Observations and predictability of internal solitons in the northern Andaman Sea

Internal solitons are potentially hazardous to sub-sea oil and gas drilling operations. The ability to predict these waves can therefore improve the cost effectiveness and safety of offshore drilling. Theory suggests that solitons are generated when strong tidal currents flow over a bathymetric feature, in a stratified water column. Therefore, with knowledge of the tidal currents, bathymetry and stratification these waves are potentially predictable. Observations were conducted between January and April 1998 at a proposed drilling location in water 440 m deep to the north-east of the Andaman Islands. These observations indicated the occurrence of internal solitons with thermocline depressions of up to 50 m and upper layer currents of up to 1.2 ms−1. The solitons only occurred on spring tides, when the tidal range exceeded 1.5 m and their probability of occurrence increased with tidal range. Thus, in this location, predictions of tidal range can be used to forecast soliton occurrence.