Observed snapshot condition of waters during El Niño Southern oscillation (ENSO) 2015-2017 events in the Maluku Channel

Abstract

The Maluku Sea acts as the east gate for the Pacific transport going to Indian Ocean via internal Indonesian Seas. The observational measurement using RV Baruna Jaya VIII, which was conducted during the second transitional monsoon in the respective years 2015,2016 and 2017, aims to figure out a snapshot condition of waters including in the Maluku Sea. The results emphasize a dominant southward current in the surface layer during the period. Despite having a variation of the meridional current pattern, a greater southward transport during 2016 and 2017 (La Niña years) with the maximum –1 Sv indicates that the air-sea interaction may have influence in the subsurface layer. While three type of water mass are observed in 2015 (El Niño year) such as North Pacific Subtropical Water (NPSW), North Pacific Intermediate Water (NPIW) and South Pacific Subtropical Water (SPSW), there is an isopycnal mixing which triggers a fluctuation of the salinity value in the 200-700 m during 2016 and 2017(La Niña years). In addition, the temperature shifting during El Niño and La Niña events contributes to the discrepancy of nutrient concentration. The higher orthophospate and nitrate are observed during El Niño event associated with the warmer temperature.