Water, Waves, and Tides

Chapter 4

Nature of Water Physical properties

of water – water is an excellent solvent– Structure of a water

molecule A water molecule

contains two atoms of _________and one atom of ________

Water molecules are_________– different parts have different electrical charges

Physical Properties of Water

All of water’s unique physical properties are caused by water’s_______________.

The unique way in which the hydrogen atoms are attached to the oxygen atom causes one side of the molecule to have a __________ charge and the area in the opposite direction to have a _____________ charge.

The resulting polarity of charge causes molecules of water to be ____________to each other forming strong molecular bonds.

The atomic structure of a water

Cohesion and Adhesion

Water is attracted to other water. This is called ____________,this is the reason why water is found in drops.

Water can also be attracted to other materials. This is called __________.

Nature of Water

The cohesiveness of water gives water a high_________ _________. Small organisms like water striders use surface tension to give them support.

Nature of Water– Freezing point and boiling point

Freezing point_______ Boiling point ________ Solid water (ice) is _______dense than liquid water, and it

floats– Water freezes at its surfaces, the water below stays liquid

allowing organisms to stay alive below the frozen surface

– When salt water freezes it leaves the ________ behind The water beneath the ice has a ________salinity

Salt ions interfere with the formation of hydrogen bonds, so seawater does not have a fixed freezing point.

• When water freezes at 0°C, a rigid web-like open structure of hydrogen-bonded molecules is formed.

• The open structure makes ice less dense than liquid water.

• This is why icebergs float.

Water density changes with temperature and salinity.

Nature of WaterWater as a solvent

Water is considered to be the universal solvent.  More substances will dissolve in water than any

other liquid.  Salt dissolves in water

Oil does not dissolve in water 

Nature of Water– Specific heat

Oceans maintain a more or less constant temperature – Because of the relatively stable temperature of the ocean marine

organisms have not evolved mechanisms for adapting to rapid fluctuations in temperature

– Water and light Water reflects some light off the surface Photosynthesis

– Photosynthetic organisms are restricted to the upper, sunlit surface waters

Vision– Objects appear more blue and green underwater– In turbid water light is absorbed in the 1st meter (3.3 feet)– In tropical waters light can penetrate 200 meters (660 feet)

Nature of Water

Chemical properties of water– The pH of pure water is ______– The pH of ocean water is determined by the _________

dissolved in it – Seawater is slightly________, with an average pH

of____– The pH of an organism’s internal and external

environment is a vital factor in determining the _______________________ Example: corals cannot grow in water that is acidic because the

low pH inhibits their ability to form external skeletons

Composition of Seawater

Ocean water is referred to as salt water and has a high quantity of dissolved salts

The proportions of the major salts in seawater are relatively_________.– ________can change,

the ______________ do not.

Major ions in Seawater %

Chloride (Cl) 55.07

Sodium (Na) 30.06

Sulfate (SO4 ) 7.72

Magnesium (Mg) 3.68

Calcium (Ca) 1.17

Potassium (K) 1.10

Bicarbonate (HC03 ) 0.40

Total 99.76

Salinity Salinity is an environmental factor that

strongly influences marine organisms–Marine organisms must maintain

appropriate levels of salts and water in their bodies

–The variety of salts are important in determining the kinds and distribution of organisms in the marine environment

Salinity is expressed as grams of salt per kilogram of water

parts per thousand (_____or 0/00 )

Winds and Currents

Winds are produced by differences in the ____________of air.

The oceans are in constant motion both from ________that generate waves and currents and from the pull of _________ that creates the tides.

Winds and Currents

El Niño-Southern Ocean Oscillation

El Niño-Southern Oscillation is a periodic change in the atmosphere and ocean of the tropical Pacific region.

El Niño is the _________ phase of the oscillation and La Niña is the ________ phase. – ENSO is associated with floods, droughts

and other weather disturbances in many regions of the world.

– An El Niño occurs about every three to eight years

El Niño

El Niño's __________current of nutrient-__________ tropical water, replaces the_________, nutrient-_______ surface water, normally found along the coast of Peru

When El Niño conditions last for many months, ocean warming occurs resulting in serious economic impact to local fishing There is a dramatic reduction in marine fish and plant life.

El Niño – how it happens

Coriolis Effect This effect is caused by

the __________of the Earth.

Winds blow at an angle to the equator.

Winds in the northern hemisphere blow to the ________and winds in the southern hemisphere blow to the_____.

The water at the ocean surface is moved by the Earth’s spin and the Coriolis Effect.

The Earth heats unevenly The earth heats unevenly because it is a sphere and

because of the tilt of its axis. It is summer in the Northern Hemisphere even though

the Earth is farther from the sun than in winter because of the Earth’s tilt

Surface Ocean Currents

The water of the ocean surface moves in a regular pattern called surface ocean currents.

Surface ocean currents can be very large. – The Gulf Stream, a surface current in the North

Atlantic, carries 4500 times more water than the Mississippi River.

– the Gulf Stream, as it flows and forms off of Florida, moves approximately 30 million cubic meters per second.

– Off the coast of Cape Hatteras, the Gulf Stream moves an estimated 80 – 90 million cubic meters per second.

Ocean Layers and Ocean Mixing

Seasonal turnover mixes the deeper nutrient-rich, oxygen-poor water with the oxygen-rich, nutrient poor surface waters.

Wave action and currents play roles in mixing deep and surface waters.

Evaporation, precipitation, and temperature affect the density of seawater.

Changes in density contribute to vertical mixing.

Density of Seawater The density of seawater varies with

temperature and salinity of the water. As temperature increases, density

decreases. As salinity increases, density also

increases.

Ocean Layers and Ocean Mixing

Water stratification occurs when water of high and low salinity (____________), as well as cold and warm water (____________), forms layers that act as barriers to water mixing.

Ocean Layers

–_________________ – a zone of rapid temperature change

–_________________- are layers of water where the water's salinity changes rapidly with depth.

–________________- are layers of water where the water density changes rapidly with depth.

Thermohaline circulation

Thermohaline circulation, occurs deep within the ocean and acts like a conveyor belt as oceans absorb, store, and redistribute vast amounts of the Sun's heat around the globe.

Thermohaline circulation Thermohaline circulation is driven by

changes in the ______________ of sea water. The conveyor belt transfers warm water from the Pacific Ocean to the Atlantic as a _____________ current and returns cold water from the Atlantic to the Pacific as a _________ current that flows further south.

The ocean conveyor belt The ocean conveyor belt plays a crucial role in the

Earth's_______________. Global climate changes could alter, or even halt,

the current as we know it today.

The ocean conveyor belt The oceanic conveyor belt is important to northern

Europe's moderate climate because of northward transport of heat in the Gulf Stream and North Atlantic Current.

The system can weaken or shut down entirely if the North Atlantic surface-water salinity somehow drops too low to allow the formation of deep-ocean water masses.

This apparently happened during the Little Ice Age (about 1400 to 1850 AD). The conveyer system shut down and northern Europe's climate became colder.

Cores extracted from deep-sea sediment deposits contain evidence of earlier cold periods.

SALINITY AND DEEP OCEAN CURRENTS

Ocean currents arise in many different ways. – __________ pushes the water along the

surface to form wind-driven currents. __________ ocean currents are caused by

differences in water temperature and salinity.

Review of Concepts

Salt water is ___________ dense than fresh water, and is therefore heavier.

When ocean water evaporates, the water becomes more dense because most of the salt remains in the water.

In some regions of the ocean, circulation is based upon the mixing between more dense surface water and less dense layers of deeper water.

Upwelling and Downwelling

the deflection due to the Coriolis effect reverses direction on either side of the equator

westward-flowing, wind-driven surface currents near the equator turn northward on the north side of the equator and southward on the south side.

surface waters are moved away from the equator and replaced by upwelling waters.

Coastal upwelling occurs where surface waters away from the coast; surface waters are replaced by water that wells up from below.

Where surface waters move toward the coast, the water piles up and sinks in the process known as coastal downwelling.

Upwelling and downwelling influence sea-surface temperature and biological

productivity upwelling waters are usually _______ in the dissolved

nutrients (e.g., nitrogen and phosphate compounds) required for phytoplankton growth.  – nutrient transport into the surface waters where

sunlight, is present, results in rapid growth of __________________, the base of marine food webs

– the world's most productive fisheries are located in areas of coastal _____________ that bring cold nutrient rich waters to the surface

– about half the world's total fish catch comes from upwelling zones.

Peruvian Anchovy Effect

Alternate upwelling of nutrient poor and nutrient rich waters off the coast of Ecuador and Peru are associated with El Niño and La Niña episodes.

During El Niño the pycnocline is so deep that the upwelled waters come from the nutrient poor waters above the pycnocline.

In extreme cases, nutrient-deficient waters coupled with over-fishing cause fisheries to _________________ bringing about severe, extended economic impacts.

Peruvian Anchovy Effect

Upwelled systems of the ocean are ______ areas _______ in nutrients and productivity. – large marine fisheries develop there.

During an El Niño, upwelling decreases, the _____________ lowers, and the warmer water near the surface _______ the nutrients found during cold conditions.

Peruvian Anchovy Effect Beginning in the 1950s, an important anchovy fishing

industry developed and grew in Peru, due to the huge numbers of anchovies that lived in the areas of cold, nutrient-rich waters welling up off the Peruvian coast.

By 1971, the Peruvian anchovy harvest had climbed to 12.5 million tons per year.

in 1972, an El Niño year, the anchovy stocks declined sharply. Only 2.5 million tons were harvested that year, leading to great economic hardship and a virtual collapse of the Peruvian fishing industry.

Peruvian Anchovy Effect The decrease in the anchovy population triggered a

series of interrelated problems. – much of the anchovy catch is processed into fishmeal.

During the growth years of the Peruvian fishing industry, the fishmeal had become a major source of feed for livestock and poultry around the world.

When the anchovy catch collapsed in 1972, nations around the world that had become dependent on the fishmeal had to find other, more expensive, sources of feed. – This caused meat prices to rise. In the United States, poultry

prices rose more than 40%

Peruvian Anchovy Effect Another result of the drop in the anchovy population

was the death of many birds, which had depended on the anchovies for food.

The death of the birds, aside from being a tragic loss in itself, caused a decrease in the harvest of bird droppings which had become an important source of fertilizer for Peruvian farmers.

Thus the loss of the anchovies affected not only Peruvian fishermen, but also Peruvian farmers.

Waves A wave represents a flow of __________

or motion, not a flow of water The ____________is either dissipated at

sea or transferred to a beach or structures on the beach when the wave strikes.

Surf zone – the area along a coast where waves slow down, become steeper, break, and disappear.

Waves Tsunamis – tidal waves

– Sudden movements of the earth’s crust produce earthquakes, which can produce large seismic sea waves (tsunamis)

– The waves surge over land can cause mass destruction

Waves 2004 Indian Ocean earthquake

– The earthquake was caused by_______________– The tsunami killed nearly 230,000 people in eleven

countries – Waves were up to 30 meters (100 ft.) high. – It was one of the deadliest natural disasters in

recorded history.– Indonesia, Sri Lanka, India, and Thailand were the

hardest hit.

Tsunami began with a 9.2 earthquake

After one hour

Tides Tides are caused by the ______________

pull of the moon and the sun. Spring tides occur at ______ moon and

______ moon when the sun and the moon’s gravity align (they are in a straight line).– Causing the highest high tides and the

lowest low tides

Tides

Neap tides occur when the moon and sun are at right angles

– Smaller tides are produced

Global Warming As the Earth heats up, there could be an

increase in precipitation and a melting of freshwater ice in the Arctic Ocean which would flow into the Atlantic Ocean.

Additional freshwater could dilute the Atlantic Gulf Stream to the point where it would not continue to sink into the depths of the ocean.