Long-term Variability of Currents moored at the northern boundary of NEC in the northwestern Pacific Ocean

Abstract

Hydrographic survey and ADCP measurements were carried out as well as biogeochemical samplings by KORDI team in the northwestern Pacific Ocean under the POSEIDON programme ever since it was launched in 2006. Long-term currents were also obtained, which were measured by moored current-meters (1 ADCP for upper 500m layers and 3~4 RCMs for deeper layers) at a station between Oct. 2007 and June 2009. After recovering the current meters from the moored station, two mooring lines for measuring currents and suspended sediments have been deployed at two different locations, which would be operated at least until 2015 when the POSEIDON programme ends. The time series of currents shows that continuous intraseasonal variability associated with the fluctuation of eddy activities, especially with three consecutive peaks of strong currents by westward propagating eddies between May and September 2008. There were also coincident peaks of positive thermal anomalies even down under the depth of 2,000 meters. The background surface currents from satellite altimeter