The Madden-Julian Oscillation's Impact on the Makassar Strait Surface Layer Transport

The Indonesian Throughflow (ITF) surface layer dynamics within the Makassar Strait, responsible for similar to 77% of the ITF, are investigated using in situ and satellite-derived observations from January 2004 to August 2011 and August 2013 to December 2016. Surface layer southward transport attains its minima during boreal winter in response to atmospheric and oceanic processes attributed to Australian-Indonesian monsoon as well as the Madden-Julian Oscillation (MJO). While the monsoon's impact on seasonal variability of the ITF transport has been well documented, the MJO's role to modulate the variability of the ITF transport is less studied. Eleven MJO events traversed from Indian Ocean to Western Pacific during boreal winter months over the course of the Makassar Strait time series. Intensified along-strait wind stress, reduced outgoing longwave radiation, increased sea surface height in the southern Makassar Strait, and a reduction in the surface layer ITF transport by up to 4 Sv marked the impact of the active phase of the MJO. Analysis of the momentum budget in the surface layer indicates that the excess of northward momentum due to the along-channel pressure gradient over northward momentum attributed to the vertical divergence of Reynold stress governs the northward acceleration of the surface layer during the MJO active phase.