Subsurface variations in the Maluku Channel of the Indonesian seas observed by an underwater glider in the winter of 2018-2019

The China-made Sea-wing glider was deployed in the Maluku Channel jointly by Institute of Oceanology of the Chinese Academy of Sciences and Sam Ratulangi University of Indonesia during December 2, 2018 through February 21, 2019. Continuous Temperature and salinity profiles of the upper ~1000 meters in nearly three months were obtained successfully for the first time in the area. Analyses indicate that the North Pacific Intermediate Water (NPIW), with a salinity minimum less than 34.4 psu, intruded into the Maluku Channel at the depths of 250-300 m since January 6 and occupied nearly the entire channel till the end of the observation. The Antarctic Intermediate Water (AAIW), with a salinity minimum less than 34.55 psu on the 27.2 σθ density surfaces, were observed to intrude into the Maluku Channel between 600 m and 800 m with significant intraseasonal variability. The surface salinity has increased substantially during the observational period. The subsurface salinity, with a maximum large than 34.8 psu, was found to intrude into the Maluku Channel episodically between 130 m to 180 m during January 11-13 and during February 2-10 of 2019. The high salinity suggests South Pacific origin of the episodic intrusions, mixed with some North Pacific waters. These subsurface variabilities are important aspects of the water exchange between the western Pacific Ocean and the Indonesian sea, the dynamics of which will be discussed using the mooring data to be recovered by the end of this year.