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  • 1
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    Relative dispersion in the Nordic Seas (2009)
    Sears Foundation for Marine Research
    In:  Journal of Marine Research, 67 (4). pp. 411-433.
    Details
    Publication Date: 2020-07-23
    Description: We examine the relative dispersion of surface drifters deployed in the POLEWARD experiment in the Nordic Seas during 2007–2008. The drifters were launched in pairs and triplets, yielding 67 pairs with an initial separation of 2 km or less. There were 26 additional pairs from drifters which subsequently came near one another. As these produced statistically identical dispersion to the original pairs, we used them as well, yielding 93 pairs. The relative dispersion exhibits three phases. The first occurs during the first two days, at spatial scales less than 10 km. The dispersion increases approximately exponentially during this period, with an e-folding time of roughly half a day. During the second phase, from 2 to roughly 10 days and scales of 10 to roughly 100 km, the dispersion increases as a power law, with r2 α t3. At the largest spatial and temporal scales, the dispersion increases linearly in time and the pair velocities are uncorrelated, consistent with diffusive spreading. We use a stochastic model with a representative mean flow to test the effect of the mean shear on dispersion. The model produces dispersion comparable to the observed during the second and third phases but fails to capture other statistics, such as the PDFs of the displacements. These statistics are instead suggestive of an inverse energy cascade, from the deformation scale up to 100 km.
    Type: Article , PeerReviewed
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  • 2
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    Dispersal of the Protozoan Folliculina Simplex Dons (Ciliophora, Heterotricha) Throughout the North Atlantic Ocean on the Shells of Gastropod Veliger Larvae (1973)
    Sears Foundation for Marine Research
    In:  Journal of Marine Research, 31 (1). pp. 11-20.
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    Publication Date: 2020-07-23
    Type: Article , PeerReviewed
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  • 3
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    An experimental study of a mesoscale vortex colliding with topography of varying geometry in a rotating fluid (2007)
    Sears Foundation for Marine Research
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    Publication Date: 2022-05-25
    Description: Author Posting. © Sears Foundation for Marine Research, 2004. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 62 (2004): 611-638, doi:10.1357/0022240042387583.
    Description: The interaction of a self-propagating barotropic cyclonic vortex with an obstacle has been investigated and the conditions for a vortex to bifurcate into two vortices determined. As in a previous study, after a self-propagating cyclonic vortex came into contact with the obstacle, fluid peeled off the outer edge of the vortex and a so-called "streamer" went around the obstacle in a counterclockwise direction. Under certain conditions, this fluid formed a new cyclonic vortex in the wake of the obstacle, causing bifurcation of the original vortex into two vortices. In the present study we performed three sets of idealized laboratory experiments with the aim of investigating the importance on the bifurcation mechanism of the obstacle's horizontal cross sectional geometry, the influence of the height of the obstacle, and the importance of the slope of the obstacle sidewalls. The present results suggest that bifurcation occurs only when the obstacle height is equal or larger than 85% of the vortex height and that steep sloping sidewalls do not influence the bifurcation mechanism. In addition, experiments performed using an obstacle with an elliptical horizontal cross section revealed that the relevant parameter governing the occurrence of bifurcation is the length which the "streamer" has to travel around the obstacle, and not the dimension of the obstacle in the direction orthogonal to the motion of the vortex. Collisions of oceanic mesoscale vortices with seamounts often result in major modifications of their structure, having significant impacts on the redistribution of water properties. Observations of a "Meddy" bifurcating after colliding with the Irving Seamount in the Canary Basin show behavior similar to these idealized laboratory experiments. This suggests that these results could be used to explain and predict the outcome of a vortex colliding with seamounts of varying geometry in the ocean.
    Description: Support was given by the National Science Foundation project number OCE-0081756.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
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    On rectification of randomly forced flows (2007)
    Sears Foundation for Marine Research
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    Publication Date: 2022-05-25
    Description: Author Posting. © Sears Foundation for Marine Research, 2005. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 63 (2005): 497-527, doi:10.1357/0022240054307894.
    Description: Nonlinear rectification of the ocean circulation driven by random forcing, which simulates the effect of unresolved eddies, is studied in an idealized closed basin. The results are based on the analysis of randomly forced solutions and linear eigenmodes. Depending on the forcing strength, two rectification regimes are found: zonal jets and isolated gyres. It is shown that both regimes are due to nonlinear interactions of resonant basin modes. In the zonal-jet regime, these interactions involve complex interplay between resonant baroclinic modes and some secondary modes. Both Rhines' scaling for zonal jets and prediction of gyres based on the maximum entropy argument are not confirmed.
    Repository Name: Woods Hole Open Access Server
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  • 5
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    Available potential energy in the world's oceans (2007)
    Sears Foundation for Marine Research
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    Publication Date: 2022-05-25
    Description: Author Posting. © Sears Foundation for Marine Research, 2005. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 63 (2005): 141-158, doi:10.1357/0022240053693770.
    Description: It is shown that in the case with bottom topography, the available gravitational potential energy cannot be represented by the available pressure potential energy. Thus, a suitable quantity for the study of large-scale circulation is the total available potential energy which is defined as the sum of available gravitational potential energy and available internal energy. A simple computational algorithm for calculating the available potential energy in the world's oceans is proposed and tested. This program includes the compressibility of seawater and realistic topography. It is estimated that the world's oceans available gravitational potential energy density is about 1474 J/m3 and the available internal energy density is -850 J/m3; thus, the net available potential energy density is 624 J/m3, and the total amount of available potential energy is 805 × 1018 J.
    Repository Name: Woods Hole Open Access Server
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  • 6
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    Buoyancy-forced circulations in shallow marginal seas (2007)
    Sears Foundation for Marine Research
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Sears Foundation for Marine Research, 2005. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 63 (2005): 729-752, doi:10.1357/0022240054663204.
    Description: The properties of water mass transformation and the thermohaline circulation in shallow marginal seas with topography and subject to surface cooling are discussed in the context of an eddy-resolving primitive equation model and an analytic planetary geostrophic model. A unique and important aspect of the model configuration is that the geostrophic contours, or characteristics of the system, extend from a region where temperature is restored toward a uniform value, providing a source of heat, through the cooling region. This removes a degree of symmetry that has often been imposed in previous studies of deep convection. The heat loss within the marginal sea is balanced by lateral advection from the restoring region. The planetary geostrophic model shows that the basic temperature distribution can be well predicted by integrating along geostrophic contours from their entry into the marginal sea to their exit. Scaling estimates for the exchange rate and density of the waters formed within the marginal sea are derived and compare well with a series of numerical model calculations. In contrast to many previous buoyancy-forced deep convection problems, basin-scale cooling is balanced mainly by the mean flow, with mesoscale eddies serving primarily to restratify locally but not to provide a net heat flux to balance cooling. However, eddy fluxes and the mean flow are locally of comparable importance for cases with a localized patch of surface cooling.
    Description: This work was supported by the Office of Naval Research under Grant N00014-03-1-0338 and by the National Science Foundation under Grant OCE-0240978.
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  • 7
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    Shear and turbulence production across subtidal channels (2007)
    Sears Foundation for Marine Research
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Sears Foundation for Marine Research, 2006. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 64 (2006): 147-171, doi:10.1357/002224006776412359.
    Description: In intertidal regions with subtidal channels, effects of bathymetry on overlying flow vary greatly with tidal stage. Around low water when mudflats and marsh are exposed, flow is constrained to channels, but when water depths are greater, tidal forcing may not necessarily be aligned with meandering channel axes. Flow across the channel can generate strong shear and turbulence at the elevation of the channel banks and can significantly increase turbulent energy in the middle of the water column. Field observations in a mudflat channel of San Francisco Bay indicate that cross-channel shear regularly occurs there early in ebb tides. With increased freshwater flow, baroclinic forcing can enhance shear by decoupling flow between dense water flooding in the channel and fresher water ebbing above the channel banks. A water column numerical model with κ-ε turbulence closure is modified to represent the cross-channel shear production. Numerical results with uniform density indicate that turbulence production increases with the angle between the barotropic tidal forcing and the channel axis. When a longitudinal salinity gradient is imposed, cross-channel shear production contributes to breakdown of periodic stratification. Turbulence produced at the channel banks locally exceeds dissipation, and the excess energy is either lost to buoyancy or diffuses vertically to lower energy regions near the surface and near the bed. The balance among shear production, buoyancy production, and diffusion of turbulence depends on the flow angle and the strength of the longitudinal salinity gradient.
    Description: This research was funded by National Institutes of Health grant no. P42ES0475 from the National Institute of Environmental Health Sciences.
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  • 8
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    A double-diffusive interface tank for dynamic-response studies (2007)
    Sears Foundation for Marine Research
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Sears Foundation for Marine Research, 2005. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 63 (2005): 263-289, doi:10.1357/0022240053693842.
    Description: A large tank capable of long-term maintenance of a sharp temperature-salinity interface has been developed and applied to measurements of the dynamical response of oceanographic sensors. A two-layer salt-stratified system is heated from below and cooled from above to provide two convectively mixed layers with a thin double-diffusive interface separating them. A temperature jump exceeding 10°C can be maintained over 1–2 cm (a vertical temperature gradient of order 103°C/m) for several weeks. A variable speed-lowering system allows testing of the dynamic response of conductivity and temperature sensors in full-size oceanographic instruments. An acoustic echo sounder and shadowgraph system provide nondisruptive monitoring of the interface and layer microstructure. Tests of several sensor systems show how data from the facility is used to determine sensor response times using several fitting techniques and the speed dependence of thermometer time constants is illustrated. The linearity of the conductivity–temperature relationship across the interface is proposed as a figure of merit for design of lag-correction filters to accurately match temperature and conductivity sensors for the computation of salinity. The effects of finite interface thickness, slow sensor sampling rates and the thermal mass of the conductivity cell are treated. Sensor response characterization is especially important for autonomous instruments where data processing and compression must be performed in-situ, but is also helpful in the development of new sensors and in assuring accurate salinity records from traditional wire-lowered and towed systems.
    Description: This research was supported by the National Science Foundation, grants OCE-97-11869 and OCE-02-40956, NOAA CORC grant 154368 and a WHOI Mellon Technical Staff Award.
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  • 9
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    Quantifying seasonal air-sea gas exchange processes using noble gas time-series : a design experiment (2007)
    Sears Foundation for Marine Research
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Sears Foundation for Marine Research, 2006. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 64 (2006): 267-295, doi:10.1357/002224006777606452.
    Description: A multi-year time-series of measurements of five noble gases (He, Ne, Ar, Kr, and Xe) at a subtropical ocean location may allow quantification of air-sea gas exchange parameters with tighter constraints than is currently available by other methods. We have demonstrated this using a one-dimensional upper ocean model forced by 6-hourly NCEP reanalysis winds and heat flux for the Sargasso Sea near Bermuda. We performed ensemble model runs to characterize the response of the modeled noble gas saturation anomalies to a range of air-sea gas exchange parameters. We then used inverse calculations to quantify the sensitivity of the parameters to hypothetical observations. These calculations show that with currently achievable measurement accuracies, noble gas concentrations in the Sargasso Sea could be used to constrain the magnitude of equilibrium gas exchange to ±11%, the magnitude of the total air injection flux to ±14%, and the magnitude of net photosynthetic oxygen production to ±1.5 mol O2 m−2 y−1. Additionally, we can use noble gases to quantify the relative contributions of bubbles that are partially dissolved to bubbles that are completely dissolved. These constraints are based on idealized assumptions and may not fully account for some of the uncertainties in the meteorological data, in lateral transport processes, and in the solubilities of the noble gases. As a limited demonstration, we applied this approach to a time series of He, Ne, Ar, and O2 measurements from the Sargasso Sea from 1985 to 1988 (data from Spitzer, 1989). Due to the limited number of gases measured and the lower accuracy of those measurements, the constraints in this example application are weaker than could be achieved with current capabilities.
    Description: This work was supported by the National Science Foundation Chemical Oceanography program (OCE-0221247) and by the Department of Defense (graduate fellowship to RHRS).
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  • 10
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    Tidal fronts and their role in air-sea gas exchange (2007)
    Sears Foundation for Marine Research
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Sears Foundation for Marine Research, 2006. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 64 (2006): 483-515, doi:10.1357/002224006778715766.
    Description: Tidal fronts are a common feature of many coastal environments. They are characterized by a surface convergence zone that enhances wave breaking and the generation of gas bubbles due to wave-current interaction. The associated downwelling currents carry bubbles to depths of up to 160 m and increase the amount of air that dissolves from them. An energetic tidal front is formed at the entrance to the Strait of Georgia, BC, Canada, by a hydraulically controlled sill flow with vertical velocities of up to 0.75 m s−1. Extensive ship-board measurements during two cruises are interpreted with models of wave-current interaction and gas bubble behavior. The observations suggest that tidal fronts may contribute significantly to the aeration of the subsurface waters in the Fraser Estuary. This process may be also of importance for other coastal environments with plunging sill flows of dense water that deliver aerated surface water to intermediate depths.
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