Gulf Stream Marine Hydrokinetic Energy Off Cape Hatteras, North Carolina

2020 ◽  
Vol 54 (6) ◽  
pp. 24-36
Author(s):  
Michael Muglia ◽  
Harvey Seim ◽  
Patterson Taylor
Keyword(s):  
Turbulent Mixing ◽  
Gulf Stream ◽  
Velocity Structure ◽  
Vertical Shear ◽  
Small Scale ◽  
Western Boundary ◽  
Horizontal Shear ◽  
Hydrokinetic Energy ◽  
Cape Hatteras ◽  
Marine Hydrokinetic

AbstractMulti-year measurements of current velocity, salinity, and temperature from fixed and vessel-mounted sensors quantify Gulf Stream (GS) marine hydrokinetic energy (MHK) resource variability and inform development off Cape Hatteras, NC. Vessel transects across the GS demonstrate a jet-like velocity structure with speeds exceeding 2.5 m/s at the surface, persistent horizontal shear throughout the jet, and strongest vertical shears within the cyclonic shear zone. Persistent equatorward flow at the base of the GS associated with the Deep Western Boundary Current (DWBC) produces a local maximum in vertical shear where stratification is weak and is postulated to be a site of strong turbulent mixing. Repeated transects at the same location demonstrate that the velocity structure depends upon whether the GS abuts the shelf slope or is offshore.Currents from a fixed acoustic Doppler current profiler (ADCP) deployed on the shoreward side of the GS exceed 1 m/s 64% of the time 40 m below the surface. The 3.75-year time series of currents from the ADCP mooring document large, roughly weekly variations in downstream and cross-stream speed (−0.5 to 2.5 m/s) and shear (± 0.05 s−1) over the entire water column due to passage of GS meanders and frontal eddies. Current reversals from the mean GS direction occur several times a month, and longer period variations in GS offshore position can result in reduced currents for weeks at a time. Unresolved small-scale shear is postulated to contribute significantly to turbulent mixing.

Gulf stream marine hydrokinetic energy resource characterization off Cape Hatteras, North Carolina USA

2016 ◽  
Author(s):  
Ruoying He ◽  
John Bane ◽  
Mike Muglia ◽  
Sara Haines ◽  
Caroline Lowcher ◽  
...  
Keyword(s):  
North Carolina ◽  
Gulf Stream ◽  
Energy Resource ◽  
Hydrokinetic Energy ◽  
Cape Hatteras ◽  
Marine Hydrokinetic

scholarly journals Sensitivity of winter North Atlantic-European climate to resolved atmosphere and ocean dynamics

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Reindert J. Haarsma ◽  
Javier García-Serrano ◽  
Chloé Prodhomme ◽  
Omar Bellprat ◽  
Paolo Davini ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Gulf Stream ◽  
Ocean Dynamics ◽  
Small Scale ◽  
Western Boundary ◽  
The North ◽  
The North Atlantic ◽  
Mean Climate ◽  
Meso Scale

Abstract Northern Hemisphere western boundary currents, like the Gulf Stream, are key regions for cyclogenesis affecting large-scale atmospheric circulation. Recent observations and model simulations with high-temporal and -spatial resolution have provided evidence that the associated ocean fronts locally affect troposphere dynamics. A coherent view of how this affects the mean climate and its variability is, however, lacking. In particular the separate role of resolved ocean and atmosphere dynamics in shaping the atmospheric circulation is still largely unknown. Here we demonstrate for the first time, by using coupled seasonal forecast experiments at different resolutions, that resolving meso-scale oceanic variability in the Gulf Stream region strongly affects mid-latitude interannual atmospheric variability, including the North Atlantic Oscillation. Its impact on climatology, however, is minor. Increasing atmosphere resolution to meso-scale, on the other hand, strongly affects mean climate but moderately its variability. We also find that regional predictability relies on adequately resolving small-scale atmospheric processes, while resolving small-scale oceanic processes acts as an unpredictable source of noise, except for the North Atlantic storm-track where the forcing of the atmosphere translates into skillful predictions.

Fused Closed-Loop Flight Dynamics and Wake Interaction Modeling of Tethered Energy Systems

2018 ◽  
Author(s):  
Joe Deese ◽  
Peyman Razi ◽  
Michael Muglia ◽  
Praveen Ramaprabhu ◽  
Chris Vermillion
Keyword(s):  
Gulf Stream ◽  
Energy Systems ◽  
Flight Dynamics ◽  
The United States ◽  
Energy Output ◽  
Eastern Coast ◽  
Hydrokinetic Energy ◽  
Wake Interaction ◽  
Interaction Modeling ◽  
Marine Hydrokinetic

In this paper, we present a fused flight dynamics and wake interaction modeling framework for arrays (farms) of tethered wind and marine hydrokinetic energy systems. The replacement of conventional towers with tethers necessitates a dynamic model that captures the flight characteristics of each system, whereas the arrangement of the systems in an array necessitates a wake interaction model. The integration of these components is unique to the tethered energy systems literature and is applicable to both airborne wind energy systems and tethered marine hydrokinetic energy systems. In the application case study of this paper, we focus specifically on arrays of ocean current turbines (OCTs), which are intended to operate in the deep waters of the Gulf Stream, adjacent to the eastern coast of the United States. In particular, we evaluate the dynamic performance and resulting projected energy output of an array of tethered OCTs, based on real Gulf Stream resource data from an acoustic Doppler current profiler (ADCP) located adjacent to Cape Hatteras, North Carolina.

Small-Scale Signal in Mean Dynamic Topographies Applying Combined Geoid Models

2020 ◽  
Author(s):  
Frank Siegismund ◽  
Xanthi Oikonomidou ◽  
Philipp Zingerle
Keyword(s):  
High Resolution ◽  
Gulf Stream ◽  
Ocean Surface ◽  
Ocean Dynamics ◽  
Small Scale ◽  
Western Boundary ◽  
Low Resolution ◽  
Geoid Model ◽  
Near Surface ◽  
Dependent Signal

<p>The Dynamic ocean Topography (DT) describes the deviation of the true ocean surface from a hypothetical equilibrium state ocean at rest forced by gravity alone. With the geostrophic surface currents obtained from its gradients the DT is an essential parameter for describing the ocean dynamics. Observation-based global temporal Mean geodetic DTs (MDTs) are obtained from the difference of altimetric Mean Sea Surface (MSS) and the geoid height, that equipotential surface of gravity closest to the ocean surface.</p><p>The geoid is provided either as a satellite-only, or a combined model including in addition gravity anomalies derived from satellite altimetry and ground data. In recent years the focus was on satellite-only models, produced from new space-born observations obtained from the Gravity Recovery and Climate Experiment (GRACE) and Gravity field and Ocean Circulation Explorer (GOCE) satellite missions. Moreover, combined geoid models are only cautiously used for MDT calculation, since it is still in question to what extent the gravity information obtained from altimetry is distorted by the MDT information included therein and how this translates into errors of the MDT.</p><p>Here we want to concentrate on MDT models based on recent combined geoid models. An assessment is provided based on comparisons to near-surface drifter data from the Global Drifter Program (GDP). Besides providing a general, global assessment, we focus on signal content on small scales, addressing mainly two questions: 1) Do MDTs obtained from combined geoid models contain signal for scales smaller than resolvable by the<br>satellite-only models? 2) Is there a maximum resolution beyond which no signal is detectable?</p><p>Until recently, these questions couldn't be answered since low resolution MDTs usually contained strong wavy-structured errors and thus needed a strong spatial filtering thereby killing the smallest scales resolved in the MDT. These errors, which worsen with lower resolution, are caused by Gibbs effects provoked by imperfections in bringing the high resolution ocean-only MSS models into spectral consistency with the much lower resolved global geoid model. A new methodology, however, improves the necessary globalization of the MSS. After subtraction of the geoid model, subsequent cutting-off the signal beyond a specific spherical harmonic degree and order (d/o) results in an MDT without any Gibbs effects, also for low resolution models.</p><p>To answer the questions posed above applying the new methodology, the scale-dependent signal in MDTs for different geoid models is presented for a list of cut off d/os. To minimize the influence of noise on the results we concentrate on strong signal Western Boundary Currents like the Gulf Stream and the Kuroshio. For the Gulf Stream results of a high resolution hydrodynamic model are available and presented as an independent method to estimate the scale dependent signal.</p>

scholarly journals Marine Hydrokinetic Energy from Western Boundary Currents

2017 ◽  
Vol 9 (1) ◽  
pp. 105-123 ◽  
Author(s):  
John M. Bane ◽  
Ruoying He ◽  
Michael Muglia ◽  
Caroline F. Lowcher ◽  
Yanlin Gong ◽  
...  
Keyword(s):  
Western Boundary ◽  
Western Boundary Currents ◽  
Hydrokinetic Energy ◽  
Boundary Currents ◽  
Marine Hydrokinetic

The Combined Effects of Gulf Stream–Induced Baroclinicity and Upper-Level Vorticity on U.S. East Coast Extratropical Cyclogenesis

2005 ◽  
Vol 133 (8) ◽  
pp. 2494-2501 ◽  
Author(s):  
Neil A. Jacobs ◽  
Gary M. Lackmann ◽  
Sethu Raman
Keyword(s):  
North Carolina ◽  
Gulf Stream ◽  
Additional Data ◽  
Large Fraction ◽  
Coastal Region ◽  
Western Boundary ◽  
Absolute Vorticity ◽  
Surface Cyclone ◽  
Cape Hatteras ◽  
Upper Level

Abstract The Atlantic Surface Cyclone Intensification Index (ASCII) is a forecast index that quantifies the strength of low-level baroclinicity in the coastal region of the Carolinas. It is based on the gradient between the coldest 24-h average air temperature at Cape Hatteras and Wilmington, North Carolina, and the temperature at the western boundary of the Gulf Stream. The resulting prestorm baroclinic index (PSBI) is used to forecast the probability that a cyclone in the domain will exhibit rapid cyclogenesis. The initial ASCII study covered the years 1982–90. This dataset was recently expanded to cover the years 1991–2002, which doubled the number of cyclone events in the sample. These additional data provide similar position and slope of the linear regression fits to the previous values, and explain as much as 30% of the variance in cyclone deepening rate. Despite operational value, the neglect of upper-tropospheric forcing as a predictor in the original ASCII formulation precludes explanation of a large fraction of the deepening rate variance. Here, a modified index is derived in which an approximate measure of upper-level forcing is included. The 1991–2002 cyclone events were separated into bins of “strongly forced,” “moderately forced,” and “weakly forced” based on the strength of the nearest upstream maximum of 500-mb absolute vorticity associated with the surface low. This separation method reduced the scatter and further isolated the contributions of surface forcing versus upper-level forcing on extratropical cyclogenesis. Results of the combined upper-level index and surface PSBI demonstrate that as much as 74% of the deepening rate variance can be explained for cases with stronger upper-level forcing.

Hydrokinetic Energy Resource Assessment of the Gulf Stream Near Cape Hatteras, North Carolina

2014 ◽  
Author(s):  
Asif Kabir ◽  
Ivan J. Lemongo ◽  
Arturo Fernandez
Keyword(s):  
North Carolina ◽  
Gulf Stream ◽  
Energy Resource ◽  
Resource Assessment ◽  
Ocean Model ◽  
Likelihood Method ◽  
Ocean Current ◽  
Hydrokinetic Energy ◽  
Cape Hatteras ◽  
Promising Source

The Gulf Stream near the coasts of North Carolina is considered a promising source of hydrokinetic energy. A statistical analysis is conducted to assess the energy available for extraction in this region. Weibull distribution is used as the Probability Density Function (PDF) for this purpose. The ocean current velocity data are collected from the ‘HYbrid Coordinate Ocean Model (HYCOM)’. The data are collected at a depth of 20 m from the sea surface which is considered a good position for energy extraction. The Weibull parameters from the analysis are calculated using the maximum likelihood method. The direction of the ocean current was found to be mostly uniform in this region. The theoretical power density of this region was estimated to be more than 275 W/m2 around 70% of the time and exceeded 2000 W/m2 around 10% of the time.

scholarly journals A Laboratory Study of Nonlinear Western Boundary Currents, with Application to the Gulf Stream Separation due to Inertial Overshooting*

2011 ◽  
Vol 41 (11) ◽  
pp. 2063-2079 ◽  
Author(s):  
Stefano Pierini ◽  
Pierpaolo Falco ◽  
Giovanni Zambardino ◽  
Thomas A. McClimans ◽  
Ingrid Ellingsen
Keyword(s):  
Gulf Stream ◽  
Functional Dependence ◽  
Western Boundary ◽  
Western Boundary Currents ◽  
Weakly Nonlinear ◽  
Boundary Currents ◽  
First Case ◽  
Highly Nonlinear ◽  
Cape Hatteras ◽  
Small Change

Abstract Various dynamical aspects of nonlinear western boundary currents (WBCs) have been investigated experimentally through physical modeling in a 5-m-diameter rotating basin. The motion of a piston with a velocity up that can be as low as up = 0.5 mm s−1 induces a horizontally unsheared current of homogeneous water that, flowing over a topographic beta slope, experiences westward intensification. First, the character of WBCs for various degrees of nonlinearity is investigated. By varying up, flows ranging from the highly nonlinear inertial Charney regime down to a weakly nonlinear regime can be simulated. In the first case, the dependence of zonal length scales on up is found to be in agreement with Charney’s theory; for weaker flows, a markedly different functional dependence emerges describing the initial transition toward the linear, viscous case. This provides an unprecedented coverage of nonlinear WBC dependence on an amplitude parameter in terms of experimental data. WBC separation from a wedge-shaped continent past a cape (simulating Cape Hatteras) due to inertial overshooting is then analyzed. By increasing current speed, a critical behavior is identified according to which a very small change of up marks the transition from a WBC that follows the coast past the cape to a WBC (nearly dynamically similar to a full-scale Gulf Stream) that separates from the cape without any substantial deflection, as with the Gulf Stream Extension. The important effect of the deflection angle of the continent is analyzed as well. Finally, the qualitative effect of a sloping sidewall along a straight coast is considered: the deflection of the flow away from the western wall due to the tendency to preserve potential vorticity clearly emerges.

scholarly journals Is Interleaving in the Agulhas Current Driven by Near-Inertial Velocity Perturbations?

2007 ◽  
Vol 37 (4) ◽  
pp. 932-945 ◽  
Author(s):  
Lisa M. Beal
Keyword(s):  
Surface Water ◽  
Sea Water ◽  
Salinity Gradient ◽  
Water Masses ◽  
Vertical Shear ◽  
Small Scale ◽  
Exact Nature ◽  
Intermediate Water ◽  
Horizontal Shear ◽  
Agulhas Current

Abstract Recent observations taken at a number of latitudes in the Agulhas Current reveal that the water mass structure on either side of its dynamical core is distinctly different. Moreover, interleaving of these distinct water masses is observed at over 80% of the stations occupied in the current, particularly within the subsurface density layer between tropical surface water and subtropical surface water masses, and within the intermediate layer between the Antarctic Intermediate Water and Red Sea water masses. Direct velocity measurements allow for a comparison between the characteristic vertical length scales of the Agulhas intrusions and those of velocity perturbations found throughout the current. It is found that the interleaving scales match those of the velocity perturbations, which are manifest as high-wavenumber vertical shear layers and are identified as near-inertial oscillations. Furthermore, the properties of the intrusions indicate that double diffusion is not an important process in their development: they are generally not associated with a density anomaly, their slope and thickness fall outside the predicted maxima for instability, and a strong horizontal shear field acts to separate water parcels more quickly than intrusions would be able to grow by double-diffusive processes. Instead, the position, thickness, and slope of Agulhas intrusions relative to the background salinity and density field suggest that they are forced by rotating inertial velocities, with subsequent growth possibly driven by small-scale baroclinic instabilities. However, not all the evidence points conclusively toward advectively driven intrusions. For instance, there is a discrepancy between the observed salinity anomaly amplitude and the predicted inertial displacement given the background salinity gradient, which deserves further examination. Hence, there is a future need for more pointed observations and perhaps the development of an analytical or numerical model to understand the exact nature of Agulhas intrusions.

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