The Makassar Strait throughflow of ~12–13 Sv, representing ~77% of the total Indonesian Throughflow, displays fluctuations over a broad range of time scales, from intraseasonal to seasonal (monsoonal) and interannual scales. We now have 13.3 years of Makassar throughflow observations: November 1996 to early July 1998; January 2004 to August 2011; and August 2013 to August 2017. Strong southward transport is evident during boreal summer, modulated by an ENSO interannual signal, with weaker southward flow and a deeper subsurface velocity maximum during El Niño; stronger southward flow with a shallower velocity maximum during La Niña. Accordingly, the southward heat flux, a product of the along‐channel current and temperature profiles, is significantly larger in summer and slightly larger during La Niña. The southward flow relaxed in 2014 and more so in 2015/2016, similar though not as extreme as during the strong El Niño event of 1997. In 2017, the throughflow increased to ~20 Sv. Since 2016, the deep layer, 300‐ to 760‐m southward transport increases, almost doubling to ~7.5 Sv. From mid‐2016 into early 2017, the transports above 300 m and below 300 m are about equal, whereas previously, the ratio was about 2.7:1. Near zero or northward flow occurs in the upper 100 m during boreal winter, albeit with interannual variability. Particularly strong winter reversals were observed in 2014/2015 and 2016/2017, the latter being the strongest winter reversal revealed in the entire Makassar time series.

Change in the Indonesian Seas with the circulation and heat and freshwater inventories and associated air-sea fluxes of the regional and global oceans. This white paper puts forward the design of an observational array using multi-platforms combined with high-resolution models aimed at increasing our quantitative understanding of water mass transformation rates and advection within the Indonesian seas and their impacts on the air-sea climate system.

Sea surface temperature (SST) variability at intraseasonal time scales across the Indonesian Seas during January 1998–mid-2012 is examined. The intraseasonal variability is most energetic in the Banda and Timor Seas, with a standard deviation of 0.4°–0.5°C, representing 55%–60% of total nonseasonal SST variance. A slab ocean model demonstrates that intraseasonal air–sea heat flux variability, largely attributed to the Madden–Julian oscillation (MJO), accounts for 69%–78% intraseasonal SST variability in the Banda and Timor Seas. While the slab ocean model accurately reproduces the observed intraseasonal SST variations during the northern winter months, it underestimates the summer variability. The authors posit that this is a consequence of a more vigorous cooling effect induced by ocean processes during the summer. Two strong MJO cycles occurred in late 2007–early 2008, and their imprints were clearly evident in the SST of the Banda and Timor Seas. The passive phase of the MJO [enhanced outgoing longwave radiation (OLR) and weak zonal wind stress) projects on SST as a warming period, while the active phase (suppressed OLR and westerly wind bursts) projects on SST as a cooling phase. SST also displays significant intraseasonal variations in the Sulawesi Sea, but these differ in characteristics from those of the Banda and Timor Seas and are attributed to ocean eddies and atmospheric processes independent from the MJO.

The Indonesian Throughflow (ITF) transport in the upper layer of Makassar Strait was reduced by an unprecedented 25–40% during June to September 2016, the weakest northern summer ITF transport measured through 2004 to mid‐2017. A negative Indian Ocean Dipole (IOD) event occurring through boreal summer and fall 2016 was the main driver for the reduced ITF transport. Elevated sea surface temperature and height off the southern coast of Sumatra and Java islands, attributed to the IOD event, suppressed the Pacific to Indian pressure gradient, resulting in a reduction in the ITF transport. Intensified Wyrtki jets, energetic westerly winds, and downwelling Kelvin waves associated with the strong IOD event contributed to the suppressed interocean pressure gradient. The influence from the 2016 La Niña event on the other hand was secondary. This study showcases the role of coupled ocean‐atmosphere interactions in Indian Ocean in regulating an extreme interannual variation of the ITF in 2016, which is a unique event in the observational record.

The Indonesian Throughflow (ITF) surface layer dynamics within the Makassar Strait, responsible for ~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.

Sea-sand mining has both advantages and disadvantages particularly in its destructive capabilities. The damages caused by sea-sand mining are mostly due to the unorganized mining zones. In order to minimize the negative effects of mining activities, the well-organized mining zones that have evaluated all related aspects are required. There are several aspects which are closely related to the sea-sand mining zones, one of those is hydro-oceanography aspect in its relation with the sea environments. A comprehensive analysis can be made by integrating hydrooceanography and GIS as a system of both data-organizer and software. This method is supported by using the remote sensing technology as a verification data comparison to the results of hydrooceanography analyses.The application of image analysis as a verification tool is a good method to proof the results given by the numerical simulation model. In this study, we use the Landsat images as the data verification. The results of the integrated system between the hydro-oceanography and the GIS analysis have indicated that the mining can be continuously conducted in several locations without imposing any hazardous impacts to the adjacent environment. By considering the results above, the integrated system between the numerical model and the GIS is highly effective as a foundation to determine the mining zone where the negative effects of the oceanographic-dynamical-changes on the environment due to the mining activities can be easily recognized and predicted.

According to UNCLOS, Indonesian marine territorial covers an area equal to around 2.8 million square kilometers inner archipelagic seas. Though the Indonesian water region is very wide, the resource within it is not yet been exploited optimally. Indonesia still has problems that have to be copped with, including identification of marine fishing ground areas. This report proposes a technology to make the fish-catching be more efficient and effective with the help of MODIS satellite image in term of Surface Temperature and chlorophyll-a computation. Data conversion from digital number to Water Brightness Temperature are performed. The determination of potential fishing ground area were conducted based on temperature and chlorophyll-a parameters which serve as an indicator of upwelling and observations were carried out on parameters which show this phenomenon. Based on the result, during May 2004 the upwelling process were not happened yet, and it seems to occur in June 2004. It showes by the decreasing of water temperature in South Coast of West Java particularly between the border of West Java and Central of Java. This phenomenon acts as an indicator for the raising of primer productivity and will takes about one month after upwelling to the bloom of phytoplankton.

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