OCEAN PHYTOPLANKTON BIOGEOGRAPHY: EARTH SYSTEM MODEL ESTIMATES AT COARSE AND FINE RESOLUTION

The base of the oceanic food web is composed of unicellular photosynthetic organisms called phytoplankton. These microscopic autotrophs are present in the photic zone and are crucial to oceanic ecological processes. A considerable amount of research has been conducted on the impact of phytoplankton on the ocean’s biogeochemical cycles. However, less is known about the geographical distribution of the different major groups of phytoplankton. Here we use the National Center for Atmospheric Research’s Community Earth System Model (CESM) to analyze the geographical distribution of diatoms and small phytoplankton in the Southern Ocean. The Southern Ocean is a major contributor to the sequestration of anthropogenic CO₂. This makes the understanding of phytoplankton in this region even more paramount for predicting how climate change will affect the world’s oceanic carbon cycles.

The CESM is capable of simulating atmospheric, oceanic, land surface, sea ice, and biogeochemical processes. Ocean phytoplankton and circulation are simulated at two horizontal resolutions: 1°x 1° and 0.1°x 0.1°. Here we seek to determine the differences in phytoplankton community structure as they are represented by the model output. Assessing these differences will help to determine whether phytoplankton growth parameterizations in one or both model resolutions are sufficiently simulating the phytoplankton dynamics of the Southern Ocean.