Ocean basics

Coastal Environments: The Basics

• 97% of all water on our planet is in the
oceans.

• Fresh water represents the remaining 3%
(2/3 is snow and ice in glaciers / polar ice
caps).

• Liquid and solid water cover roughly 3/4 of
Earth's surface area.

• 29% of the earth’s surface is above sea level
(71% is below )

Unique properties of water
• Absorbs or releases more heat than most
other substances for every temperature
degree of change
• Water is a good solvent and can dissolve
more substances than other fluids, even
rocks
• Water exists in 3 physical states that can
power thunderstorms/hurricanes and help
transport the sun's energy, nutrients, and
organisms

More than half the
world's population
live within 60km
of a coastline

[In the US, half live within
80 km, on less than 17%
of the land area…]

South Florida, USA

Overview
• Chemical properties of water
– H bonds
– Ice
– Salinity and Sources
• Physical properties of water
– Biomechanics
– Density
– Temperature
• Major ocean basins of the world
– Chemical signatures (depth and latitude)
• Coastal Systems
– Sandy beaches, rocky coasts, estuaries, deltas, reefs

Chemical properties of water

A. Hydrogen Bonds E. Specific Heat
B. Crystalline Structure F. Evaporation
C. Surface Tension G. Molecular Interactions
D. Tensile Strength H. Movement and Transport

Hydrogen Bonds

O d-

d+ H H d+

Hydrogen Bonds
3 physical states of water:

WATER VAPOR

Surface tension
Water has high surface tension due to
lateral and downward attraction between
individual molecules, which stretches the
water's surface, creating a thin skin

O d-

d+ H H d+

Surface tension
Water has high surface tension due to
lateral and downward attraction between
individual molecules, which stretches the
water's surface, creating a thin skin

Surface tension
• Water striders can walk upon the water's surface.

• Members of the neuston depend upon the surface film of
water for transport and food.

• Liquid water on surfaces to which it does not adhere well
"beads-up."

• Surface tension of the water allows wind to push against
it, generating waves in large water bodies.

• [Detergents reduce the surface tension of water (by as
much as 70%) and allows it to spread out on a surface.]

Tensile strength
Water is strong under tension.

The force needed to pull pure water apart can be as
much as 3 x 107 Newtons/m2

120 lbs = 530 Newtons

Limpet attachment strength = 1 x 106 Newtons/m2

Specific heat
Water can absorb a great deal of energy which goes to
breaking hydrogen bonds but does not lead to measurable
temperature increases.

Because of the massive number of hydrogen bonds in water,
it requires a lot of energy to see even a small change in
water temperature.

Evaporation

 A water molecule makes the transition from
a liquid phase into a gas phase.

Because the escaping molecule had a higher
than average energy level, it leaves the
liquid cooler (lower in energy) upon
evaporation.

Hydrogen Bonds - Summary

• High heat capacity (1 cal/g/C);
• Heat of vaporization (540 cal/g);
• Heat of fusion (-80 cal/g);
• Solid less dense than liquid phase;
• High surface tension

Molecular interactions
Solutes
Dissociation of Water Molecules
KD = [H+][OH-]/[H2O] = 1.8 x 10-16 M

where KD is the dissociation constant
(equilibrium constant) for the dissociation
of a proton from a water molecule (the
smaller the KD, the stronger the binding)

pH of solutions
pH - an index of the relative concentration of
H+ ions in solution

[H+] = [OH-] = 10-7 M in pure water ([H2O] = 55 M)

pH  -log10[H+]

In pure water, pH = 7

pH of solutions
• The pH scale ranges from 0 to 14
• The higher the pH, the lower the [H+]
(alkaline, basic solutions have a high pH)
• The lower the pH, the higher the [H+]
(acidic solutions have a lower pH)

pH of solutions
Examples:

Gastric juice = 1.0 Seawater  8.0
Orange juice = 4.3 Urine = 6-8.0
Blood plasma = 7.4 Ammonia = 12.0

pH and the sea
• A difference in pH from 8 to 7.8 can
significantly decrease coral growth rates
• Increased CO2 in the atmosphere lowers pH
• Active photosynthesis and nitrogenous
waste excretion can increase local pH

Water as a polar solvent and Salinity

Strong Electrolytes (substances that dissociate
completely when dissolved in water - ions)
Salts consist of ions:
NaCl  Na+ + Cl- salt
HCl  H+ + Cl- strong acid
NaOH  Na+ + OH- strong base

For strong electrolytes, KD  

Water as a polar solvent

Weak Electrolytes (substances that dissociate in
water only to a small extent (KD  10-3 M to
10-11 M)
H2CO3  H+ + HCO3- KD = 1.7 x 10-4 M

KD  10-3 M to 10-11 M

Carbon dioxide-carbonate equilibrium
CO2(g) CO2(aq) (CO2 from the atmosphere
dissolves into seawater)

CO2(aq) + H2O(l) H2CO3(aq) (Carbonic acid)

bicarbonate
H2CO3 H+ + HCO3- KD = 4.2 × 10-7
carbonate
HCO3- H+ + CO32- KD = 4.8 × 10-11

CaCO3(s) + 2 H+(aq) Ca2+(aq) + H2CO3(aq)

High CO2= low [CO32- ]
Ocean acidification

Water as a polar solvent

Because of its small size and polar nature, water
dissolves many materials, more than any other
liquid

Oceans of water act as sink for CO2 molecules –
leads to acidification

Seawater contains almost every known naturally
occurring element

Seawater constituents
Component Concentration Percentage of Salinity

chloride 18.98 55.03

sodium 10.56 30.59

sulfate 2.65 7.68

magnesium 1.27 3.68

calcium 0.40 1.18

potassium 0.38 1.11

bicarbonate 0.14 0


•Average ocean water has a salinity of 35.0
•This means that 1000 g of average seawater contains 965 g
of water and 35 g of salts.

Dissolved
chemicals Wind, water, and
ice erosion

Biological uptake, or
absorption of
particles, or
precipitation
Eroded rock
particles Wind, water, and
ice erosion

Seawater River and wind
transport and
deposition

constituents Sediments Fallout of volcanic
ash over oceans
Volcanic ash and
igneous rocks
on land

Compaction and
water loss Subduction, melting,
and vulcanism

Scraped of and uplifted
ot subduction zone
Sedimentary rock Sedimentary rock
on oceanic crust on land


From U.S. Geological Survey Open-File Report 03–028, January
2003 African Dust Carries Microbes Across the Ocean: Are They
Affecting Human and Ecosystem Health?

Movement and Transport

Diffusion – high concentrations  low concentration

Air vs. water

Mass transport – particles carried by fluid flow

Diffusion

high concentration  low concentration

C = concentration
D = diffusion coefficient
x = length
t = time

Mass Transport
high concentration  low concentration

Physical properties of water
•Viscosity
•Reynolds number, Boundary
Layers, and Mass transport
•Density
•Temperature

Water as a fluid
Fluid (flu·id) French fluide, from Latin fluidus,
from fluere to flow; akin to Greek phlyzein to boil
over):
 having particles that easily move and change their
relative position without a separation of the mass and
that easily yield to pressure; capable of flowing.

What is a fluid?
Viscosity (m): the resistance of a fluid to motion or internal
friction

Reynolds number (Re): the ratio of inertial forces to viscous
forces in a fluid

Density (r): the mass of a substance per unit volume

Viscosity
The viscosity of liquids can vary drastically and
decreases rapidly with an increase in temperature.

m = 50 N s/m2 At 20º C m = 1 x 10-3 N s/m2

m = 0.07 N s/m2 At 100º C

Reynolds number
Re = rUx/m

Re = 108

Re = 1

Boundary Layers and Mass Transport

Re = 101

Laminar Turbulent

Boundary Layers and Mass Transport

Re = 103

Re = 108

Major basins
4

2

1
3

5

Major basins –
General Characteristics
Pacific Ocean Indian Ocean
• average depth 3,940 m • average depth 3,840 m
• extensive marginal seas, volcanic • large sediment input (Indus and Ganges
island systems, and trenches River Deltas)
Arctic Ocean
• considerable mountain building and
earthquake activity along • average depth 1,038 m
boundaries (Ring of Fire) • centered on the north pole
• little freshwater input • shallow and land-locked
• covered by sea ice
Atlantic Ocean
• large sediment input from active glaciers
• average depth 3,310 m
Southern Ocean
• large freshwater input (Amazon, • average depth 4,000 m
Congo, Mississippi, Niger, Orinoco
• continuous ring of water around Antarctica
Rivers)
• coldest of all oceans (near freezing)
• extensive winter sea ice coverage
• most biologically productive ocean

Marginal Seas

Surrounding the Atlantic Ocean is the Sargasso Sea (1), Weddell Sea (2), the
Caribbean Sea (3), the North Sea (4), and the Mediterranean Sea (5).
Surrounding the Pacific Ocean is the Ross Sea (6), the Coral Sea (7), the
South China Sea (8), the Sea of Japan (9), the Sea of Okhotsk (10), the Bering
Sea (11), and the Sea of Cortez (12) (also called the Gulf of California).
Surrounding the Indian Ocean is the Red Sea (13), the Arabian Sea (14), and
the Bay of Bengal (15). Surrounding the Arctic Ocean is the Bering Sea (11),
the Laptev Sea (16), the Barents Sea (17), and the Beaufort Sea (18).

Largest, smallest, deepest, saltiest
The Arctic Ocean is the
smallest (area = 9,485,000
sq km, or < 1/10 Pacific)

Pacific Ocean =
1/3 globe (18 x US)
1/2 world ocean

Top 10 Deepest Trenches
1 Mariana
2 Tonga
3 Philippine
4 Kermadec 81 9
35
5 Bonin 7 10
6 2
6 New Britain
4
7 Kuril
8 Izu
9 Puerto Rico
10 Yap
Mariana Trench = 35,802 ft (10,912 m)

Puerto Rico Trench

8,400 m (5.2 miles)

Highest Salinity

Red Sea salinity ranges
between 36 and 38 psu

Dead Sea salinity = 360 psu

Ocean basins

To “sail the seven seas” (< 1400’s) =

1. Adriatic Sea
2. Black Sea
3. Caspian Sea
4. Mediterranean Sea
5. Red Sea
6. Persian Gulf
7. Indian Ocean

Ocean basics

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