INTRODUCTION TO OCEANOGRAPHY

Instructor: Prof. ANAMARIJA FRANKIĆ

Office Number: S-1-061Office Hours: Posted on office door or by appointment

Telephone: 617-287-4415Email Address: anamarija.frankic@umb.edu

Web Page: http://alpha.es.umb.edu/faculty/af/frankic.hmlDepartment Website: http://www.es.umb.edu/

Oceanography is an observationally driven field!

What are the independent variables/parameters for the ocean?

What do they measure and what is there use?

Geology: coastlines, bathymetry, movement of tectonic plates

Chemistry: Carbon, Nitrogen, Iron, Oxygen…

Physics: T, U, V, S, SSH

Biology: Chl-a, Productivity, Zooplankton, Phytoplankton, Fish and Egg counts, etc…

How was the ocean observed so far?

http://www.amazon.com/gp/reader/0393317552/ref=sib_dp_pt/103-3317661-1512644#reader-page

Lots of historical account of earlyexplorations – (see book).

HMS Challenger

International Observational Programs

Deep Sea Drilling Project - DSDP

1985, Joides Resolution Replace G. Challenger

1968, Glomar Challenger

Theory of Plate Tectonics and much more…

International Observational Programs

The Joint Global Ocean Flux Study (JGOFS) (launched in 1987 at a planning meeting in Paris)

The Operational Goal of JGOFS :

Spatial Scale: regional to global Temporal Scale: seasonal to interannual

1) Fluxes of carbon between the atmosphere-surface ocean-ocean interior.2) Sensitivity to climate changes

International Observational Programs

The World Ocean Circulation Experiment1990-1998

http://woce.nodc.noaa.gov/wdiu/

International Programme on Climate Variability and Predictability, 1995-present

http://www.clivar.org/index.htm

http://www.wmo.ch/web/wcrp/wcrp-home.html

World Climate Research Programme

http://www.clivar.org/publications/other_pubs/clivar_transp/index.htm

US Programs sponsors:

http://www.nsf.gov/

http://www.noaa.gov/

http://www.onr.navy.mil/focus/ocean/habitats/default.htm

http://science.hq.nasa.gov/oceans/

e.g. GLOBEC http://www.pml.ac.uk/globec/

http://www.csc.noaa.gov/coos/

U.S. Coastal Observing Systems

Remote Sensing/Satellite Imagery: Geostationary Server -http://www.goes.noaa.gov/ Satellite significant events: http://www.osei.noaa.gov/ National Geophysical Data Center: http://www.ngdc.noaa.gov/ngdc.html  

Technologies for ocean observing

Floating devices in the ocean: Argo FLoats - http://www.argo.ucsd.edu/ Drifter Programs: http://www.aoml.noaa.gov/phod/graphics/pacifictraj.gif

 Remotely Operated Vehicles (ROVs) : Amazing discoveries…http://oceanexplorer.noaa.gov/technology/subs/rov/rov.html Automated Underwater Vehicles (AUVs) : 

How do we define the science of Oceanography?

WHAT PEOPLE NEED TO KNOW ABOUT OCEAN SCIENCES

• Ways of knowing – “Reflection on how we know what we believe will help our understanding”

• Human interactions – “Currently, the human species is significantly affecting earth systems, but has the ability to choose its relationship with the environment”

• Ecosystems – “The survival and health of individuals and groups of organisms are intimately coupled to their environment”

• Earth system science – “The Earth as a whole acts as a complex set of interacting systems with emergent properties”

• Evolution & Biodiversity – “Evolution explains both the unity and diversity of life”

• Energy flow and transformation – “Energy transformation drive physical, chemical, and biological processes. Total energy is conserved and flows to more diffuse forms”

• Conservation of mass – “Mass is conserved as it is transferred from one pool to another”

• Spatio-temporal relationships – “Choosing the appropriate reference frame is the key to understanding one’s environment”

Beginnings

1. Earth’s formation2. Earth’s timeline

The Universe - formed 10-15 billion years ago Currently referred to as the ‘Big Bang‘

• current theory is that the universe was formed from something smaller than an atom

• the atom exploded and everything was blown outward with great heat and speed

Earth’s Formation

Our Solar System was formed 4.6 billion years agoThe Earth is assumed to be the same age • At this time, Earth had a surface

~ known from radiometric dating of meteorites (uranium and potassium)

• We think water condensed on the planet 3.9 billion years ago~ known from radiometric dating of sedimentary rocks that

formed by processes requiring water

Earth’s Formation

Old Theory:

a) H2O came from big comets during period of heavy bombardment

a) H2O locked up in minerals released from differentiation and heating

Earth’s FormationWhere did oceans come from?

New Theory:

a) Oceans still forming and H2O comes from many small cometessimals that continually bombard the Earth

a) H2O came from big comets during period of heavy bombardment

a) H2O locked up in minerals released from differentiation and heating

Where did oceans come from? (cont’d)

Earth’s Formation

Mother Earth formed 4.6 billion years ago..

What has happened during this time?

Earth’s Timeline

Divide by 4.6 billion by 100 million years - makes Earth 46 years old

0-3 yrs no record3 yrs dated from rocks in Canada, Africa

and Greenland8-11 yrs 1st living cells - primitive bacteria22-23 yrs oxygen production by cells begins31 yrs atmosphere has enough oxygen to

support life39th yr first invertebrates-hard shelled fossils41rst yr primitive fish and corals

Earth’s Timeline (cont’d)

41-42 yrs land plants, fish43 yr reptiles, dinosaurs, sharks44 yr dinosaurs dominate45 yr dinosaurs die

1 yr ago plants and flowers proliferate7 mos. ago insects, mammals, birds proliferate25 days ago first humans6 days ago homosapiens1/2 hour ago 1st recorded civilization1 minute ago industrial revolution

change Earth and relationship with Earth for all time…

Earth’s Timeline (cont’d)

Earth

1. Coordinates2. Earth’s Water3. Earth’s Structure

Earth • Highest mountain is Mt. Everest at 8840m above sea level• Lowest trench is the Mariana Trench (Pacific) at 11,000m

below sea level

Earth has a huge mass!!!

Think of earth like a basketball - the bumps would be the mountains and the dimples would be the trenches.

Coordinates

Latitude and Longitude

Latitude• Parallel to the equator

• Expressed as degrees N or S of the equator where equator = 0

Coordinates (cont’d)

Longitude • Lines of longitude are meridians• Longitudinal lines are at a right angle to

latitudinal grid• 0° longitude is known as the prime meridian

Goes right through Royal Observatory in Greenwich, England

Greenwich Mean Time = ‘Universal Time’, when sun is directly above 0 longitude• Expressed as degrees E or W of prime meridian

where prime meridian = 0

Latitude and Longitude (cont’d)

Coordinates (cont’d)

Connected by 2 processes:evaporation and precipitation See fig 1.18 (Intro 7e) or 2.13 (Fund. 4e)

Earth’s water reservoirs:

Oceans 97.2%Lakes, rivers and inland seas 0.017%Glaciers 2.14%Atmosphere 0.001%Ground H20 0.61%Biosphere 0.005%

Earth’s WaterHow Earth's water reservoirs are connected

WORLDS WATER SOURCES:

• Layered system (like an onion, concentric regions)~ differentiation of mineral material

Not only Earth’s mineral material, but also:

1. hydrosphere2. biosphere3. atmosphere

Earth’s Structure

Classification according to chemical compositionEarth’s Structure (cont’d.)

4 concentric regions of mineral material:

1. crust2. mantle3. outer core - molten4. inner core - solid

1. Crust Two types:continental granite – composed of silicates rich in Na, K & Al

ocean basalt – composed of silicates rich in Ca, Mg & Fe• represents 0.4% of Earth’s mass• extends down to 75 km

Classification according to chemical compositionEarth’s Structure (cont’d.)

2. Mantle Three parts:uppermost/middle/innermost• Composed of Mg-Fe silicates• represents 68% of Earth’s mass• extends down from base of

crust to ~2,900 km

Classification according to chemical compositionEarth’s Structure (cont’d.)

3. Core Two parts:Outer Inner• Composed of Fe & Ni• Represents 28% of Earth’s

mass• Extends down from base of

mantle ~ 6400km

Classification according to chemical compositionEarth’s Structure (cont’d.)

1. lithosphere - rigid outer shell (crust & uppermost mantle)• 100 - 150km thick• does not change shape

(factor in temperature and pressure)Classification according to physical properties

Earth’s Structure (cont’d.)

4 concentric regions:

2. Asthenosphere - soft, flows over geologic time under the weight of the lithosphere (small fraction of middle mantle)• lithosphere ‘floats on top’• zone where magma formed• 200 – 350km thick• easily deformed, can be pushed down by overlying lithosphere –

“plastic” – tar or asphalt

Earth’s Structure (cont’d.)

3. Mesosphere - rigid but not as hard as lithosphere• higher temp than asthenosphere, but not molten because of

compression pressure• 4950km thick

Classification according to physical propertiesEarth’s Structure (cont’d.)

4. Core - outer is molten, inner is solid

Classification according to physical propertiesEarth’s Structure (cont’d.)

IsostacyPrinciple that dictates how different parts of the lithosphere stand in relation to each other in the vertical direction

• Continental crust less dense (granitic) therefore rises higher relative to ocean crust (basaltic)

• Continents move up and down depending on weight on top (i.e. from glaciers - ‘isostatic rebound’)

~ Continents pop up after glaciers melt

~ Canada and Scandinavia rising at a rate of 1m/100yrs because the glaciers are receding

Earth’s Structure (cont’d.)

Five oceans:1. Atlantic – shallowest, greatest number of adjacent seas-

regional seas: i.e. Gulf of Mexico, Caribbean, Mediterranean, North), has the largest freshwater input (i.e. Amazon, Congo, Mississippi)

2. Pacific – largest, deepest

3. Indian – smallest, muddiest

4. Arctic – covers N. Pole, saltiest

5. Southern Ocean – coldest, most productive

Earth’s Water (cont’d.)

(Some) OCEANS’ related FACTS:

Our planet is actually the Ocean Planet - 77% of the Earth’s surface is covered by oceans and seas. However, less than 10% has been investigated.

Oceans provide more than 70% of oxygen we breathe

80% of world’s plant and animal species live in oceans

More than 60% of the current human population (5.8 billion) lives in the coastal zones (~60 km wide), the areas representing only 8% of the Earth surface!

‘Poorest of the poor’ - 1.1 billion people ‘survive’ on less than 1$/day 1 billion people rely on fish as the only daily source of protein

Global climate change and the humans’ well being depend on the conditions and health of the oceans;

Poverty, hunger, diseases as well as casualties from natural disasters can be alleviated by improving the health of the environment and by sustainable use and management of the coasts and oceans!

Plate TectonicsHorizontal Movement of

Earth’s Lithosphere

Plate Tectonics

1. The Theory of Plate Tectonics

2. Plate Boundariesa) Spreading Centersb) Subduction Zonesc) Transform Faults

3. Plate Movement

“Continental Drift” - theory* proposed by Alfred Wagner, a German meteorologist (1915)

* Not accepted by scientific community- no mechanism to explain plate movement

The Theory of Plate Tectonics

Explained by:• geologic fit• fossils

Plate Tectonics - evidence for theory of

continental drift Hess, Heezen and Tharp (1960’s)

found lithospheres plate boundaries, 3 types: 1) ridges (spreading centers) 2) trenches (subduction zones) 3) transform faults (plates sliding past one

another)

The Theory of Plate Tectonics (cont’d.)

major plates:

1. Pacific – 105 x106 km2

2. Eurasian - 70 x106 km23. Antarctic - 60 x106 km24. Australian - 45 x106 km25. S. American - 45 x106 km26. African - 80 x106 km27. N. American - 60 x106 km2

Lithospheric Plates

minor plates:

1. Cocos - 5 x106 km2

2. Phillipine - 6 x106 km2

3. Caribbean - 5 x106 km2

4. Nazca - 15 x106 km2

5. Arabian - 8 x106 km2

6. Indian - 10 x106 km2

7. Scotia - 5 x106 km2

8. Juan de Fuca - 2 x106 km2From Fundamentals of Oceanography, 5h edition, DuxburyDuxbury, and Sverdup. The McGraw-Hill Companies

The Theory of Plate Tectonics (cont’d.)

1) Convection cells form• Density differences – cool vs. hot

2) Convection cells cause frictional drag on lithosphere3) Lithosphere stretches due to convective movement4) Lithospheric crust weakens

Plate Boundaries

a) Spreading centers - ‘rift zones’ (cont’d.)

5) Faulting – break in overlying lithosphere6) Magma flows upward7) New lithospheric crust formed

Plate Boundaries (cont’d.)

a) Spreading centers - ‘rift zones’ (cont’d.)

• Plates split apart -‘divergent plate’ boundary• New crust formed - ‘constructive’ plate

boundary

a) Spreading centers - ‘rift zones’ (cont’d.)

Ex. 1 - oceans: mid Atlantic Ridgeeast Pacific Rise

Ex. 2 - continents: E. Africa Rift ValleyBaikal Rift Valley

Evolution of a mid-ocean ridge system1. Upwarping2. Rift valley3. Linear sea4. Mid-ocean ridge system

Plate Boundaries (cont’d.)

• Lithospheric Plates collide - ‘convergent’ plate boundary

• Crust destroyed - ‘destructive’ plate boundary• Forms trenches and mountains

Plate Boundaries (cont’d.)

b) Subduction zones

3 types of subduction zones:

1. Ocean crust into continental crust – form trenches and mountain ranges

Ex. a): Juan de Fuca plate into the N. American plate - forms Cascade Mtn. RangeEx. b): Nazca plate into the S. American plate - forms Peru-Chile Trench and

the Andes Mtn. Range

Plate Boundaries (cont’d.)

b) Subduction zones (cont’d.)

b) Subduction zones (cont’d.)

2. Ocean crust into ocean crust – forms trenches and island arcs

Ex. A): Philippine plate into the Pacific plate – formed the Marianna Trenchand the Marianna Island Arc system

Ex. B): N. American plate into the Caribbean plate and then the N. American plate into the S. American plate – formed the Isthmus of Panama

Plate Boundaries (cont’d.)

3. Continental crust into continental crust – form mountain ranges

Ex. A): Indian plate into the Eurasian plate – formed the HimalayasEx. B): Eurasian plate into the African plate - closing up of the

Mediterranean sea

Plate Boundaries (cont’d.)

b) Subduction zones (cont’d.)

• Plates slide past one another• Lithospheric crust neither created nor destroyed - ‘conservative’ plate

boundary

Ex. A) Pacific plate sliding past N. American plate – forms the San Andreas Fault

c) Transform faults

Plate Boundaries (cont’d.)

• New crust is created at spreading centers at a rate of approximately 1-10cm per year

• Old crust is destroyed at the same rate at subduction zones

How do we know these rates? (Rate=distance/time)

Plate Movement

• Magnetic anomalies in ocean crust...look at spreading centers paleomagnetism every so often Earth’s magnetic field flips (every 300K-500K years)

Plate Movement (cont’d.)

magnetic signal recorded in crust at spreading center as it’s formed, forms bands of crust with either a weak or strong magnetic signal

determine rate of plate movement by distance of band from spreading center divided by age of rock in band (r=d/t)

Hot spots Emperor Sea Mount chain islands or sea mountains formed over hotspots (fixed area where magma comes up)

lithosphere moves over hotspot and end up have volcanic mountain over hotspot as well as a series of mountains in ‘front’ of hotspot

determine rate of plate movement by distance of mountain from hotspot divided by age of rock in mountain (r=d/t)

Plate Movement (cont’d.)

Learning Objectives 

Understand the processes that are continuously changing Earth’s surface as lithospheric plates move relative to one another. Identify the role of oceanic ridges, transform faults and deep-sea trenches in defining the edges of lithospheric plates. Understand the importance of asthenospheric thermal convection in plate tectonics and the resulting compression or tensional forces at the plate boundaries. Explain the distribution of magnetic anomaly stripes, seismicity, and volcanism in terms of the concept of global plate tectonics. Calculate spreading rates of ocean basins.

Age of Ocean Crusthttp://www.ngdc.noaa.gov/mgg/geology/geology.html

Creating new ocean crust

More evidence of plate moving..

Oceanic crust moves away from MOR (Mid Oceanic Ridge) and cools and subsides

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Driving Mechanisms for Plate Motions

Destructive margins Subduction zones

Constructive margins Midocean ridges

Type of boundary between plates:

Constructive margins Mid ocean ridges

Destructive margins Subduction zones

Conservative margins Transform faults

Conservative marginsTransform faults

The San Andreas fault in southern California

Conservative marginsTransform faults

Hot Spots ?

• Mantle plumes originate deep within the asthenosphere as molten rock which rises and melts through the lithospheric plate forming a large volcanic mass at a “hot spot”.

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Mantle Plume

Coral Reefs

Air view

Spreading rates

Geological Periods

Precambrian 4.6 B - 570 Ma solidificationCambrian 514 Ma Gondwana, hard shell anim.Ordovician 458 Ma separation, coldestSilurian 425 Ma Laurentia collides with BalticaDevonian 390 Ma pre-Pangea, equatorial forestsEarly Carboniferous 356 MaLate Carboniferous 306 Ma western Pangea is completePermian 255 Ma deserts, reptiles, major ext.Triassic 237 Ma Life begins to rediversify,PangeaJurassic 195 Ma Dinosaurs, Pangea starts to breakLate Jurassic 152 Ma Pangea rifts apart, AtlanticCretaceous 94 Ma New oceans, IndiaK/T extinction 66 Ma end of dinosaursEocene 50.2 Ma India collides with AsiaMiocene 14 Ma Modern lookModernFuture World +50 Ma N. Atlantic widens, Med. vanishFuture +100 Ma new subductionFuture +250 Ma new Pangea

Geological Periods

Precambrianbreak-up of the supercontinent, Rodinia, which formed 1100 million years ago.   The Late Precambrian was  an "Ice House" World, much like the present-day.

Source: www.scotese.com

CambrianAnimals with hard-shells appeared in great numbers for the first time during the Cambrian.  The continents were flooded by shallow seas.  The supercontinent of Gondwana had just formed and was located near the South Pole.

OrdovicianDuring the Ordovician ancient oceans separated the barren continents of Laurentia, Baltica, Siberia and Gondwana.  The end of the Ordovician was one of the coldest times in Earth history.  Ice covered much of the southern region of Gondwana.

SilurianLaurentia collides with Baltica closing the northen branch of the Iapetus Ocean and forming the "Old Red Sandstone" continent.  Coral reefs expand and land plants begin to colonize the barren continents.

DevonianBy the Devonian the early Paleozoic oceans were closing, forming a "pre-Pangea".  Freshwater fish were able to migrate from the southern hemisphere continents to North America and Europe.  Forests grew for the first time in the equatorial regions of Artic Canada.

Early CarboniferousDuring the Early Carboniferous the Paleozoic oceans between Euramerica and Gondwana began to close, forming the Appalachian and Variscan mountains.   An ice cap grew at the South Pole as four-legged vertebrates evolved in the coal swamps near the Equator.

Late CarboniferousBy the Late Carboniferous the continents that make up modern North America and Europe had collided with the southern continents of Gondwana to form  the western half of Pangea.  Ice covered much of the southern hemisphere and vast coal swamps formed along the equator.

PermianVast  deserts covered western Pangea during the Permian as reptiles spread across the face of the supercontinent.

TriassicThe supercontinent of Pangea, mostly assembled by the Triassic, allowed land animals to migrate from the South Pole to the North Pole; and warm-water faunas spread across Tethys. The first mammals and dinosaurs appeared;

JurassicBy the Early Jurassic, south-central Asia had assembled.  A wide Tethys ocean separated the northern continents from Gondwana. 

Subduction zone Rocky Mountains

Formation of the Rocky Mountainshttp://wrgis.wr.usgs.gov/docs/parks/province/rockymtn.html

Late JurassicIn the Late Jurassic the Central Atlantic Ocean was a narrow ocean separating Africa from eastern North America. 

CretaceousDuring the Cretaceous the South Atlantic Ocean opened.  India separated from Madagascar and raced northward on a collision course with Eurasia. Notice that North America was connected to Europe, and that Australia was still joined to Antarctica.

K/T extinctionThe bull's eye marks the location of impact site of a 10 mile wide comet caused global climate changes that killed the dinosaurs and many other forms of life.  By the Late Cretaceous the oceans had widened, and India approached the southern margin of Asia.

Eocene50 - 55 million  years ago India began to collide with Asia forming the Tibetan plateau and Himalayas (destroying the last of Tethys ocean).  Australia, which was attached to Antarctica, began to move rapidly northward.

Collision of continental crust

• Whereas oceanic ridges indicate tension, continental mountains indicate compressional forces are squeezing the land together.

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Sedimentary Rocks Squeezed by Compression

Miocene20 million years ago, Antarctica was covered by ice and the northern continents were cooling rapidly.  The world has taken on a "modern" look, but notice that Florida and parts of Asia were flooded by the sea. Arabia moved away from Africa forming Gulf of Aden and Red Sea;

Last Ice AgeWhen the Earth is in its "Ice House" climate mode, there is ice at the poles.  The polar ice sheet expands and contacts because of variations in the Earth's orbit (Milankovitch cycles).  The last expansion of the polar ice sheets took place about 18,000 years ago. 

Modern World

If we continue present-day plate motions the Atlantic will widen, Africa will collide with Europe closing the Mediterranean, Australia will collide with S.E. Asia, and California will slide northward up the coast to Alaska.

Future +100

Earth is ~ 4.6 bill years old – suggested cyclic of 500 mill year pattern of assembling and disassembling the land masses;

Future +250

The Wilson Cycle

The Wilson Cycle