Vertical mixing and elements of mesoscale dynamics over North Carolina shelf and contiguous Gulf Stream waters

2017 ◽  
Vol 67 (6) ◽  
pp. 783-798 ◽  
Author(s):  
Iossif Lozovatsky ◽  
Jesus Planella-Morato ◽  
Kipp Shearman ◽  
Qing Wang ◽  
Harindra Joseph S. Fernando
Keyword(s):  
North Carolina ◽  
Gulf Stream ◽  
Vertical Mixing ◽  
Mesoscale Dynamics ◽  
Stream Waters

scholarly journals The East Greenland Spill Jet*

2005 ◽  
Vol 35 (6) ◽  
pp. 1037-1053 ◽  
Author(s):  
Robert S. Pickart ◽  
Daniel J. Torres ◽  
Paula S. Fratantoni
Keyword(s):  
Gulf Stream ◽  
Current System ◽  
Vertical Mixing ◽  
Relative Vorticity ◽  
Boundary Current ◽  
Velocity Measurements ◽  
East Greenland ◽  
Irminger Sea ◽  
Denmark Strait ◽  
Vorticity Analysis

Abstract High-resolution hydrographic and velocity measurements across the East Greenland shelf break south of Denmark Strait have revealed an intense, narrow current banked against the upper continental slope. This is believed to be the result of dense water cascading over the shelf edge and entraining ambient water. The current has been named the East Greenland Spill Jet. It resides beneath the East Greenland/Irminger Current and transports roughly 2 Sverdrups of water equatorward. Strong vertical mixing occurs during the spilling, although the entrainment farther downstream is minimal. A vorticity analysis reveals that the increase in cyclonic relative vorticity within the jet is partly balanced by tilting vorticity, resulting in a sharp front in potential vorticity reminiscent of the Gulf Stream. The other components of the Irminger Sea boundary current system are described, including a presentation of absolute transports.

scholarly journals Submesoscale Cold Filaments in the Gulf Stream

2014 ◽  
Vol 44 (10) ◽  
pp. 2617-2643 ◽  
Author(s):  
Jonathan Gula ◽  
M. Jeroen Molemaker ◽  
James C. McWilliams
Keyword(s):  
Life Cycle ◽  
Gulf Stream ◽  
Baroclinic Instability ◽  
Vertical Mixing ◽  
Thermal Wind ◽  
Filament Dynamics ◽  
Oceanic Surface ◽  
Secondary Circulations ◽  
Order Of Magnitude ◽  
Surface Buoyancy

Abstract A set of realistic, very high-resolution simulations is made for the Gulf Stream region using the oceanic model Regional Oceanic Modeling System (ROMS) to study the life cycle of the intense submesoscale cold filaments that form on the subtropical gyre, interior wall of the Gulf Stream. The surface buoyancy gradients and ageostrophic secondary circulations intensify in response to the mesoscale strain field as predicted by the theory of filamentogenesis. It can be understood in terms of a dual frontogenetic process, along the lines understood for a single front. There is, however, a stronger secondary circulation due to the amplification at the center of a cold filament. Filament dynamics in the presence of a mixed layer are not adequately described by the classical thermal wind balance. The effect of vertical mixing of momentum due to turbulence in the surface layer is of the same order of magnitude as the pressure gradient and Coriolis force and contributes equally to a so-called turbulent thermal wind balance. Filamentogenesis is disrupted by vigorous submesoscale instabilities. The cause of the instability is the lateral shear as energy production by the horizontal Reynolds stress is the primary fluctuation source during the process; this contrasts with the usual baroclinic instability of submesoscale surface fronts. The filaments are lines of strong oceanic surface convergence as illustrated by the release of Lagrangian parcels in the Gulf Stream. Diabatic mixing is strong as parcels move across the filaments and downwell into the pycnocline. The life cycle of a filament is typically a few days in duration, from intensification to quasi stationarity to instability to dissipation.

FATE OF PETROLEUM COMPONENTS IN ESTUARINE WATERS OF THE SOUTHEASTERN UNITED STATES

1977 ◽  
Vol 1977 (1) ◽  
pp. 611-616 ◽  
Author(s):  
Richard F. Lee
Keyword(s):  
Water Samples ◽  
Gulf Stream ◽  
Atlantic Coast ◽  
Low Molecular Weight ◽  
Degradation Rates ◽  
Polycyclic Aromatic ◽  
Benzene Toluene ◽  
South Atlantic Coast ◽  
Detrital Particles ◽  
Stream Waters

ABSTRACT Radiolabeled hydrocarbons and phenols were added to water samples from the Skidaway and Cooper Rivers, two estuarine rivers on the U.S. south Atlantic coast. The adsorption of hydrocarbons to particles and microbial degradation of different petroleum components were the processes studied. Alkanes, low molecular weight aromatics (benzene, toluene, naphthalene and methylnaphthalene) and phenols were rapidly degraded to 14CO2. Low degradation rates were observed for the higher weight polycyclic aromatic hydrocarbons, fluorene, anthracene, benz(a)anthracene, and benz(a)pyrene, and from 12 to 70% of these hydrocarbons were absorbed to suspended particles in the water. Radioauto graphs of particles after the addition of 3H-benz(a)pyrene and 3H-hexadecane to the water samples indicated the hydrocarbons associated with detrital particles. This detritus was composed of a mixture of clay, organic matter, plankton remains and living microbes. One area of the Cooper River had visible oil slicks and the degradation rates of added heptadecane (20 μg/l), naphthalene (30 μg/l) and methylnaphthalene (30 μg/l) were 0.4, 2.8 and 1.1 μg/I/day, respectively. In contrast, at a downstream site, where there were no visible slicks, the degradation rate of these same hydrocarbons were 0.1, 0.7 and 0.1 μg/l/day, respectively. Estuarine water had much higher hydrocarbon degradation rates than offshore and Gulf Stream waters.

Characterization of Patches Along Transects Using High-Resolution 70-kHz Integrated Acoustic Data

1989 ◽  
Vol 46 (12) ◽  
pp. 2056-2064 ◽  
Author(s):  
R. W. Nero ◽  
J. J. Magnuson
Keyword(s):  
North Carolina ◽  
High Resolution ◽  
Gulf Stream ◽  
Window Size ◽  
Recognition Algorithm ◽  
Pass Filter ◽  
Acoustic Data ◽  
Cape Hatteras ◽  
High Pass

A patch recognition algorithm was applied to high-resolution (1 m vertical and 25 m horizontal) daytime sonar date collected from a 20-km-length transect to a depth of 200 m. The transect was oriented perpendicular to the Gulf Stream frontal zone, 105 km east–northeast ENE of Cape Hatteras, North Carolina, on August 8 1985. An adaptive high-pass filter was used to identify patches of high-intensity echo strengths. For a broad based averaging "window size" of 13 m deep by 1.4 km long and an echo strength threshold of 1.4 × integrated echo units patches resemble fine-scale features of the original echogram. A discrimination of patches using sonar statistics from within the patches gave good separation of slope water patches from patches belonging to four other water masses Slope water patches were characteristically small and of low mean scattering. Large but infrequent targets were present In the Gulf Stream, by contrast, patches contained more uniformly distributed targets with a higher mean scattering The observed correlation between echo patches, biological structures, and oceanographic features suggests that the measurement of echo statistics and our patch recognition techniques produce biologically meaningful parameters.

scholarly journals A Trajectory Approach to Analyzing the Ingredients Associated with Heavy Winter Storms in Central North Carolina

2013 ◽  
Vol 28 (3) ◽  
pp. 647-667 ◽  
Author(s):  
Christopher M. Fuhrmann ◽  
Charles E. Konrad
Keyword(s):  
Boundary Layer ◽  
North Carolina ◽  
Atmospheric Boundary Layer ◽  
Gulf Stream ◽  
Lower Troposphere ◽  
Marine Atmospheric Boundary Layer ◽  
Vertical Temperature Profile ◽  
Winter Storms ◽  
Ice Storms ◽  
Trajectory Approach

Abstract Winter storms, namely snowstorms and ice storms, are a major hazard and forecasting challenge across central North Carolina. This study employed a trajectory approach to analyze the ingredients (i.e., temperature, moisture, and lift) associated with heavy snowstorms and ice storms that occurred within the Raleigh, North Carolina, National Weather Service forecast region from 2000 to 2010. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) tool was used to calculate 72-h backward (i.e., upstream) air parcel trajectories from three critical vertical pressure levels at the time and location of heaviest precipitation for each storm. Analysis of composite trajectories revealed the source regions and meteorological properties of air parcels associated with heavy winter storms. Adiabatic and diabatic contributions to air parcel temperature and moisture content were also estimated along each trajectory to assess the physical processes connected with heavy winter precipitation in the region. Results indicate that diabatic warming and cooling contribute significantly to the vertical temperature profile during heavy winter storms and therefore dictate the resulting precipitation type. The main source of diabatic warming is fluxes of sensible and latent heat within the marine atmospheric boundary layer over the Gulf Stream. These fluxes contribute to a warming and moistening of air parcels associated with heavy ice storms. In contrast, heavy snowstorms are characterized by diabatic cooling in the lower troposphere above the marine atmospheric boundary layer. The most significant moisture source for heavy snowfall is the Caribbean Sea, while heavy ice storms entrain moisture from the Gulf of Mexico and Gulf Stream region near the Carolina coast.

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