A large body of literature has shown that ecosystem dynamics is strongly influenced by large scale climate variations. A primary way by which climate can affect marine biological processes is through wind-driven changes of the ocean circulation, which are influenced by both natural and anthropogenically-induced variability. Simulations performed with 23 state-of-the-art climate models in support of the Intergovermental Panel for Climate Change (IPCC) Assessment Report 4 (AR4) are the principle means for examining climate change. The IPCC-AR4 simulations include runs with fixed external (solar, volcanoes, greenhouse gases) forcing (control simulations), as well as simulations where external forcing is prescribed according to the observed 20th century record (20th century simulations) or according to different climate change scenarios. These climate integrations are global and provide complete information on a large number of variables, including those relevant for marine ecosystems, at each model grid point. The output from the IPCC-AR4 simulations will be used to examine climate variability and change in the three GLOBEC regions (northeast Pacific, northwest Atlantic, and Southern Ocean) focusing on the following questions:
1. Does the present generation of climate models show connections between large-scale low-frequency wind forcing variations and ocean circulation changes in the three GLOBEC study areas similar to those that are believed to exist in nature? Can the IPCC-AR4 multi-model ensembles be used to extend the observational record and test hypotheses on the climate-circulation links with a larger statistical confidence?
2. Based on the most reliable climate models, to what extent will the influence of climate upon regional processes change over the 21st and 22nd centuries?
3. Can statistical downscaling methods be developed and used for relating variations at the regional (ecosystem) scale to large-scale climate forcing? Can specific parameters be identified that are more amenable to statistical downscaling?
The first question will be addressed by analyzing the control and 20th century simulations, while projections of the influence of climate on regional processes in the next century will be examined using the scenario simulations. Available data, as well as output from a regional model at different resolutions will be used to assess the feasibility of statistical downscaling.
This study will improve understanding of the links between large-scale climate forcing and physical processes important for ecosystem dynamics in different regions. The global nature of climate models enables a consistent means of establishing connections within and between different geographical regions. Thus, results from this study support the pan-regional synthesis phase of the GLOBEC program.
The present study has the potential to enhance the ability to predict ecosystem changes due to natural and/or anthropogenically induced climate variations. Results from this project can support regional ecosystem studies by providing a perspective of the large-scale forcing and its evolution in a changing climate, as well as boundary condition and forcing fields for regional models. Specifically, a key aspect of this project will be to provide output from the IPPC model simulations and guidance in how to use the output to other researchers funded through this phase of the GLOBEC program. Results from this study will also be presented to middle and high school students through the outreach programs at NOAA and at the investigators' Universities.
