Near-surface current measurements by two high-frequency oceanic surface radars of the Frequency Modulated Interrupted Continuous Wave (FMICW) type were carried out during December 2000-March 2001 in order to investigate the characteristics of short-period fluctuations of surface circulation in Sagami Bay induced by Kuroshio wann water (KWW) intrusions. When the KWW intrudes into the bay through Ooshima west channel (OWC), cyclonic and anti-cyclonic circulations are generated in the central part of the bay and in the lee of Ooshima Island, respectively, as suggested by previous studies based on mooring and drifting buoy observations (e.g. Taira and Teramoto, 1986; Iwata and Malsuyama, 1989). These two circulations fluctuate with periods of about 811 days. When the KWW strongly intrudes into the bay from OWC, cyclonic and anti-cyclonic circulations become large and the centers of the circulations move south west ward and northeastward, respectively. In addition, warm water intrudes into the mouth of Tokyo Bay and a coastal front appears at the bay month. Statistical analyses, including standard Empirical Orthogonal Function (EOF) analysis, and satellite infrared images of the Knroshio indicate that the dominant fluctuation of the circulation is caused by temporal change in strength of the KWW intrusion due to small-scale (10-15 km) offshore-inshore movement of the Kuroshio front. This movement is thought to, be due to the Ekman transport induced by a southwestward-northeastward wind.

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Water discharge and milrient concentrations were investigated in eight, rivers and a power plant drainage in order to reveal the nutrient, loadings through rivers into Funka Bay. The river water discharge changed seasonally with a remarkable peak in April. The volume-weighted mean concentrations for all rivers of nitrate, ammonium, phosphate and silicate were 24μM, 2.9μM, 0.30μM, and 270μM, respectively. Annual nutrient loadings of dissolved inorganic nitrogen, phosphate and silicate were 57x10⁹mol 0.63×10⁶mol, and 570×10⁶mol, respectively. The river waters had higher DIN:DIP ratios than surface waters in Funka Bay, indicating that the former was highly enriched in nitrogen compared with phosphorus. The contributions of riverine nutrient, loadings to primary production in Funka Bay were only 1% when total annual production was considered. In terms of newproduction, however, riverine nutrient, loadings seem to support a significant part. (10%) of summer new production in Funka Bay.

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Variability in intraseasonal current fluctuations (periods between 10 and 60 days) on the western shelf in Hidaka Bay was examined by using an Acoustic Dopplcr Current Profiler (ADCP) installed on a regular ferry shuttling between Aomori and Muroran from April 2000 to April 2001. After ten primary tidal current constituents were subtracted from the ADCP data, two types of spectral analysis were carried out. and three periodic variations, around 10-, 25-, and 60-day periods, respectively, were identified on the shelf. A new band-pass method, the Harmonic Analysis Band-pass (HAB) method, which can be applied to irregularly sampled data, is proposed to extract the horizontal and vertical current structures of each periodic variation. Very little phase lag between ADCP points was found in any of these periodic variations on the western shelf. Slight vertical phase lag was observed in the 10- and 25-day periodic variations, and a significant vertical phase lag of several days (i.e., lower current always leads upper current) was observed for the 60-day periodic variation. Cross-spectral analysis between current and sea surface wind showed that among signals in the periodic variations, only those in the 10-day period wore coherent, and their phase lag indicates that the northwesterly wind leads the northwestward flow by about, 1.5 days. This estimated phase lag agrees well with that of the wind-forced barotropic model of Hidaka Bay by Ohshima and Miyake (1990). Also, the current variation in the 10-day period was dominant from autumn to winter. Therefore, we infer that this 10-day current variation is effectively induced by the northwesterly monsoon wind.

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We deployed two profiling floats south of the Kuroshio Extension in March 2000 as a prelirninary study of the Japan Argo project. Temperature and salinity profiles from the depth of 1, 500×10⁴Pa to the surface are reported every two and four weeks, respectively. On the bases of the float obserbations, together with altimeter data, we investigated the water masscs in the region and analyzed the vertial structure ofthe cyclonic eddy, that advected the two floats from May through July 2000. The analysis showed that the eddy had typical characteristics of the mesoscale eddies commonly seen south of the Kuroshio Extension.

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