All Climate Events

Wednesday, November 28, 2018. 12:00PM. Tracing Nitrogen Across the River-Coast-Ocean Continuum. Xiao Liu, Cooperative Institute for Climate Science. Sponsored by NOAA GFDL. More information here.

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 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. We investigate coastal retention time scales, transport pathway of river nitrogen, and its biogeochemical impact through application of high-resolution global ocean-ice-ecosystem models (MOM6-SIS2-COBALT) with time varying river 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, 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.