北太平洋热带水体积的年际变化及其变化机制

The inter-annual variations of the volume of North Pacific Tropical Water and its mechanism

利用EN4(the UK Met Office EN4.2.1 analyses)盐度数据发现北太平洋副热带高盐中心--北太平洋热带水(NPTW)的海表面积与体积在2000-2008年、2014-2017年存在下降趋势,2008-2014年期间存在上升趋势,进一步的研究表明,这些变化与太平洋年代际震荡(PDO)的位相转换紧密相关。利用淡水通量数据以及ECCO2(Circulation and Climate of the Ocean,Phase Ⅱ)流场数据计算分析后表明,淡水通量对NPTW的变化贡献较小,而水平输运对NPTW的表面积以及体积变化贡献较大,这与PDO正(负)位相期间北赤道流(NEC)的向北(南)摆动有关。

The UK Met Office EN4 analyses product revealed that the surface area and the volume of the North Pacific subtropical high-salinity center,namely North Pacific Tropical Water(NPTW),decreased in the period of 2000-2008 and 2014-2017,and grew in 2008-2014.The changing period of NPTW was highly correlated with Pacific Decadal Oscillation(PDO).Using the ECCO2 reanalyzing data,the fresh water flux was calculated through the NPTW surface.Our results show that the fresh water flux has less contribution to changes of NPTW,while the horizontal advection contributes significantly to the surface area and volume changes of NPTW,which is related to the northward(southward)swing of North Equatorial Current(NEC)during the PDO positive(negative)phase.