Hunter
Elias J.
Hunter
Elias J.
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DatasetProcessed data from Particle Imaging Velocimetry (PIV) observations of Tritia trivittata and Tritia obsoleta behavior in various flow tanks(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2018-07-13) Fuchs, Heidi L. ; Gerbi, Gregory P. ; Hunter, Elias J. ; Christman, Adam J.Dispersing marine larvae can alter their physical transport by swimming vertically or sinking in response to environmental signals. However, it remains unknown whether any signals could enable larvae to navigate over large scales. We tested whether flow-induced larval behaviors vary with adults' physical environments using congeneric snail larvae from the wavy continental shelf (Tritia trivittata) and from turbulent inlets (Tritia obsoleta). This dataset includes observations of larvae in turbulence, in rotating flows dominated by vorticity or strain rates, and in rectilinear wave oscillations. Larval and water motion were observed using near-infrared particle image velocimetry (IR PIV), and analyses identified threshold signals causing larvae to change their direction or magnitude of propulsive force. The two species reacted similarly to turbulence but differently to waves, and their transport patterns would diverge in wavy, offshore regions. Wave-induced behaviors provide evidence that larvae may detect waves as both motions and sounds useful in navigation. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/739790
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ArticleThe impact of wind forcing on the thermal wind shear of a river plume(American Geophysical Union, 2019-10-31) Mazzini, Piero L. F. ; Chant, Robert J. ; Scully, Malcolm E. ; Wilkin, John L. ; Hunter, Elias J. ; Nidzieko, Nicholas J.A 38-day long time series obtained using a combination of moored Wirewalkers equipped with conductivity-temperature-depth profilers and bottom-mounted and subsurface acoustic Doppler current profilers provided detailed high-resolution observations that resolved near-surface velocity and vertical and cross-shelf density gradients of the Chesapeake Bay plume far field. This unprecedented data set allowed for a detailed investigation of the impact of wind forcing on the thermal wind shear of a river plume. Our results showed that thermal wind balance was a valid approximation for the cross-shelf momentum balance over the entire water column during weak winds (|𝜏w 𝑦 | < 0.075 Pa), and it was also valid within the interior during moderate downwelling (−0.125< 𝜏w 𝑦 < −0.075 Pa). Stronger wind conditions, however, resulted in the breakdown of the thermal wind balance in the Chesapeake Bay plume, with thermal wind shear overestimating the observed shear during downwelling and underestimating during upwelling conditions. A momentum budget analysis suggests that viscous stresses from wind-generated turbulence are mainly responsible for the generation of ageostrophic shear.
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ArticleTurbulent mixing in a far‐field plume during the transition to upwelling conditions : microstructure observations from an AUV(John Wiley & Sons, 2018-09-23) Fisher, Alexander W. ; Nidzieko, Nicholas J. ; Scully, Malcolm E. ; Chant, Robert J. ; Hunter, Elias J. ; Mazzini, Piero L. F.A REMUS 600 autonomous underwater vehicle was used to measure turbulent mixing within the far‐field Chesapeake Bay plume during the transition to upwelling. Prior to the onset of upwelling, the plume was mixed by a combination of energetic downwelling winds and bottom‐generated shear resulting in a two‐layer plume structure. Estimates of turbulent dissipation and buoyancy flux from a nose‐mounted microstructure system indicate that scalar exchange within the plume was patchy and transient, with direct wind mixing constrained to the near surface by stratification within the plume. Changing wind and tide conditions contributed to temporal variability. Following the separation of the upper plume from the coast, alongshore shear became a significant driver of mixing on the shoreward edge of the plume.
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ArticleEstuarine boundary layer mixing processes : insights from dye experiments(American Meteorological Society, 2007-07) Chant, Robert J. ; Geyer, W. Rockwell ; Houghton, Robert ; Hunter, Elias J. ; Lerczak, James A.A series of dye releases in the Hudson River estuary elucidated diapycnal mixing rates and temporal variability over tidal and fortnightly time scales. Dye was injected in the bottom boundary layer for each of four releases during different phases of the tide and of the spring–neap cycle. Diapycnal mixing occurs primarily through entrainment that is driven by shear production in the bottom boundary layer. On flood the dye extended vertically through the bottom mixed layer, and its concentration decreased abruptly near the base of the pycnocline, usually at a height corresponding to a velocity maximum. Boundary layer growth is consistent with a one-dimensional, stress-driven entrainment model. A model was developed for the vertical structure of the vertical eddy viscosity in the flood tide boundary layer that is proportional to u2*/N∞, where u* and N∞ are the bottom friction velocity and buoyancy frequency above the boundary layer. The model also predicts that the buoyancy flux averaged over the bottom boundary layer is equal to 0.06N∞u2* or, based on the structure of the boundary layer equal to 0.1NBLu2*, where NBL is the buoyancy frequency across the flood-tide boundary layer. Estimates of shear production and buoyancy flux indicate that the flux Richardson number in the flood-tide boundary layer is 0.1–0.18, consistent with the model indicating that the flux Richardson number is between 0.1 and 0.14. During ebb, the boundary layer was more stratified, and its vertical extent was not as sharply delineated as in the flood. During neap tide the rate of mixing during ebb was significantly weaker than on flood, owing to reduced bottom stress and stabilization by stratification. As tidal amplitude increased ebb mixing increased and more closely resembled the boundary layer entrainment process observed during the flood. Tidal straining modestly increased the entrainment rate during the flood, and it restratified the boundary layer and inhibited mixing during the ebb.
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DatasetHudson River estuary 2002 field experiment: moorings(Woods Hole Oceanographic Institution, 2023-09-20) Geyer, W. Rockwell ; Chant, Robert J. ; Houghton, Robert ; Lerczak, James A. ; Hunter, Elias J. ; Conley, MargaretThis dataset includes data from moorings deployed in the Hudson River estuary during the spring of 2002. The moorings were deployed at Spuyten Duyvil for 43 days and included a cross-channel array of temperature and conductivity sensors as well as 4 upward-looking ADCPs and 2 pressure sensors flanking the channel.