DOCSLIB.ORG

What Are Waves? What Causes Waves? Tidal Waves Tsunamis Wind Generated Waves Swell

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
What Are Waves? What Causes Waves? Tidal Waves Tsunamis Wind Generated Waves Swell What are waves? toward the moon. An equal bulge in the surface of Tsunamis The strength of the wind the ocean occurs on the side of the earth opposite Water waves are a manifestation of energy moving of the moon due to the centrifugal force generated Often misnamed tidal waves, Tsunamis are long through the ocean. In their simplest form, waves are by the earth’s rotation. In between the 2 bulges the period waves that originate when a strong The amount of time the wind blows sinusoidal in shape. The high water levels are the ocean surface is depressed due to the movement of earthquake or landslide occurs under the ocean. wave crests and the low water levels are the wave water toward the bulges. The motion of the earth sends a strong impulse of The distance (called fetch) over which the troughs. The vertical distance between a crest and energy into the water generating surface waves wind blows in a straight line across the trough is the wave height H. The distance between with open ocean heights of less than 2 feet but ocean two crests or troughs is the wave length L and the with wave lengths of over 100 miles and wave time it take for two crests or troughs to pass the speeds approaching 500 miles per hour! same point is the wave period T. The velocity, C, at which a wave moves through the ocean is related to the ratio of its wave length to wave period: C = L/T The wave length is proportional to the square of the wave period, L ~ T2 so longer waves move As the moon rotates around the earth, the bulges faster than move as well resulting in 2 high and 2 low tides per shorter ones. day at most locations on the coast with a tidal period The amount of of approximately 12 ½ hours. energy, E, in the wave is a The exact number of the tides is dependent on the The stronger the wind and the longer it blows function of the shape of the ocean bottom along the coast. This can across the fetch, the larger the sea will become. A wave height and have a significant effect on the height and period of As a tsunami approaches the coast, the wave fully developed sea occurs when the waves is proportional to: the tide along the coast as seen in the tidal curves interacts with the shallow bottom. Because of their reach the maximum size possible for a specific E ~ 1/8 H2. for the east coast. long wave lengths tsunamis rarely break along the wind, duration and fetch. coast. Instead the water runs up along the shore Some coastal geometries have the right size and similar to the tide. In some cases where the coast shape to produce amplified tides that result in very Swell is close to the center of the earthquake the water large tidal ranges. Some locations in the Bay of surge associated with a tsunami can reach What causes waves? Fundy, Nova Scotia experience a tidal range of over When waves travel out of the region of strong elevations over 100 feet high. Damage to winds, they become sorted as the longer waves 40 ft! lighthouses over 150 feet above sea level has A disturbing force is necessary to create waves on travel out from the storm faster than the shorter the ocean surface. The type of disturbing force been documented during tsunami events. waves. This results in waves of similar In shallow coastal regions, the currents generated determines the characteristics of the generated by the incoming tide can produce Tidal Bores, characteristics moving together across the ocean waves. The 3 main wave generation forces in order visible waves that move inland from the coast. Wind Generated Waves in groups. Waves lose very little energy as they of decreasing wave period are: propagate across the deep ocean. Removed from Wind blowing across the surface of the ocean the influence of the wind the wave crests of the transfers energy into the water. Initially, light winds swell become rounded. Gravitational Attraction of Moon and Sun generate small Ripples called capillary waves on producesTides the water surface. Earthquakes and Underwater Landslides If the wind increases, the added roughness generate Tsunami created by the capillary waves increases the rate of energy transfer and waves begin to form on the Wind Stress over the ocean generates ocean surface. Wind Waves In the the region where wind is blowing across the ocean surface and waves are being generated, Tidal Waves the sea surface is characterized by steep waves with many different lengths moving randomly in Tides are generated by the gravitational attraction of the direction of the wind. This condition is referred the earth, moon and sun. On the side of the earth to as sea. How large the waves get is dependent closest to the moon, the ocean surface bulges out on3factors: Wave Shoaling and Refraction On beaches with gentle slopes, the When waves enter shallow water (water depths wave crest breaks equal to ½ the wave length) friction generated by first and the white the seabed begins to slow the motion of the waves water spills down . If part of the wave is still in deep water, the slower the face of the wave. portion of the wave will bend toward the coast. On very steep This process is beaches, the does called not break at all but wave surges up the beach COASTAL PROCESSES refraction. instead. COOPERATIVE EXTENSION Current Wave Conditions For real-time information about ocean wave photo by Jon Sullivan conditions see the following web pages: As the bottom of the wave slows, the waves crest Surf’s Up! This fact sheet was prepared through the SSuurrff’’ss UUpp!! becomes more peaked and the distance between wave crests shortens. This process is referred to Stevens – New Jersey Sea Grant Coastal as wave shoaling. Processes Cooperative Extension formed to promote the sustainability and wise use of our coastal resources that provide the basis of a strong coastal economy. For additional information contact: Dr. Thomas Herrington Coastal Processes Specialist, Stevens Institute of Technology Castle Point on Hudson, Hoboken, NJ 07030 Photo courtesy of the NOAA Marine Prediction PH (201) 216-5320 FX (201) 216-8214 Wave Breaking email:[email protected] Merchant Vessel in fully developed sea. or When waves reach a critical wave height to length http://attila.stevens- ratio of 1/7, the wave will begin to break. In the surf tech.edu/%7Etherring/SeaGrant.html zone, this critical ratio generally occurs when the photo by Jon Sullivan wave height is ¾ of the water depth. There are 3 types of breakers that occur along the shore: This publication was supported by the National Sea Grant plunging, spilling and surging. The type of College Program of the U.S. Department of Commerce’s breaker depends on the slope of the seabed National Oceanic and Atmospheric Administration under offshore of the beach. When waves go from deep NOAA Grant #NA16RG1047. The views expressed herein do water to shallow water quickly the bottom of the not necessarily reflect the views of any of these organizations. NJSG-03-549. wave slows so quickly that the crest of the wave plunges forward creating a tubing wave like those found in Hawaii. (Cartoons courtesy of Office of All About Naval Research). Photo courtesy of the Pacific Tsunami Museum Surge associated with the 1946 tsunami that struck Hawaii. Notice height of white water along tree trunks. Waves .
Load more

Recommended publications
  • Wind-Caused Waves Misleads Us Energy Is Transferred to the Wave
    WAVES IN WATER is quite similar. Most waves are created by the frictional drag of wind blowing across the water surface. A wave begins as Tsunami can be the most overwhelming of all waves, but a tiny ripple. Once formed, the side of a ripple increases the their origins and behaviors differ from those of the every­ day waves we see at the seashore or lakeshore. The familiar surface area of water, allowing the wind to push the ripple into waves are caused by wind blowing over the water surface. a higher and higher wave. As a wave gets bigger, more wind Our experience with these wind-caused waves misleads us energy is transferred to the wave. How tall a wave becomes in understanding tsunami. Let us first understand everyday, depends on (1) the velocity of the wind, (2) the duration of wind-caused waves and then contrast them with tsunami. time the wind blows, (3) the length of water surface (fetch) the wind blows across, and (4) the consistency of wind direction. Once waves are formed, their energy pulses can travel thou­ Wind-Caused Waves sands of kilometers away from the winds that created them. Waves transfer energy away from some disturbance. Waves moving through a water mass cause water particles to rotate in WHY A WIND-BLOWN WAVE BREAKS place, similar to the passage of seismic waves (figure 8.5; see Waves undergo changes when they move into shallow water­ figure 3.18). You can feel the orbital motion within waves by water with depths less than one-half their wavelength.
    [Show full text]
  • Turning the Tide on Trash: Great Lakes
    Turning the Tide On Trash A LEARNING GUIDE ON MARINE DEBRIS Turning the Tide On Trash A LEARNING GUIDE ON MARINE DEBRIS Floating marine debris in Hawaii NOAA PIFSC CRED Educators, parents, students, and Unfortunately, the ocean is currently researchers can use Turning the Tide under considerable pressure. The on Trash as they explore the serious seeming vastness of the ocean has impacts that marine debris can have on prompted people to overestimate its wildlife, the environment, our well being, ability to safely absorb our wastes. For and our economy. too long, we have used these waters as a receptacle for our trash and other Covering nearly three-quarters of the wastes. Integrating the following lessons Earth, the ocean is an extraordinary and background chapters into your resource. The ocean supports fishing curriculum can help to teach students industries and coastal economies, that they can be an important part of the provides recreational opportunities, solution. Many of the lessons can also and serves as a nurturing home for a be modified for science fair projects and multitude of marine plants and wildlife. other learning extensions. C ON T EN T S 1 Acknowledgments & History of Turning the Tide on Trash 2 For Educators and Parents: How to Use This Learning Guide UNIT ONE 5 The Definition, Characteristics, and Sources of Marine Debris 17 Lesson One: Coming to Terms with Marine Debris 20 Lesson Two: Trash Traits 23 Lesson Three: A Degrading Experience 30 Lesson Four: Marine Debris – Data Mining 34 Lesson Five: Waste Inventory 38 Lesson
    [Show full text]
  • Time and Tides in the Gulf of Maine a Dockside Dialogue Between Two Old Friends
    1 Time and Tides in the Gulf of Maine A dockside dialogue between two old friends by David A. Brooks It's impossible to visit Maine's coast and not notice the tides. The twice-daily rise and fall of sea level never fails to impress, especially downeast, toward the Canadian border, where the tidal range can exceed twenty feet. Proceeding northeastward into the Bay of Fundy, the range grows steadily larger, until at the head of the bay, "moon" tides of greater than fifty feet can leave ships wallowing in the mud, awaiting the water's return. My dockside companion, nodding impatiently, interrupts: Yes, yes, but why is this so? Why are the tides so large along the Maine coast, and why does the tidal range increase so dramatically northeastward? Well, my friend, before we address these important questions, we should review some basic facts about the tides. Here, let me sketch a few things that will remind you about our place in the sky. A quiet rumble, as if a dark cloud had suddenly passed overhead. Didn’t expect a physics lesson on this beautiful day. 2 The only physics needed, my friend, you learned as a child, so not to worry. The sketch is a top view, looking down on the earth’s north pole. You see the moon in its monthly orbit, moving in the same direction as the earth’s rotation. And while this is going on, the earth and moon together orbit the distant sun once a year, in about twelve months, right? Got it skippah.
    [Show full text]
  • Moons Phases and Tides
    Moon’s Phases and Tides Moon Phases Half of the Moon is always lit up by the sun. As the Moon orbits the Earth, we see different parts of the lighted area. From Earth, the lit portion we see of the moon waxes (grows) and wanes (shrinks). The revolution of the Moon around the Earth makes the Moon look as if it is changing shape in the sky The Moon passes through four major shapes during a cycle that repeats itself every 29.5 days. The phases always follow one another in the same order: New moon Waxing Crescent First quarter Waxing Gibbous Full moon Waning Gibbous Third (last) Quarter Waning Crescent • IF LIT FROM THE RIGHT, IT IS WAXING OR GROWING • IF DARKENING FROM THE RIGHT, IT IS WANING (SHRINKING) Tides • The Moon's gravitational pull on the Earth cause the seas and oceans to rise and fall in an endless cycle of low and high tides. • Much of the Earth's shoreline life depends on the tides. – Crabs, starfish, mussels, barnacles, etc. – Tides caused by the Moon • The Earth's tides are caused by the gravitational pull of the Moon. • The Earth bulges slightly both toward and away from the Moon. -As the Earth rotates daily, the bulges move across the Earth. • The moon pulls strongly on the water on the side of Earth closest to the moon, causing the water to bulge. • It also pulls less strongly on Earth and on the water on the far side of Earth, which results in tides. What causes tides? • Tides are the rise and fall of ocean water.
    [Show full text]
  • Intracratonic Asthenosphere Upwelling and Lithosphere Rejuvenation
    Earth and Planetary Science Letters 260 (2007) 482–494 www.elsevier.com/locate/epsl Intracratonic asthenosphere upwelling and lithosphere rejuvenation beneath the Hoggar swell (Algeria): Evidence from HIMU metasomatised lherzolite mantle xenoliths ⁎ L. Beccaluva a, , A. Azzouni-Sekkal b, A. Benhallou c, G. Bianchini a, R.M. Ellam d, M. Marzola a, F. Siena a, F.M. Stuart d a Dipartimento di Scienze della Terra, Università di Ferrara, Italy b Faculté des Sciences de la Terre, Géographie et Aménagement du Territoire, Université des Sciences et Technologie Houari Boumédienne, Alger, Algeria c CRAAG (Centre de Recherche en Astronomie, Astrophysique et Géophysique), Alger, Algeria d Isotope Geoscience Unit, Scottish Universities Environmental Research Centre, East Kilbride, UK Received 7 March 2007; received in revised form 23 May 2007; accepted 24 May 2007 Available online 2 June 2007 Editor: R.W. Carlson Abstract The mantle xenoliths included in Quaternary alkaline volcanics from the Manzaz-district (Central Hoggar) are proto-granular, anhydrous spinel lherzolites. Major and trace element analyses on bulk rocks and constituent mineral phases show that the primary compositions are widely overprinted by metasomatic processes. Trace element modelling of the metasomatised clinopyroxenes allows the inference that the metasomatic agents that enriched the lithospheric mantle were highly alkaline carbonate-rich melts such as nephelinites/melilitites (or as extreme silico-carbonatites). These metasomatic agents were characterized by a clear HIMU Sr–Nd–Pb isotopic signature, whereas there is no evidence of EM1 components recorded by the Hoggar Oligocene tholeiitic basalts. This can be interpreted as being due to replacement of the older cratonic lithospheric mantle, from which tholeiites generated, by asthenospheric upwelling dominated by the presence of an HIMU signature.
    [Show full text]
  • Global Ship Accidents and Ocean Swell-Related Sea States
    Nat. Hazards Earth Syst. Sci. Discuss., doi:10.5194/nhess-2017-142, 2017 Manuscript under review for journal Nat. Hazards Earth Syst. Sci. Discussion started: 26 April 2017 c Author(s) 2017. CC-BY 3.0 License. Global ship accidents and ocean swell-related sea states Zhiwei Zhang1, 2, Xiao-Ming Li2, 3 1 College of Geography and Environment, Shandong Normal University, Jinan, China 2 Key Laboratory of Digital Earth Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, 5 Beijing, China 3 Hainan Key Laboratory of Earth Observation, Sanya, China Correspondence to: X.-M. Li (E-mail: [email protected]) Abstract. With the increased frequency of shipping activities, navigation safety has become a major concern, especially when economic losses, human casualties and environmental issues are considered. As a contributing factor, sea state conditions play 10 a significant role in shipping safety. However, the types of dangerous sea states that trigger serious shipping accidents are not well understood. To address this issue, we analyzed the sea state characteristics during ship accidents that occurred in poor weather or heavy seas based on a ten-year ship accident dataset. The sea state parameters, including the significant wave height, the mean wave period and the mean wave direction, obtained from numerical wave model data were analyzed for selected ship accidents. The results indicated that complex sea states with the co-occurrence of wind sea and swell conditions represent 15 threats to sailing vessels, especially when these conditions include close wave periods and oblique wave directions. 1 Introduction The shipping industry delivers 90% of all world trade (IMO, 2011).
    [Show full text]
  • A Numerical Study of the Long- and Short-Term Temperature Variability and Thermal Circulation in the North Sea
    JANUARY 2003 LUYTEN ET AL. 37 A Numerical Study of the Long- and Short-Term Temperature Variability and Thermal Circulation in the North Sea PATRICK J. LUYTEN Management Unit of the Mathematical Models, Brussels, Belgium JOHN E. JONES AND ROGER PROCTOR Proudman Oceanographic Laboratory, Bidston, United Kingdom (Manuscript received 3 January 2001, in ®nal form 4 April 2002) ABSTRACT A three-dimensional numerical study is presented of the seasonal, semimonthly, and tidal-inertial cycles of temperature and density-driven circulation within the North Sea. The simulations are conducted using realistic forcing data and are compared with the 1989 data of the North Sea Project. Sensitivity experiments are performed to test the physical and numerical impact of the heat ¯ux parameterizations, turbulence scheme, and advective transport. Parameterizations of the surface ¯uxes with the Monin±Obukhov similarity theory provide a relaxation mechanism and can partially explain the previously obtained overestimate of the depth mean temperatures in summer. Temperature strati®cation and thermocline depth are reasonably predicted using a variant of the Mellor±Yamada turbulence closure with limiting conditions for turbulence variables. The results question the common view to adopt a tuned background scheme for internal wave mixing. Two mechanisms are discussed that describe the feedback of the turbulence scheme on the surface forcing and the baroclinic circulation, generated at the tidal mixing fronts. First, an increased vertical mixing increases the depth mean temperature in summer through the surface heat ¯ux, with a restoring mechanism acting during autumn. Second, the magnitude and horizontal shear of the density ¯ow are reduced in response to a higher mixing rate.
    [Show full text]
  • Tsunami, Seiches, and Tides Key Ideas Seiches
    Tsunami, Seiches, And Tides Key Ideas l The wavelengths of tsunami, seiches and tides are so great that they always behave as shallow-water waves. l Because wave speed is proportional to wavelength, these waves move rapidly through the water. l A seiche is a pendulum-like rocking of water in a basin. l Tsunami are caused by displacement of water by forces that cause earthquakes, by landslides, by eruptions or by asteroid impacts. l Tides are caused by the gravitational attraction of the sun and the moon, by inertia, and by basin resonance. 1 Seiches What are the characteristics of a seiche? Water rocking back and forth at a specific resonant frequency in a confined area is a seiche. Seiches are also called standing waves. The node is the position in a standing wave where water moves sideways, but does not rise or fall. 2 1 Seiches A seiche in Lake Geneva. The blue line represents the hypothetical whole wave of which the seiche is a part. 3 Tsunami and Seismic Sea Waves Tsunami are long-wavelength, shallow-water, progressive waves caused by the rapid displacement of ocean water. Tsunami generated by the vertical movement of earth along faults are seismic sea waves. What else can generate tsunami? llandslides licebergs falling from glaciers lvolcanic eruptions lother direct displacements of the water surface 4 2 Tsunami and Seismic Sea Waves A tsunami, which occurred in 1946, was generated by a rupture along a submerged fault. The tsunami traveled at speeds of 212 meters per second. 5 Tsunami Speed How can the speed of a tsunami be calculated? Remember, because tsunami have extremely long wavelengths, they always behave as shallow water waves.
    [Show full text]
  • Tsunamis in Alaska
    Tsunami What is a Tsunami? A tsunami is a series of traveling waves in water that are generated by violent vertical displacement of the water surface. Tsunamis travel up to 500 mph across deep water away from their generation zone. Over the deep ocean, there may be very little displacement of the water surface; but since the wave encompasses the depth of the water column, wave amplitude will increase dramatically as it encounters shallow coastal waters. In many cases, a El Niño tsunami wave appears like an endlessly onrushing tide which forces its way around through any obstacle. The image on the left illustrates how the amplitude of a tsunami wave increases as it moves from the deep ocean water to the shallow coast. Over deep water, the wave length is long, and the wave velocity is very fast. By the time the wave reaches the coast, wave length decreases quickly and wave speed slows dramatically. As this takes place, wave height builds up as it prepares to inundate the shore. Why do Tsunamis occur in Alaska? Subduction-zone mega-thrust earthquakes, the most powerful earthquakes in the world, can produce tsunamis through fault boundary rupture, deformation of an overlying plate, and landslides induced by the earthquake (IRIS, 2016). Megathrust earthquakes occur along subduction zones, such as those found along the ring of fire (see image to the right). The ring of fire extends northward along the coast of western North America, then arcs westward along the southern side of the Aleutians, before curving southwest along the coast of Asia.
    [Show full text]
  • Prioritization of Oxygen Delivery During Elevated Metabolic States
    Respiratory Physiology & Neurobiology 144 (2004) 215–224 Eat and run: prioritization of oxygen delivery during elevated metabolic states James W. Hicks∗, Albert F. Bennett Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA Accepted 25 May 2004 Abstract The principal function of the cardiopulmonary system is the matching of oxygen and carbon dioxide transport to the metabolic V˙ requirements of different tissues. Increased oxygen demands ( O2 ), for example during physical activity, result in a rapid compensatory increase in cardiac output and redistribution of blood flow to the appropriate skeletal muscles. These cardiovascular changes are matched by suitable ventilatory increments. This matching of cardiopulmonary performance and metabolism during activity has been demonstrated in a number of different taxa, and is universal among vertebrates. In some animals, large V˙ increments in aerobic metabolism may also be associated with physiological states other than activity. In particular, O2 may increase following feeding due to the energy requiring processes associated with prey handling, digestion and ensuing protein V˙ V˙ synthesis. This large increase in O2 is termed “specific dynamic action” (SDA). In reptiles, the increase in O2 during SDA may be 3–40-fold above resting values, peaking 24–36 h following ingestion, and remaining elevated for up to 7 days. In addition to the increased metabolic demands, digestion is associated with secretion of H+ into the stomach, resulting in a large metabolic − alkalosis (alkaline tide) and a near doubling in plasma [HCO3 ]. During digestion then, the cardiopulmonary system must meet the simultaneous challenges of an elevated oxygen demand and a pronounced metabolic alkalosis.
    [Show full text]
  • Tidal Hydrodynamic Response to Sea Level Rise and Coastal Geomorphology in the Northern Gulf of Mexico
    University of Central Florida STARS Electronic Theses and Dissertations, 2004-2019 2015 Tidal hydrodynamic response to sea level rise and coastal geomorphology in the Northern Gulf of Mexico Davina Passeri University of Central Florida Part of the Civil Engineering Commons Find similar works at: https://stars.library.ucf.edu/etd University of Central Florida Libraries http://library.ucf.edu This Doctoral Dissertation (Open Access) is brought to you for free and open access by STARS. It has been accepted for inclusion in Electronic Theses and Dissertations, 2004-2019 by an authorized administrator of STARS. For more information, please contact [email protected]. STARS Citation Passeri, Davina, "Tidal hydrodynamic response to sea level rise and coastal geomorphology in the Northern Gulf of Mexico" (2015). Electronic Theses and Dissertations, 2004-2019. 1429. https://stars.library.ucf.edu/etd/1429 TIDAL HYDRODYNAMIC RESPONSE TO SEA LEVEL RISE AND COASTAL GEOMORPHOLOGY IN THE NORTHERN GULF OF MEXICO by DAVINA LISA PASSERI B.S. University of Notre Dame, 2010 A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Civil, Environmental, and Construction Engineering in the College of Engineering and Computer Science at the University of Central Florida Orlando, Florida Spring Term 2015 Major Professor: Scott C. Hagen © 2015 Davina Lisa Passeri ii ABSTRACT Sea level rise (SLR) has the potential to affect coastal environments in a multitude of ways, including submergence, increased flooding, and increased shoreline erosion. Low-lying coastal environments such as the Northern Gulf of Mexico (NGOM) are particularly vulnerable to the effects of SLR, which may have serious consequences for coastal communities as well as ecologically and economically significant estuaries.
    [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]