The Inner-Shelf Dynamics Experiment

Abstract

The inner shelf, the transition zone between the surf zone and the mid shelf, is a dynamically complex region with the evolution of circulation and stratification driven by multiple physical processes. Cross-shelf exchange through the inner shelf has important implications for coastal water quality, ecological connectivity, and lateral movement of sediment and heat. The Inner-Shelf Dynamics Experiment (ISDE) was an intensive, coordinated, multi-institution field experiment from Sep.-Oct. 2017, conducted from the mid shelf, through the inner shelf and into the surf zone near Point Sal, CA. Satellite, airborne, shore- and ship-based remote sensing, in-water moorings and ship-based sampling, and numerical ocean circulation models forced by winds, waves and tides were used to investigate the dynamics governing the circulation and transport in the inner shelf and the role of coastline variability on regional circulation dynamics. Here, the following physical processes are highlighted: internal wave dynamics from the mid shelf to the inner shelf; flow separation and eddy shedding off Point Sal; offshore ejection of surfzone waters from rip currents; and wind-driven subtidal circulation dynamics. The extensive dataset from ISDE allows for unprecedented investigations into the role of physical processes in creating spatial heterogeneity, and nonlinear interactions between various inner-shelf physical processes. Overall, the highly spatially and temporally resolved oceanographic measurements and numerical simulations of ISDE provide a central framework for studies exploring this complex and fascinating region of the ocean.

Vorticity Recirculation and Asymmetric Generation at a Small Headland With Broadband Currents

“…As part of the Inner Shelf Dynamics Experiment (Kumar et al., 2020), two months of fixed ADCP velocity measurements in ∼ 20 m depth near the asymmetric headland Pt. Sal CA are used to investigate headland vorticity generation and recirculation.…”

“…In the fall of 2017, multiple institutions participated in the Inner Shelf Dynamics Experiment funded by an Office of Naval Research Departmental Research Initiative (ISDE; Kumar et al., 2020; Lerczak et al., 2019). The experiment consisted of observations spanning 50 km alongshore on the Central CA coast, centered on the asymmetric rocky headland Pt.…”

“…Sal (Colosi et al., 2018; Feddersen et al., 2020; Kumar et al., 2019), adding complexity. During the experiment, a broad array of 173 moorings and bottom landers were deployed from 100 m to 9 m depth along the 50 km stretch of coastline with many ADCPs, thermistors, and wave buoys in conjunction with multiple coastal high‐frequency radars and meteorological stations (Kumar et al., 2020). In addition, two week‐long intensive operations periods (IOPs) were conducted, one in mid‐September (IOP1) and the other in mid‐October (IOP2) with multiple vessels and aircraft sampling concurrently.…”

“…Here, we address these headland vorticity related questions with a two‐month (fall 2017) time‐series of vorticity estimated at two locations across Pt. Sal, a small O (1 km) asymmetric headland with O (1) aspect ratio located on the central California coast (Figure 1), during the Inner‐shelf Dynamics Experiment (Kumar et al., 2020). This region often has a headland wake as illustrated with a long‐wave infrared (LWIR) surface temperature and ADCP‐measured flow (e.g., Figure 1) with cool water (blue/green colors) streaming off Pt.…”

Warm and Cool Nearshore Plumes Connecting the Surf Zone to the Inner Shelf

“…Airborne remote sensing observations were collected on the Central California coast near Point Sal in September–October 2017 as part of the Office of Naval Research Inner Shelf Departmental Research Initiative (Kumar et al., 2020). Observations spanned 60 km of coastline with multiple headlands, channeled nearshore morphology, and little freshwater influence.…”