Mechanisms of US West Coast Climate Variability and Change in Observations and Models

The US West Coast (USWC) hosts an extremely productive marine ecosystem and supports
important ecosystem services. The El Niño Southern Oscillation (ENSO) is known to influence
USWC upwelling through both atmospheric teleconnections and oceanic wave processes, but not
all El Niño events have a significant impact on USWC sea surface temperatures (SSTs).

Conversely, extreme SST conditions can occur in this region even without significant El Niño
warming in the tropical Pacific. Other modes of variability like the Pacific Decadal Oscillation
(PDO) and the North Pacific Gyre Oscillation (NPGO) modulate USWC conditions at decadal
timescales, but their interplay in USWC variability, and their roles in the development, evolution
and decay of extreme USWC conditions are not fully understood. Similarly, not much is known
about the influence of long-term climate change on USWC conditions. While the frequency and
severity of extreme warm conditions are generally projected to increase in a warming climate, the
exact mechanisms and characteristics of these extreme conditions have not yet been investigated.
To address the above gaps in knowledge, this project will: 1) Examine the leading dynamical
processes responsible for interannual/decadal temperature variations along the USWC and their
extreme expressions; 2) Assess the fidelity of the latest generation of climate models in simulating
USWC variability in general and extreme USWC conditions in particular, and how they are
influenced by larger-scale climate variability; and 3) Investigate how USWC variability and its
extremes will change in a warming climate.

We will use observational data sets in conjunction with oceanic and coupled reanalysis products
to identify the key dynamical processes underlying temperature variations along the USWC and
their extremes, and to provide a baseline for evaluating the fidelity of state-of-the-art climate
models in representing the full range of observed USWC conditions. The more realistic models in
this regard will then be used to examine how USWC conditions will change in the future. The
above questions will be addressed using a broad set of diagnostic approaches, ranging from heat-
budget analysis for process understanding to multivariate regressions and Linear Inverse Modeling
methodologies.

The proposed project directly addresses Priority Area A of the solicitation in seeking to “identify
key climate/oceanic processes that affect ocean biogeochemistry of relevance to fisheries and
other living marine resources” along the USWC, a region of great value for NMFS. The careful
inter-comparisons of models and observations performed in this project will provide an assessment
of the models’ ability to realistically simulate climate variability along the USWC for the right
reasons, and will thus also closely align with Priority Areas B and C.

Climate Risk Area: Marine Ecosystems