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

B. Crystalline Structure

C. Surface Tension

D. Tensile Strength

E. Specific Heat

F. Evaporation

G. Molecular Interactions

H. Movement and Transport

Hydrogen Bonds

O

H H

d-

d+ d+

Hydrogen Bonds

Hydrogen Bonds

WATER VAPOR

3 physical states of water:

Crystalline Structure

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

H H

d-

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

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

H2CO3 H+ + HCO3

- KD = 4.2 × 10-7

HCO3- H+ + CO3

2- KD = 4.8 × 10-11

CO2(g) CO2(aq) (CO2 from the atmosphere

dissolves into seawater)

bicarbonate

carbonate

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.

Seawater

constituents

Dissolved

chemicals

Sediments

Eroded rock

particles

Volcanic ash and

igneous rocks

on land

Wind, water, and

ice erosion

River and wind

transport and

deposition

Sedimentary rock

on oceanic crust

Sedimentary rock

on land

Biological uptake, or

absorption of

particles, or

precipitation

Wind, water, and

ice erosion

Fallout of volcanic

ash over oceans

Compaction and

water loss Subduction, melting,

and vulcanism

Scraped of and uplifted

ot subduction zone


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

At 100º C m = 0.07 N s/m2

Reynolds number

Reynolds number

Re = rUx/m

Reynolds number

Re = rUx/m

Re = 1

Re = 108

Copepod swimming Low Re

movies/copepod swimming.avi

Boundary Layers and Mass Transport

Re = 101

Laminar Turbulent

Boundary Layers

Boundary Layers and Mass Transport

Re = 103

Re = 108

Major basins

Major basins

1

2

3

4

5

Major basins –

General Characteristics Pacific Ocean

• average depth 3,940 m

• extensive marginal seas, volcanic

island systems, and trenches

• considerable mountain building and

earthquake activity along

boundaries (Ring of Fire)

• little freshwater input

Atlantic Ocean


• large freshwater input (Amazon,

Congo, Mississippi, Niger, Orinoco

Rivers)

Indian Ocean


• large sediment input (Indus and Ganges River Deltas)

Arctic Ocean


• centered on the north pole

• shallow and land-locked

• covered by sea ice

• large sediment input from active glaciers

Southern Ocean


• continuous ring of water around Antarctica

• 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

Pacific Ocean =

1/3 globe (18 x US)

1/2 world ocean

The Arctic Ocean is the

smallest (area = 9,485,000

sq km, or < 1/10 Pacific)

Top 10 Deepest Trenches 1 Mariana

2 Tonga

3 Philippine

4 Kermadec

5 Bonin

6 New Britain

7 Kuril

8 Izu

9 Puerto Rico

10 Yap

1

2

3

4

5 7 6

8

10

9

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

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

Technology

surface tension of water

liquid water

solid water

evenrocks water

water ionssalts

water vapor

fresh water

surface tension water