surface water & deep water circulation

Surface Water &

Deep Water

CIRCULATION

• NOTES– Turn in Homework -2– Pick Up Homework – 1

– Homework 3 – Assigned Due Next Wednesday

– MIDTERM • Get 2 GREEN SCANTRONS from Bookstore

– #2 pencil

– Exam based on Lecture Notes

– 40 Multi Choice Qs

– 5 Short Answer

• World Ocean Circulation

– Traditionally divided into 2 components:• 1) Surface Water Circulation

• 2) Deep Water Circulation

• Actually Both Influence each other. . .

• Best TERM: WORLD OCEAN Circulation

• We’ll Review each separately for Simplicity Sake . . .

• World Ocean Circulation– Based on Dynamic Physical Oceanography

• Describes Ocean based on:– Physical laws & conservation equations in conjunction with

» Atmospheric and oceanographic observations

• GOAL:– Quantify flow patterns & property distributions in the Ocean

• Many PRACTICAL Applications:– Ship Routing

– Search and Rescue

– Marine pollutant trajectories

• OUR GOAL:– Explore the Nature of Ocean Circulation –

– become aware of Forces that govern .http://www.mindfully.org/Plastic/Nike-Pacific-Dump-Ebbsmeyer.htm

• World Ocean Circulation• Foundations of Physical Oceanography• Motion in the Ocean• Upwelling/Downwelling• Patterns of Surface water Circulation• Patterns of Deep water Circulation• What Drives Deep water Circulation• Global Conveyer Belt

OUTLINE

• Foundations of Physical Oceanography– Ben Franklin (1706-1790)

• US Postmaster General (reduce transit time)

• Publishes First Maps of Gulf Stream

• By 1800 many

circulation patterns

worked out by seaman

• Via Trial and error

• Little understanding of– Why?

• Foundations of Physical Oceanography– Many Early Scientists contributed to

• Modern view of Ocean Circulations Patterns (1750-1900)– Based on Convection Currents Model

» Ben Thompson, Henry Ellis, John Buchanan, Alex Buchan

» Alfred Merz, Geoarge Wust

– 1958, Henry Stommel (1920-1992)

» Proposed global model of abyssal circulation . . .

» Most Important Physical Oceanographer- All time

1958, Henry Stommel (1920-1992)Proposed global model of abyssal circulation

Deep H2O formation

Subsurface flows. . ..

Deep flows. . ..

Deep flows

• World Ocean Circulation• Foundations of Physical Oceanography• Motion in the Ocean• Upwelling/Downwelling• Patterns of Surface water Circulation• Patterns of Deep water Circulation• What Drives Deep water Circulation• Global Conveyer Belt

OUTLINE

• Motion in the Ocean – Challenge Questions– The existence of the 4 Big Gyres- Where are they?

• How do they arise? See next slides– What direction are their rotations Clockwise or Counterclockwise?– WHY? see next

slides

•

• Motion in the Ocean– The existence of the Gyres

• How do they arise? V. Walfrid Ekman (1861-1930)

– Understand Ekman Transport

Remember:In N. HemisphereCoriolis deflects this to Right

NOTE:Arrows indicate:-direction-intensity

((Wind stress))Friction drags layer belowAnd so on. . .

NOTE:Arrows indicate:-current direction-current intensity

• Motion in the Ocean– Ekman Transport

– Challenge Question?What 2 phenomena occur to the currents as you go deeper in depth layers?

1. The currents deflect Right (N. Hemisphere)

2. The currents intensity weakens

• CHALLENGE Question

Why do the Gyres spin Clockwise or Counter Clockwise?

N. Hemisphere

S. Hemisphere

RECALLThe Westerlies &The Trade Winds

Provide Wind stressUnder influence of CoriolisCurves currents to rightVia Ekman Transport

NOTE:–There is a mistake

in the Text

– where is it and why?

S. Pacific Gyre should be counter clockwise

clockwise

How Should this look in the S. Hemisphere?

•CHALLENGE Question

v

• Gyres – – N. Hemisphere = Clockwise

– S. Hemisphere = Counter Clockwise

• What is so important about Gyres anyway?

Anthropogenic activity causing harm: See the Great Ocean wasteland. . .KQED

http://www.youtube.com/watch?v=g9fEbqxyNl0

clockwise

Counter clockwise

• WHAT CAN YOU DO?– You’re probably not Going to Stop Using all Plastics

• RECYCLE

• RECYCLE

• RECYLCE!

• Santa Cruz one of the best County’s for RECYCLING!!!(#1-6 or higher!)

• JUST DO IT

• Set an EXAMPLE for you FAMILY, Friends & – the Next Generation

• Geostrophic Flow: The Hill in the Gyre– What does geostrophic stand for?

• “Earth-turning” –refers to “flow under influence of Coriolis”

• EKMAN Transport Directs H2O to middle of Oceans (Gyres)– Creates sloping Sea Surface (a Hill)

– H2O flows from High Pressure to Low pressure

– Forms geostrophic currents (gyres)

– A balance of:

» Horiz. Press. Gradient

» Coriolis force

• Geostrophic Flow: The Hill in the Gyre– Another rendition

• Geostrophic Flow: The Hill in the Gyre– Consequences .. (see TOPEX Satellite Alimeters)

• Elevated Sea Surface Heights across the Oceans

• Geostrophic Flow: The Hill in the Gyre– Satellite Jason 2001

• 32 cm difference in elevation b/w Pt. A vs Pt. B

• Upwelling/Downwelling– What is upwelling?

• The flow of subsurface waters to the surface– What are the two types:

» Coastal

» Equatorial

EQUATORIAL Upwelling

nutrients

• Satelite Image of Upwelling – Cooler waters in Purple

• Upwelling– COASTAL Upwelling (e.g. California)

• In N. California, what direction does the Coastal wind Come From?

– North (Alaska) Winds . . . .

• Surface waters are:» blown west

» (via Ekman transp.)

» Deep H2O is upwelled to fill gap

» Cold water upwelled

• Downwelling• What is it?

• the movement of water downward in the water column

– Warmer surface water migrates onto the coastline

VS

Versus heading out to sea (UPWELLING)

• Serious Upwelling in N. California– Lots of biological Production f/ Nutrients (photosynthesis)

• Kelp Forests

marine life etc.

Warmest Spot N. of Pt. Conception

SATELLITE IMAGE-Cold Water (Purple)

• World Ocean Circulation• Foundations of Physical Oceanography• Motion in the Ocean• Upwelling/Downwelling

– BREAK• Patterns of Surface water Circulation• Patterns of Deep water Circulation• What Drives Deep water Circulation• Global Conveyer Belt

OUTLINE

• Patterns of Surface water Circulation– Harald Sverdrop (1888-1957)

• Early theoretical Understanding

• Effects of a Boundary (continent) on Ocean Circulation– His Theories allowed for calculation of surface flows

» via wind stress

» In his Honor created …

Water transport unit the “Sverdrup” = 1x106 m3 sec -1

• Patterns of Surface water Circulation– What does the Long-term averages of Surface H2O transport look

like in terms of surface circulation?

• Western Boundary Currents– What are they and What do they arise from?

• Currents located along the western sides of Ocean basins

• Arise from an intensification of Gyre circulation– In response to variations in the Coriolis effect with lattitude

v

Where are they Below?

• Western Boundary Currents– All fast moving & narrower then most currents– e.g. in N. Atlantic - Gulf Stream (Most Famous)

• ~2.3 m s-1 (Knots)

• Transports Warm H2O from Gulf of Mexico to N. Atlantic

Florida

• Western Boundary Currents– e.g. in N. Pacific – what Current?– Kuroshio ~ > 2.5 m s-1 (>5 Knots) ~ 2 miles sec!

• Flow is complicated, Japan archipelago wakes, eddies etc.

• Western Boundary Currents– e.g. in S. Atlantic – what Current?– Brazil Current ~ 2.2 m s-1 (<5 Knots)

• Forms Highly Productive Large Marine Ecosystem (LME)– aka Patagonian Shelf

Western Intensification

• Challenge Question?– What is it - And what is it caused by?

• Increase in flow rates of W. boundary currents caused by:– Coriolis effect which

– Increases @

» Higher latitudes

CORIOLIS Force

STRONGESTStrongermodestweak

Latitude

TAKE HOMEWestern Boundary Currents = Fast/ Narrow, b/c Coriolis

What aboutEastern Boundary Currents?Next slide. . ..

Gulf Stream orKuroshio

• Eastern Boundary Currents – examples?– e.g. California Current– Slow moving (1 foot/ sec)

• Bring cool water – coastal Upwelling Moderate Climate

• aka Mediterranean

• Also produce considerable fog

• Equatorial Counter Currents– Weak seasonal currents ~ return some (warm) flow East

• May play a role in Hurricane formation. . .

• Equatorial Counter Currents– Satellite imagery, warmer temp (yellow)

Hurricane Alley

• Antarctic Circumpolar Current (ACC)– Only continuous current unimpeded by land masses

• Important exchange pt for Waters or all three Oceans:– Atlantic, Pacific, Indian

• Summary – Warm & Cold Surface Water Currents

• World Ocean Circulation• Foundations of Physical Oceanography• Motion in the Ocean• Upwelling/Downwelling• Patterns of Surface water Circulation• Patterns of Deep water Circulation• What Drives Deep water Circulation• Global Conveyer Belt

OUTLINE

• Patterns of DEEP Water Circulation - T-S Diagrams– What are they and what are they used for?

• Temp vs Salinity Diagrams: – mea. @ different pressures (depths)

• Allow for the determination of diff. types of water masses &– How they are influencing mixing and current flow, their properties etc..

. .

SurfaceOcean

DeepOcean

T-S Diagram

Patterns of DEEP Water Circulation - T-S Diagrams

• Patterns of Deep water Circulation– Confirming your knowledge:

• What is Needed to Form Deep Water?– Cold air/H2O temperatures, high salinity (downward flux)– Colder/ salty water = dense

» sinks

– e.g. N. Atlantic• Gulf Stream transports

– Warm/Salty H2O Greenland

• S. of Greenland– Cold Air cools water

» Cool/salty water sinks. . .» N.Atlantic deep water» aka (NADW)

• Patterns of Deep water Circulation• Ocean is Stratified (layered)- influenced by

– Thermocline • Rapid change in temperature

– Pycnocline• What is it?

– Rapid change in density

» (salinity & Temp)

Influences the Major Water Masses . . .

Saltier

More abundantInflu deep circulationOver greater region

Thought to confer greatestShut down of NADWAbrupt climate changes

Colder

Most dense in World

NOTES:

• World Ocean Circulation

• Foundations of Physical Oceanography

• Motion in the Ocean

• Upwelling/Downwelling

• Patterns of Surface water Circulation

• Patterns of Deep water Circulation

• What Drives Deep water Circulation

• Global Conveyer Belt

OUTLINE

• Deep water Circulation– Challenge Question – Current Philosophy

• What Drives Deep water Circulation?– @ Highest latitudes (downward flux – sinking)

» Density changes form (Cold & salty) sinking H2O

– @ lower Latitudes

» Upward flux (upwelling) – does the WORK (pulling)

upwelling

• Places where the seawater is cold enough and salty enough to form bottom water.

• World Ocean Circulation

• Foundations of Physical Oceanography

• Motion in the Ocean

• Upwelling/Downwelling

• Patterns of Surface water Circulation

• Patterns of Deep water Circulation

• What Drives Deep water CirculationGlobal Conveyer Belt

OUTLINE

• All this Deep Water movement – Global Conveyer Belt –

– aka ThermoHaline Circulation• What is it?

– Thermo (temp) & haline (salt) dependent circulation

– Heat of Earth’s oceans dissipated from circulation process. .

• Global Ocean Conveyer Belt (ThermoHaline Circulation)

– Wally Broecker’s Model – shows deep H2O formations + returns • Broecker et al., 1991, Oceanography

– Challenge Question?• Where are the 2 major cites for DEEP water Formation?

– N. Atlantic Deep Water (NADW)

– Antarctic Bottom Water (AABW)

NADW

AABW

• The Global Conveyer Belt aka~

http://www.youtube.com/watch?v=3niR_-Kv4SM

http://www.youtube.com/watch?v=MZbsMlr9WRI&feature=related

http://www.youtube.com/watch?v=L9zjmC8InKAFOR More Animated Effects See:

• NOTE: Global Conveyer Model: – Oversimplified representation– Schmitz Model (1995)

• More accurate– Ocean Mixing

= complex

» Surface

» Intermediate

» Deep Waters all mix

FINAL THOUGHTS

Know the 2 Major -Cites of Deep Water formation-Why and how they would occur

• NOTES– Turn in Homework -2– Pick Up Homework – 1

– Homework 3 – Assigned Due Next Wednesday

SEE you FRIDAY (() brrrr)

Fig. 9.21

Fig. 9.22

PHOTOS

Opener

Page 165

Fig. 9.1

Fig. 9.13

Fig. 9.16

TABLES

Tab. 9.1

Tab. 9.2

Tab. 9.3