[AOS17-P04] Development of low trophic ecosystem model for land sea integral management in the Toyama Bay, Japan
Keywords:Toyama Bay, low trophic ecosystem model, river discharge, submarine ground water, global warming
The hydrodynamic model for the Toyama Bay is called DREAMS-T here, which is based on Data assimilation Research of the East Asian Marine System (DREAMS; Hirose et al., 2013). This model has a resolution of 1/60°×1/75° (approx. 1.5 km) in longitude and latitude directions, respectively, and has 36 layers in the vertical direction. The calculation period is 2006/3/1~2007/12/31. A NPZD type low trophic ecosystem model is combined with the DREAMS-T. Results of DREAMS-M are given as lateral conditions for the DREAMS-T and GPV-MSM data are used as air sea boundary conditions. Daily river discharges of major five rivers (Oyabe, Shou, Jintsu, Jyouganji, and Kurobe River) are added from the grids corresponding to the river mouths. Nutrient concentrations of river water are from Tsujimoto (2012). The effects of SGW is included by doubling the nutrient concentration of river waters in the model because the SGW discharge is little compared to the river discharges but the nutrient flux from SGW is at the same order as those from rivers.
Using model results, we carry out a budget calculation of DIN for the water shallower than 100 m depth in the Toyama Bay. The DIN fluxes by the lateral and vertical advections, especially vertical advection, is dominant in spring, autumn and winter. In summer (June - August), the DIN influx by the advections decreases while those by river discharge and SGW increase and becomes larger than the DIN influx by the advections. This indicates that the nutrients needed by primary production are supplied mainly by upwelling in spring, autumn, and winter, but mainly by river and SGW in summer. In the meeting, we will also report the influences of seasonal shift in river discharge (increasing of river discharge in winter and decreasing in summer) due to change in melting snow with global warming on the ecosystem in the Toyama Bay.