea(SCS)circulation using the Hybrid Coordinate Ocean Model(HYCOM)global reanalysis product.The results reveal that annual cycle is a dominant compone...This study aims to investigate variability of the deep South China Sea(SCS)circulation using the Hybrid Coordinate Ocean Model(HYCOM)global reanalysis product.The results reveal that annual cycle is a dominant component in the deep SCS circulation.Meanwhile,the boundary circulation strength is the weakest in January and peaks between June and September.The eastern and southern boundary currents strengthen/weaken one to three months earlier than that in the western and northern boundaries.Vector Empirical Orthogonal Functions(VEOF)analysis results reveal that semiannual and intraseasonal fluctuations are significant components,of which the spatial patterns are mainly confined in the northern and western boundary areas as well as the southwestern sub-basin.Wavelet analysis results show the strength of significant fluctuation varies year to year.Trend analysis results indicate a decadal weakening in the deep SCS circulation.An anomalous anticyclonic circulation,50–70 km apart from the slope break,tends to weaken the cyclonic boundary circulation in the western and northern boundaries as well as the southwestern sub-basin.This trend is similar to the observed decadal weakening in the North Atlantic deep circulation.Thus,the findings of this study reveal that the variation of the deep SCS circulation has a remarkable response to the climate change.The mechanisms responsible for the variation are worth pursuing if more observations are available.展开更多
基金The National Key Research and Development Program of China under contract No.2019YFC1408400the National Natural Science Foundation of China under contract Nos 41876029,41821004 and 41776042.
文摘Deep water in the South China Sea is renewed by the cold and dense Luzon Strait overflow.However,from where and how the deep water upwells is poorly understood yet.Based on the Hybrid Coordinate Ocean Model reanalysis data,vertical velocity is derived to answer these questions.Domain-integrated vertical velocity is of two maxima,one in the shallow water and the other at depth,and separated by a layer of minimum at the bottom of the thermocline.Further analysis shows that this two-segmented vertical transport is attributed to the vertical compensation of subsurface water to the excessive outflow of shallow water and upward push of the dense Luzon Strait overflow,respectively.In the abyssal basin,the vertical transport increases upward from zero at the depth of 3500–4000 m and reaches a maximum of 1.5×10^(6) m^(3)/s at about 1500 m.Deep water upwells mainly from the northeastern and southwestern ends of the abyssal basin and off the continental slopes.To explain the upward velocity arising from slope breaks,a possible mechanism is proposed that an onshore velocity component can be derived from the deep western boundary current above steep slopes under bottom friction.
基金The National Key Research and Development Program of China under contract No.2019YFC1408400the National Natural Science Foundation of China under contract Nos 41876029 and 41821004.
文摘This study aims to investigate variability of the deep South China Sea(SCS)circulation using the Hybrid Coordinate Ocean Model(HYCOM)global reanalysis product.The results reveal that annual cycle is a dominant component in the deep SCS circulation.Meanwhile,the boundary circulation strength is the weakest in January and peaks between June and September.The eastern and southern boundary currents strengthen/weaken one to three months earlier than that in the western and northern boundaries.Vector Empirical Orthogonal Functions(VEOF)analysis results reveal that semiannual and intraseasonal fluctuations are significant components,of which the spatial patterns are mainly confined in the northern and western boundary areas as well as the southwestern sub-basin.Wavelet analysis results show the strength of significant fluctuation varies year to year.Trend analysis results indicate a decadal weakening in the deep SCS circulation.An anomalous anticyclonic circulation,50–70 km apart from the slope break,tends to weaken the cyclonic boundary circulation in the western and northern boundaries as well as the southwestern sub-basin.This trend is similar to the observed decadal weakening in the North Atlantic deep circulation.Thus,the findings of this study reveal that the variation of the deep SCS circulation has a remarkable response to the climate change.The mechanisms responsible for the variation are worth pursuing if more observations are available.