, Volume 16, Issue 3, pp 206-213

Dynamic and thermohaline properties of the Mindanao Undercurrent, part II: Thermohaline structure

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Abstract

Hydrographic data from eleven 1986–1991 cruises at zonal sections near 8°N from the Philippine coast to 130°E were used to examine thermohaline structures and water mass properties of the western boundary currents there, especially those of the Mindanao Undercurrent (MUC). The finding that the MUC consisted of two water masses with salinity of 34.6 at 26.9 σt and 34.52 at 27.2 σt which were remnants of the lower part of the Southern Pacific Subtropical Water (SPSW) and of the Antarctic Intermediate Water (AAIW) of South Pacific origin, respectively, showed that the MUC was not a local transient but originated elsewhere. As the MUC flowed from 7.5°N to 8°N, part of it carrying the SPSW turns anticyclonically and eastward. The Northern Pacific Intermediate Water (NPIW) often joins the MUC, which suggests that the NPIW carried by the MC partly returns northward as a result of the shear between the MC and the MUC or other processes. The shear instability provides the energy for the irregular fluctuation of the MUC.

Contribution No. 3256 from the Institute of Oceanology, Chinese Academy of Sciences.
Project 49176255 and 49706066 supported by NSFC, and also by Foundation of Post-doctoral Research.