ABSTRACT

The four main Eastern Boundary Upwelling Systems (EBUS) regions, i.e., the U.S. West Coast, the Humboldt Current, the Canary Current, and Benguela Current, are host to some of the most productive marine ecosystems on the planet. All four are also characterized by large inter-annual to inter-decadal variability and vulnerability to climate change through systematic changes in alongshore winds, upwelling, cloud, and gyre-scale ocean currents. Unfortunately, the evolution of these critical environments over the coming decades has received comparatively little attention. This is partly because their essential characteristics (alongshore winds and cloud shaped by local topography and upwelling ribbons) are only tens of km in width and are not well-resolved by current climate models. In addition, processes smaller in scale than the model resolution mediate the relationship between key ecosystem properties and the physical system, making it very difficult to understand consequences of changes in the physical system for marine ecosystems based on model output alone. In this project the team of investigators will address this gap by undertaking an unprecedented suite of high-resolution regional earth system model simulations. The result of this project will be a comprehensive understanding of the consequences of climate change and its interplay with decadal variability over the coming decades for all four EBUS regions. Members of a cross-disciplinary team consisting of a climate scientist, two oceanographers, a marine biogeochemist and a software engineer will train two graduate students. The project will lay essential groundwork for further study of climate impacts on upper trophic levels and prediction of fish populations in EBUS regions. Moreover, the earth system model development work will lay the groundwork for the scientific community to study higher-trophic-level response of marine ecosystems to climate variability and change. Marine ecosystem variability has profound implications for natural resource management, and it is anticipated that this project will be of great interest to stakeholders and the general public. With the help of an environmental communications expert, the team will develop and execute an outreach effort that includes identification and coordination of stakeholders for the U.S. West Coast EBUS. A stakeholder workshop will be organized where the project team will present their research, and stakeholders will present information needs to the project team. An outcome of the workshop will be a white paper outlining research needs and next steps for marine conservation and management in the context of a changing climate.

This project is focused on the future evolution of the four Eastern Boundary Upwelling Systems (EBUS). Three interconnected research themes will be pursued: (1) Air-sea-land interaction at the regional scale, (2) Climate change signals in EBUS regions, and (3) Climate controls on marine ecosystems. A suite of high-resolution regional earth system model simulations will be undertaken. They involve: (1) Historical reconstructions of the variations of the recent past in all four EBUS regions. These reanalysis-driven simulations will be used to validate the regional model against available observations and characterize the substantial variability of the regions' physical and ecosystem states. All sets of experiments will be performed for the U.S. West Coast and Humboldt EBUS regions first, and then the lessons learned will be leveraged to perform the same series of experiments for the two other major upwelling systems. (2) Mid-century future climate simulations for all EBUS regions. These simulations, driven by global climate model (GCM) output, will be used to quantify and understand physical and ecosystem changes due to anthropogenic forcing. They will also be analyzed together with the historical reconstructions to quantify the importance of anthropogenic signals relative to the regions' natural variability, and detect anthropogenic signals in the recent past. To maximize relevance to decadal prediction, the future climate experiments will emphasize the mid-21st-century time frame. However, we will also undertake one experiment focused on end-of-century to have a more extreme climate change signal to analyze. (3) Process evaluation simulations in select EBUS regions. These are also reanalysis-driven, but with key processes disabled. These experiments will allow for a quantification and understanding of the key processes shaping variability and change. The EBUS regions will be compared to one another to understand processes driving upwelling variability and associated biogeochemical responses. The major ecosystem dynamics of interest will include: controls on magnitude and seasonality of upwelling and temperature; controls on magnitude and seasonality of productivity; controls on intensity and spatial scale of hypoxia, and its relationship to circulation and productivity.

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