Water Mass Formation, Modification and Subduction in and around the Subarctic Frontal Zone in the North Pacific

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Other Title
  • 北太平洋亜寒帯前線帯とその周辺における水塊の形成・変質と沈み込み
  • キタタイヘイヨウ アカンタイ ゼンセンタイ ト ソノ シュウヘン ニ オケル スイカイ ノ ケイセイ ・ ヘンシツ ト シズミ コミ

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Abstract

In the subarctic frontal zone(SAFZ)where the subtropical lower ventilated pycnocline(σθ=26.3-26.6kg m-3)outcrops in winter, Argo data revealed that the Transition Region Mode Water(TRMW ; S<34.0)was dominantly formed. Doublediffusive salt finger convection within TRMW was indicated widely in SAFZ, which was probably caused by geostrophic currents with vertical shear crossing the density-compensating temperature-salinity front. The resulting rapid increase of temperature and salinity at the TRMW cores possibly converted part of TRMW into the denser variety of Central Mode Water(D-CMW ; S> 34.0). Analysis of the synoptic quasi-zonal expendable conductivity-temperature-depth(XCTD)section suggested that part of the low-potential-vorticity water such as TRMW and D-CMW subducted from SAFZ was transported to the south across the eastward mean flow by mesoscale eddies and then spread along the subtropical gyre. The eddy transport of the water mass originating in SAFZ, along with its modification due to salt fingering, possibly serves as a mechanism maintaining the subtropical ventilated pycnocline.

Journal

  • Bulletin on Coastal Oceanography

    Bulletin on Coastal Oceanography 50 (2), 103-118, 2013

    Coastal Oceanography Research Committee, the Oceanographic Society of Japan

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