DOCSLIB.ORG

OCNG 251: Oceanography and Developing Our Wings on the Way Down Spring 2012 Kurt Vonnegut the Surface of the Ocean: 1) Waves 1

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
OCNG 251: Oceanography and Developing Our Wings on the Way Down� Spring 2012 Kurt Vonnegut the Surface of the Ocean: 1) Waves 1 We have to continually be jumping off cliffs OCNG 251: Oceanography and developing our wings on the way down Spring 2012 Kurt Vonnegut The surface of the Ocean: 1) Waves 1. Waves: Beware of the man who works hard to learn a. Anatomy of a wave something, learns it, and finds himself no b. Wave motion: speed and energy c. Deep- & Shallow-water waves wiser than before. […] He is full of murderous resentment of people who are ignorant without having come by their ignorance the hard way. Kurt Vonnegut, "Cat's Cradle" a. Anatomy of a wave a. Anatomy of a wave A wave can be regarded initially as an ideal a sinusoidal wave (though Ideal waves: If some water is lifted up and allowed to fall back the ideal regular waves bears little resemblance to real waves under the action of gravity, its inertia will cause it to overshoot observed at sea ! irregular in form and period) the equilibrium position. Pressure forces will then push it back up and oscillation will ensue. Energy can be transmitted at the interface (boundary) between A two fluids of different densities ! progressive orbital waves Characteristics: • H: Height (2 x A) • L: Wavelength (from crest to crest) • T: Period (time required for two successive crests to pass a point) • h: Depth of water column below mean surface level a. Anatomy of a wave a. Anatomy of a wave All waves can be regarded as A few waves: A case of temporal- and spatial-scales " Progressive waves, in that energy is travelling through, or across the surface of, the material (i.e. water) " Standing waves (i.e. plucked guitar strings) can be considered as the sum of two progressive waves of equal dimensions but traveling in opposite direction (later…) Waves can result from periodic and non-periodic disturbance of the water surface: In the case of non-periodic disturbances, the water particles are displaced from an equilibrium position ! restoring force acts to bring back equilibrium to the system (flat water level): # Gravitational force exerted by Earth # Surface tension (tendency of water molecules to stick together and present the smallest possible surface to the air) Water waves are affected by both of these forces: $ When L ≤ 1.7 cm ! capillary waves $ When L > 1.7 cm ! gravity waves (main interest of oceanography!) Waves are classified according to their wave period Sea level Sea level change Sea level change ! Oscillation due to geological changes in the Sea level change ! Oscillation due to geological changes in the hydrological cycle hydrological cycle a.Anatomy of a wave a. Anatomy of a wave The ideal relationship among wave properties. If one Wind waves: characteristic can be measured, the other two can be calculated. As the wind blows ! formation of ripples (capillary waves) As the wind increases in speed ! waves become larger (gravity waves) Variety and size of wind-generated waves are controlled by four principal factors: • Wind velocity • Wind duration • Unobstructed distance over which wind blows (fetch) • Original sea state a. Anatomy of a wave a. Anatomy of a wave Although the Wind as a causing factor: The relationship is a direct one… relationship is a direct one… Wind Wave Wave Wave Fetch Duration One condition will Speed Height Length Period (km) (h) always be limiting as (km/h) (m) (m) (s) to the maximum 20 25 2.8 0.33 10.6 3.2 development of wave 30 77 7 0.88 22.2 4.6 height and period! 60 660 27.5 5.1 89.2 9.9 e.g. Wind Speed: 30 kn 90 2446 65 13.9 201.6 13.9 Fetch: 200 nm Time: 40 hrs H ~ 7 m T ~ 12 sec a. Anatomy of a wave b. Wave motion: Speed and energy Although the There are mathematical relationships linking the characteristics relationship is a of wavelength (L), wave period (T) and wave height (H) to direct one… wave speed and to wave energy. One condition will Wave speed (celerity) ! speed = distance/time always be limiting as to the maximum C = L/T (time one wavelength takes to pass a certain point) development of wave Wave speed can also be represented by the equation: height and period! gL 2πh e.g. C = tanh( ) Wind Speed: 30 kn 2π L Fetch: 100 nm Where: Time: 10 hrs " g = acceleration due to gravity " L = Wavelength H ~ 3.5 m " tanh = hyperbolic tangent T ~ 7.5 sec " h = water depth c. Wave motion: Speed Approximations b. Wave motion: Speed Approximations 1) For h > L/2 ! Deep-water waves 1) For h > L/2 (L < 2h) ! Deep-water waves If x is larger than π, then tanh x ~ 1 tanh (2πh/L) = 1 (within 0.5%) gL 2πh C = tanh( ) 2π L gL or 1.25 L 2π Circular motion of particles ! Exponential decrease of path with depth! Wavelength (or period) is the only variable affecting the wave speed! The change in pressure (size of the orbit) is undetectable at a water depth ≥ L/2 (the wave base) € c. Wave motion: Speed Approximations b. Wave motion: Speed Approximations 2) For h < L/20 (L > 20h) ! Shallow-water waves 2) For h < L/20 ! Shallow-water waves If x is small, then tanh x ~ x tanh (2πh/L) = (2πh/L) (within 3%) gL 2πh C = tanh( ) 2π L gh or 3.1 h Or: C= L/T = (gh)1/2 ! L = 3.13 (h)1/2.T Elliptical motion of particles The water depth is the only variable affecting the wave speed! Exponential decrease of vertical path with depth Not of horizontal path! c. Wave motion: Speed Approximations c. Wave motion: Speed Approximations 1) For h > L/2 ! Deep-water waves (L < 2h) 2) For h < L/20 ! Shallow-water waves (L > 20h) Deep-water waves that have the longest wavelength and greatest period, will arrive first in regions distant from the storm which 3) For L/20<h<L/2 (2h < L < 20h) generated them: The separation of waves by virtue of their differing rates of travel (speed) is known as dispersion. For h > L/2 (L < 2h) ! Deep-water waves gL 2π or 1.25 L € c. Wave motion: Group Speed c. Wave motion: Group Speed Individual waves do not persist for long in the open Ocean. They usually only exist for as long as they take to pass through a group of waves. i.e. two sets of waves: in phase and out of phase Individual waves do not persist for long in the open Ocean. They usually only exist for as long as they take to pass through a group of waves. If two sets of waves are interfering to produce a succession of wave groups, the group speed (Cg) is: C1× C2 C 2 C Cg = Cg = Cg = C1+ C2 2C 2 € c. Wave motion: Speed Approximations c. Wave motion: Speed Approximations Assume You have a storm blowing at 30 knots (nautical mile = Assume You have a storm blowing at 30 knots (nautical mile = 1.853 km) over a fetch of 100 nautical miles for 10 hours. 1.853 km) over a fetch of 100 nautical miles for 10 hours. 1) What is the longest wave period generated by the storm? 2) What is the longest wavelength of the waves generated by the storm? L gL L2 gT 2 C = = = L =1.56 × T 2 T 2π L 2π ~88 m H ~ 3.5 m 3) When will the first wave reach€ a boat that is 500 km away? T ~ 7.5 sec € € ~12 hrs d. Tsunamis c. Wave motion: Group Speed Seismic waves created by sudden movements of the Earths Wave energy travels at the group speed (not at the phase crust (Earthquake), volcanic activity, or mudslide event speed of individual waves) ! disturbance of the whole water column! C = C /2 Shallow-water wave g p C = gh p For shallow-water waves the group speed (energy) is the 3) Tsunamis reaching the coast: h = 4000m; L = 200 km same as the phase speed (the energy is in the wave!) ! L > 20h C = 200 m/s p Cg = Cp (Cg = Cp ! the energy is in the wave) Examples: 1) Mid-oceanic swell: h > 3000 m; L = 120 m ! L < 2h Cp = 13.7 m/s 2) Mid-oceanic swell reaching the coast: h = 5m ! L > 20h Cp = 7 m/s Sumatra Tsunami e. Standing waves (Resonance) On December 25, 2004, a series of about 15 earthquakes occurred one Standing waves do not move horizontally but remain stationary after another along the west coast of Sumatra. The strongest (Guitar string). earthquake measured 9.0 magnitude and is the fourth strongest this century. Current estimates put the death toll at about 234,000. The water oscillates back and forth about a fixed point: Node. Millions more were at risk from disease and starvation The properties of a standing wave depend on the geometry of the Bay of Bengal/ Indian Ocean littoral regions of Indonesia, Malaysia, basin. The larger the “container”, the longer its characteristic Thailand, Burma, Bangladesh, India, Sri Lanka and Maldives. standing wave will take to oscillate. In an open basin: seiche L 4l 4l T gh C p = = = gh ←!→T = ←!→l = T T gh 4 e. Standing waves (Resonance) f. Refraction Refraction of waves in progressively shoaling waters can be described by L 4l 4l T gh C p = = = gh ←!→T = ←!→l = a relationship similar to Snell s law (refraction of light) T T gh 4 Shallow-water wave C1 gh1 h1 h1 = = = C2 gh2 h2 h2 g. Breaking waves As a wave nears the shore, only the period remains constant! For Next Time Shallow-water wave L T = Tides (Chap.
Load more

Recommended publications
  • Basic Concepts in Oceanography
    Chapter 1 XA0101461 BASIC CONCEPTS IN OCEANOGRAPHY L.F. SMALL College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, United States of America Abstract Basic concepts in oceanography include major wind patterns that drive ocean currents, and the effects that the earth's rotation, positions of land masses, and temperature and salinity have on oceanic circulation and hence global distribution of radioactivity. Special attention is given to coastal and near-coastal processes such as upwelling, tidal effects, and small-scale processes, as radionuclide distributions are currently most associated with coastal regions. 1.1. INTRODUCTION Introductory information on ocean currents, on ocean and coastal processes, and on major systems that drive the ocean currents are important to an understanding of the temporal and spatial distributions of radionuclides in the world ocean. 1.2. GLOBAL PROCESSES 1.2.1 Global Wind Patterns and Ocean Currents The wind systems that drive aerosols and atmospheric radioactivity around the globe eventually deposit a lot of those materials in the oceans or in rivers. The winds also are largely responsible for driving the surface circulation of the world ocean, and thus help redistribute materials over the ocean's surface. The major wind systems are the Trade Winds in equatorial latitudes, and the Westerly Wind Systems that drive circulation in the north and south temperate and sub-polar regions (Fig. 1). It is no surprise that major circulations of surface currents have basically the same patterns as the winds that drive them (Fig. 2). Note that the Trade Wind System drives an Equatorial Current-Countercurrent system, for example.
    [Show full text]
  • Geology of Hawaii Reefs
    11 Geology of Hawaii Reefs Charles H. Fletcher, Chris Bochicchio, Chris L. Conger, Mary S. Engels, Eden J. Feirstein, Neil Frazer, Craig R. Glenn, Richard W. Grigg, Eric E. Grossman, Jodi N. Harney, Ebitari Isoun, Colin V. Murray-Wallace, John J. Rooney, Ken H. Rubin, Clark E. Sherman, and Sean Vitousek 11.1 Geologic Framework The eight main islands in the state: Hawaii, Maui, Kahoolawe , Lanai , Molokai , Oahu , Kauai , of the Hawaii Islands and Niihau , make up 99% of the land area of the Hawaii Archipelago. The remainder comprises 11.1.1 Introduction 124 small volcanic and carbonate islets offshore The Hawaii hot spot lies in the mantle under, or of the main islands, and to the northwest. Each just to the south of, the Big Island of Hawaii. Two main island is the top of one or more massive active subaerial volcanoes and one active submarine shield volcanoes (named after their long low pro- volcano reveal its productivity. Centrally located on file like a warriors shield) extending thousands of the Pacific Plate, the hot spot is the source of the meters to the seafloor below. Mauna Kea , on the Hawaii Island Archipelago and its northern arm, the island of Hawaii, stands 4,200 m above sea level Emperor Seamount Chain (Fig. 11.1). and 9,450 m from seafloor to summit, taller than This system of high volcanic islands and asso- any other mountain on Earth from base to peak. ciated reefs, banks, atolls, sandy shoals, and Mauna Loa , the “long” mountain, is the most seamounts spans over 30° of latitude across the massive single topographic feature on the planet.
    [Show full text]
  • NANOOS Asset List 1 National Oceanic and Atmospheric
    NANOOS Asset List 2008 NANOOS Asset List 1 National Oceanic and Atmospheric Administration 1.1 The CoastWatch West Coast Regional Node http://coastwatch.pfel.noaa.gov Daily – Monthly composites of satellite observations Sea Surface Temperature (GOES & POES) Ocean Color (MODIS and SeaWiFS) Ocean Winds (QuikSCAT) 1.2 The National Data Buoy Center http://seaboard.ndbc.noaa.gov/maps/Northwest.shtml 6 Minute – Hourly buoy observations Meteorological Observations (Air Temp., Pressure, Wind Speed and Direction) Ocean Observations (Water Temp., Wave Height, Period and Direction) 1.3 The Center for Operational Oceanographic Products and Services http://tidesandcurrents.noaa.gov http://opendap.co-ops.nos.noaa.gov/content 6 Minute near-shore station observations Meteorological Observations (Air Temp., Pressure, Wind Speed and Direction) Ocean Observations (Water Temp., Water Level) 1.4 NOAAWatch http://www.noaawatch.gov Information related to ongoing environmental events NOAAWatch themes include Air Quality, Droughts, Earthquakes, Excessive Heat, Fire, Flooding, Harmful Algal Blooms (HABs), Oil Spills, Rip Currents, Severe Weather, Space Weather, Tsunamis, and Volcanoes 1.5 National Weather Service http://www.weather.gov Environmental observations and forecasts Coastal and Marine Forecasts Weather Warnings 1 NANOOS Asset List 2008 Surface Pressure Maps Coastal and Marine Observations (Wind, Visibility, Sky Conditions, Temperature, Dew Point, Relative Humidity, Atmospheric Pressure, Pressure tendency) GOES Satellite Observations (Visible,
    [Show full text]
  • Part II-1 Water Wave Mechanics
    Chapter 1 EM 1110-2-1100 WATER WAVE MECHANICS (Part II) 1 August 2008 (Change 2) Table of Contents Page II-1-1. Introduction ............................................................II-1-1 II-1-2. Regular Waves .........................................................II-1-3 a. Introduction ...........................................................II-1-3 b. Definition of wave parameters .............................................II-1-4 c. Linear wave theory ......................................................II-1-5 (1) Introduction .......................................................II-1-5 (2) Wave celerity, length, and period.......................................II-1-6 (3) The sinusoidal wave profile...........................................II-1-9 (4) Some useful functions ...............................................II-1-9 (5) Local fluid velocities and accelerations .................................II-1-12 (6) Water particle displacements .........................................II-1-13 (7) Subsurface pressure ................................................II-1-21 (8) Group velocity ....................................................II-1-22 (9) Wave energy and power.............................................II-1-26 (10)Summary of linear wave theory.......................................II-1-29 d. Nonlinear wave theories .................................................II-1-30 (1) Introduction ......................................................II-1-30 (2) Stokes finite-amplitude wave theory ...................................II-1-32
    [Show full text]
  • World Ocean Thermocline Weakening and Isothermal Layer Warming
    applied sciences Article World Ocean Thermocline Weakening and Isothermal Layer Warming Peter C. Chu * and Chenwu Fan Naval Ocean Analysis and Prediction Laboratory, Department of Oceanography, Naval Postgraduate School, Monterey, CA 93943, USA; [email protected] * Correspondence: [email protected]; Tel.: +1-831-656-3688 Received: 30 September 2020; Accepted: 13 November 2020; Published: 19 November 2020 Abstract: This paper identifies world thermocline weakening and provides an improved estimate of upper ocean warming through replacement of the upper layer with the fixed depth range by the isothermal layer, because the upper ocean isothermal layer (as a whole) exchanges heat with the atmosphere and the deep layer. Thermocline gradient, heat flux across the air–ocean interface, and horizontal heat advection determine the heat stored in the isothermal layer. Among the three processes, the effect of the thermocline gradient clearly shows up when we use the isothermal layer heat content, but it is otherwise when we use the heat content with the fixed depth ranges such as 0–300 m, 0–400 m, 0–700 m, 0–750 m, and 0–2000 m. A strong thermocline gradient exhibits the downward heat transfer from the isothermal layer (non-polar regions), makes the isothermal layer thin, and causes less heat to be stored in it. On the other hand, a weak thermocline gradient makes the isothermal layer thick, and causes more heat to be stored in it. In addition, the uncertainty in estimating upper ocean heat content and warming trends using uncertain fixed depth ranges (0–300 m, 0–400 m, 0–700 m, 0–750 m, or 0–2000 m) will be eliminated by using the isothermal layer.
    [Show full text]
  • The Emergence of Magnetic Skyrmions
    The emergence of magnetic skyrmions During the past decade, axisymmetric two-dimensional solitons (so-called magnetic skyrmions) have been discovered in several materials. These nanometer-scale chiral objects are being proposed as candidates for novel technological applications, including high-density memory, logic circuits and neuro-inspired computing. Alexei N. Bogdanov and Christos Panagopoulos Research on magnetic skyrmions benefited from a cascade of breakthroughs in magnetism and nonlinear physics. These magnetic objects are believed to be nanometers-size whirling cylinders, embedded into a magnetically saturated state and magnetized antiparallel along their axis (Fig. 1). They are topologically stable, in the sense that they can’t be continuously transformed into homogeneous state. Being highly mobile and the smallest magnetic configurations, skyrmions are promising for applications in the emerging field of spintronics, wherein information is carried by the electron spin further to, or instead of the electron charge. Expectedly, their scientific and technological relevance is fueling inventive research in novel classes of bulk magnetic materials and synthetic architectures [1, 2]. The unconventional and useful features of magnetic skyrmions have become focus of attention in the science and technology Figure 1. Magnetic skyrmions are nanoscale spinning magnetic circles, sometimes teasingly called “magic knots” or “mysterious cylinders (a), embedded into the saturated state of ferromagnets (b). particles”. Interestingly, for a long time it remained widely In the skyrmion core, magnetization gradually rotates along radial unknown that the key “mystery” surrounding skyrmions is in the directions with a fixed rotation sense namely, from antiparallel very fact of their existence. Indeed, mathematically the majority of direction at the axis to a parallel direction at large distances from the physical systems with localized structures similar to skyrmions are center.
    [Show full text]
  • Sea State in Marine Safety Information Present State, Future Prospects
    Sea State in Marine Safety Information Present State, future prospects Henri SAVINA – Jean-Michel LEFEVRE Météo-France Rogue Waves 2004, Brest 20-22 October 2004 JCOMM Joint WMO/IOC Commission for Oceanography and Marine Meteorology The future of Operational Oceanography Intergovernmental body of technical experts in the field of oceanography and marine meteorology, with a mandate to prepare both regulatory (what Member States shall do) and guidance (what Member States should do) material. TheThe visionvision ofof JCOMMJCOMM Integrated ocean observing system Integrated data management State-of-the-art technologies and capabilities New products and services User responsiveness and interaction Involvement of all maritime countries JCOMM structure Terms of Reference Expert Team on Maritime Safety Services • Monitor / review operations of marine broadcast systems, including GMDSS and others for vessels not covered by the SOLAS convention •Monitor / review technical and service quality standards for meteo and oceano MSI, particularly for the GMDSS, and provide assistance and support to Member States • Ensure feedback from users is obtained through appropriate channels and applied to improve the relevance, effectiveness and quality of services • Ensure effective coordination and cooperation with organizations, bodies and Member States on maritime safety issues • Propose actions as appropriate to meet requirements for international coordination of meteorological and related communication services • Provide advice to the SCG and other Groups of JCOMM on issues related to MSS Chair selected by Commission. OPEN membership, including representatives of the Issuing Services for GMDSS, of IMO, IHO, ICS, IMSO, and other user groups GMDSS Global Maritime Distress & Safety System Defined by IMO for the provision of MSI and the coordination of SAR alerts on a global basis.
    [Show full text]
  • This Content Is Prepared from Various Sources and Has Used the Study Material from Various Books, Internet Articles Etc
    This content is prepared from various sources and has used the study material from various books, internet articles etc. The teacher doesn’t claim any right over the content, it’s originality and any copyright. It is given only to the students of PG course in Geology to study as a part of their curriculum. WAVES Waves and their properties. (a) Regular, symmetrical waves can be described by their height, wavelength, and period (the time one wavelength takes to pass a fixed point). (b) Waves can be classified according to their wave period. The scales of wave height and wave period are not linear, but logarithmic, being based on powers of 10. The variety and size of wind-generated waves are controlled by four principal factors: (1) wind velocity, (2) wind duration, (3) fetch, (4) original sea state. Significant Wave Height? What is the average height and what is the significant height? Wind-generated waves are progressive waves, because they travel (progress) across the sea surface. If you focus on the crest of a progressive wave, you can follow its path over time. But what actually is moving? The wave form obviously is moving, but what about the water just below the sea surface? Actually, two basic kinds of motions are associated with ocean waves: the forward movement of the wave form itself and the orbital motion of water particles beneath the wave. The motion of water particles beneath waves. (a) The arrows at the sea surface denote the motion of water particles beneath waves. With the passage of one wavelength, a water particle at the sea surface describes a circular orbit with a diameter equal to the wave’s height.
    [Show full text]
  • Sea State Effect on the Sea Surface Emissivity at L-Band
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by UPCommons. Portal del coneixement obert de la UPC IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. 41, NO. 10, OCTOBER 2003 2307 Sea State Effect on the Sea Surface Emissivity at L-Band Jorge José Miranda, Mercè Vall-llossera, Member, IEEE, Adriano Camps, Senior Member, IEEE, Núria Duffo, Member, IEEE, Ignasi Corbella, Member, IEEE, and Jacqueline Etcheto Abstract—In May 1999, the European Space Agency (ESA) temperature images will provide looks of the same pixel under selected the Earth Explorer Opportunity Soil Moisture and incidence angles from 0 to almost 65 , which requires the Ocean Salinity (SMOS) mission to obtain global and frequent soil development of soil and sea emission models in the whole moisture and ocean salinity maps. SMOS single payload is the Microwave Imaging Radiometer by Aperture Synthesis (MIRAS), range of incidence angles, and suitable geophysical parameters an L-band two-dimensional aperture synthesis radiometer with retrieval algorithms. multiangular observation capabilities. At L-band, the brightness The dielectric permittivity for seawater is determined, among temperature sensitivity to the sea surface salinity (SSS) is low, other variables, by salinity. Therefore, in principle, it is possible approximately 0.5 K/psu at 20 C, decreasing to 0.25 K/psu at to retrieve SSS from passive microwave measurements as long 0 C, comparable to that to the wind speed 0.2 K/(m/s) at nadir. However, at a given time, the sea state does not depend only as the variables influencing the brightness temperature (TB) on local winds, but on the local wind history and the presence signal (sea surface temperature, roughness, and foam) can be of waves traveling from far distances.
    [Show full text]
  • Introduction to Oceanography
    Introduction to Oceanography Introduction to Oceanography Lecture 14: Tides, Biological Productivity Memorial Day holiday Monday no lab meetings Go to any other lab section this week (and let the TA know!) Bay of Fundy -- low tide, Photo by Dylan Kereluk, . Creative Commons A 2.0 Generic, Mudskipper (Periophthalmus modestus) at low tide, photo by OpenCage, Wikimedia Commons, Creative http://commons.wikimedia.org/wiki/File:Bay_of_Fundy_-_Tide_Out.jpg Commons A S-A 2.5, http://commons.wikimedia.org/wiki/File:Periophthalmus_modestus.jpg Tides Earth-Moon-Sun System Planet-length waves Cyclic, repeating rise & fall of sea level • Earth-Sun Distance – Most regular phenomenon in the oceans 150,000,000 km Daily tidal variation has great effects on life in & around the ocean (Lab 8) • Earth-Moon Distance 385,000 km Caused by gravity and Much closer to Earth, but between Earth, Moon & much less massive Sun, their orbits around • Earth Obliquity = 23.5 each other, and the degrees Earth’s daily spin – Seasons Photos by Samuel Wantman, Creative Commons A S-A 3.0, http://en.wikipedia.org/ wiki/File:Bay_of_Fundy_Low_Tide.jpg and Figure by Homonculus 2/Geologician, Wikimedia Commons, http://en.wikipedia.org/wiki/ Creative Commons A 3.0, http://en.wikipedia.org/wiki/ File:Bay_of_Fundy_High_Tide.jpg File:Lunar_perturbation.jpg Tides are caused by the gravity of the Moon and Sun acting on Scaled image of Earth-Moon distance, Nickshanks, Wikimedia Commons, Creative Commons A 2.5 Earth and its ocean. Pluto-Charon mutual orbit, Zhatt, Wikimedia Commons, Public
    [Show full text]
  • Exploration of the Deep Gulf of Mexico Slope Using DSV Alvin: Site Selection and Geologic Character
    Exploration of the Deep Gulf of Mexico Slope Using DSV Alvin: Site Selection and Geologic Character Harry H. Roberts1, Chuck R. Fisher2, Jim M. Brooks3, Bernie Bernard3, Robert S. Carney4, Erik Cordes5, William Shedd6, Jesse Hunt, Jr.6, Samantha Joye7, Ian R. MacDonald8, 9 and Cheryl Morrison 1Coastal Studies Institute, Louisiana State University, Baton Rouge, Louisiana 70803 2Department of Biology, Penn State University, University Park, Pennsylvania 16802-5301 3TDI Brooks International, Inc., 1902 Pinon Dr., College Station, Texas 77845 4Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, Louisiana 70803 5Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Ave., Cambridge, Massachusetts 02138 6Minerals Management Service, Office of Resource Evaluation, New Orleans, Louisiana 70123-2394 7Department of Geology, University of Georgia, Athens, Georgia 30602 8Department of Physical and Environmental Sciences, Texas A&M – Corpus Christi, Corpus Christi, Texas 78412 9U.S. Geological Survey, 11649 Leetown Rd., Keameysville, West Virginia 25430 ABSTRACT The Gulf of Mexico is well known for its hydrocarbon seeps, associated chemosyn- thetic communities, and gas hydrates. However, most direct observations and samplings of seep sites have been concentrated above water depths of approximately 3000 ft (1000 m) because of the scarcity of deep diving manned submersibles. In the summer of 2006, Minerals Management Service (MMS) and National Oceanic and Atmospheric Admini- stration (NOAA) supported 24 days of DSV Alvin dives on the deep continental slope. Site selection for these dives was accomplished through surface reflectivity analysis of the MMS slope-wide 3D seismic database followed by a photo reconnaissance cruise. From 80 potential sites, 20 were studied by photo reconnaissance from which 10 sites were selected for Alvin dives.
    [Show full text]
  • Marine Forecasting at TAFB [email protected]
    Marine Forecasting at TAFB [email protected] 1 Waves 101 Concepts and basic equations 2 Have an overall understanding of the wave forecasting challenge • Wave growth • Wave spectra • Swell propagation • Swell decay • Deep water waves • Shallow water waves 3 Wave Concepts • Waves form by the stress induced on the ocean surface by physical wind contact with water • Begin with capillary waves with gradual growth dependent on conditions • Wave decay process begins immediately as waves exit wind generation area…a.k.a. “fetch” area 4 5 Wave Growth There are three basic components to wave growth: • Wind speed • Fetch length • Duration Wave growth is limited by either fetch length or duration 6 Fully Developed Sea • When wave growth has reached a maximum height for a given wind speed, fetch and duration of wind. • A sea for which the input of energy to the waves from the local wind is in balance with the transfer of energy among the different wave components, and with the dissipation of energy by wave breaking - AMS. 7 Fetches 8 Dynamic Fetch 9 Wave Growth Nomogram 10 Calculate Wave H and T • What can we determine for wave characteristics from the following scenario? • 40 kt wind blows for 24 hours across a 150 nm fetch area? • Using the wave nomogram – start on left vertical axis at 40 kt • Move forward in time to the right until you reach either 24 hours or 150 nm of fetch • What is limiting factor? Fetch length or time? • Nomogram yields 18.7 ft @ 9.6 sec 11 Wave Growth Nomogram 12 Wave Dimensions • C=Wave Celerity • L=Wave Length •
    [Show full text]