Interannual Variability of Along‐Strait Flow in the Malacca Strait and Its Dynamics
Abstract
The Malacca Strait (MS) is located between Malay Peninsula and the Sumatra Island. It plays important role as a conduit enabling water exchanged between South China Sea (SCS) and the Andaman Sea (AS). In this study, we formulate a quasi‐steady model for an idealized narrow, constant‐depth channel to estimate the interannual along‐strait flow. While this simplified framework does not fully resolve the complex geometry, shallow bathymetry, and frictionally dominated local dynamics of the Malacca Strait, it is used to capture the first order basin scale response to sea level slope forcing. The results suggest that the along‐strait velocity speed varies interannually from −10 to 20 cm/s (positive northwestward), primarily driven by sea level difference between two sides of the MS. Indian Ocean Dipole (IOD), via coastal Kelvin wave propagation, induces interannual sea‐level variability in the northern part of the MS, whereas the mechanisms controlling the interannual signal in the southern MS are less well understood. To determine which side of the MS has dominant influence on the flow, we computed the time‐averaged, depth‐integrated energy flux. The result shows that the flux is negative, indicating dominantly incoming energy from the AS. Since, for long waves, energy is transported in the same direction as wave propagation, we infer that the along‐strait flow is strongly influenced by the remote forcing from the Indian Ocean.