Remote sensing of coastal discharge of SE Sumatra (Indonesia)

Abstract

The coastal discharge of Indonesia is driven by high precipitation throughout the year. Monsoon and tides form a highly variable dynamical system that satellite remote sensing is the only method to acquire synoptic information. The large rivers of SE-Sumatra belong to the major tropical carbon and sediment sources for the world ocean. Knowledge of carbon sources is important because of their potential impact on coastal ecosystems and on climate change. Drainage of peatlands enhances the concentration of dissolved organic matter (DOM) and strong tidal currents the suspended particulate matter (SPM) load in the rivers. The high concentrations strongly reduce the available light in the water column of coastal regions. The coloured part of DOM (CDOM) absorbs light in the short wavelength range. Measured very high absorptions changed the colour brownish that the tributaries belong to so-called black water rivers. High SPM concentrations made the water milky and bright. Different compositions of water constituents led to large variations of water colour, which made ocean colour remote sensing to the preferred method for investigating river discharge and coastal transport in different spatial and temporal scales. Sources of different water masses were identified, the estuarine turbidity maximum zone and the spreading of river water in relation to tidal phases were detected. The transport processes in adjacent Malacca and Karimata Straits are described in relation to monsoon phases and ENSO. In addition to available satellite derived level 2 products, CDOM and DOC charts were retrieved using regional algorithms derived from measurements.