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北太平洋の亜熱帯と亜寒帯をつなぐ海流と移行領域の形成
三寺, 史夫;西川, はつみ;松田, 拓朗
Permalink : http://hdl.handle.net/2115/91754
JaLCDOI : 10.14943/lowtemsci.82.135
KEYWORDS : 北太平洋移行領域;磯口ジェット;海底地形;transition domain;Isoguchi jets;bottom topography
Abstract
北海道の東方の北緯40度付近には，北太平洋移行領域という海域がある．そこでは，黒潮と親潮の水が混ざり合い，中間の性質を持つ特徴的な水塊が形成される．この移行領域は海洋生態系にとって好環境であること，またその海面水温変動は北半球中緯度の気候変動に関わるなど，海洋科学にとって重要な海域である．2000年代に入って，この海域に黒潮水を運ぶ準定常な海流が発見された．この海流は表層流にもかかわらず，6000mもの深海底の500m程度の高さの海膨に沿って流れており，そのメカニズムは謎とされていた．本稿では，この海流が形成されるメカニズムを解説するとともに，その移行領域における役割を解明するためのドリフターや仮想粒子追跡によるラグランジュ的解析結果について紹介する．
A boundary region between the subtropical gyre and subarctic gyre in the North Pacific exists around 40°N eastward from Hokkaido. The region is called the Transitional Domain. There, the Kuroshio origin water and Oyashio origin water are mixed and form a unique water. Recently, quasi-stationary surface currents that carry the Kuroshio water into the Transition Domain were discovered. The surface currents flow along ocean bottom rises of a height of ~500 m, despite the bottom depth there exceeds 6000 m. In this article, we explain the mechanism of the formation of the quasi-stationary currents and describe the results from Lagrangean analyses to elucidate roles of these currents for the formation of the Transitional Domain, including observations using in-situ drifters as well as the particle tracking using current information retrieved from satellite altimeters.
A boundary region between the subtropical gyre and subarctic gyre in the North Pacific exists around 40°N eastward from Hokkaido. The region is called the Transitional Domain. There, the Kuroshio origin water and Oyashio origin water are mixed and form a unique water. Recently, quasi-stationary surface currents that carry the Kuroshio water into the Transition Domain were discovered. The surface currents flow along ocean bottom rises of a height of ~500 m, despite the bottom depth there exceeds 6000 m. In this article, we explain the mechanism of the formation of the quasi-stationary currents and describe the results from Lagrangean analyses to elucidate roles of these currents for the formation of the Transitional Domain, including observations using in-situ drifters as well as the particle tracking using current information retrieved from satellite altimeters.
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