Northern Andaman Sea Research Articles

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.

Tidal influence on suspended sediment distribution and dispersal in the northern Andaman Sea and Gulf of Martaban

Surface and water column profiles of suspended matter collected during April–May 2002, and satellite images were used to study factors influencing suspended sediment concentrations (SSCs) and dispersal in the northern Andaman Sea and Gulf of Martaban, one of the largest highly turbid areas of the world's oceans. Perennial high SSC in the Gulf of Martaban is due to a combination of factors including resuspension of sediments by strong tidal currents, shallow bathymetry and seasonal sediment influx from rivers. From satellite images, it was observed that in the central portion of the Gulf of Martaban, the turbidity front oscillates about 150 km in phase with spring-neap tidal cycles and the area covered by the turbid zone (SSC>15 mg l −1) increases from less than 15 000 km 2 during neap tide to more than 45 000 km 2 during spring tide. The sediment discharged by the Ayeyarwady River is transported mainly eastward, along the coast, into the Gulf of Martaban. Occasionally, during the winter monsoon period, sediment plumes are seen heading westward into the Bay of Bengal. Turbidity profiles show that bottom nepheloid layers are actively transporting some of the sediments into the deep Andaman Sea via the Martaban canyon.