Future climate change will impact on eastern boundary upwelling ecosystems such as the California Current System (CCS). How do the warming-induced stratification and intensification of upwelling-favorable winds will affect ocean productivity in the CCS? We used a coupled and nested physical-biogeochemical model to examine and predict changes in the physical and biogeochemical fields by the end of 2050. The large global model is an earth system model (ESM) with dynamic atmosphere-ocean general circulation and marine biogeochemistry dynamics developed at NOAA’s GFDL. The nested regional model was based the ROMS coupled to a biogeochemical model CoSiNE. The full model was run from 1970 to 2050 and model outputs from two periods were analyzed (1990-2009 and 2030-2049). The model has predicted increased upwelling intensity associated with stronger alongshore winds in the coastal region, and enhanced upper stratification in the open ocean. These two changes both contribute to the increased vertical nutrient flux and biological productivity in CCS. The difference of isothermal deepening between the open ocean and the coast reflecting the basin-scale adjustment creates elevated onshore nutrient transport that increase nutrient concentrations of the upwelling source water and eventually supporting higher productivity in CCS. We found this basin-scale adjustment of nutrient plays a larger contribution than the enhanced wind-generated upwelling in terms of vertical nutrient flux increase in the coastal region. Our model also predicted increasing eddy activities in the CCS that will increase vertical nutrient transport mostly in the coastal region. This study takes advantage of high-resolution models and highlights mechanisms of future productivity enhancements in the coastal upwelling ecosystems.

主持：曹知勉副教授