THE MEAN STRUCTURE AND VARIABILITY OF THE MINDANAO CURRENT AT 8-DEGREES-N

Citation
S. Wijffels et al., THE MEAN STRUCTURE AND VARIABILITY OF THE MINDANAO CURRENT AT 8-DEGREES-N, J GEO RES-O, 100(C9), 1995, pp. 18421-18435
Citations number
33
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Oceanografhy
Journal title
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
ISSN journal
2169-9275 → ACNP
Volume
100
Issue
C9
Year of publication
1995
Pages
18421 - 18435
Database
ISI
SICI code
2169-9275(1995)100:C9<18421:TMSAVO>2.0.ZU;2-W
Abstract
On the basis of eight surveys along 8 degrees N in the western Pacific Ocean taken between September 1987 and June 1990, the mean structure and transport of the Mindanao Current is presented. Direct acoustic Do ppler current profiler (ADCP) velocity measurements show the Mindanao Current to be an intense 200- km-wide coastally trapped jet with a typ ical inshore velocity maximum of Im s(-1). Though the individual geost rophic velocity estimates were strongly contaminated by dynamic height noise, the survey averaged geostrophic and directly measured shears w ere identical to within the estimated errors. The ADCP mean velocity f ield was taken as a reference for the geostrophic flow estimate based on the mean density distribution. Relative to a bottom reference level , a barotropic correction was required near the coast to make the mean geostrophic and directly measured velocities agree. Integrated from t he Mindanao Coast to 130 degrees E, the average transport above sigma( theta) = 26.7 kg m(-3) is 25 +/- 4 x 10(9) kg s(-1), while that betwee n 0 and 2000 dbar is 39 +/- 10 x 10(6) kg s(-1) based on the mean ADCP -referenced geostrophic fields. The velocity structure of the Mindanao Current was remarkably stable from cruise to cruise. However, two cru ises in the spring of 1989 sampled an: anomalous velocity structure of fshore which is attributed to the presence or a 400-km-diameter warm-c ore feature containing South Pacific water masses. We speculate that t his feature is either a pinched-off eddy or meander from the confluenc e of northern and southern hemisphere waters that occurs near 5 degree s N. The sense of circulation of the eddy is anticyclonic, opposite ir i sign to the recirculation which has been historically termed the Min danao Eddy. Only two of the eight cruises sampled northward thermoclin e flow offshore df the Mindanao Current; the average of all cruises co ntains no significant recirculation. Hence for the time period of thes e surveys the Mindanao Eddy and Undercurrent were essentially absent a t 8 degrees N.