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Oceanography

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on 11 May 2014

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Transcript of Oceanography

Ocean Circulation
Waves
1. What causes waves?
2. What characteristics do waves posses?
3. How do wind-generated waves develop?
4. How do waves change in the surf zone?
5. How are Tsunami created?
6. Can power from waves be harnessed as energy?
Oceanography
Oceanography does not just cover 70% of the Earth.
Oceanography
Oceanography includes the interactions between the Biological, Chemical, and Geological interactions between the Earth and the Oceans.
Oceanography includes the Ocean's impact on the entire planet, including Climate and Weather Patterns.
Plankton
Tiny organisms that are essential to the biological
structure of the ocean environment

Phytoplankton:
coccolithophores, diatoms, dinoflagellates
Zooplankton:
fish larva, jelly fish, arrow worms, tintinnids

Benefit to humans and ocean environment:
source of food for larger marine animals
provide oxygen and nutrients in deep sea environments
Nekton
Any animal capable of moving independently of the ocean currents by swimming or other means of propulsion

Examples: whales, sharks and other fish, squid and marine reptiles

Benefit to humans and ocean environment: food for larger nekton, economic benefit for humans


Benthos
Organisms living on the ocean bottom

Examples: sponges, sand dollars, sea anemones, mussels, sea urchins, crabs, and clams

Benefits: many benthos species have economic benefit such as crabs, and other shell fish. Mussels filter water.

Microscopic planktonic bacteria and algae that photosynthesize represent the largest biomass in the ocean.
primary producers
foundation of the ocean’s food web.

Organic biomass is also produced near deep-sea hydrothermal springs through chemosynthesis
Marine Environments
Marine environment - divided into pelagic (open sea) and benthic (sea bottom)

Regions divided based on depth and have varying physical conditions

Euphotic Zone - One of the most important layers of the pelagic environment
contains enough sunlight to support photosynthesis
Animals of the Pelagic Environment
Biological Oceanography
The study of oceanic life forms and their relationships to one another; adaptations to the marine environment; and developing sustainable methods of harvesting seafood.
Marine Life
Classified into one of three groups based on habitat and mobility.
Plankton
Nekton
Benthos
Tides
Pelagic animals comprise the majority of the oceans biomass

Remain mostly within the upper surface waters of the ocean, where their primary food source exists.

Those animals that are not planktonic depend on buoyancy or their ability to swim to help them remain in food-rich surface waters
Animals of the Benthic Environment
More than 98% of the 250,000 known marine species live in diverse environments on the ocean floor.

Species diversity depends on their ability to adapt

The biomass of benthic organisms closely matches the photosynthetic productivity in surface waters above
Geological Oceanography
As time has passed, the continents have shifted, changing the Earth's Surface. As the continents separated, oceans have formed between them.
As continents have collided, oceans that rested between them have closed up.
This
Continental Drift
, which shapes the Earth, is caused convection of the Earth's mantle moving Tectonic Plates, according to a theory called
Plate Tectonics
.
(Figure G-1.)
Tectonic Plates separate at
Divergent Boundaries
, where magma solidifies and joins onto the preexisting tectonic plate as it is pulled away from the divergent boundary.
Mid-Ocean Rifts
and
Rift Valleys
form at these points.
Tectonic Plates clash at
Convergent Boundaries
, where a tectonic plate is pulled under another plate and returns to the mantle. Mountain building may occur at these points when Islands or Continents collide with a Continent.
Volcanoes
may form.
Tectonic Plates move past one another at
Transform Boundaries
. Unlike convergent and divergent boundaries, volcanoes do not occur here, but
Faults
do.
Transport Mechanisms of Ocean Currents
Movement of the Plates
Surface Current Measurement
Direct Methods
Floating device released into current and tracked over time
Fixed-position propeller flow meter (used on piers or stationary ships)
Indirect Methods
Using density distribution and corresponding pressure gradients
Dynamic topography: uses radar altimeters to observe lumps and bulges at the surface
Doppler Flow Meter: measures shifts in low frequency sound waves caused by water particle movement
(Figure G-2.)
Earthquakes and Tsunamis.
The friction between plate boundaries and faults can cause
Earthquakes
.
As a result, Earthquakes can create Tsunamis.
Tsunamis
are coastal disasters, potentially caused by displacement of water caused by Earthquakes.
Tsunamis
Tsunamis may also be caused by Underwater Volcanoes and Underwater Avalanches.
Tsunamis are not exactly waves, but instead are several oceanic surges that cause massive coastal flooding and property damage.
The
Pacific Tsunami Warning Center
(
PTWC
) was developed to warn of
tsunamis using Seismic Activity
and Pressure Sensors.
(Figure
G-3.)
Climate Patterns and Ocean Interactions
The Climate affects the Salinity of the Ocean in the region. The more precipitation there is, the more diluted the ocean water. More evaporation means there is more salt concentrated in the ocean water.
The Climate is affected by circulation of air and moisture in the atmosphere. At the equator, warm, moist air rises and causes precipitation, forming Rain Forests. When the air is cool and dry, it descends to the surface, picking up moisture as it moves along, leaving the regions
as arid, dry Deserts.
(Figure G-4.)
Sediment Deposition
Sediments are moved and deposited by the energy in the environment.
High Energy Depositional Environments
can move larger grains (such as glaciers moving boulders, or rushing water moving pebbles).
Low Energy Depositional Environments
can move only very fine grain sediments (such as Clay settling on a deep-sea abyssal plain).
Coarse-Grains tend to be deposited in high energy depositional environments, while Fine-Grains are deposited in low energy depositional environments.
(Figure G-5).
Surface Currents
- wind driven motion horizontally
Deep Current Measurement
ARGO - device with free-drifting profiling floats that sinks down to a programmed depth to collect general water characteristics.
Climate Change
Increase in average world wide temperature is called global warming

Natural process - greenhouse effect

Human greenhouse gas emissions is a phenomenon that is often referred to as the enhanced greenhouse effect.
Changes in oceans due to global warming:
increased ocean temperatures
more intense hurricane activity
changes in deep-water circulation
melting of polar ice
increase in ocean acidity
rising sea level

Ocean and Climate
The ocean removes carbon dioxide from the atmosphere


The ocean also acts as a thermal sponge by soaking up excess heat from the atmosphere, thereby minimizing the amount of warming experienced.
Questions?
Thank you!
Works Cited
Trujillo, A. P., Thurman. H. V. (2013).
Essentials of Oceanography
. Pearson College Division.
(Figure G-1):
Continental Drift [Diagram], Retrieved April 27, 2014, from:
http://www.clemson.edu/caah/history/Facultypages/pamMack/lec124/originalnature.html
(Figure G-2):
Geobit 10: Plate Boundaries
[Diagram], Retrieved April 27, 2014,
http://crystal.isgs.uiuc.edu/maps-data-pub/publications/geobits/plates.shtml
(Figure G-3):
Liekens, A.
Diagram of a Forming Tsunami
[Diagram], Retrieved April 27, 2014, from:
http://www.thesurfchannel.com/news/20130211/tsunamis-what-to-do-when-disaster-hits/
(Figure G-4):
Cloudless Earth (Day)
[Photograph], Retrieved April 27, 2014, from:
http://nssdc.gsfc.nasa.gov/planetary/planets/earthpage.html
Figure (G-5):
Diagram Illustrating some Depositional Environments
[Diagram],
Retrieved April 27, 2014, from: http://higheredbcs.wiley.com/legacy/college/levin/0471697435/chap_tut/chaps/chapter05-02.html
As continents have collided, oceans that rested between them have closed up.
What causes waves?
3 main ways
- Storms and Wind
- Splash waves
- Icebergs falling off glaciers
- Both land based and underwater
landslides and seismic activity
- Movement of fluids with differing densities
Fig 8.1a
What characteristics do waves posses?
Wave Terminology
How do wind-generated waves develop?
Wind causes ripples that gravity
moves into bigger and bigger waves
How do waves change in the surf zone?
Fig. 8.9
Figs. 8.7a-c
Fig 8.17
How are Tsunami created?
Can power from waves be harnessed
as a source of energy?
Technologies use wave motion
as a source of energy
Fig 8.28
Main Causes of
Upwelling & Downwelling
Notable Surface
Circulation Patterns
Harnessing Power From
Ocean Currents
Hydroelectricity Today
Upwelling
is the vertical movement of cold, deep, nutrient-rich water to the surface
Equatorial Upwelling
Coastal Winds
Seafloor Geography
In Relation to Geology
Large belts of water that redistribute heat and nutrients throughout the ocean
Sea-level defines depositional environments, which result in the deposition of different sediments in the past.
Tectonic activity affects the appearance of the world, (oceans included) and may cause tsunamis.
Environments and their rates of precipitation and evaporation affect salinity of water.
Horizontal direction determined by frictional resistance between wind and the ocean below
Ekman transport
Deep Currents
- density driven motion vertically
Downwelling
is the vertical movement of surface water to deeper parts of the ocean
Coastal Downwelling from Ekman Transport
Convergence of Surface Currents
Causes of Ocean Tides
It has been estimated that ocean currents on the
eastern coast of Florida have the potential of producing
2000 MW of electricity
Gravitational Attraction to the Moon and Sun:
Moon has twice the effect of the sun
Ignoring frictional effects ans assuming uniform depth, gravitational pull creates small horizontal forces that produces two bulges
One bulge towards the Moon or Sun and another bulge on the opposite side
Zero tide-generating forces occur at the Zenith and Nadir shown below
Since water has a greater density than air, currents
have a much greater yield of energy than wind farms
Obstacles:
Avoidance of cavitation
Prevention of marine growth buildup
High maintenance costs
Corrosion resistance (saltwater)
Tidal Cycles
Can operate at low current speeds ~ 1 m/s
(A)
(B)
(C)
(D)
In ideal conditions time between successive high tides would be 12 hrs 25 min with 29.5 day tidal cycles between
spring
and
neap
tides
Spring tides: max tidal range (E->M->S)
Moon in
syzygy
with the Sun
Neap tides: min tidal range
Moon in
quadrature
with the Sun
Complicating Factors:
Declination of the Moon (28.5) and Sun (23.5)
Elliptical orbits of the Moon and Sun
Complications cause "higher high tides" and "lower low tides" depending on latitude location (12 hr delay)
True Tidal Shape
With frictional forces and true form of ocean basins and trenches are considered, tidal movement does not follow ideal diagram
Continents interfere with free movement of tidal bulges
Coastline depth and offshore shape also influence tidal movement

Amphidromic Points
: near center of each cell where no tidal range occurs
Cotidal Lines
: lines connecting locations where high tide occurs simultaneously
Existing Tidal Patterns
Diurnal
: consisting of one high and one low tide each lunar day
Semidiurnal
: consisting of two high and two low tides, with approximately the same heights from each corresponding high or low tide
Mixed
: combination of characteristics present in diurnal and semidiurnal patterns
Higher density from low temperature & high salinity
Thoroughly mixes deep water masses
Importance to Wildlife Science?
The biodiversity of the oceans is important to the entire biosphere of the planet

Understanding marine environments can help us understand the animals that live there: their niches

Understanding climate change will help us understand the effect it has on marine and terrestrial animals
1. Antarctic

Only current to encircle Earth
Moves more water than any other current
2. Atlantic Ocean
Complex circulation from trade winds, prevailing westerlies and the Coriolis effect
Ocean Engineering and Tides
3. Indian Ocean
Seasonal monsoon that reverses the direction of the wind and causes either little or heavy precipitation
Coastal Region Tide Effects
4. Pacific Ocean
Two large subtropical gyres bigger than those of the Atlantic
Tidal Bores
: "true tidal waves" produced in rivers or bay areas by incoming high tides.
Flood Current
: produced when water rushes into a bay or river with incoming high tide.
Ebb Current:
produced when water flows seaward accompanied by decreasing tide.
High and Low Slack Water
: time between tidal currents occurring at peak high or low tides.
Whirlpools
: created in restricted coastal passages where reversing tidal currents take place.
Grunion
: small fish that time spawning cycles to tides
Threats to the marine environments
Conveyor Belt Circulation
An useful model that combines deep thermohaline circulation with surface currents
Crucial for deep water organism survival
Nutrient & oxygen mixing
Ekman Spiral & Transport
V. Walfrid Ekman
determined in 1905 that wind drives surface water in a direction that is 45 degrees to the right of the wind
The direction continues to spiral to the right with
depth leading to the conclusion that
net transport is 90 degrees to the right
(a) Traditional wind turbine

(b) Artist rendering of deep water turbines (prototype)

(c) Open Hydro system used for harnessing
tidal energy

(d) Seagen, the worlds first commercial tidal
energy turbine
Figures (A-D):
Bureau of Ocean Energy Management [Text & Photograph], Retrieved April 28, 2014 from:
http://www.boem.gov/Renewable-Energy-Program/Renewable-Energy-Guide/Ocean-Current-Energy.aspx
Like wave or current energy tides can also be used to harness energy as a clean alternative to fossil fuels
Trapping tidal waters to tun through a turbine creates an energy source
To produce tidal plants that can effectively harvest energy there need to be significant tidal impacts, making it hard to implement smaller working tidal pants
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