Generalized Surface Circulation

Slides:

Advertisements

Similar presentations

Making water move How it is mixed & transported

Advertisements

Chapter 16 The Dynamic Ocean.

Chapter 7 Ocean Circulation

How Does Air Move Around the Globe?

© 2011 Pearson Education, Inc. CHAPTER 7 Ocean Circulation.

Wind Forced Ocean Circulation. Ekman Spiral and Ekman Mass Transport.

1 Surface Circulation Pathways Generally, warm currents move poleward and cool currents move equatorward.

Steady State General Ocean Circulation “steady state” means: constant in time, no accelerations or Sum of all forces = 0 Outline:1. Ekman dynamics (Coriolis~Friction)

Ocean Gyres - combine knowledge of global winds and Ekman flow - surface transport can be determined from wind direction/velocity - surface transport alters.

Earth Systems Science Chapter 5 OCEAN CIRCULATION I: SURFACE Winds, surface currents Flow within gyres: convergence, divergence, upwelling, downwelling,

1 Trade Winds in Equatorial Pacific. 2 ITCZ Location July January ITCZ.

ATMOSPHERIC CIRCULATION. Atmospheric and Oceanic Circulation Wind Essentials Driving Forces Within the Atmosphere Atmospheric Patterns of Motion Oceanic.

Oceanic Circulation Current = a moving mass of water.

Ocean Circulation II Ekman transport & Geostrophic currents.

Highways in the Sea (Chapter 9)

Gyres and Currents Made by Michael Kramer.

Lecture 7: The Oceans (1) EarthsClimate_Web_Chapter.pdfEarthsClimate_Web_Chapter.pdf, p

Potential temperature ( o C, Levitus 1994) Surface Global zonal mean.

CIRCULATION OF OCEANS.

Surface wind stress Approaching sea surface, the geostrophic balance is broken, even for large scales. The major reason is the influences of the winds.

Video Field Trip 1. How are waves created? 2. Describe the way in which the moon influences the tides.

1. 2 ocean circulation thermohaline conceptual model.

Evaporative heat flux (Q e ) 51% of the heat input into the ocean is used for evaporation. Evaporation starts when the air over the ocean is unsaturated.

Class 8. Oceans II. Ekman pumping/suction Wind-driven ocean flow Equations with wind-stress.

General Ocean Circulation. Wind driven circulation About 10% of the water is moved by surface currents Surface currents are primarily driven by the wind.

Quiz #1, Part 1 results (You can see the statistics yourself in “My Grades”)

Ocean circulation Surface circulation driven by wind Subsurface circulation driven by density.

OCEAN CURRENTS AND CLIMATE. Ocean Currents and Climate There are two types of Ocean Currents: 1. Surface Currents are driven by surface wind circulation.

OCEAN CURRENTS.

Surface Ocean Circulation and Geostrophy Fig. CO7 S.

Ocean Circulation.

Ekman Flow September 27, 2006.

Basic dynamics ●The equations of motion and continuity Scaling

The Ocean General Circulation. Mean Circulation in the Ocean Gulf Stream.

OCN 5401 Chapter 6 Effect of Earth’s Rotation Instructor: Dr. George A. Maul / X 7453.

The Ocean General Circulation (satellite). Mean Circulation in the Ocean Gulf Stream.

The Surface Currents An Introduction to the World’s Oceans Sverdrup et al. - Chapter Nine - 8th Ed.

Current Weather Introduction to Air-Sea interactions Ekman Transport Sub-tropical and sub-polar gyres Upwelling and downwelling Return Exam I For Next.

An example of vertical profiles of temperature, salinity and density.

How Does Air Move Around the Globe?

Ekman pumping Integrating the continuity equation through the layer:. Assume and let, we have is transport into or out of the bottom of the Ekman layer.

Ocean Circulation – Ch Ag Earth Science – Chapter 15.2.

Question: Why 45 o, physics or math? andare perpendicular to each other 45 o relation holds for boundary layer solution Physics: Coriolis force is balanced.

12.808, Problem 1, problem set #2 This is a 3 part question dealing with the wind-driven circulation. At 26 o N in the N. Atlantic, the average wind stress.

Geopotential and isobaric surfaces

 p and  surfaces are parallel =>  =  (p) Given a barotropic and hydrostatic conditions, is geostrophic current. For a barotropic flow, we have and.

Ocean Currents Oceans have a slower, much longer-lasting effect on climate than winds. Ocean currents are basically driven by the sun and the rotation.

Forces and accelerations in a fluid: (a) acceleration, (b) advection, (c) pressure gradient force, (d) gravity, and (e) acceleration associated with viscosity.

Inter-tropical Convergence Zone (ITCZ)

Measuring Deep Currents

99 Surface and Deep Circulation. Chamberlin and Dickey, 2008 Exploring the World Ocean Questions to Consider What are the patterns of the surface circulation?

Ocean Currents (see “ships in storm” video.  By some estimates, as many as cargo containers are lost, during storms, every year.

Boundary Currents - combine knowledge of global winds and Ekman flow - surface transport can be determined from wind direction/velocity - surface transport.

For a barotropic flow, we have is geostrophic current.

Surface circulation Deep ocean circulation

Define and we have • At the sea surface (z=0), the surface current flows at 45o to the right of the wind direction Depends on constant Az => • Current.

How to create a subtropical gyre circulation I

Gyres of the world oceans

Ocean Circulation.

MONSOONS AND OCEAN CURRENTS Figure 10.15

Check for Understanding

Week 5: Thermal wind, dynamic height and Ekman flow

Heat Transport by the Atmosphere and ocean

Week 6-7: Wind-driven ocean circulation Tally’s book, chapter 7

(Pinet) Major ocean current systems 4 Surface patterns extend as deep as 1000 m 5.

TALLEY Copyright © 2011 Elsevier Inc. All rights reserved

Ocean Surface Circulation

Global Scale Winds.

Ocean Currents.

Presentation transcript:

Generalized Surface Circulation

Nansen’s Trip in the “frozen” Fram (1893-96)

Nansen’s Observations about Surface Currents

Ekman’s Force Balance Current Coriolis Wind Walfred Ekman Drag Current direction is to the right of the wind in N. Hemisphere

Ekman’s Three Force Vector Balance (in the northern hemisphere) Wind Stress Force Current Direction (not a force) Coriolis Force (always perpendicular to the Current direction) Frictional Force (always opposes direction of current) Resulting Force (the combination of the Coriolis Force and Frictional Force yields a Resulting force that is equal to and in opposite direction to the Wind Stress Force)

Ekman Spiral

Ekman Spiral Observations (surface layer in the N. Atlantic) Wind Direction Measured Current Directions and Velocities at 5, 10, 15 and 25 m depths

Generalized Pattern of Surface Winds July Arrows indicate direction of Ekman Transport January

Map of Sea Surface Height (ARGO floats) (in dynamic cms relative to 1500 dbar) Sea surface height range is ~300cm or 3 m.

Pressure P = g ρ Z

Horizontal Pressure Gradients

Geostrophic Force Balance

Geostrophic Current Flow around a dome of pressure

Sea Surface Height Anomaly (dynamic centimeters) (dynamic height is relative to 1000dbar) (Arrows represent direction of geostrophic current flow)

Barotropic and Baroclinic Conditions Size of arrow indicates speed of current

Depth Profile of Typical Geostrophic Current Velocity

Cross Section of Density in Pacific Ocean What meridional trend in sea surface height would be implied under baroclinic conditions?

Phosphate Distribution in Surface Ocean

Chlorophyll in the Surface Ocean

Gulf Stream Franklin’s map of Gulf Stream and ‘gyre’ in 1785

Temperature and Salinity Sections across the Gulf Stream Pot. Temp. Temperature and Salinity Sections across the Gulf Stream Salinity

Current Velocities in the Region of the Gulf Stream White= northward flow Blue = southward flow

Sea Surface Temperatures and Major Warm and Cool Currents

Gulf Stream Rings picture of SST observed from satellites Gulf Stream Ring Movie

Temperature Anomalies of Gulf Stream Rings