Fenty, I.G., Wang, O., Lee, T., and Fukumori, I. (2024)
Presented at:
Ocean Sciences Meeting 2024The US West Coast is subject to extreme sea level variations on interannual timescales that can exceed the long-term sea level rise trend by an order of magnitude or more. It is well established that sea level anomalies along the US West Coast are correlated with the multivariate El Nino/Southern Oscillation index, the Pacific Decadal Oscillation index, and the Pacific-North America index. Each of these indices are themselves associated with large-scale atmospheric forcing anomalies which then begs the question: exactly which atmospheric forcing anomalies are responsible for driving the observed interannual coastal sea surface variations? In this study we employ a global ocean state estimate from the ECCO Consortium and its adjoint to 1) identify the dynamical sensitivity pathways that link atmospheric forcing anomalies to US West Coast sea level anomalies and 2) quantify the relative contributions of local and nonlocal wind stress, buoyancy forcing, and air/sea freshwater fluxes to past interannual sea level variations. The main findings build on earlier research (e.g., Verdy et al. 2014) that show that on timescales longer than 1 day, nonlocal winds are overwhelming responsible for driving sea level anomalies. Extending previous work, we find that the relevant wind stress anomalies can be split into two well-defined regions: a near-coastal box spanning the equator to the US/Canadian border (where alongshore wind stress anomalies generate coastally-trapped waves) and an offshore box spanning the entire Pacific Ocean between 10S and 10N (where zonal wind stress anomalies generate equatorial Kelvin waves. Finally, we describe the implications for improving predictions of US West Coast sea level anomalies.
