Numerical Simulation of the Influence of Long-Term Sea Level Change on Semi-Diurnal Tidal Waves in the Northeast Indian Ocean

The sea level change in the Northeast Indian Ocean in low emission (SSP1-2.6) scenarios and high emission (SSP5-8.5) scenarios in 2100 to 2020 is analyzed with the data provided by the Intergovernmental Panel on Climate Change Sixth Assessment Report. Based on the Finite Volume Coast and Ocean Model (FVCOM), a tidal wave model is established and meets the requirements of both nearshore and oceanic simulation accuracy and computational efficiency for the Northeast Indian Ocean. Simulations of tidal waves under the influence of current and future sea level changes, including the influences on semi-diurnal tides M₂ and S₂ in the Northeast Indian Ocean and its internal areas such as the top of the Bay of Bengal, the Gulf of Martaban and the northern part of the Strait of Malacca were studied. It shows that both the amplitude and Greenwich phase-lag changes are greater in the high emission scenario than in the low emission scenario. In the high emission scenario, the maximum tidal amplitude changes of M₂ and S₂ are 52.26 cm and 28.59 cm, respectively, while in the low emission scenario, those of M₂ and S₂ are 39.07 cm and 23.34 cm, respectively. In the same emission scenario, the amplitude changes have similar spatial distribution characteristics. The amplitude changes decrease in most areas to the north of 6°N except a few shallow nearshore estuaries. However, in the area to the south of 6°N, the increase and decrease areas exhibit a staggered distribution pattern. The amplitude in deep water areas is less affected by sea level changes than shallow water areas. The spatial distribution of the Greenwich phase-lag changes of M₂ and S₂ is basically the same, and in the deep water region the amplitude change is usually less than 1°. However, the phase-lag changes are more obvious in shallow coastal areas such as the top of the Bay of Bengal. The phase-lag shows a decreasing trend in the top of the Bay of Bengal and the northern part of the Strait of Malacca, and an increasing trend in the Gulf of Martaban.