Evolution and modulation of a poleward‐propagating anticyclonic eddy along the Japan and Kuril‐Kamchatka trenches

Abstract

To investigate the relationships between the movement of an eddy and its interior structure and water properties, four profiling floats were deployed in an anticyclonic eddy in the western North Pacific in 2013 (April-October). Daily float profiles showed rapid changes in temperature and salinity corresponding to strong interactions between eddies north of the subtropical Kuroshio Extension. After the first interaction with a warm-core eddy in April, the isolation of the winter mixed layer from the surface was observed, forming a subsurface remnant layer. Another interaction with a cold fresh eddy at middepths in May resulted in the formation of a multilayer structure. The eddy then moved poleward along the Japan and Kuril-Kamchatka trenches, indicating changes in its propagation pattern coupled to its interior structure. The eddy then moved northward (June-July), stalled (July-August), and moved eastward (August-October). In addition to a general declining trend, the properties of the warm saline core changed over a short time period, coinciding with changes in propagation. A density anomaly at middepths of the eddy changed location during the stalled period; however, denser waters were continuously observed in the southeast part of the eddy during its northward and eastward movement. This unidirectional density anomaly pattern was consistent with the structure of the poleward-propagating eddy, which interacted with the western topographic boundary. Meridional exchanges of heat and material were potentially elevated by the eddy's advection and movement, as well as by water modifications in the eddy associated with exchanges along its perimeter.

Impacts of mesoscale activity on the water masses and circulation in the Coral Sea

“…[] who demonstrated that a theoretical circular eddy is able to transport within its core the waters trapped during the eddy formation. However in our case of study we found in eddy A, the signature of NVJ waters mixed with waters encountered along its track [ Kaneko et al ., ]. The position of the CTD 1 and 2, almost on the edge of this eddy as well as the irregular shape of the latter may explain the differences between the characteristics of PEW waters at the entrance of the Coral Sea [ Gasparin et al ., ] and those sampled during the cruise.…”

Community Composition and Photosynthetic Physiology of Phytoplankton in the Western Subarctic Pacific Near the Kuril Islands With Special Reference to Iron Availability

“…The cluster analysis indicated that the community composition at Station A5 was more similar to the coastal communities at Stations D9 and A2, whereas Station A6 showed a similar community composition to that of Station OP3 in the SS waters (Figure ), where a low DFe concentration was observed even in the coastal region (Table ). These heterogeneous distributions of DFe and diatoms might relate to complex physical properties around the Kuril Islands such as intense vertical tidal mixing (Ono et al, ; Yagi & Yasuda, ) and anticyclonic eddies that occur in summer along the Kuril‐Kamchatka Trench (Yasuda, ; Kaneko et al, ).…”

Float observations of an anticyclonic eddy off Hokkaido

“…This density range corresponds to that of the Transient Mode Water found in the MWR [e.g., Oka et al ., ]. The second layer was the salinity minimum layer (σ θ = 26.7 to 26.9 kg m −3 ) observed in the CTD cross section; this density range corresponds to that of NPIW, which has been shown to be renewed within eddies in the MWR [e.g., Itoh et al ., ; Kaneko et al ., ]. The third layer was the main thermocline layer (σ θ = 27.0 and 27.2 kg m −3 ); this layer, which corresponded to subarctic water, was located between the salinity minimum and oxygen minimum layers.…”

“…[] and Kaneko et al . [] reported large, abrupt water property changes in an eddy core on the basis of data from a few profiling floats and shipboard measurements across the eddy. As indicated by Itoh and Yasuda [], these interactions might eventually enhance the vertical contrast between upper saline and lower fresh waters.…”