Time series of model simulated phyto- and zoo-plankton nutrients data from 1995 to 2000 in the Bering Sea

The most prominent climate trends resulting from global climate warming in the southeastern Bering Sea, reduced sea ice cover and rising seawater temperature, have profound impacts on lower trophic level production and fishery production. Some explanatory hypotheses relating sea ice variability to marine ecosystems have been proposed, but have not been studied through a coupled ice-ocean ecosystem model yet. This study established a coupled ice-ocean ecosystem model including both pelagic and sea ice habitats, based on the existing pelagic ecosystem model for the Bering Sea and the ice-ocean ecosystem model for offshore Barrow. The model equations and parameters were studied for 1-D and 3-D applications. Model sensitivity studies and long-time simulations enable us to investigate ecosystem processes and how each ecosystem component responses to physical environmental change. Our 1-D model application successfully reproduced the observed ice-associated blooms in 1997 and 1999 at the NOAA-PMEL mooring M2. The model results suggest that the ice-associated blooms were seeded by sea ice algae released from melting sea ice. Model sensitivity studies reveal nitrification rate is an important control on the dominant phytoplankton functional type, and the amount of nitrate in summer bottom waters and in the winter water column. A several-decadal model run (1960-2004) show that before 1977 primary production was dominated by ice algae in icy cold water with only light grazing, favoring the bottom and benthos community. After 1977, primary production was dominated by open water species of diatom and flagellates in later and warmer water with higher grazing and contributed more toward upper ocean pelagic community.