Fig. 1. Map of study area showing locations of USGS/WHOI instrumentation (triangles), and NOAA instrumentation (circles). Bathymetric contours every 5 m. USGS tripods A–F shown as triangles, sites B and C were also instrumented with moorings (see Table 1). NOAA instrumentation includes the Ambrose Light Station (AL), Fire Island Buoy (44025), and Sandy Hook Tide Gage (SH).

Fig. 2. Wave velocities, near-bed currents, and suspended sediment concentration for the entire deployment. Forcing summarized using (a) wave-orbital velocities, and (b) near-bed currents measured at sites A and D. Suspended sediment concentrations (panels c and d) show resuspension during December–January, but high turbidity during times of low energy in February–March.

Fig. 3. Half-hourly values of along and across-valley current observed 5 mab. (a–d) Velocities from Hudson Shelf Valley (sites A, B, C, and F) rotated to the direction of net velocity; (e–f) values from adjacent shelves (sites D and E) in N/E coordinate system. Ninety hours of data missing from site E filled with data synthesized as described in text; synthesized data plotted using dashed lines.

Fig. 4. December–January time-series of (a) winds, (b) sea-level setup relative to mean sea level, (c) wave-orbital velocity, and (d) along-valley currents from site A. Wind stress calculated from wind speeds measured at the Ambrose Light Station (see NODC, 1993). Wind stress values plotted as >0 indicate wind components from the east (gray) or north (black). Wave orbital velocities calculated from tripod-measured values at sites A, B, and D (described in text). Low-pass filter (<1/35 h) applied to Sandy Hook tide gauge data (NOAA, 2000) to estimate setup in (b).

Fig. 5. (a–e): Suspended sediment concentration for sites A, B, C, D, and E at heights of 1.2 mab and 0.5 mab (black, gray lines, respectively; see legend in panel a). (f): Sediment concentrations estimated by light attenuation from transmissometers moored 10–40 mab at sites B and C (see legend). Note different scales on panels (a)–(f). Values plotted represent values interpolated to a half-hourly timebase.

Fig. 6. Half-hourly averaged sediment flux based on OBS measurements and near-bed current velocities 0.5 mab (sites A, B, C, and E), and 1 mab (site D). Vectors for A–C rotated so that vertical represents flux along the axis of the shelf valley. North/east coordinate system used for sites D and E. Up-valley transport events identified by light gray shading; darker shading designates down-valley directed events.

Fig. 7. Time-integrated wind stress (Pa s/1000) calculated using hourly winds from Ambrose Light (see NODC, 1993); shown as direction from which the wind blows. Momentum from each directional bin for (a) entire record December 1999–January 2000; (b) during up-valley transport events; and (c) during down-valley transport events with 10-fold change in scale.

Fig. 8. Sea-level setup, relative to mean sea level, for December 1999–January 2000 calculated by applying a low-pass filter to the tide gage record from Sandy Hook, N.J. (NOAA, 2000). Shading indicates times identified as up-valley and down-valley transport events, and times that were not distinguished as transport events in the shelf valley.

Fig. 9. (a) Model estimates of combined wave-current bed shear stress (τ_b), bed shear stress due to currents (τ_c), and bed shear stress due to waves (τ_w) for tripod site A based on BASS measurements of current velocity 1 mab. (b) Ratio of current shear stress to total shear stress. Shading identifies the 12 up-valley (light gray), and 2 down-valley (dark gray) directed transport events.

Fig. 10. Comparison of model estimates of shear velocity induced by currents to Reynolds’ stress values obtained from BASS sensor for December 1999–January 2000 at site A. The agreement is good during times when wave influence is small, but wave-orbital motions corrupt Reynolds’ stress estimates during energetic waves (u₀>5 cm/s and u₀/u_1mab>0.3; shown as “o”).

Fig. 11. Seventeen year record of (a) winter (December–January) and (b) springtime (February–April) wind conditions from Ambrose Light Tower. Bar height equal to average wind stress magnitude; shading represents relative strength of winds from directional bins (E, NE, N, NW, etc.). The NW and NE bins marked with black and white asterisks (*), respectively. Each winter period labeled by new year; for example, the December 1999–January 2000 interval is labeled “2000”.

Fig. 12. Sixteen year record of sea level at Sandy Hook, N.J. for winter (December–January) and springtime (February–April) conditions. The frequency of time that a 10 cm (a) set-down or (b) setup occurred is indicated by bar heights. Each winter period labeled by new year.

Fig. 13. Eleven year record of the frequency of energetic waves from Ambrose Light Station for winter (December–January) and springtime (February–April) conditions. Each winter period labeled by new year.

Table 1. Instruments deployed from December 1999–April 2000

Field sites provided as site name (A–F, see Fig. 1), and water depth in meters. Instrument locations listed as height (meters above the bed, mab) or depth (meters below water surface, mbs). Tripod deployments included measurements of temperature and conductivity near the water surface from SEA-CAT sensors mounted beneath surface floats.

Table 2. Grain-size distribution of disaggregated surface sediment collected within 150 m of tripod sites in December 1999 and April 2000

Two samples were obtained at all sites except B; values represent average of two samples. Size distributions of material recovered from sediment traps deployed 1.1 and 2.1 mab on tripods A and D also provided.

Table 3. Vertical structure of currents during December 1999 and January 2000

(a) in the Hudson Shelf Valley and (b) on adjacent shelves. Mean current speed (average magnitude of current, |Not-found|), mean velocity (vector average of current, |Not-found|), anisotropy of variance (based on standard deviations of minor and major axis of currents: σ_min and σ_maj), and direction of net current (° clockwise from north) for near-bed and bottom boundary layers. The direction chosen as “up-valley” for sites A, B, C, and F provided in bold.

Table 4. Correlation coefficients (−1<ρ<1) between the principle component of sub-tidal velocities measured 5 mab

Also shown are the correlations between these velocity components and sub-tidal sea-level at Sandy Hook (SH).

Table 5. Sediment transport summarized for sites A–E by the magnitude and direction of cumulative flux (directions provided in parenthesis) derived from point measurements of concentration and velocity

The “Dec–Jan” column provides cumulative flux from the beginning of the deployment (December 4, 1999) through the end of the 14 identified transport events (January 30, 2000). Transport during 14 coherent transport events summarized by the cumulative flux during 12 up-valley and 2 down-valley directed events. The final column summarizes transport during periods not included in coherent transport events. Cumulative flux provided as g/cm². Directions of net flux provided as clockwise from North (0°=to the north, 90°=to the east, etc.).