National Science Foundation, Division of Ocean Sciences, Earth System Models

EASM-3: Collaborative Research: Quantifying Predictability Limits, Uncertainties, Mechanisms, and Regional Impacts of Pacific Decadal Climate Variability

Arthur J. Miller and Aneesh Subramanian

Award: $586,827
Duration: 2014-2017

Collaborators: Yu-Heng Tseng (NCAR), Hyodae Seo (Woods Hole Oceanographic Institution), Emanuele Di Lorenzo (Georgia Tech)

Project Summary.
Climate in the Pacific sector is well known to vary on decadal timescales, but the mechanisms that control these long-term climate variations are still unclear. If the mechanisms can be better understood, then the uncertainties associated with making climate predictions on these timescales can be assessed more accurately. Decadal variability of Pacific climate is of particular interest in the U.S. due to its downstream influence over the western U.S. and its direct influence on climate in Alaska. This leads to the primary focus of our proposal:
Overarching Question: What are the predictability limits, mechanisms, and regional impacts for decadal modes of the Pacific climate system?
There is clearly a large gap in our understanding of what controls Pacific decadal climate variability, what limits the predictability of the flows, and what practical skill might be useful in regional impacts on land and in the ocean. Given the availability of a major new climate model, the Community Earth System Model (CESM), a coordinated research effort is needed to better understand basic physical dynamics of Pacific decadal variability and assess the skill of Pacific decadal predictability, along with its uncertainties and practical value.
We propose a wide-ranging, coordinated research effort to address key issues of Pacific decadal climate predictability, driving mechanisms, and regional impacts. The proposed work brings together scientists skilled with developing decadal climate diagnostics, making both statistical and dynamical predictions, and executing regional coupled climate downscaling and regional high-resolution ocean modeling to work together to address a suite of important issues in a multi-faceted research program involving senior scientists, early career scientists, post-docs, and graduate students. The research focuses on CESM, with its vast repository of archived runs supplemented with targeted predictability experiments. The analysis focuses on using sophisticated statistical models (Linear Inverse Models) to identify statistical relations among variables, diagnose physical processes, and isolate potentially predictable components of the flows. It also involves using regional coupled atmosphere-ocean, along with uncoupled ocean and atmosphere models, to enhance the understanding of regional response and its potential for practical use in forecasting.
The results will be important in assessing how long-term changes in the environment drive changes in economically important variables such as rainfall, soil moisture, snowfall, temperatures, as well as oceanic temperatures, currents and sea levels, which impacts fisheries, agriculture, and coastal infrastructure along the U.S. West Coast and Asian Marginal Seas. We expect that our techniques will be transferable to other global sectors that also exhibit decadal variability.
The team will mentor graduate students and post-docs, whose educational experiences will include cross-disciplinary exposure to ocean science, atmospheric science, and societal impacts that will be unique in this context. We also will continue our various efforts of community outreach by giving lectures and educational presentations in public forums, mentoring K-12 students, educating grass-roots climate action organizations, informing the media, and posting our research results on web pages.