Long-term Variability of Upper Oceanic Condition in Suruga Bay and its Surrounding Area

Abstract

Observational data along the regular sections in last 40 years (1965～2004) which have been performed by the Shizuoka Prefectural Fisheries Experiment Station were used toa nalyze long-term variabilities ofte mperature and salinity fields in the upper ocean layer of Suruga Bay and its surrounding area. Interannual variability of the temperature field showed (1) high amplitude in the subsurface layer ofar eas near the baym outha nd outside ofth e bay, byc haracterized as warmingi nt he lasth alfof 19 70s, and (2) the amplitude was eminent in the near-surface layer inside of the bay by warming since the last half of 1990s. The former change had high correlation with off-shore distance of the Kuroshio axis from Daiozak i, possibly because it is controlled by open oceanic condition. Similar interannual changew as also found int he salinity field ofth e subsurface layer in the same region, and thus the subsurface temperature and salinity became both higher when the Kuroshio had taken a large meander path. We detected a long-term salinity change which is dominant in the near-surface layer. This had a significant correlation with the lag of a half year with the precipitation change at Shizuoka, by suggesting the importance of freshwater flux through the sea surface or volume flux change from rivers.