Numerical modeling of ocean circulation to investigate the regional marine environment and climate around Sultanate of Oman

The oceanographic conditions and their impact on the marine ecosystems within Sea of Oman (formerly known as the Gulf of Oman) and in the northwestern Arabian Sea have several concerns that are yet unresolved. The numerical modeling of regional ocean circulation enhances quantitative understanding of ocean processes and addresses the present and future concerns related to marine ecology and regional climate. An anomalous increase in sea surface temperature was noticed before the disastrous cyclones such as Gonu in 2007 and Phet in 2009 that have hit Oman. The super cyclone Gonu alone inflicted a loss of about USD 4 billion besides loss of life and damages to the infrastructure. Massive fish kills in the Sea of Oman have been reported for more than two decades. Investigations suggested that the cause is associated with large phytoplankton blooms and toxic effects of HABs. Oman s fishery sector earns about OMR 104.4 million from fish exports each year, which is the second highest contributor to the national gross domestic product (GDP) from natural products. The depletion of dissolved oxygen levels by organic decomposition and the biogeochemical changes that are forced by circulation are also suspected to increase in frequency of HABs around Oman. The Arabian Sea is the world's largest reservoir of oxygen depleted waters and it is likely to spread towards Oman due to the circulation forced by the monsoons. The suboxic water from the Arabian Sea's oxygen minimum zone (OMZ) can seriously impact the coastal ecosystems and fishery resources of Oman. The seas around Oman are dominated by seasonally and inter-annually changing current jets and eddies which are difficult to explore through observations alone as it requires huge investments in terms of instruments and manpower. Satellite images often show that the circulation along Oman coast is dominated by jets of surface currents, filaments of chlorophyll rich waters and eddies. Satellite observations have severe limitations due to cloud cover and dust during various seasons. The complexity of circulation due to local winds, remotely forced currents, bathymetric steering, low-frequency changes and biologically productive zones along Oman on different time and space scales is not understood yet. The low intensity current driven upwelling along northern Oman coast is often noticed to be associated with red tide events and it is apparently driven by open ocean circulation over-riding the local wind set-up. In order to understand these intricate dynamics it is imperative to undertake a theoretical study of the circulation along Oman and its surrounding region. The emphasis is put on developing a regional circulation model to simulate the critical features of circulation and quantify its impact on coastal ecology. This can be achieved when the physical, biological and fishery data are analyzed together as planned in this proposal. The approach as proposed will contribute substantially to the knowledge of marine ecosystems and their vulnerability to the changes in circulation. The model domain would be 10anddeg; 30anddeg;N and 50anddeg; 70anddeg;E to cover the essential aspects of Oman coastal circulation features. It is expected that the horizontal and vertical resolutions of the model has to be fairly high so as to resolve the bathymetric and boundary effects. The ideal grid spacing that is required is determined by the Rossby radius of deformation. The model domain and the grid resolution will be determined after assessing the computational requirement and other resources. We propose to investigate the ocean circulation and its impact around Oman using a Regional Ocean Modeling System (ROMS). The ROMS model will be customized with regionally observed winds, heat fluxes and hydrographic conditions. The model will further carry out the biogeochemical simulations to understand the ecosystem changes along Oman. ROMS is a sigma co-ordinate numerical model that solves the primitive equations governing ocean dynamics and thermodynamics. The model offers several numerical schemes, horizontal and vertical mixing and there are options to couple the physical model with ecosystem models. The model can also be used for forecasting the physical and biological fields in the seas around Oman. The significance of the proposed research is transformation from descriptive to quantitative assessment of the circulation. The model will explore the regional and global climatic events that are likely to force regime shifts in productivity in this region. The database developed in the process of modeling will meet both long and short-term goals to monitor and forecast the dynamics of seas around Oman. The applications of the circulation modeling are of extreme economic and environmental importance to Oman as it helps in identifying the disaster prone areas along the coast and develop adequate management plans. The changes in inventory of biogeochemical properties of waters around Oman and their consequences are best studied and quantified by modeling the regional circulation as proposed. The deliverables will be presented in the form of scientific papers in peer reviewed journals, International and national conferences. This proposal envisages training of young Omani Masters and Ph.D students in the field of mathematical modeling of the ocean circulation. The outcome of the proposal will advance the teaching of marine science at the university. The mathematical modeling reduces the cost of ocean research by providing selective sampling strategies. Scientific cooperation between the Sultan Qaboos University and the Indian Institute of Science will be expanded through involvement of M.Sc and Ph.D students with experts in the field of mathematical modeling of ocean circulation in the region.