This document provides information on various topics related to oceanography. It discusses features of the ocean floor like the continental shelf and slope. It also covers properties of water such as its incompressibility and transparency to sound. Additionally, it summarizes the dissolved salts in seawater, how fresh water density varies with temperature, and temperature variations in the ocean. Further topics include salinity, density, freezing points, energy spectrums, sound speed, and ocean circulation forces like winds, Coriolis effect, and Ekman transport. The document also briefly outlines surface currents, deep water currents, upwelling and downwelling, and interactions between surface and deep sea currents.

1. Ocean Bottom
-12000
-10000
-8000
-6000
-4000
-2000
0
2000 Parts of the Sea Floor
Distancefrom
surfaceinm
Continental Shelf
Continental
Slope
Continental
rise
abyssal plain
Sea mount Submarine Ridge
Ocean Trench
Volcanic Island

2. Water Properties
 Highly Incompressible
 Extremely Large Heat capacity and Thermal
conductivity
 Largely Opaque to Electromagnetic Energy in the
Visible part of Spectrum
 Largely opaque to Electromagnetic Energy in the
Radio and Radar Frequency Range
 Extremely Transparent to Acoustic Energy

3. Dissolved salts in sea water (atoms):
55.3 % Chlorine
30.8 % Sodium
3.7 % Magnesium
2.6 % Sulfur
1.2 % Calcium
1.1 % Potassium

4. Fresh Water Density
 Water behaves like normal fluid expanding when
heated and contracting when cooled between
100°C and 4°C
 Water expands from 4°C to 0°C thus giving
maximum density at 4°C
 At 0°C water changes to solid phase forming ice
crystals with a volume increase of about 9%. Thus
ice floats
 This change in property gives rise to vertical
circulation of water

5. Temperature in the ocean
 The Sun hits the surface layer of the
ocean, heating the water up.
 Wind and waves mix this layer up from
top to bottom, so the heat gets mixed
downward too.
 The temperature of the surface waters
varies mainly with latitude.
 The polar seas (high latitude) can be as
cold as -2 degrees Celsius (28.4 degrees
Fahrenheit) while the Persian Gulf (low
latitude) can be as warm as 36 degrees
Celsius (96.8 degrees Fahrenheit).
 Ocean water, with an average salinity of
35 psu, freezes at -1.94 degrees Celsius

6. Temperature cont…
 Thermocline- a distinct
zonation of waters based
on temperature. In large
bodies of water this is a
natural process occurring
between the air and wind
influenced surface waters,
which have relatively
rapidly changing
temperatures, with the
colder, more constant
temperature deeper
waters.

7. Salinity and Density
 Density of water increases with increase in salinity – 1.025 at
20°C with salinity of 35gm/Kg (35‰)
 Temperature of Maximum density decrease from 4°C with
increase in salinity
 Freezing Temperature decrease from 0°C with increase in
salinity
 T(ρ max) in°C = 3.95-0.200S-0.0011S²
 T(freezing) in°C = -0.003-0.0527S-0.00004S²

8. Salinity cont…
 Halocline- vertical zone in
the oceanic water
column in which salinity
changes rapidly with
depth, located below the
well-mixed, uniformly
saline surface water layer.
 Especially well developed
haloclines occur in the
Atlantic Ocean, in which
salinities may decrease by
several parts per thousand
from the base of the
surface layer to depths of
about one kilometre
(3,300 feet). In higherﾉ

9. Density and Oceans
Cont…

10. Variation of temperature of
max density and freezing
with temperature

11. Freezing of Sea Water
 It would seem that at 35‰ salinity, the maximum
density would occur in solid phase thus freezing
water at bottom of the sea
 This does not happen
 Salt is precipitated as the temperature
approaches freezing point thus making the ice of
fresh water only with increased salinity just below
the formed ice
 This leads to a denser fluid strata just below the
formed ice on the sea surface.
 This leads to a type of vertical circulation

12. Energy Spectrum of incident
radiation at ocean depth

13. Speed of sound in water

14. Why is Ocean Circulation
Important?
 Transport ~ 20% of
latitudinal heat
 Equator to poles
 Transport nutrients and
organisms
 Influences weather and
climate
 Influences commerce

15. Sailors have know about ocean
currents for centuries
Sailors have know that “rivers” flow in the seas since ancient
times. They used them to shorten voyages, or were delayed
by trying to stem them.
If navigators do not correct to deflection by currents, they may
be far away from where they think they are and meet
disaster.
Fridtjof Nansen scientifically observed ice pack drift for two
years and recorded it in 1893-96. This was later put to
theory by Ekman
Another systematic study of currents was done by Maury
based on logbooks in the US Navy’s Depot of Charts and
Instruments. His charts and “Physical Geography of the
Sea” assisted navigators worldwide.

16. Surface Currents - The upper 100 to 200
meters of the ocean
Deep Water Currents – Mainly
Geostrophic flow (98% of volume)
Bottom Current
Ocean Currents

18. Physical properties of the
atmosphere: Water vapor
•Cool air cannot hold much
water vapor, so is typically dry
•Warm air can hold more water
vapor, so is typically moist
•Water vapor decreases the
density of air

19. Physical properties of the
atmosphere: Density
• Warm, low
density air rises
• Cool, high
density air sinks
• Creates circular-
moving loop of
air (convection
cell)

20. Convectio
n cell
model
Non-rotating Earth

21. The Coriolis effect
• The Coriolis effect
– Is a result of Earth’s rotation
– Causes moving objects to
follow curved paths:
• In Northern Hemisphere, curvature is to right
• In Southern Hemisphere, curvature is to left
– Changes with latitude:
• No Coriolis effect at Equator
• Maximum Coriolis effect at poles

22. The Coriolis effect on Earth
• As Earth rotates,
different
latitudes travel
at different
speeds
• The change in
speed with
latitude causes
the Coriolis
effect

23. Earth’s Rotation and
Variation of Tangential
Velocities

24. Surface Currents
Forces
1. Solar Heating (temp, density)
2. Winds
3. Coriolis

25. Winds and surface water
 Wind blowing over the ocean can move it due to
frictional drag.
 Waves create necessary roughness for wind to couple
with water.
 One “rule of thumb” holds that wind blowing for 12 hrs
at 100 cm per sec will produce a 2 cm per sec current
(about 2% of the wind speed)

26. Wind-Driven and Density-Driven
Currents
Wind-driven currents occur in the
uppermost 100 m or less
Density differences causes by
salinity and temperature produce
very slow flows in deeper waters.

27. Top-down drag
 Wind acts only on the surface water layer.
 This layer will also drag the underlying
water, but with less force.
 Consequently, there is a diminution of
speed downward and Turbulent mixing.
 Direction of movement is also influenced
by the Coriolis Effect and Ekman Spiral

28. Ekman spiral
Ekman spiral describes
the speed and
direction of flow of
surface waters at
various depths
 Factors:
 Wind
 Coriolis effect

29. Ekman transport
Ekman transport is the overall
water movement due to Ekman
spiral
 Ideal transport is 90º from the
wind
 Transport direction depends on
the hemisphere

30. Ekman Transport
Water flow in the Northern hemisphere- 90o to the right of the wind direction
Depth is important

31. Geostrophic Flow
Surface currents generally mirror average
planetary atmospheric circulation patterns

33. Currents in the “Real” Ocean
Currents rarely behave exactly as predicted by
these theoretical explanations due to factors such as
 Depth—shallow water does not permit full
development of the Ekman spiral
 Density—deeper currents moving in different directions
influence the overlying surface movement

34. Eddy
Warm core ring
1. Rotates clockwise
2. Found on the landward side of the current
Cold core ring (cyclonic eddy)
1. Rotates counterclockwise
2. Forms on the ocean side of the current
A circular movement of water formed along the edge of a
permanent current
In an average year, 10-15 rings are formed
150-300 km in diameter
Speed 1 m/sec

36. Upwelling and downwelling
Vertical movement of water ()
 Upwelling = movement of deep water to surface
 Hoists cold, nutrient-rich water to surface
 Produces high productivities and abundant marine life
 Downwelling = movement of surface water down
 Moves warm, nutrient-depleted surface water down
 Not associated with high productivities or abundant marine life

37. Circulation
 As water becomes cold it sinks, which causes
the under water currents in the oceans.
 This mixes the layers of water which allow
food from the surface to reach the bottom.
This along with upwelling and downwelling
(the upward and downward motion of sub-
surface water toward the surface and bottom
of the ocean. This is often a source of cold,
nutrient-rich water.
 Strong upwelling occurs along the equator
where easterly winds are present. Upwelling
also can occur along coastlines).
 This increases the productivity ( the amount of
carbon available to the system as a result of
photosynthesis) of the marine ecosystem.

38. Circulation Cont…
 circulation of surface waters of the ocean are
driven by winds, the circulation of the deep
waters are driven by density differences.
 Circulation in the depths of the ocean is referred
to as thermohaline circulation.
 The deep ocean is layered with the densest water
on bottom and the lightest water on top.
 Water tends to move horizontally throughout the
deep ocean, moving along lines of equal density.
 Vertical circulation is limited because it is easier
for water to move along lines of constant density
than across them.

39. Surface and Deep-Sea Current
Interactions
Unifying concept: “Global Ocean Conveyor Belt”
http://seis.natsci.csulb.edu/rbehl/ConvBelt.htm

40. White sections represent warm surface currents.
Purple sections represent deep cold currents