Surface Water & Deep Water CIRCULATION
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Transcript of 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