Altimetric Studies of the Oceanic Pathways in the Northeast Pacific Ocean
Event: 2022 Ocean Surface Topography Science Team Meeting
Session: Science II: Large Scale Ocean Circulation Variability and Change
Presentation type: Type Oral
Contribution: PDF file
Our research addresses a long-standing question in Eastern Boundary Upwelling Systems (EBUS): Over what distances are water parcels and passive species carried along the coast or onshore/offshore by the normal seasonal progression of currents or by anomalous events? A well-discussed example is the varying presence and absence of warm-water and cold-water zooplankton species in the northern region of the California Current System (CCS) during both seasonal variability and ENSO extremes. Observations of changes in water properties and species have been used to hypothesize transports from tropical or subarctic domains, but there have been few efforts to quantify realistic transport distances. Numerical circulation models have been used in a few regions to estimate Lagrangian trajectories, but to verify these hypothesized and modeled transports, Lagrangian trajectories based on observations are needed. We are using time series of mapped geostrophic velocities, derived from 28+ years of satellite altimeter observations, to calculate geostrophic Lagrangian trajectories of passive water parcels in the upper ocean around and within the California Current System, during normal seasonal cycles and anomalous climate events (ENSO extremes, marine heat waves, etc.). The geostrophic trajectories represent approximate movements beneath the Ekman layer. To include the wind-driven effects and the deeper currents, we employ results of a high-resolution numerical ocean circulation model to calculate 3-D tracer and water parcel trajectories, complementing the altimeter analysis. We also calculate trajectories using two data sets that combine geostrophic and Ekman components. In this presentation we show examples of the trajectories calculated from the various fields, addressing the question of transports between the northern and southern CCS during seasonal cycles and interannual events.