Program     Pushing the frontiers of marine ecological modeling: where are we now and how can we move forward?       1130 Global and localized impact of river nitrogen export on ocean primary productivity and oxygen Monday 7th @ 1130-1150, Conference Room 5 Xiao Liu* , Princeton University Charles A Stock, NOAA GFDL John P Dunne, NOAA GFDL Minjin Lee, Princeton University Elena Shevliakova, Princeton University Sergey Malyshev, Princeton University Chris Milly, USGS Presenter Email: xiao.liu@noaa.gov The marine environment is increasingly threatened in a high carbon dioxide, urbanized world. Coastal and oceanic stressors, such as occurrences of harmful algal blooms and oxygen deprivation, are forecast to intensify over the next century owing to the combined effects of global warming and enhanced nutrient inputs. As a major terrestrial source of nutrients to the ocean, rivers play a critical yet poorly quantified role in driving both coastal biogeochemical processes and global carbon cycle. In this study we investigate the global-scale and localized impact of river nitrogen export through application of a state-of-the-art, high-resolution global ocean-ice-ecosystem model (MOM6-SIS2-COBALT) with time varying river nitrogen inputs derived from an offline land model (LM3-TAN). Focused on ocean chlorophyll and oxygen, our century-long model simulations depict a global view of river impacted zones with boundaries extended up to thousands of kilometers from their discharge points. At regional scales, we show that intensity and distribution of coastal extremes (i.e. blooms and hypoxia) in some coastal systems are strongly influenced by temporal variability of river nitrogen loading, while these events are driven more by climate and oceanic dynamics in other systems. Our results emphasize that future prediction of marine ecosystem tipping points requires resolution of both oceanic and terrestrial (e.g. riverine) drivers of ocean change.

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