Comparison of the currents measured by electromagnetic current meter and bottom mounted ADCP in Otsuchi bay

Near-surface current data obtained by bottom-mounted Acoustic Doppler Current Profilers (ADCP) are compared with those by electromagnetic current meter (ACM) in Otsuchi bay, Sanriku ria coast in northern Japan during the two periods from October 2003 to March 2004 and from April to October 2004. Although near-surface data obtained by upward looking ADCP is affected by the acoustic beam reflected from the sea surface, the results show that those data have significant correlation with each other. This means that bottom-mounted ADCP is useful for estimating the transport from the sea-surface to bottom

Influences of mesoscale anticyclonic eddies on the zooplankton community south of the western Aleutian Islands during the summer of 2010

Mesoscale anticyclonic eddies have been observed south of the Aleutian Islands. Eddies farther east, in the Gulf of Alaska, are known to transport coastal water and coastal zooplankton to the offshore open ocean. The impacts of mesoscale anticyclonic eddies formed south of the western Aleutian Islands (Aleutian eddies) on the zooplankton community are not fully understood. In the present study, we describe zooplankton population structures within an Aleutian eddy and outside the eddy during July 2010. Based on the sea-level anomaly, the Aleutian eddy was formed south of Attu Island (172 degrees 54'E) in February 2010, and it moved southeastward in the next 5 months. Large oceanic copepods, Neocalanus cristatus, Eucalanus bungii and Metridia pacifica were more abundant inside the eddy than the outside. Inside the eddy, the life stage distribution of N. cristatus was more advanced than that outside, and Neocalanus spp. had accumulated more lipids. These conditions probably reflect the greater primary production in the eddy, production enhanced by nutrients advected into the eddy. The Aleutian eddy contained mostly oceanic copepods because it was formed in the offshore water and/or eddy-eddy interaction occurred after its formation. The sufficient food condition in the eddy presumably resulted in higher growth and survival rates of these oceanic copepods, resulting in the greater abundance, advanced development stages and greater lipid accumulation

Estimation of water circulation in Otsuchi Bay, Japan inferred from ADCP observation

In order to understand the seasonal water circulation system of Otsuchi Bay, direct current measurements were taken by using bottom-mounted Acoustic Doppler Current Profilers (ADCPs) during two periods, from October 2003 to March 2004 and from May 2004 to October 2004. During the first observation period, a remarkable estuary-type vertical circulation was observed. An anti-clockwise circulation, flowing into the bay along the northern coast and out along the southern coast was dominant during the second observation period. It was found that this clear seasonal variation was generated by both seasonal changes of wind and tide-induced residual current

Estimation of water circulation in Otsuchi Bay, Japan inferred from ADCP observation

In order to understand the seasonal water circulation system of Otsuchi Bay, direct current measurements were taken by using bottom-mounted Acoustic Doppler Current Profilers (ADCPs) during two periods, from October 2003 to March 2004 and from May 2004 to October 2004. During the first observation period, a remarkable estuary-type vertical circulation was observed. An anti-clockwise circulation, flowing into the bay along the northern coast and out along the southern coast was dominant during the second observation period. It was found that this clear seasonal variation was generated by both seasonal changes of wind and tide-induced residual current