Climate change impacts on nutrient and export production (EP) distributions

Yi Liu, University of California, Irvine, Department of Earth System Science, Irvine, CA, United States and Jefferson Keith Moore, University of California Irvine, Earth System Science, Irvine, United States
We use a simulation with the Community Earth System Model 1.0 (hereafter CESM) to examine global nutrient distributions and export production from 1850-2300 under a strong global warming scenario (RCP8.5-ECP8.5). Global nutrient distributions are regulated by both biogeochemical and physical dynamics. In the Southern Ocean, biological production around Antarctica steadily increases, leading to localized nutrient trapping in the subsurface layer and a large reduction in the northward transport of nutrients in the Ekman layer. This helps to initiate a net transfer of nutrients to the deep ocean (Moore et al., 2018). In low and mid-latitudes, nutrients steadily decrease in the surface and subsurface water and increase in the deep ocean. Export production (EP), which is measured by the sinking flux at the depth of 100m, is also steadily decreasing mainly due to net primary production (NPP) decreases and magnified by the phytoplankton community structure shift. In the Arctic, surface nutrients steadily decrease due to larger biological production whereas subsurface nutrient trapping occurs in the 21st century and disappears after 2100s. EP in Arctic increases first and then decreases after 2100s which are highly related to the NPP change. To fully understand the regulating factors of nutrient and EP distributions in different latitudes (i.e. Southern Ocean, low- and mid-latitudes and Arctic), we will examine and quantify the relative roles of each physical and biological process by nutrient budgets. Slowing thermohaline circulation appears to play an important role in sequestering nutrients in the deep ocean under persistent, multicentury global warming.