Lamon Bay Birth of the Kuroshio Water mass
Lamon Bay, Birth of the Kuroshio Water mass origin, circulation patterns and Kuroshio transport within Lamon Bay and their response to NEC Bifurcation shifts, based on a paper soon to be submitted by A. Gordon, P. Flament and C. Villanoy R/V Revelle May-June 2011 April-May 2012 Transit from Freemantle, April 2012 Stars and disks: CTD Red: moorings: [Flament presentation, next]
Collaborative research with Philippeans researchers SHELF PACIFIC INTERACTION IN LUZON (SPIL, N 6290910 -1 -7126) Villanoy CL, Cabrera OC, David LT, Yniguez AT, Jacinto GS, San Diego-Mc. Glone ML, Siringan FP, Alabia ID, Fernandez IQ, Solera LA, Bollozos IS, Escobar MT, Saban RC, Quevedo JD Marine Science Institute, University of the Philippines • CTD-rosette sampling, underway sampling, plankton net tows, sediment cores, mooring and radar data, satellite ocean color, SST, and SSH data • Intensive multibeam bathymetric survey at shelf break • Delineation of offshore, cyclonic eddy area, shelf waters • Eddies originate at promontory and shelf breaks, dispersing shelf waters • Variations in NEC bifurcation latitude has localized effects: 1 Kuroshio and eddy strength 3 dissolved oxygen levels temperature up to 100 m and depth of 26°C 2 chlorophyll 4 depth-averaged isotherm) 2
Changing Lamon Bay circulation pattern 21 -53 m vectors, color coded for SSS; with water mass regimes May-June 2011 April-May 2012 n tic yc lon rc at io an ic dip ole La La m on b ifu at ion rc b ifu m on anticyclonic dipole hio SSS color coded ros t Ku cen Kuroshio recirculation gyre hio ros t Ku cen Nas Kuroshio recirculation gyre o hi os ur K cyclonic dipole fe er ed Polillo current nt re Polillo current r cu Weak NEC signal Strong NEC signal
Lamon Bay Circulation & Stratification Port Irene Bay Polillo Bay NEC S-max, S-min 2012 T/S stratification reflects dominance of North Equatorial Current (NEC) water; whereas 2011 T/S reflects Kuroshio ‘subtropical’ recirculation gyre regime. The cyan 2012 northeastern stations, display Kuroshio. T/S. Po li llo Ba y Kuroshio S-max, S-min 2012 2011 NEC S-max, S-min
Lamon Bay Circulation & Stratification Arnold L. Gordon & Pierre Flament +10. 0 Sv May 2011 +16. 7 Sv May 2012 Speeds from Ship ADCP Transports: 0 -600 db +9. 2 Sv +14. 3 Sv 18° 20’ 16° 30’
T/S al pic T/S pic al tro btro pic al T /S tro Su Su Timing of the water mass transition btro pic al T / S Lamon Bay Circulation & Stratification
Lamon Bay Circulation & Stratification T/S from long mooring (within Kuroshio feeder current), leads the SW Lamon Bay T/S (cyclonic gyre) by ~ 2 months Long mooring, 169 m TRBM 3 Long mooring Dec’ 11 Feb’ 12 Dec’ 11 al T/S ) reg im e TRBM 3, 178 m Re dd ot (tro pic Feb’ 12 the data is 6 hour block mean; there are 328 data points in the trbm 'red' data set and 694 in the long mooring Number of red dots
13°N Cesar Villanoy NEC bifurcation latitude using the method of Bo Qiu and S. Chen (2010) finds Linear trend in NEC bifurcation of – 1. 16°/decade Bo Qiu: pc (July 2012) Trend after regressing out PDO index = – 0. 52°/decade Trend after regressing out nino 3. 4 index = – 0. 92°/decade LB 02 LB 01 Hypothesis: the more southern bifurcation = stronger (Lamon Bay) Kuroshio; Also- weaker Mindanao Current; and reduced SCS throughflow, warmer. Stronger ITF.
Weaker Kuroshio Stronger Kuroshio, enriched in Equatorial water Kuroshio Luzon Strait throughflow Kuroshio Weak or ~0 Luzon Strait throughflow W th ou k. S w rcat n atio bifu flo gh ou w flo urc bif gh ou hr at Se ina Ch North Equatorial Current ea h ut North Equatorial Current So ion Mind anao Mind ng er M ak a ss ar IT F April 2012 La Niña St ro May 2011 Neutral
Lamon Bay, Birth of the Kuroshio § A sharp contrast of the Lamon Bay circulation and stratification (water mass compostion) is observed between the May/June 2011 (LB 01, neutral ENSO phase) and April/May 2012 (LB 02, La Niña ENSO phase), with a stronger ‘nascent’ (pre. Luzon Straits) Kuroshio, enriched in equatorial water types in 2012, relative to 2011. § The Kuroshio subtropical recirculation gyre, which had a dominant presence within Lamon Bay in 2011, retreated to the north in 2012. § The shift is a western boundary response to ENSO/PDO induced changes of circulation of the western tropical Pacific, specifically to latitude of the North Equatorial Current Bifurcation (further south in 2012). § Time series obtained from moorings, identify the timing of the transition of water mass regimes as late December 2011 in the eastern Lamon Bay, to early February 2012 within the southwestern Lamon Bay. § There are significant larger scale implications of our findings, related to North Pacific meridional fluxes and to the Indonesian Throughflow.
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