摘要
Hydrographic data from eleven 1986-1991 cruises at zonal sections near 8°N from the Philippine coast to 130°E were used to examine the dynamic structure of the western boundary currents there in the present study focusing on the Mindanao Undercurrent (MUC).The MUC with maximum velocity >10 cm/ was found to be a feature of both the individual cruises and multiyear mean velocity field as a countercurrent below the Mindanao Current (MC). Usually, the MUC occupies depths below 200 dbar and consists of more than one core.Its vertical and horizontal scales are 500 - 1000 m and 100-250 km, respectively , and vary greatly and irregularly . The spatial distribution of the MUC agreed with that of the westward deepening isopycnals in and below the thermocline . In the individual cruises , the volume transports of the MUC relative to 1500 dbar varied from 6.2 to 28.4×106m3 (average of 14.4× 10 6m3/s) while those relative to 3000 dbar varied from 15.4 to 43.9 ×106 m3/s (average of 25.4 ×106 m3/s ). The multiyear mean MUC transport was 5.9×106 m3/s relative to 1500 dbar and 8.7 × 106m3/s relative t0 3000 dbar . The difference between the multiyear mean MUC transport and that of individual cruises resulted from the MUC spatial variation .
Hydrographic data from eleven 1986-1991 cruises at zonal sections near 8°N from the Philippine coast to 130°E were used to examine the dynamic structure of the western boundary currents there in the present study focusing on the Mindanao Undercurrent (MUC).The MUC with maximum velocity >10 cm/ was found to be a feature of both the individual cruises and multiyear mean velocity field as a countercurrent below the Mindanao Current (MC). Usually, the MUC occupies depths below 200 dbar and consists of more than one core.Its vertical and horizontal scales are 500 - 1000 m and 100-250 km, respectively , and vary greatly and irregularly . The spatial distribution of the MUC agreed with that of the westward deepening isopycnals in and below the thermocline . In the individual cruises , the volume transports of the MUC relative to 1500 dbar varied from 6.2 to 28.4×106m3 (average of 14.4× 10 6m3/s) while those relative to 3000 dbar varied from 15.4 to 43.9 ×106 m3/s (average of 25.4 ×106 m3/s ). The multiyear mean MUC transport was 5.9×106 m3/s relative to 1500 dbar and 8.7 × 106m3/s relative t0 3000 dbar . The difference between the multiyear mean MUC transport and that of individual cruises resulted from the MUC spatial variation .
