Seawater Seawater and the and the

World OceanWorld Ocean

Chemical Chemical and Physical and Physical Properties Properties

All matter is made of atoms!All matter is made of atoms!1. Elements are made of one 1. Elements are made of one

kind of atomkind of atom2. Compounds are elements 2. Compounds are elements

that are combined.that are combined.

A. A. Ionic compoundsIonic compounds are made are made of ions (ionic bonding )of ions (ionic bonding )

B. B. Molecular compoundsMolecular compounds are are made of atoms that share made of atoms that share

electrons (covalent bonding)electrons (covalent bonding)Water is a compound, whose Water is a compound, whose molecules are held together by molecules are held together by

hydrogen bondshydrogen bonds. .

A hydrogen bond is formed when a charged part of a molecule having polar covalent bonds forms an electrostatic (charge, as in positive attracted to negative) interaction with a substance of opposite charge.

States of WaterStates of Water

Solid (ice)Solid (ice) - definite volume and shape, - definite volume and shape, little molecular movement, only vibrationlittle molecular movement, only vibration

LiquidLiquid - definite volume, take the shape of - definite volume, take the shape of the container. Molecules role over each the container. Molecules role over each otherother

Gas (water vapor)Gas (water vapor) - indefinite volume, fills - indefinite volume, fills

its container. Molecules are in constant its container. Molecules are in constant movement. movement.

<---remove or add heat ----->

Ice (solid) Ice (solid)  Water (liquid)Water (liquid) Water Vapor (gas)Water Vapor (gas)

temp temp << 32 °F, 0 °C 32 °F, 0 °C 32 °F, 0 °C < temp < 212 °F, 100 °C32 °F, 0 °C < temp < 212 °F, 100 °C temp temp >> 212°F,100°C 212°F,100°C

molecular movement = molecular movement = slowslow

molecular movement = fastmolecular movement = fast molecular movement = fastestmolecular movement = fastest

H bonds fixed (vibrate in H bonds fixed (vibrate in place)place)

H bonds not fixed (can move)H bonds not fixed (can move) no H bonds (all are broken)no H bonds (all are broken)

molecules closemolecules close; H atoms ; H atoms 109° apart109° apart

molecules closestmolecules closest; H atoms 105° ; H atoms 105° apartapart molecules distantmolecules distant

low density low density  highest density highest density  lowest densitylowest density

                                

                                                                                    

                                                  

                                                                  

                                                                

                                                    

Why it’s so important that ice Why it’s so important that ice can float on water can float on water

Allows ample liquid habitat for organismsAllows ample liquid habitat for organisms

Acts as an insulatorActs as an insulator

By floating on the surface, it prevents By floating on the surface, it prevents lakes from freezing completely.lakes from freezing completely.

Ice insulates life in the Arctic Ocean.

Heat Capacity of Water - Heat Capacity of Water - the the amount of heat needed to raise amount of heat needed to raise the temperature of water 1 the temperature of water 1 degree Celsius degree Celsius

High heat capacity means that High heat capacity means that organisms are not subject to organisms are not subject to huge changes in temperature.huge changes in temperature.

Latent Heat of EvaporationLatent Heat of Evaporation is the amount of heat that is the amount of heat that water must absorb in order to water must absorb in order to evaporate.evaporate.

Hydrogen bondingHydrogen bonding makes makes evaporation difficult and keeps evaporation difficult and keeps water a liquid which allows life water a liquid which allows life to exist on earth.to exist on earth.

Solvent PropertiesSolvent Properties

Called the Called the universal solventuniversal solvent because most because most things dissolve in itthings dissolve in itWater easily dissolves saltsWater easily dissolves salts - ions are surrounded by polar water - ions are surrounded by polar water moleculesmolecules - molecular substances will not dissolve in - molecular substances will not dissolve in waterwaterLike dissolves like!Like dissolves like!

SEA WATER is a mixture of dissolved solids

- some material comes from the weathering of rocks- other material from hydrothermal vents- much material is emitted by volcanoes

Composition of Seawater99% of solids in seawater are ions85% of ions are Na and ClSalinity is given in grams/1000 grams of water, ranges from 33 to 37%, averaging at 35%enclosed seas, such as the Dead Sea, may be as high as 40% in salinityseas fed by run off from glaciers or other ice, such as the Baltic Sea, are only 7%

Ions in Seawater

Salinity is tested by a conductivity meter Units are PSUs: practical salinity units

The Rule of Constant Proportions states that the percentages of various ions in sea water remainsconstant.

The proportions vary only due to the introduction of pure water from streams, rivers or melting glaciers.

Most oceans are chemically well mixed having a constant composition of ions in solution.

Density of Seawater is dependent upon

temperature - as temperature increases, density density decreases

salinity - as salinity increases, density increases

Since temperature varies more than salinityin the ocean, density is more dependent upontemperature.

A CTD (Conductivity, Temperature, and depth) is a device with electronic sensors that scientists use to detect conductivity, temperature and depth (CTD) within a column of water.

A temperature profile can be obtained with a CTD or with a Niskin bottle which records temperature and salinity within a water column.

Dissolved Gases in Seawater

O2 and N2 and CO2 are dissolved or released tothe environment at the surface.

Gases dissolve to a greater extent in cold water.Polar regions have more gases dissolved.

0 to 8 ml/L of O2 is dissolved in seawater210 ml/L of O2 is dissolved in the atmosphere

The amount of O2 is affected by photosynthesis and respiration. O2 in the sea is subject to depletion by respiration much more than in the atmosphere.

Carbon Dioxide

CO2 is more soluble because it reacts with water.CO2 makes up > 80% of all gases in the sea and< .04% of all gases in the air

The ocean stores 50 times as much CO2 as is in the atmosphere.

Transparency

Measured with a secchi disk.Important because light must penetrate the water for photosynthesis to take place.

Clear ocean water is most transparent to blue light.As depth increases, other colors are absorbed.At 1000ft, there is only darkness.

secchi disk measurement

Pressure

Changes dramatically with depth.

Sea level - 1 atm10 meters - 2 atm20 meters - 3 atm30 meters - 4 atm

As gases compress, air bladders, floats and lungs collapse.Pressure limits the depth of many marine organisms.

This grouper has a swim bladder which This grouper has a swim bladder which blows up ike a balloon if brought to the blows up ike a balloon if brought to the surface too quickly because of decreased surface too quickly because of decreased pressure.pressure.

Circulation

It is most intense near the surface, driven bywinds and the Coriolis Effect. Because the earth turns, anything that moves across thesurface winds up moving in a curved line.

The Coriolis Effect deflects winds in theNorthern Hemisphere to the right and

in the Southern Hemisphere to the left.

A missle fired from the center (equator) appears to move upward (Pole) because it maintains its speed as the ground below moves slower. It appears to curve relative to the earth’s surface.

WINDS-are driven by heat energy from the sun

- less dense air rises at the equator and air from adjacent areas gets drawn in to replace the air thatmoved upward. (It is bent by the Coriolis Effect and approaches the equator at a 45 degree angle)

- these winds are called Trade Winds

- they are the steadiest winds on the surface of the sea

How wind is created!How wind is created!

Other Winds Other Winds

Westerlies - move in opposite Westerlies - move in opposite directions to trade winds at directions to trade winds at

middle latitudesmiddle latitudes

Polar Easterlies - most Polar Easterlies - most variable winds, occur at high variable winds, occur at high

latitudeslatitudes

Surface CurrentsSurface Currents

The major wind fields of the earth push the surfaceof the sea and create currents.

The uppermost layer of the water moves in a directionthat is a 450 angle because of the Coriolis Effect.The top layer pushes on the next layer which moves slightly to the right of it.Each layer in succession does the same thing untila spiral is created - called the Eckman Spiral.

Ekman SpiralEkman Spiral

DefinitionsDefinitions Ekman layer Ekman layer - the uppermost part of - the uppermost part of the water column that isthe water column that isaffected by the wind.affected by the wind.

Equatorial currentsEquatorial currents - those produced - those produced by winds that move parallel to the by winds that move parallel to the equator.equator.

GyresGyres - huge circular systems made - huge circular systems made up of wind driven currentsup of wind driven currents

Gyres of the Oceans

(a) Salinity profile (b) deepwater temp. (a) Salinity profile (b) deepwater temp. and salinity profile (c) thermoclineand salinity profile (c) thermocline

The Three Layered OceanThe Three Layered Ocean

Oceans are Oceans are stratifiedstratified because the densest because the densest layer sinks.layer sinks.The water column remains stable if there The water column remains stable if there is a significant difference in density.is a significant difference in density.When the surface water is denser than When the surface water is denser than lower layers, it will sink in a process called lower layers, it will sink in a process called overturn.overturn.Changes in salinity and temperature occur Changes in salinity and temperature occur primarily on the surface layerprimarily on the surface layer

Three LayersThree Layers

Surface layer – 100 to 200 meters, mixed Surface layer – 100 to 200 meters, mixed by wind waves and currentsby wind waves and currents

Intermediate layer – to a depth of 1500 Intermediate layer – to a depth of 1500 meters, contains the main thermoclinemeters, contains the main thermocline

Deep and bottom layers - below 1500 Deep and bottom layers - below 1500 metersmeters

WavesWaves

WavesWaves

In general, water particles allow a wave to In general, water particles allow a wave to pass through pass through them. They are the medium through which energy is them. They are the medium through which energy is transferred.transferred.Waves form when the wind blowsWaves form when the wind blows1. “fetch” is the span of open water over which the wind 1. “fetch” is the span of open water over which the wind blowsblows2. When the wind blows it pushes up crests into peaks 2. When the wind blows it pushes up crests into peaks and stretches out the troughs creating waves called and stretches out the troughs creating waves called “seas”.“seas”.3. When the waves have moved away from the wind, they 3. When the waves have moved away from the wind, they become “swells”become “swells”4. When waves approach the shore they 4. When waves approach the shore they feelfeel the bottom, the bottom, slow down and pile up creating “surf”slow down and pile up creating “surf”

Wind has blown over this bay for an entire day. On the top Wind has blown over this bay for an entire day. On the top side of the bay, wind is blowing over a longer stretch of side of the bay, wind is blowing over a longer stretch of

water. The water. The fetch fetch is longer on the top side and waves are is longer on the top side and waves are bigger here.bigger here.

Water particles move in circles as a Water particles move in circles as a wave passes through them.wave passes through them.

Storm winds generate Storm winds generate seas,seas, peaked waves with relatively peaked waves with relatively flat troughs. When they move out of the storm area, they flat troughs. When they move out of the storm area, they

become swells with rounded crests and troughs. In shallow become swells with rounded crests and troughs. In shallow water they get closer together, become unstable and break. water they get closer together, become unstable and break.

TIDESTIDES

Tides are a major influence on nearshore Tides are a major influence on nearshore life, drive bay circulation and trigger life, drive bay circulation and trigger spawning.spawning.

Tides are caused by the gravitational pull Tides are caused by the gravitational pull of the moon and sun and by rotations of of the moon and sun and by rotations of earth, moon and sun.earth, moon and sun.

If the earth were covered with If the earth were covered with water…….water…….

Water would form two bulges on opposite sides Water would form two bulges on opposite sides of the planetof the planetOn the side of earth closest to moon, water is On the side of earth closest to moon, water is pulled toward the moonpulled toward the moonOn the side away from moon, centrifugal force On the side away from moon, centrifugal force wins and pushes water away from moon.wins and pushes water away from moon.

This is because the centrifugal force that results This is because the centrifugal force that results from the earth and moon rotating about a from the earth and moon rotating about a common point is not always balanced by the common point is not always balanced by the moon’s gravity.moon’s gravity.

DefinitionsDefinitions

Tidal rangeTidal range – the difference in water level – the difference in water level between high and low tidesbetween high and low tides

Spring tidesSpring tides – occur throughout the year, once – occur throughout the year, once every two weeks when the sun and moon are in every two weeks when the sun and moon are in line with each other (full and new moons) causing line with each other (full and new moons) causing huge changes in tide levels.huge changes in tide levels.

Neap tidesNeap tides – sun and moon are at right angles – sun and moon are at right angles and their effects partly cancel each other, causing and their effects partly cancel each other, causing small tidal ranges (1small tidal ranges (1stst and 3 and 3rdrd quarters of the quarters of the moon)moon)

Types of TidesTypes of TidesSemidiurnal – two high and tow low tides Semidiurnal – two high and tow low tides each day (east coast of NA, Europe, Africa)each day (east coast of NA, Europe, Africa)

Mixed semidiurnal tides – successive high Mixed semidiurnal tides – successive high tides of different height (west coast of US tides of different height (west coast of US and Canada)and Canada)

Diurnal tides – one high and one low tide Diurnal tides – one high and one low tide each day (uncommon, occur on east coast each day (uncommon, occur on east coast of Antarctica, parts of G. of M., Caribbean of Antarctica, parts of G. of M., Caribbean and Pacific)and Pacific)

Distribution of types of tides

Thermohaline Circulation andThermohaline Circulation andThe Great Ocean ConveyorThe Great Ocean Conveyor

CondensationCondensation

EvaporationEvaporation

ThermoclineThermocline

HaloclineHalocline

PycnoclinePycnocline

SublimationSublimation

ThermoclineThermocline