DOCSLIB.ORG

Practice Exam 2

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Practice Exam 2 1 OCEANOGRAPHY 101 NAME____________________ EXAM 2 WINTER ‘00 STUDENT NUMBER___________ Map, and temperature, salinity & density profiles of the water column at X, near mouth of the Columbia River. P a WA c i f X i c Columbia R O c OR e a n HYPOTHETICAL DISASTER SCENARIO: An oil tanker broke up off the coast of Washington near the mouth of the Columbia River during Monday’s storm, and you have been called in to lend your expertise to the NOAA (National Oceanic & Atmospheric Administration) team that investigates such accidents. The oil tanker was carrying two types of oil: • CRUDE OIL which can be seen floating at the surface, and • BUNKER FUEL, which immediately sank to a depth of 100 meters and is spreading out at that level. 1. The water column at X is ___ with respect to density. a. stable b. unstable c. neutral d. not enough information to answer 2. Based on the depth to which the BUNKER FUEL sank, determine its sigma-t value (st). a. 10 b. 15 c. 20 d. 25 e. 100 3. What direction do you predict the CRUDE OIL at the sea surface will drift over the next several days? [NOTE: Assume normal winter conditions.] a. to the south, and on-shore (toward the land) c. to the north, and on-shore b. to the south, and off-shore (out to sea) d. to the north, and off-shore 4. Based on your knowledge of Ekman transport, do you predict the BUNKER FUEL will drift the same direction as the crude oil? a. Yes. It is within the Ekman layer, all of which moves the same direction. b. Yes. Although it is below the Ekman layer, movement of the Ekman layer will drag it along in the same direction. c. No. Although it’s in the Ekman layer, the deeper water will move in a different direction than the surface water. d. No. It is below the Ekman layer, so it will move the opposite direction. e. NO. It is below the Ekman layer, so the only thing that controls its movement is density. 5. Since it’s winter, ___ should be occurring right along the coast. a. upwelling b. downwelling 2 Questions __: Note the following locations & features: G East coast, N America, 45°N H Mediterranean J Current K Current L Current M Current N Mouth of Amazon River, 0° P Eastern equatorial Atlantic R Open ocean, 30°S S West coast, S. America, 55°S T West coast of Africa, 30°S U Open ocean, 45°S W Open ocean, 60°S 6. In eastern equatorial Atlantic (P) you would find a. high salinity c. frequent hurricanes b. upwelling of cold water d. higher sealevel than at N 7. To the east of point H in the Mediterranean you'd expect to find ___ productivity due to ___ a. low / downwelling b. low / upwelling c. high / downwelling d. high / upwelling 8. Arrange locations H, N, P, R in order from the lowest salinity to the highest salinity. a. H, N, P, R b. N, R, P, H c. H, N, R, P d. N, P, R, H 9. Of the following currents, which is strongest, fastest and most intense? a. J b. K c. L d. M 10. Copepods, are small floating animals that live in surface seawater. One of these comes from location N and one from W. Assume that the overall body weight of these two copepods is the same. Comparing body form, Copepod 1 most likely lives at __; the frilly appendages are adaptations that __. Picture missing; copepod1 is has frilly appendages; 2 has simpler, sleeker lines a. W / keep it warm in the colder water at W. b. W / help it float in the water at W, which has a higher density than at N. c. N / help it actively swim in the water at N, which is more viscous than at W d. N/ help it float in water at N, which is less viscous and less dense than the water at W. 11. Considering locations P, R, T & W, where does convergence occur in the surface water? a. Only at P d. R in the summer & W in the winter b. At R all year, & at T in the winter e. P, R & W, all year c. At W all year, & at T in the summer 12. The photic zone a. reaches greater at R than at N b. is the zone in which respiration proceeds faster than photosynthesis c. becomes deeper when there is a big wind storm like the one we had last week. d. is the same thing as the pycnocline e. all of the above 13. In each of the ocean basins on the map, there are four currents that flow around that basin, forming an oceanographic feature known as a ___. a. cyclone b. hydrologic cycle c. eddy d. gyre e. Ekman spiral 3 14. Coriolis Effect forces water into a “hump”, more or less in the middle of each ocean basin, but is countered by the force of gravity which pulls the water down hill. When these two forces are in balance, the flow of water that is established is known as a. thermohaline circulation d. centrifugal force b. pycnocline e. convection c. geostrophic flow 15. Which of the following results in an increase of nutrients in surface seawater? a. increasing sea surface temperature b. the motion of Antarctic Bottom Water through the Atlantic Ocean c. formation of Mediterranean Water d. heavy precipitation directly into the ocean at the equator e.the motion of North Atlantic Deep Water in the vicinity of the Antarctic Divergence 16. Suppose a huge dam was built on the Amazon River in order to generate electricity and control floods. Which of the following would likely occur as a result of the dam construction? a. increased the biological productivity at the mouth of the river d. all of the above b. increase in the nutrient concentration at the mouth of the river e. none of the above c. increased salinity at the mouth of the river 17. According to Dr. Wally Broecker in the video The Big Chill, the North Atlantic Conveyor a. is strongest when there is NO formation of the watermass North Atlantic Deep Water b. shuts “off” when ice covers North America during major ice ages c. promotes the flow of warm water into high latitudes to warm England and northern Europe when it is “on” d. is a combination of the thermohaline circulation and Ekman transport in the North Atlantic e. c & d 18. At location R on the map on the previous page, the water column has the temperature and salinity profiles shown to the right. Which surface process could account for these profiles? a. freezing of sea water c. melting of glaciers b. evaporation d. precipitation 19. The water column shown in these profiles is ___. a. stable b. unstable c. neutral d. not enough information to answer 20. Which of the following is NOT a western boundary current? a. Agulhas b. Brazil c. California d. Gulf Stream e. Kuroshio 21. The warmer the water is, the ___ a. more gases will dissolve in it d. a & b b. more salts will dissolve in it e. b & c c. faster chemical reactions proceed in it 22. What is produced by the process of photosynthesis? a. light d. a & b b. food, in the form of sugars and carbohydrates (organic matter) e. b & c c. oxygen 23. Carbon dioxide a. is taken up by plants during photosynthesis and released during decay. d. a & b b. absorbs infrared radiation, which warms up the atmosphere e. a, b & c c. is less abundant in the deep ocean than in the surface water 24. Which of the following is a density driven phenomenon? a. thermohaline circulation d. all of the above b. hurricane e. none of the above c. atmospheric circulation 4 Imagine that you have won the lottery and manage to buy a large, mountainous, tropical island. Unfortunately, the agent who sells you the island neglects to tell you basic things about it, including where it is. You receive the map to the right, which shows the outline of the island and the prevailing winds that blow across the region all year, along with a note that says that the seawater on the southwest side of the island is quite cold, compared to the water on all the other sides (ah, yes… upwelling!). The following 5 questions refer to this island. 25. With upwelling of cold water on the southwest side, you would expect ___ to be greater there than on the other three sides of the island. a. abundance of plankton b. clarity of the water c. gas solubility d. a & b e. a & c 26. Based on the direction of the prevailing winds and location of the upwelling, you can conclude that your island is in the _____ hemisphere. a. northern b. southern c. eastern d. western 27. The proper name of this band of prevailing (“ideal”) winds would be the a. Easterlies b. Westerlies c. Tradewinds d. Doldrums e. Horse Winds 28. As the winds blow over the island, the air rises up to go over the mountain. The air will undergo adiabatic ___, resulting in ___ that will make the southeast side of the island ___ than the northwest side. a. cooling / evaporation / drier c. warming / evaporation / drier b. cooling / precipitation / wetter d. warming / precipitation / wetter 29. Consider two fish, both of which have internal body fluids with a salinity of 25 ‰.
Load more

Recommended publications
  • Chapter 5 Frictional Boundary Layers
    Chapter 5 Frictional boundary layers 5.1 The Ekman layer problem over a solid surface In this chapter we will take up the important question of the role of friction, especially in the case when the friction is relatively small (and we will have to find an objective measure of what we mean by small). As we noted in the last chapter, the no-slip boundary condition has to be satisfied no matter how small friction is but ignoring friction lowers the spatial order of the Navier Stokes equations and makes the satisfaction of the boundary condition impossible. What is the resolution of this fundamental perplexity? At the same time, the examination of this basic fluid mechanical question allows us to investigate a physical phenomenon of great importance to both meteorology and oceanography, the frictional boundary layer in a rotating fluid, called the Ekman Layer. The historical background of this development is very interesting, partly because of the fascinating people involved. Ekman (1874-1954) was a student of the great Norwegian meteorologist, Vilhelm Bjerknes, (himself the father of Jacques Bjerknes who did so much to understand the nature of the Southern Oscillation). Vilhelm Bjerknes, who was the first to seriously attempt to formulate meteorology as a problem in fluid mechanics, was a student of his own father Christian Bjerknes, the physicist who in turn worked with Hertz who was the first to demonstrate the correctness of Maxwell’s formulation of electrodynamics. So, we are part of a joined sequence of scientists going back to the great days of classical physics.
    [Show full text]
  • Coastal Upwelling Revisited: Ekman, Bakun, and Improved 10.1029/2018JC014187 Upwelling Indices for the U.S
    Journal of Geophysical Research: Oceans RESEARCH ARTICLE Coastal Upwelling Revisited: Ekman, Bakun, and Improved 10.1029/2018JC014187 Upwelling Indices for the U.S. West Coast Key Points: Michael G. Jacox1,2 , Christopher A. Edwards3 , Elliott L. Hazen1 , and Steven J. Bograd1 • New upwelling indices are presented – for the U.S. West Coast (31 47°N) to 1NOAA Southwest Fisheries Science Center, Monterey, CA, USA, 2NOAA Earth System Research Laboratory, Boulder, CO, address shortcomings in historical 3 indices USA, University of California, Santa Cruz, CA, USA • The Coastal Upwelling Transport Index (CUTI) estimates vertical volume transport (i.e., Abstract Coastal upwelling is responsible for thriving marine ecosystems and fisheries that are upwelling/downwelling) disproportionately productive relative to their surface area, particularly in the world’s major eastern • The Biologically Effective Upwelling ’ Transport Index (BEUTI) estimates boundary upwelling systems. Along oceanic eastern boundaries, equatorward wind stress and the Earth s vertical nitrate flux rotation combine to drive a near-surface layer of water offshore, a process called Ekman transport. Similarly, positive wind stress curl drives divergence in the surface Ekman layer and consequently upwelling from Supporting Information: below, a process known as Ekman suction. In both cases, displaced water is replaced by upwelling of relatively • Supporting Information S1 nutrient-rich water from below, which stimulates the growth of microscopic phytoplankton that form the base of the marine food web. Ekman theory is foundational and underlies the calculation of upwelling indices Correspondence to: such as the “Bakun Index” that are ubiquitous in eastern boundary upwelling system studies. While generally M. G. Jacox, fi [email protected] valuable rst-order descriptions, these indices and their underlying theory provide an incomplete picture of coastal upwelling.
    [Show full text]
  • A Laboratory Model of Thermocline Depth and Exchange Fluxes Across Circumpolar Fronts*
    656 JOURNAL OF PHYSICAL OCEANOGRAPHY VOLUME 34 A Laboratory Model of Thermocline Depth and Exchange Fluxes across Circumpolar Fronts* CLAUDIA CENEDESE Physical Oceanography Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts JOHN MARSHALL Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts J. A. WHITEHEAD Physical Oceanography Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts (Manuscript received 6 January 2003, in ®nal form 7 July 2003) ABSTRACT A laboratory experiment has been constructed to investigate the possibility that the equilibrium depth of a circumpolar front is set by a balance between the rate at which potential energy is created by mechanical and buoyancy forcing and the rate at which it is released by eddies. In a rotating cylindrical tank, the combined action of mechanical and buoyancy forcing builds a strati®cation, creating a large-scale front. At equilibrium, the depth of penetration and strength of the current are then determined by the balance between eddy transport and sources and sinks associated with imposed patterns of Ekman pumping and buoyancy ¯uxes. It is found 2 that the depth of penetration and transport of the front scale like Ï[( fwe)/g9]L and weL , respectively, where we is the Ekman pumping, g9 is the reduced gravity across the front, f is the Coriolis parameter, and L is the width scale of the front. Last, the implications of this study for understanding those processes that set the strati®cation and transport of the Antarctic Circumpolar Current (ACC) are discussed. If the laboratory results scale up to the ACC, they suggest a maximum thermocline depth of approximately h 5 2 km, a zonal current velocity of 4.6 cm s21, and a transport T 5 150 Sv (1 Sv [ 106 m3 s 21), not dissimilar to what is observed.
    [Show full text]
  • Physical Oceanography - UNAM, Mexico Lecture 3: the Wind-Driven Oceanic Circulation
    Physical Oceanography - UNAM, Mexico Lecture 3: The Wind-Driven Oceanic Circulation Robin Waldman October 17th 2018 A first taste... Many large-scale circulation features are wind-forced ! Outline The Ekman currents and Sverdrup balance The western intensification of gyres The Southern Ocean circulation The Tropical circulation Outline The Ekman currents and Sverdrup balance The western intensification of gyres The Southern Ocean circulation The Tropical circulation Ekman currents Introduction : I First quantitative theory relating the winds and ocean circulation. I Can be deduced by applying a dimensional analysis to the horizontal momentum equations within the surface layer. The resulting balance is geostrophic plus Ekman : I geostrophic : Coriolis and pressure force I Ekman : Coriolis and vertical turbulent momentum fluxes modelled as diffusivities. Ekman currents Ekman’s hypotheses : I The ocean is infinitely large and wide, so that interactions with topography can be neglected ; ¶uh I It has reached a steady state, so that the Eulerian derivative ¶t = 0 ; I It is homogeneous horizontally, so that (uh:r)uh = 0, ¶uh rh:(khurh)uh = 0 and by continuity w = 0 hence w ¶z = 0 ; I Its density is constant, which has the same consequence as the Boussinesq hypotheses for the horizontal momentum equations ; I The vertical eddy diffusivity kzu is constant. ¶ 2u f k × u = k E E zu ¶z2 that is : k ¶ 2v u = zu E E f ¶z2 k ¶ 2u v = − zu E E f ¶z2 Ekman currents Ekman balance : k ¶ 2v u = zu E E f ¶z2 k ¶ 2u v = − zu E E f ¶z2 Ekman currents Ekman balance : ¶ 2u f k × u = k E E zu ¶z2 that is : Ekman currents Ekman balance : ¶ 2u f k × u = k E E zu ¶z2 that is : k ¶ 2v u = zu E E f ¶z2 k ¶ 2u v = − zu E E f ¶z2 ¶uh τ = r0kzu ¶z 0 with τ the surface wind stress.
    [Show full text]
  • Lecture 4: OCEANS (Outline)
    LectureLecture 44 :: OCEANSOCEANS (Outline)(Outline) Basic Structures and Dynamics Ekman transport Geostrophic currents Surface Ocean Circulation Subtropicl gyre Boundary current Deep Ocean Circulation Thermohaline conveyor belt ESS200A Prof. Jin -Yi Yu BasicBasic OceanOcean StructuresStructures Warm up by sunlight! Upper Ocean (~100 m) Shallow, warm upper layer where light is abundant and where most marine life can be found. Deep Ocean Cold, dark, deep ocean where plenty supplies of nutrients and carbon exist. ESS200A No sunlight! Prof. Jin -Yi Yu BasicBasic OceanOcean CurrentCurrent SystemsSystems Upper Ocean surface circulation Deep Ocean deep ocean circulation ESS200A (from “Is The Temperature Rising?”) Prof. Jin -Yi Yu TheThe StateState ofof OceansOceans Temperature warm on the upper ocean, cold in the deeper ocean. Salinity variations determined by evaporation, precipitation, sea-ice formation and melt, and river runoff. Density small in the upper ocean, large in the deeper ocean. ESS200A Prof. Jin -Yi Yu PotentialPotential TemperatureTemperature Potential temperature is very close to temperature in the ocean. The average temperature of the world ocean is about 3.6°C. ESS200A (from Global Physical Climatology ) Prof. Jin -Yi Yu SalinitySalinity E < P Sea-ice formation and melting E > P Salinity is the mass of dissolved salts in a kilogram of seawater. Unit: ‰ (part per thousand; per mil). The average salinity of the world ocean is 34.7‰. Four major factors that affect salinity: evaporation, precipitation, inflow of river water, and sea-ice formation and melting. (from Global Physical Climatology ) ESS200A Prof. Jin -Yi Yu Low density due to absorption of solar energy near the surface. DensityDensity Seawater is almost incompressible, so the density of seawater is always very close to 1000 kg/m 3.
    [Show full text]
  • Tidal Effect on the Dense Water Discharge, Part 1 Analytical Model
    ARTICLE IN PRESS Deep-Sea Research II 56 (2009) 874–883 Contents lists available at ScienceDirect Deep-Sea Research II journal homepage: www.elsevier.com/locate/dsr2 Tidal effect on the dense water discharge, Part 1: Analytical model$ Hsien-Wang Ou a,Ã, Xiaorui Guan a, Dake Chen b a Division of Ocean and Climate Physics, Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY 10964, USA b The State Key Lab of Satellite Ocean Environment Dynamics, SIO, Hangzhou, China article info abstract Article history: It is hypothesized that tidally induced shear dispersion may significantly enhance the spread and Accepted 26 October 2008 descent of the dense water. Here, we present an analytical model to elucidate the basic physics, to be Available online 18 November 2008 followed (in Part 2) by a numerical study using a primitive-equation model. Keywords: While tides enhance the vertical mixing and thicken the Ekman layer, the tidal dispersion is seen to Shear dispersion produce a disparate benthic layer several times the Ekman depths. With its top boundary lying above Benthic layer the frictional shear, the diapycnal mixing with the overlying water would be curtailed on account of its Dense outflow Richardson-number dependence. Over the shelf, this reduced erosion of the dense water and the generation of the Ekman flow by the thermal wind within the layer would act in concert to propel the dense water much beyond the deformation radius, which thus may reach the shelf break with less densification by the air-sea fluxes. Over the slope, even with the strong Ekman flow induced by the sloping interface, the dense water remains confined to the Ekman layer in the absence of tides, hence subjected to strong diapycnal mixing that would curb its descent.
    [Show full text]
  • Vertical Structure of Bottom Ekman Tidal Flows: Observations, Theory, and Modeling from the Northern Adriatic J
    University of Rhode Island DigitalCommons@URI Graduate School of Oceanography Faculty Graduate School of Oceanography Publications 2009 Vertical structure of bottom Ekman tidal flows: Observations, theory, and modeling from the northern Adriatic J. W. Book P. J. Martin See next page for additional authors Follow this and additional works at: https://digitalcommons.uri.edu/gsofacpubs Terms of Use All rights reserved under copyright. Citation/Publisher Attribution Book, J. W., P. J. Martin, I. Janeković, M. Kuzmić, and M. Wimbush (2009), Vertical structure of bottom Ekman tidal flows: Observations, theory, and modeling from the northern Adriatic, J. Geophys. Res., 114, C01S06, doi: 10.1029/2008JC004736. Available at: https://doi.org/10.1029/2008JC004736 This Article is brought to you for free and open access by the Graduate School of Oceanography at DigitalCommons@URI. It has been accepted for inclusion in Graduate School of Oceanography Faculty Publications by an authorized administrator of DigitalCommons@URI. For more information, please contact [email protected]. Authors J. W. Book, P. J. Martin, I. Janeković, M. Kuzmić, and Mark Wimbush This article is available at DigitalCommons@URI: https://digitalcommons.uri.edu/gsofacpubs/445 JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 114, C01S06, doi:10.1029/2008JC004736, 2009 Vertical structure of bottom Ekman tidal flows: Observations, theory, and modeling from the northern Adriatic J. W. Book,1 P. J. Martin,1 I. Janekovic´,2 M. Kuzmic´,2 and M. Wimbush3 Received 14 January 2008; revised 10 October 2008; accepted 8 January 2009; published 17 April 2009. [1] From September 2002 to May 2003, fifteen bottom-mounted, acoustic Doppler current profilers measured currents of the northern Adriatic basin.
    [Show full text]
  • Organization of Stratification, Turbulence, and Veering in Bottom Ekman Layers A
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, C05S90, doi:10.1029/2004JC002641, 2007 Click Here for Full Article Organization of stratification, turbulence, and veering in bottom Ekman layers A. Perlin,1 J. N. Moum,1 J. M. Klymak,1,2 M. D. Levine,1 T. Boyd,1 and P. M. Kosro1 Received 3 August 2004; revised 17 November 2006; accepted 7 December 2006; published 24 May 2007. [1] Detailed observations of the Ekman spiral in the stratified bottom boundary layer during a 3-month period in an upwelling season over the Oregon shelf suggest a systematic organization. Counter-clockwise veering in the bottom boundary layer is constrained to the weakly stratified layer below the pycnocline, and its height is nearly identical to the turbulent boundary layer height. Veering reaches 13+/À4 degrees near the bottom and exhibits a very weak dependence on the speed and direction of the interior flow and the thickness of the veering layer. A simple Ekman balance model with turbulent viscosity consistent with the law-of-the-wall parameterization modified to account for stratification at the top of the mixed layer is used to demonstrate the importance of stratification on the Ekman veering. The model agrees reasonably well with observations in the lower 60–70% of the bottom mixed layer, above which it diverges from the data due to the unaccounted physics in the interior. Neglect of stratification in an otherwise identical model results in far worse agreement with the data yielding veering in the bottom Ekman layer which is much smaller than measured, but distributed over a much thicker layer.
    [Show full text]
  • ATM 500: Atmospheric Dynamics End-Of-Semester Review, December 5 2019 Here, in Bullet Points, Are the Key Concepts from the Second Half of the Course
    ATM 500: Atmospheric Dynamics End-of-semester review, December 5 2019 Here, in bullet points, are the key concepts from the second half of the course. They are not meant to be self-contained notes! Refer back to your course notes for notation, derivations, sketches, and deeper discussion. Pressure coordinates Any variable that has a one-to-one (monotonic) relationship with height z can be used as a vertical coordinate instead of z. This works for pressure if the flow is in hydrostatic balance. In this case the adiabatic primitive equations are D~u Dθ + f~ × ~u = −∇ Φ = 0 Dt p Dt @Φ @! = −α r ~u + = 0 @p p @p The density ρ no longer appears explicitly in the momentum equation, which is a considerable mathematical simplification. Geostrophic balance in pressure coordinates ~ f × ~ug = −∇pΦ or in components 1 @Φ 1 @Φ u = − v = g f @y g f @x The flow is parallel to lines of constant geopotential height, and rp · ~ug = 0 on an f-plane. Thermal wind relation The generalization of the Taylor-Proudman theorem to a baroclinic fluid. For flow that is in geostrophic and hydrostatic balance, @~u R f~ × g = r T @p p p or in components @v R @T @u R @T g = − g = @p fp @x @p fp @y The vertical shear of the geostrophic wind is proportional to (quasi-horizontal) temperature gradients on pressure surfaces If cold air lies to the north and f > 0, the wind must become more westerly with height. 1 Static stability The vertical variation of density in the environment determines whether a parcel, disturbed upward from an initial hydrostatic rest state, will accelerate away from its initial position, or oscillate about that position.
    [Show full text]
  • 2.011 Motion of the Upper Ocean
    2.011 Motion of the Upper Ocean Prof. A. Techet April 20, 2006 Equations of Motion • Impart an impulsive force on the surface of the fluid to set it in motion (no other forces act on the fluid, except Coriolis). • Then, for a parcel of water moving with zero friction: Simplify the equations: • Assuming only Coriolis force is acting on the fluid then there will be no horizontal pressure gradients: • Assuming then the flow is only horizontal (w=0): • Coriolis Parameter: Solve these equations • Combine to solve for u: • Standard Diff. Eq. • Inertial Current Solution: (Inertial Oscillations) Inertial Current • Note this solution are equations for a circle Drifter buoys in the N. Atlantic • Circle Diameter: • Inertial Period: • Anti-cyclonic (clockwise) in N. Hemisphere; cyclonic (counterclockwise) in S. Hemi • Most common currents in the ocean! Courtesy of Prof. Robert Stewart. Used with permission. Source: Introduction to Physical Oceanography, http://oceanworld.tamu.edu/home/course_book.htm Ekman Layer • Steady winds on the surface generate a thin, horizontal boundary layer (i.e. Ekman Layer) • Thin = O (100 meters) thick • First noticed by Nansen that wind tended to blow ice at 20-40° angles to the right of the wind in the Arctic. Courtesy of Prof. Robert Stewart. Used with permission. Source: Introduction to Physical Oceanography, http://oceanworld.tamu.edu/home/course_book.htm Ekman’s Solution • Steady, homogeneous, horizontal flow with friction on a rotating earth • All horizontal and temporal derivatives are zero • Wind Stress in horizontal
    [Show full text]
  • Strati Ed Ekman Layers
    May 12, 1999 Strati ed Ekman Layers James F. Price DepartmentofPhysical Oceanography,Wo o ds Hole Oceanographic Institution, Wo o ds Hole, Massachusetts 1 Miles A. Sundermeyer Joint Program in Physical Oceanography, Massachusetts Institute of Technology, and Wo o ds Hole Oceanographic Institution, Wo o ds Hole, Massachusetts 1 Now at the Center for Marine Science and Technology, University of Massachusetts, New Bedford. Abstract: Under fair weather conditions the time-averaged, wind-driven current forms a spiral in which the currentvector decays and turns cum sole with increasing depth. These spirals resemble classical Ekman spirals. They di er in that their rotation depth scale exceeds the e-folding depth of the sp eed by a factor of two to four and they are compressed in the downwind direction. A related prop erty is that the time-averaged stress is evidently not parallel to the time-averaged vertical shear. We develop the hyp othesis that the at spiral structure may b e a consequence of the temp oral variability of strati cation. Within the upp er 10-20 m of the water column this variability is asso ciated primarily with the diurnal cycle and can b e treated bya time-dep endent di usion mo del or a mixed-layer mo del. The latter can b e simpli ed to yield a closed solution that gives an explicit account of strati ed spirals and reasonable hindcasts of midlatitude cases. At mid and higher latitudes the wind-driven transp ort is found to b e trapp ed mainly within the upp er part of the Ekman layer, the diurnal warm layer.
    [Show full text]
  • Journal of Physical Oceanography (Proof Only) Rise
    JOBNAME: JPO 00#0 2011 PAGE: 1 SESS: 8 OUTPUT: Fri Oct 21 16:44:34 2011 Total No. of Pages: 14 /ams/jpo/0/jpoD11061 MONTH 2011 Q I U A N D C H E N 1 Multidecadal Sea Level and Gyre Circulation Variability in the Northwestern Tropical Pacific Ocean BO QIU AND SHUIMING CHEN Department of Oceanography, University of Hawaii at Manoa, Honolulu, Hawaii (Manuscript received 17 March 2011, in final form 22 July 2011) ABSTRACT Sea level rise with the trend .10 mm yr21 has been observed in the tropical western Pacific Ocean over the 1993–2009 period. This rate is 3 times faster than the global-mean value of the sea level rise. Analyses of the satellite altimeter data and repeat hydrographic data along 1378E reveal that this regionally enhanced sea level rise is thermosteric in nature and vertically confined to a patch in the upper ocean above the 128C isotherm. Dynamically, this regional sea level trend is accompanied by southward migration and strength- ening of the North Equatorial Current (NEC) and North Equatorial Countercurrent (NECC). Using a 1½- layer reduced-gravity model forced by the ECMWF reanalysis wind stress data, the authors find that both the observed sea level rise and the NEC/NECC’s southward migrating and strengthening trends are largely at- tributable to the upper-ocean water mass redistribution caused by the surface wind stresses of the recently strengthened atmospheric Walker circulation. Based on the long-term model simulation, it is further found that the observed southward migrating and strengthening trends of the NEC and NECC began in the early 1990s.
    [Show full text]