A Principal Oscillation Pattern Analysis of the Circulation Variability in the California Current System Associated With the El Niño Southern Oscillation. Issue 11 (24th November 2019)

• Record Type: Journal Article
• Authors: Crawford, William J.; Moore, Andrew M.; Fiechter, Jerome; Edwards, Christopher A.
• Is Part Of: Journal of geophysical research. Volume 124:Issue 11(2019)
• Page Start: 8241
• Page End: 8256
• Publication Date: 2019-11-24
• Subjects: California Current -- POPs -- ENSO; Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2019JC015346
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: A linear inverse model of the circulation of the California Current System was constructed from a 31‐year sequence of circulation estimates based on a data assimilative configuration of the Regional Ocean Modeling System. Principal oscillation pattern (POP) analysis of the linear inverse model has identified several distinct dynamical modes, one with an oscillation period of 3.6 years that describes much of the observed circulation variability of the California Current System associated with the El Niño Southern Oscillation (ENSO). This POP captures not only the circulation changes due to large amplitude ENSO events but also that associated with many of the weak‐to‐moderate events as well. The POP describes both nearshore and offshore variability and captures many of the previously identified phase relations between different circulation variables, unifying them as part of a coherent three‐dimensional time‐evolving mode of the circulation. The connection between the POP and the ocean surface forcing was also explored revealing their spatiotemporal connections to the ENSO circulation variability. Analysis of the dynamical balances of POP circulation anomalies reveals fundamentally different dynamical regimes in nearshore and offshore regions and sheds light on the possible role of wind‐induced baroclinic instability in modulating eddy kinetic energy during large ENSO events. Plain Language Summary: A computer model and observations of the ocean were combined to compute a best estimate of the ocean circulation along the west coast of North America. These circulation estimates were then used to explore the variations in the circulation of the California Current system that are associated with the El Niño Southern Oscillation phenomenon. The analysis is based on isolating variations in the circulation that occur simultaneously in space and time in ocean temperature, salinity, ocean currents, and sea surface height. While most previous studies have focused primarily on just a few aspects of the circulation in isolation, this study is unique in its contemporaneous treatment of all aspects of the circulation. The result is a detailed and coherent view of the circulation changes that occur in the California Current system during what are known to be major climate events. Key Points: A dynamical mode of variability associated with ENSO along the California coast is identified Dynamic balances of some important circulation features are identified Unifies previously identified features as a consistent, coherent, three‐dimensional, time‐dependent mode