Physical Oceanography Exam 1

The four branches of oceanography

1. Biological

2. Chemical

3. Geological

4. Physical

Pacific Ocean

The largest and deepest ocean with the most island. Has the average depth of 3,940 m

Atlantic ocean

Most land area drains into this ocean. It has an average depth of 3, 840 m

Indian ocean

Has the average depth of 3, 840 m (almost all south)

Artic ocean

Under debate on if it’s an ocean, smallest ocean. 3.4% of the ocean area, very shallow. Has an average depth of 1.117 m

Marginal sea

Partially enclosed sea adjacent to or widely open to the ocean at the surface but bounded by submarine ridges on the seafloor.

Temperature

A physical property of matter that quantitatively expresses the common notions of hot and cold

Temperature (thermodynamics)

The derivative of the internal energy with respect to the entropy

Temperature scales in regard to water

32 F - 212 F

0 C - 100 C

Importance of temperature

• Effect on deep-ocean currents

• Effect on storm formation

• Effect on marine organisms and on us

• Effect on climate

Surface temperature

• Can measure by using a thermometer

• Shade vs Sun

• Wind vs no wind (wing cools water)

• Is there metal nearby? (Metal can conduct heat)

• Depth (top mm is the warmest)

Deep-water temperatures

• Reversing thermometer

• BT - less resistance = warm. More resistance = cold

• xBT

• Niskin rosette with CTD

• BT = Bathythermograph

Temperature range in the ocean

-2 C - +36 C

28.4 F - 96.8 F

Surface temperature distribution

• Warmest water at the equator

• Coldest water at the poles

In the _____ ______ there is not a lot of change in temperature with depth

polar regions

In the ____________ the temperature does change with depth, but changes with seasons. How much of a change there is varies with seasons

Mid-regions

In the _______ ________ there is a definite change with depth, but it stays the same year round

Equatorial regions

Thermocline

Rapid decline of temperature

Mid-latitudes and low-latitudes have a _______

thermocline

High-latitudes / polar regions are ________

Isothermal

Salinity

The amount (in grams) of dissolved substances in one kilogram of seawater

What is seawater?

965 g of water and 35 g of dissolved substances

Atlantic salinity

34.92%

Pacific salinity

34.60%

Indian salinity

34.78%

Artic salinity

Lowest, varies with seasons

Distilled water salinity

0

Tap water salinity

0-5

Lake worth salinity

20-30

Typical seawater salinity

35

Bahamas salinity

40

Great Salt Lake, Utah salinity

50-270

Dead Sea, Isreal salinity

337

Salinity distribution in surface waters

In surface waters, the addition or subtraction of water is a major thing that changes salinity, not temperature

________ leads to water leaving the ocean. ______ is going to cause salinity to increase

Evaporation

_________ leads to water entering the ocean. ______ causes salinity to decrease

Precipitation

Water added =

decreased salinity

Water subtracted =

More salinity

Salinity distribution in deep waters

• Generally, salinity is higher in deep waters than in surface waters

• Salt makes the water denser, heavier, so it sinks to the bottom

Salinity distribution in water columns

Thermoclines and Haloclines are both controlled by the wind

Halocline

rapid change in salinity

Salinity distribution

Low salinities are typically low near land and rivers

SSS

Sea Surface Salinity

Lines connecting areas of equal saline are called _____

Isohalines

Reasons why high salinity water is a problem

• Can’t drink

• Corrosion

• Many plants can’t tolerate it

• Some animals can’t tolerate it

Reasons why high salinity water is a good thing

• Source of salt for diet

• Improves buoyancy of ships

• Nothern harbors generally free from ice

Measuring salinity

• Evaporation

• Electronics (e.g., conductivity meter, CTD)

• Refractometer

Residence Time

The average length of time that an element spends in the ocean

Density

Mass per unit volume

Depth (ft) Pressure (atm)

0 1

33 2

66 3

99 4

132 5

• Salinity and temperature influence ______

Common density measurements

Object Density (kg/m³)

Freshwater 1,000

Seawater 1,020-1,030

Ice (in general) 920

Measuring density

• Hydrometer

• Electronic method

Surface distribution of density

• Sigma + - density factor

• Range 22-27

Density is ____ near the equator because of warm water and low salinity

Lower

Density is ______ at the poles because of cold water and high salinity

Higher

Density increases with _____

Depth

Pycnocline

Rapid change of density

Coastlines have _____ density water

Low

Artic has ____ density water

High

Importance of density

• Drives deep-water currents

• Increases buoyancy for ships

• Important factor for subs

T-S Diagrams

A way of calculating density

Air Pressure

The pressure exerted by the weight of the air above

Average: 14.7 pounds/inch²

Air pressure is typically measured in ________, but the media uses inches of mercury

Millibars

Wind

The phenomenon where air moves horizontally

• ____ is the result of horizontal differences in air pressure

• Solar radiation is the ultimate energy source

Wind is controlled by the following factors:

• Pressure-gradient force

• Coriolis effects

• Friction

Pressure-gradient force

On a map, lines of equal pressure are connected by isobars

Coriolis effect

The deflective force of earth’s rotation on all free-moving objects

Friction

Only affects winds <6 km above the Earth’s surface

_______ (______) are centers of low pressure

• Winds blow inward and counterclockwise

Lows (cyclones)

_______ (_________) are centers of high pressure

• Winds flow outward and clockwise

Highs (anticyclones)

What creates wind?

The pressure-gradient force

What controls the direction of the wind?

Coriolis effect

What controls the direction and speed of wind?

Friction

North =

Right

South =

Left

Why study the Coriolis effect?

• Winds

• Ocean currents

• Long range launches

• Hurricanes

FCE =

2 w Sin0

w =

Rate of Earth’s spin (7.2921 × 10^-5 rad/s)

0 =

Latitude

R0 =

U / FCE L

U =

Velocity

L =

length of time object is in motion

Rossby # large =

Coriolis not important

Rossby # small =

Coriolis dominate

Laminar flow

Wind on ice

Ekman Spiral

1. Wind

2. Force from friction

3. Direction of water movement

4. Force from Coriolis effect

(Doesn’t do a complete spiral)

(Shallow, deepest found at 50 m)

Ekman layer '/ transport

Geostrophic motion

Mound of water (Geostrophic flow)