The Impact Of Meso-scale Eddies On The Subtropical Mode Water In The Western North Pacific

Temperature and salinity data from Argo profiling floats and altimeter-derivedgeostrophic velocity anomaly (GVA) data in the western North Pacific during2002-2011have been analyzed to investigate the North Pacific Subtropical Mode Water (NPSTMW)and meso-scale eddies distribution and variation and the statistical features of the NPSTMWin the Cyclonic eddies (CEs) or Anticyclonic eddies (AEs). About2992eddies have beendetected which lifespans are greater than30-days. It almost propagation westward with anaveraged velocity4.6cms-1. Combining eddies identified by GVA data and Argo profilingfloat data, in the north of28°N, we found that the NPSTMW in AEs is60dbar thicker thanthat in CEs, and the frequency of the thickness of the NPSTMW greater than150dbar inAEs is18%,whereas that in CEs is less than1%. Thick NPSTMW will be rarely found in thenorth of28°N, due to there will be no NPSTMW formation. The profiles whichNPSTMW are thicker than100dbar are used to investigate the inter-annual variation of corepotential temperature and core salinity. It is clear that the core potential temperature changeswith the KE index, while the core salinity is associated with the E-P flux of the mainNPSTMW formation region in the warm season of last year.About3377(3517) profiles which located less than twice radius of the nearest CEs(AEs) were used to construct the CE (AE). The AE can trap large amount of low PV waterin the centers and with a convex shape in the vertical section in the non-NPSTMWformation season. The ’trapped depth’ of the composite CE (AE) is300m (550m) where the rotational velocity exceeds the transitional velocity. It suggests that the anticyclonic eddiesare more likely not only to form larger amounts of NPSTMW, and but also trap moreNPSTMW than cyclonic eddies do.