GREENCYCLESII
2.5 Impacts of future climate change on marine phytoplankton
The main goal of this project is to improve our ability to project and assess the impact of future climate change on marine phytoplankton production and assemblages, with special emphasis on the relative contribution of the key phytoplankton functional types to production and export.
Two types of methods will be employed. The first approach consists of a semi-empirical model, i.e. a model that combines a simple prognostic model of production on the basis of chlorophyll with statistical relationships to determine the relative contribution of each phytoplankton functional group to production (Jin et al., 2006, Deutsch et al., 2007). This model can be used to predict the future distribution of phytoplankton functional groups and their contribution to production and export once one knows the physical environment and the total amount of chlorophyll. The latter can be estimated using the empirical relationships of Sarmiento et al. (2004), while the former can be extracted from a large suite of global climate models that were run as part of WCRP CMIP3 (IPCC) and available through the openly accessible archive (PCMDI).
For this project, we will use an upper range (IPCC A2) and a lower range (IPCC B1) scenario, focusing on the 21st century, but extending, where possible, the time range until 2200. The second approach is the more commonly used fully prognostic approach of forcing coupled physical-biogeochemical-ecological ocean models with future surface ocean/lower atmosphere boundary conditions extracted from coupled climate models. To this end, the ocean component of the NCAR CCSM will be employed at ETH. As its ecological/biogeochemical component, this model employs the Biogeochemical Elemental Cycling (BEC) of Moore/Doney, which considers 4 phytoplankton functional types. At a later stage, simulation output from the 2ndphase of the MAREMIP project will be investigated as well.
This dual approach will permit to assess the possible future changes in phytoplankton functional types with substantially greater robustness. First, because it permits us to consider a much wider range of possible physical changes in the ocean through our use of many climate models (more than 20 are currently available through PCMDI). Second, because the semi-empirical and the fully prognostic model approaches are completely independent, and have complementary strengths and weaknesses, permitting us to assess also the robustness of the ecological models across a wider range of approaches.
Primary Supervisor: Prof Nicolas Gruber (Eidgenössische Technische Hochschule Zürich)
Secondary Supervisor: Dr Laurent Bopp (Commisariat de l'Energie Atomique)
Fellow: Charlotte Laufkoetter (ESR)