Model Evidence for Interdecadal Pathway Changes in the Subtropics and Tropics of the South Pacific Ocean  

作　　者：张荣华 王彰贵 

机构地区：[1]Earth System Science Interdisciplinary Center,University of Maryland,College Park,Maryland,USA [2]College of Global Change and Earth System Science,Beijing Normal University [3]National Marine Environmental Forecasting Center,State Oceanic Administration

出　　处：《Advances in Atmospheric Sciences》2013年第1期1-9,共9页大气科学进展（英文版）

基　　金：supported in part by NSF Grants (Grant Nos. ATM-0727668 and AGS-1061998);NOAA Grant(Grant No. NA08OAR4310885);NASA Grants (Grant Nos. NNX08AI74G,NNX08AI76G,and NNX09AF41G);supported by the National Key Basic Research Program of China (Grant No. 2010CB950303)

摘　　要：Numerical simulations using a version of the GFDL/NOAA Modular Ocean Model （MOM 3） are analyzed to demonstrate interdecadal pathway changes from the subtropics to the tropics in the South Pacific Ocean. After the 1976 -77 climate shift, the subtropical gyre of the South Pacific underwent significant changes, characterized by a slowing down in its circulation and a southward displacement of its center by about 5°- 10° latitude on the western side. The associated circulation altered its flow path in the northwestern part of the subtropical gyre, changing from a direct pathway connecting the subtropics to the tropics before the shift to a more zonal one after. This effectively prevented some subtropical waters from directly entering into the western equatorial Pacific. Since waters transported onto the equator around the subtropical gyre are saline and warm, such changes in the direct pathway and the associated reduction in equatorward exchange from the subtropics to the tropics affected water mass properties downstream in the western equatorial Pacific, causing persisted freshening and cooling of subsurface water as observed after the late 1970s. Previously, changes in gyre strength and advection of temperature anomalies have been invoked as mechanisms for linking the subtropics and tropics on interdecadal time scales. Here we present an additional hypothesis in which geographic shifts in the gyre structure and location （a pathway change） could play a similar role.Numerical simulations using a version of the GFDL/NOAA Modular Ocean Model （MOM 3） are analyzed to demonstrate interdecadal pathway changes from the subtropics to the tropics in the South Pacific Ocean. After the 1976 -77 climate shift, the subtropical gyre of the South Pacific underwent significant changes, characterized by a slowing down in its circulation and a southward displacement of its center by about 5°- 10° latitude on the western side. The associated circulation altered its flow path in the northwestern part of the subtropical gyre, changing from a direct pathway connecting the subtropics to the tropics before the shift to a more zonal one after. This effectively prevented some subtropical waters from directly entering into the western equatorial Pacific. Since waters transported onto the equator around the subtropical gyre are saline and warm, such changes in the direct pathway and the associated reduction in equatorward exchange from the subtropics to the tropics affected water mass properties downstream in the western equatorial Pacific, causing persisted freshening and cooling of subsurface water as observed after the late 1970s. Previously, changes in gyre strength and advection of temperature anomalies have been invoked as mechanisms for linking the subtropics and tropics on interdecadal time scales. Here we present an additional hypothesis in which geographic shifts in the gyre structure and location （a pathway change） could play a similar role.

关 键 词：water pathway interdecadal changes ocean modeling South Pacific Ocean 

分 类 号：P732[天文地球—海洋科学]