Chapter 6- Water and Ocean Structure

Why light does not penetrate the ocean to great depths?

--Because the wavelengths of light get scattered and absorbed quickly. --Light is scattered as it is bounced between air or water molecules, dust particles, water droplets other objects. Water rapidly absorbs nearly all electromagnetic radiation (visible light). --The greater the water density = The greater the light scattering.

Thermocline Zone

-A layer of water in which there is a rapid change in temperature with depth - A layer of ocean at about 300-1,000 meters where there is a rapid change of temperature with depth -separates surface warm water from deep cold water -deeper & pronounced because surface water is warmer due to more solar flux

SOFAR Layer

-A unique layer in the ocean where certain sound waves travel long distances due to a combination of pressure and water Temperature. -Between the depths of 800 and 1000 meters

Precipitation

-Any form of water that falls from clouds and reaches Earth's surface. -80% of precipitation falls back into the ocean

Why water is good at dissolving substances

-Because it is a polar molecule. -Because it has a positive (+) end and a negative (-) end, it can separate a compound's elements that are held together by the attraction of opposite electrical charges (most salts).

Thermal Properties of Seawater: ( Seawater and pure water have slightly different thermal properties)

-Dissolved solids in seawater -Lower freezing point -The More dissolved solids, the lower the freezing point -Evaporates more slowly

Latent Heat of Vaporization

-Heat needed to change state from liquid to gas -VERY high for water (highest known) -Difficult to break the hydrogen bonds -hydrogen bonds have to be broken to allow water to evaporate -takes a high amount of energy 540 calories per gram, 540 cal/g

Properties of Water

-It is a Polar molecule -It forms Hydrogen bonds -Heat is needed to change its Temperature -Heat is needed to change its state

Deep Zone

-Level of the ocean in which no light penetrates -The bottom layer of the ocean that extends from the base of the thermocline to the ocean floor. -Bottom layer of the ocean; Made of cold dense water; 80% of ocean water resides in this zone;

How is sound transmitted through a medium?

-Sound is transmitted by rapid pressure changes in an elastic medium. -The sound waves move through a medium by vibrating the molecules in the matter.

Hydrogen bonds in liquid water.

-The attractions between adjacent polar water molecules form a webwork of hydrogen bonds. -These bonds are responsible for surface tension and cohesion, the properties of water that cause surface tension and wetting. Hydrogen bonds among water molecules also make it difficult for individual molecules to escape from the surface.

What is causing the ocean to become more acidic?

-The ocean is becoming more acidic as it absorbs additional carbon dioxide from the atmosphere. -About 25% or the CO2 emitted by human activity is taken up by the ocean.

How the refractive index of seawater compares to freshwater

-The refractive index of water increases with increasing salinity and decreases with increasing temperature. -So seawater has a higher refractive index than freshwater.

Surface Zone/mixed layer is ...

-it is the upper layer of ocean density -Temperature and salinity relatively constant due to mixing

Dissolution

-the breaking up or dissolving of something into parts; disintegration -separation into component parts

Evaporation

-the process by which water changes from liquid form to an atmospheric gas -85% of all water entering the atmosphere evaporates from the ocean

How long water stays in the ocean before evaporating

4,100 years!

Speed of sound in the ocean

5 times the speed in air Increases as T & P increase Decreases with increasing depth min at 1000m Below 1000m , increasing P increases speed

Molecule

A group of Atoms held together by chemical bonds

Halocline Zone

A layer of water in which the salinity changes rapidly with changes in depth

Compound

A substance that contains Two or more elements in fixed proportion

Temperature

An objects response to input or removal of heat. Only measures how rapidly the molecules vibrate

Why ice floats

As water cools and freezes into ice, it actually becomes less dense than liquid water so ice floats.

Hydrogen

Atomic # 1, number of electrons equals 1

Oxygen

Atomic # 8, Number of electrons (2,6)

Why CO2 is slow to return from the ocean to the atmosphere?

Because much of the CO2 in the ocean is stored in sediments and it takes longer for the sediments to dissolve and reform CO2 that can enter the atmosphere.

Water Density

Becomes denser as it cools but becomes less dense as it approaches freezing (4 degree C to 0 degrees C) Unlike most substances, water's density curve is not linear

Refraction

Bending of waves Occurs when waves travel from one medium to another at an angle other than 90 degrees Magnifies objects in water

Water Mass

Body of water with characteristic temperature and salinity Little vertical movement in the tropics and the arctic South polar ocean only weakly stratified

Water freezes

Bond angle expands from 105 degrees to 109 degrees Allows hydrogen bonds in ice to form a crystal lattice Space taken by 27 water molecules = 24 ice molecules Transition from liquid to solid requires continue removal of heat

What type of water mass can dissolve a higher concentration of gases (and where it's found)

COLD Seawater can dissolve a higher concentration of gases and COLD seawater at the OCEAN'S SURFACE is the best.

What form of CO2 do many marine organisms use to build shells?

Calcium Carbonate CaCO3

Water Becomes Less ___________ When It Freezes

Dense

Density Stratified

Dense cold and salty water underlies less dense warm and fresher water

Water's Temperature Affects Its _______________.

Density

Hydrogen Bonds Link Water Molecules Together by _________________ _______________.

Electrostatic Forces

Chemical bonds

Energy relationships energy relationships that hold elements together

Water molecule

Formed when electrons are shared between two hydrogen atoms and one oxygen atom.

Water Special Property

Freezes at 0 degrees When water cools below 0 degrees C, density increases as temperature decreases When water warms above 40C, Density increases as T decreases

Sea Water Density

Function of temperature and salinity Increases with salinity, increasing pressure, and decreasing temperature

Heat Capacity of Water

Has a very high heat capacity. Water can absorb and release large amounts of heat with little or no change in temperature

Geometry molecule

Has bent or angular shape. Angular shape makes it electrically asymmetrical polar

Density Stratification in the Ocean

Has three zones: 1) Surface zone/Mixed Layer -upper layer Temp and salinity relatively constant due to mixing 2) Pycnocline - Density increases with depth 3) Deep Zone -Below 1000 m

Latent Heat

Heat input doesn't cause change in temperature but produces state in change

Thermostatic balancing effect

Heat is stored in the ocean during the day/summer and released in the night/winter

How salinity and temperature differ in surface waters around the world

High salinity can be found in waters where there is a high rate of evaporation. (Atlantic Ocean, Mediterranean Sea) Lower salinity can be found in Polar regions, and areas near great rivers, because of low rates of evaporation and increase in freshwater (rivers) flowing into the ocean.

Sofar Layer (Sound fixing and Ranging)

Layer at which sound velocity reaches a minimum Depth of this layer varies but approx. 1200m in the North Atlantic or 600m in the North Pacific Transmission of sound is very efficient within this layer Refraction causes sound to stay within this layer: sound is horizontally concentrated rather than diffused as it moves through the water.

Heat Capacity

Measure of the heat required to raise the temp of 1g of a substance 1º Celsius Measured in calories/gram

Annual Freeze/Thaw of Ice

Moderate Earth's temperature, more than 18,000 cubic kilometers of ice thaws and refreezes in the Southern hemisphere each year

Density of Water

Most substances get more dense as Temperature drops So does water until it gets near its freezing point Max density at 3.98ºC Then it starts expanding slightly

Electrons

Negative charge

Neutrons

No charge

Net Effect

Oceanless Earth would be colder in the winter and hotter in the summer

Water is a polar molecule

One end is positively charged One end is negatively charged.

Protons

Positive charge

Which frequencies of light are quickly absorbed in ocean water?

Red gets absorbed quickly, then yellow and orange Ocean looks blue because blue light can travel through water far enough to be scattered back to the surface

What is the average pH of the ocean?

Seawater pH about 8.0 due to dissolved CO2

Sonar (sound navigation & ranging)

Side-scan active sonar : Geological, archeological studies Multibeam active sonar Use sound to detect underwater objects

Sound energy decreases in water because

Spreading: energy loss is proportional to square of distance from source Scattering : sound bounces off bubbles, suspended particles, organisms, surface, bottom etc. Absorption: proportional to square of the frequency; converts into small amount of heat

Residence time

The amount of element in the ocean divided by the rate at which the element is added to (or removed from) the ocean.

Residence Time

The average length of time a dissolved substance spends in the ocean.

Depth to which light penetrates the ocean depends on

The dust, cloud cover, and gases in the atmosphere. The angle of the sun above the horizon. The smoothness or roughness of the sea surface. The amount of suspended material in the water.

Heat

The measure of how many molecules are vibrating and how rapidly

The difference between the thermal inertia of land and water

The ocean's thermal inertia is much greater than the land's. The ocean's temperature rises VERY LITTLE as it absorbs heat.

What is the source of oxygen in surface water?

The source of the oxygen in the ocean is the photosynthetic activity of plants and plant-like organisms and the diffusion of oxygen from the atmosphere.

Thermal Inertai

The tendency of something (seawater) to resist change in Temperature

Cohesion

Water molecules stick to each other, creating surface tension

Adhesion

Water molecules stick to other substances

Why water molecules stick together

Water molecules stick together because of Hydrogen bonding. This property is called "Cohesion"

What causes the refraction of sound and light waves?

When a sound or light wave leaves a medium of one density and and enters a medium of a different density at an angle other than 90º, it is bent from its original path. - Refracted. Water's refractive index increases with salinity.

Latent Heat Fusion

When heat is being added or removed but the temperature is not changing. Example: When water continues to cool at 0 degrees celsius, as it freezes to ice, the temp doesn't fall, but heat is lost

Hydrogen bonds

When the hydrogen atom (+) of one water molecule is attracted to the oxygen atom (-) in another water molecule About 5 to 10% as strong as the covalent bond

Sensible Heat

When water cools to 0 degrees celsius the fall in the temp records the loss in heat

Why seawater evaporates more slowly than freshwater

When we have saltwater, the surface now contains both salt and water. Dissolved salts attract water molecules so saltwater takes longer to evaporate. Salt does not like to evaporate

Pycnocline Zone

a layer in an ocean or other body of water in which water density increases rapidly with depth.

Covalent Bonds

a type of strong chemical bond in which two atoms share one pair of valence electrons

Thermostatic Properties

act to moderate temperature changes

Transition zone

between mixed zone & deep ocean

Scattering

bouncing of light between molecules

Capillary Action

caused by Cohesion and Adhesion. The tendency of water to spread through a towel when one corner is dipped in water.

Deep Water

cool, high density

Absorption

depends on structure of molecules, light energy converted to heat

Suface Tension of Water

enables aquatic insects to stride on water

State

expression of internal form of substance Changes accompanied by input or output of energy

Ice

is lighter than equal volume of water, ice floats over instead of under 80 calories of heat energy must be removed from 1 gram of pure water to turn to turn it into

Increase in Density

may be due to decrease in Temp. with depth or to increase in salinity with depth.

What does the pH scale measure?

pH scale - measures concentration of hydrogen ions in a solution

Aphotic Zone

perpetually dark

Sunlight

scattering and absorption rapidly weakens the light and prevents penetration

Photic Zone

sunlight zone, upper 200m pf primary productivity

Thermal Inertia

tendency to resist change in temperature with gain of loss of heat energy

Refraction Index

the degree to which light is retracted from one medium to another, expressed as a ratio Increases with salinity

Surface Water

warm, low density mixed zones 60-100m depth all atmosphere-ocean interaction

Picnocline

zone of changes in density

Thermocline

zone of changes in temperature separates surface warm water from deep cold water deeper & pronounced because surface water is warmer due to more solar flux

Halocline

zone of max changes in salinity