Objectives
Hypotheses and Objectives
Hypothesis 1: The Gulf Stream influences Shelfbreak Front detachment and shelf-open ocean exchange near Cape Hatteras through variability in its cross-slope position, path curvature, and velocity structure.
Objective 1.1: Quantify variability in Gulf Stream position, path curvature, and velocity structure at daily to interannual timescales using in situ and remotely-sensed observations. Reproduce observed Gulf Stream variability with a realistic numerical simulation.
Objective 1.2: Measure temporal changes in Shelfbreak Jet detachment latitude, detached Jet trajectory, and export of MAB shelf waters carried in the detached jet. Relate these variations to Gulf Stream metrics (Objective 1.1). Use numerical modeling with realistic forcing and bathymetry to evaluate the role of pressure gradients in Shelfbreak Jet detachment and to quantify momentum and vorticity balances.
Objective 1.3: Investigate the role of Gulf Stream position, path curvature, and velocity structure on bidirectional exchange south of the Shelfbreak Front detachment, both north and south of the Gulf Stream separation point.
Hypothesis 2: Wind-driven changes in the position of the Hatteras Front relative to spatial gradients in shelf bathymetry significantly influence shelf-open ocean exchange along the seaward flank of the Hatteras Front, drive episodic export adjacent to Diamond Shoals, and modulate shoreward flow and recirculation associated with the nose of the Hatteras Front.
Objective 2.1: Use idealized numerical modeling to examine the impact of changes in shoreline orientation, bathymetric features and barriers (e.g., Diamond Shoals), and wind direction and magnitude on along-shelf position and cross-shelf/slope exchange along an idealized Hatteras Front.
Objective 2.2: Measure temporal changes in Hatteras Front position and associated circulation with high-resolution observations near Cape Hatteras. In combination with measurements of meteorological variables north and south of Diamond Shoals, including during storms, correlate forcing with shelf response. Use realistic numerical modeling to quantify and diagnose shelf-open ocean exchange during typical conditions and the passage of major storms.
Hypothesis 3: Density changes in MAB and SAB shelf waters and upper continental slope waters determine the cross-frontal density gradients and key dynamical parameters that define the circulation associated with these fronts. Density changes that result from events, seasonal variability, and long- term trends affect frontal velocities and the response of the fronts to wind and Gulf Stream forcing.
Objective 3.1: Quantify variability in cross-frontal density gradients, frontal positions, and corresponding frontal parameters (e.g., Rossby number, Burger number, Richardson number) to evaluate evolution of the Hatteras Front and Shelfbreak Front near Cape Hatteras at synoptic, seasonal, and longer timescales using in situ and remote sensing observations.
Objective 3.2: Use realistic numerical modeling to quantify the variability of these frontal parameters and determine the sensitivity of front-associated shelf circulation and shelf-open ocean exchange as functions of frontal characteristics determined from observations.