Transcript Chemical and Physical Properties of Seawater

Chemical and Physical
Properties of Seawater
Chapter 3, p 44 - 68
Specifics
Properties of water
Ocean Circulation
Waves and Tides
Brainstorm with a partner!
Unique properties
of water
All 3 states of matter on Earth
Very polar molecule
Hydrogen bonding
Evaporation
Liquid  Gas
Hydrogen bonds broken
Density and temperature
Unique Nature of Water
With lower temperatures, water molecules move
closer to one another.
Imagine a gallon bucket of seawater.
At 75 degrees, the molecules are further apart than
when this same gallon of water is at 35 degrees.
When molecules are closer together, the substance is
said to have more density.
Higher density = heavier, even when volume is the
same.
Unique properties of
Water
So… cold water sinks below warmer water
Colder water also holds more oxygen than the same
volume of water.
Great for all those organisms living at the ocean floor.
Now, even though colder water is more dense than
warmer water, this changes when the water gets cold
enough to freeze.
Ice floats and acts as barrier to cold air for marine
organisms living in the water.
Temperate and State
Less dense as a solid than a liquid.
Habitat and insulation for organisms
H+ bonds result in higher melting and freezing temp.
High Heat Capacity
Water is able to absorb a lot of heat with a relatively
small increase in temperature
HIGH heat capacity – amount of heat needed to raise
a substance’s temperature by a given amount
Important for marine organisms
Not exposed to rapid changes in temperatures
Latent heat of melting
Latent heat of melting – the amount of heat required
to melt a substance
Absorbs A LOT of heat when it melts –
Hydrogen bonds break, but motion of molecules does
not speed up until all of the ice melts.
It takes A LOT of energy to break hydrogen bonds!
Without H+ bonds, ice would melt at about -90°C instead
of 0°C
Water Cycle
Properties of Seawater
Water is the universal solvent
Ion dissociation
Seawater
Salinity – total amount
of salt dissolved in
seawater
Not just Na+ and ClLots of salts!
See p. 48, Table 3.1
Where do the salts
come from?
Where might ion concentrations of seawater differ from the
normal amounts?
Salinity, Temperature,
Density
More salty = More dense
Lower temperature  more dense
Measuring temperature and salinity at specific points
in the ocean – Niskin bottles
Let’s take a look!
Temperature Profile
Temperature, salinity,
other physical
characteristics and
even plankton can be
sampled at several
depths at once
SST
Satellite Images
Current Conditions
Temperature and Salinity
SST of NE coast of the United States. Do you know the current?
Dissolved Gases
Oxygen (O2) – not very soluble
Most released through photosynthesis
Amounts also dependent upon respiration
Carbon Dioxide (CO2) – more soluble
80% of dissolved CO2 is in ocean
Nitrogen (N2)
Exchange occurs at surface of water
Atmosphere to ocean
Gas dissolves best in cold water
Oxygen Content of Ocean
High oxygen content near
the sea surface
Low oxygen at mid-depth
Increase in oxygen in the
water ~ 1 km water below
sea level
CO2 in the Ocean
FACT: 80% of the world’s CO2 is found in the ocean.
How is this affecting our oceans?
CO2 Emissions
CO2 is much more soluble than oxygen
CO2 makes up more than 80% of the dissolved gas in the ocean, compared to
less than 0.04% of air
Ocean stores more than 50x as much total CO2 as the atmosphere.
Amounts of CO2 in the oceans are increasing.
Light Conditions
CO2 + H2O + sun energy  C6H12O6 + O2
C6H12O6 + O2  CO2 + H2O + energy
Must have the right light conditions to fuel
photosynthesis!
Light levels change with depth.
Visible Light Spectrum
Colors of the Ocean
Photos courtesy of www. science.nasa.gov
Depth of 30 m: Only blue light remains:
(a)Under natural lighting this sea star appears light blue, with the
tips of the arms almost black.
(b)A flash reveals the sea star’s true colors.
Light Zones
1. Photic zone – sunlit, 200 meters below the surface of the ocean
2. Twilight zone - from about 200 - 2000 meters below the surface.
3. Abyssal zone – no sunlight, from 2000 - 5000 meters below the
surface to the bottom of the ocean.
Light Penetration of
Surface Waters
Gathering Data
Pressure in the Ocean
Organisms on land are under 1 atm (14.7 lbs/sq in or
psi) at sea level. The weight of all the air above them.
Marine organisms are under the weight of water
AND the atmosphere.
Since water is much heavier than air, marine
organisms are under much more pressure than those
on land.
As the pressure increases, gases are compressed.
Gas-filled structures inside organisms like air
bladders, floats, and lungs shrink or collapse.
Limits depth range of organisms
We need special equipment to go deep or special
instruments that can withstand pressure
Pressure in the Ocean
Ocean Circulation
Currents move ocean waters around the world’s
oceans at different depths (Ocean Conveyer Belt)
Waves, currents, tides, and gyres
Wind patterns
Ultimately driven by sunlight energy
Currents circulate heat, nutrients, pollution, and
organisms
Drives Earth’s climate
New Gulf Current
Winds
As sunlight heats air, air rises.
Cooler air rushes in to take the place of air that has
risen.
This movement is the source of winds.
Ever notice how the winds at the coast are stronger
during the day than at night?
Winds created in this manner continuously at the
equator are known as the Trade Winds.
The Westerly's in the mid latitude and the Easterlies at
the poles are less consistent than the Trade Winds.
Trade Winds
30°N
Doldrums
30°S
Air near equator is warmed by solar heating and rises. Air from
higher latitudes moves in over the Earth’s surface to replace the
rising air, creating winds. The TRADE WINDS are deflected by the
Corliolis effect and approach the Equator at an angle of about 45°.
Global Wind Patterns
The major wind patterns are created by the rising of sun-warmed air
and the sinking of cold air.
How do the continents effect the wind patterns?
Major Surface Currents
The Coriolis Effect
www.oceanservice.noaa.gov
If the Earth did not rotate on its axis, the atmosphere
would only circulate back and forth between the
poles and the equator
The Coriolis Effect
www.oceanservice.noaa.gov
Because the Earth rotates on its axis, circulating air is
deflected toward the right in the Northern Hemisphere
and toward the left in the Southern Hemisphere. This
deflection is called the Coriolis effect.
Wind Patterns
Winds in atmosphere are driven by heat energy from
the sun.
Equator is warmer than poles – more heat energy
absorbed here
Less dense hot air rises
Cooler air replaces it
Wind is formed!
Remember, winds to not travel straight, they are
bent by Coriolis Effect
Ekman Transport
If the ocean current is regarded as layered, then each deeper layer
moves more slowly than the overlying layer.
Ocean Gyres
Created by wind-driven surface currents
Moderate climate by bringing warm water north and cold
water south
Ocean Circulation
In some locations, large volumes of water may sink or rise.
Water sinks due to changes in temperature and salinity – this is
known as an area of down-welling.
Down-welling brings gases from the surface to deeper layers.
Areas of upwelling come from currents that push deeper waters
toward the surface.
Nutrients are much more plentiful in the deeper layers, so these
areas of upwelling are beneficial for organisms in an upwelling
area.
Thermoclines
Depth profiles for salinity,
temperature, and density
What is a thermocline and
how does it develop?
Seasonal vs. permanent
thermoclines
Temperature Profile
Stable water column = less dense shallow
and more dense deeper
Unstable water column = surface water
sink and mixes with deeper water
DOWNWELLING
Polar regions in winter
Ocean Mixing
These two water masses originate at the surface in the
extreme North and South Atlantic, then sink and spread
along the bottom.
Thermohaline Circulation
The movement (circulation) of water in the ocean
over great distances that is driven by changes in
density
Changes in density determined by temperature and
salinity.
“Fingerprint” of the water mass is how currents are
tracked
Circulation of the Ocean
The Great Ocean Conveyor – Global current pattern
Deep circulation of the oceans is part of the global
pattern known as great ocean conveyor. This constantly
replenishes the oxygen supply to the depths.
Waves
- Dependent upon the wind – longer and faster wind = larger wave
- Water particles do not move along with a wave but instead move in
circles. When under the crest they move up and forward with the
wave, then they are pulled back down. As wave after wave passes,
the water and anything floating in or on it moves in circles.
Waves
As waves near the shore (shallower water), the bottom of the wave
“drags” the bottom.
Forces waves to slow and move closer together (short wavelength)
The “drag” causes the wave crest to fall over - we call this a wave
break. The surf caused from breaking waves displaces lots of sand
which affects the organisms living there.
Influence of the bottom causes the particle motion to flatten out into
a back and forth movement known as surge
Waves
Fetch - the span of open water
over which the wind blows
Fetch is important in
determining the size of waves
Wind starts the wave which
eventually settles out into a
swell as it gets farther from the
source of wind.
What kind of waves
are these?
Tides
Gravitational pull of the moon and
sun and by the rotations of the
earth, moon, and sun.
The moon and earth are held
together by gravitational attraction.
The moon’s gravitational pull is
strongest on the side of the earth
closest to the moon.
Centrifugal force produced by the
earth’s motion causes water to
bulge outward, away from the
moon.
On the side of the earth closest to
the moon, the gravitational pull
overcomes the centrifugal force and
pulls the water into a bulge toward
the moon.
How does a grunion (Leuresthes tenuis) use the tide?
Tides
Because the moon moves while the earth is rotating, a full tidal
cycle takes 50 minutes longer than the 24 hrs it takes the earth
to make a complete rotation.
Tides
1. Spring Tide - The tidal bulges are largest, and therefore the tidal
range is greatest, when the moon and sun are in line - new and full
moon.
2. Neap Tide - Tidal ranges smallest when moon and sun are puling
at right angles, which occurs when the moon is in quarter.
Tides
Semidiurnal tides – 2 high tides and 2 low tide per day
Bay of Fundy
How tides work
Tides
Worldwide distribution of semidurinal (2H, 2L), mixed semidiurnal
(2H and 2L of different heights), and diurnal (1H, 1L) tides.