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Wind Controlled Kuroshio Warm Water Intrusion into Sagami Bay


Hirofumi Hinata
National Institute for Land and Infrastructure Management
3-1-1 Nagase, Yokosuka, Kangawa 239-0826, Japan
Phone +81-46-844-5023, Fax +81-46-844-1145


The mechanism of the periodic Kuroshio warm water intrusion (KWWI) into Sagami Bay through the Oshima west channel (OWC) was investigated using a) HF radar observation, b) satellite imagery, and c) other conventional hydrographic data, plus d) numerical experiments based on the three-dimensional, primitive equation, sigma coordinate Princeton Ocean Model. During the period from December 15, 2000 to January 16, 2001, the Kuroshio took a non-large meander path (Kawabe, 1985), looping south around the Kii Peninsula and then turning sharply north towards Honsyu, flowing north to northwest towards the Izu Peninsula (IP). The Kuroshio warm water (KWW) then flowed into Sagami Bay through the OWC with synoptic time scales of 8 to 11 days. Statistical analysis of the observation data indicated that the occurrence of the KWWI and the variability in the Kuroshio front were highly coherent with wind field fluctuations due to the passage of cyclones across northern Japan. When southward to southwestward winds dominated in and around Sagami Bay, the Kuroshio front approached the southern coast of the IP, and then the KWW intruded into the Bay through the OWC. When eastward to northeastward winds prevailed, the front moved to the offshore a distance of about 20 km, ending the intrusion. Results of the numerical experiments demonstrated that the small-scale movements of the Kuroshio front are induced by on- and offshore surface Ekman transports corresponding to the shifts in the wind field regime.

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