Hydrosphere� The hydrosphere includes all water on

Earth.

� The abundance of water on Earth is a unique feature that clearly distinguishes our "Blue Planet" from others in the solar system. Not a drop of liquid water has been foundanywhere else in the solar system.

� the "Goldilocks" principle permits water to exist mainly as a liquid.

Distribution of Water on Earth

Hydrosphere� The range of surface temperatures and

pressures of our planet permit water to exist in all three states: solid (ice), liquid (water), and gas (water vapour).

� Water is the universal solvent and the basis of all life on our Planet. It is an essential life-sustaining resource.

Ocean basins� Cover 70% of the surface

� Lower than continents

� Oceanic crust

� Collect sediments

Echo Sounders for Measuring Ocean Depths and Floor Profiles

Major Topographic Divisions and Profile of the North Atlantic Ocean Basin

The World’s Ocean Floors

Typical Elevation Profile of Oceanic Margins

Oceans � Oceans are responsible for keeping the planet from burning up or freezing

� The large mass of liquid serves as a buffer for the sun’s heat and it keeps earth in a state of homeostasis by not allowing any drastic changes in temperature

� Why would it be important to keep the earth’s temperature at a relatively constant state?

Water’s heat capacity� It takes 1 calorie of heat to raise the temperature of 1 cubic centimeter of water

by 1 degree celsius.

� Most of the water is contained in the oceans and the high heat capacity of this large volume of water (1.35 million cubic kilometres) buffers the Earth surface from large temperature changes

Ocean Currents� pull CO2 down to the deeper portions of

the ocean

� carry warm waters from equatorial regions to those near the poles

� These currents are sent in motion by prevailing winds

� Coriolis force, which is the force created by the rotation of the earth influences direction

� account for 1/4 of the heat transport on the earth

Deep ocean currents� The Great Ocean Conveyor - thermohaline circulation

� Differences in density – temperature & salinity

� More heat than 1 million nuclear power plants

� Strongly influences climate

When the conveyor breaks down

� Last time it broke down – ice age

� Could it happen again, or could it melt the ice caps?

� The Pentagon is concerned.

ICE AGES

� The most recent “ice age” ended about 12,000 years ago, which was prior to the advent of civilized human history.

� It is still unknown as to what causes the advent of ice ages, but it is thought that the last one occurred when Panama closed off

Ice Age North Polar Coverage

GLOBAL WARMING

� At the current time, we are experiencing a slow global warming, but it is not known to what extent this is part of a natural cycle as distinct from human-induced

� Could also result in melting of the polar ice caps, which would raise the water level of the oceans and cause flooding of coastal areas of the continents.

Sea Level Changes due to Ice Ages and Ice Cap Melting

The Ocean and

the Atmosphere� The oceans are the earth’s main

reservoirs of readily available carbon dioxide (CO2).

� Why do you think that this would be important to the earth’s atmosphere?

� Carbon dioxide is an important greenhouse gas

� CO2 is important in the process of photosynthesis in plants

� It is the deep circulation that allows the creates the cycle that allows the entrapment of CO2 at the deeper, colder regions of the ocean

Oceans and Oxygen� Half of Earth’s atmospheric oxygen comes from

phytoplankton

Tides� rise and fall of sea

levels caused by the combined effects of the gravitational forces

� Most places in the ocean usually experience two high tides and two low tides each day

Tides and gravity� Caused by the Moon

� Moon’s gravity pulls the water towards it

� Side opposite the Moon, has a tidal bulge

� rebound

Spring and Neap tides� Spring tide – Moon and Sun gravity combine to

produce a higher than normal tides

� Neap tide – moon and Sun at 90º to each other. Results in lower than normal tides

Salt water� Most water on Earth is salty

� Makes it more conductive� Electricity

� Heat

� Mostly NaCl dissolved

Salinity� A measure of saltiness

How much is usable by Humans?� although our planet is nearly ¾

covered by water, there is only a

small percentage of it usable by

humans

� It is the saline (salt) content in the

water that makes it unusable to

humans

� Humans have found ways to filter the

water and make it usable, but these

processes are still slow and costly

�

"When the well's

dry, we know the

worth of water."

Water resources� Adult humans need 2.7 to 3.7 liters of water every day

� There are 7 billion people on Earth

� That’s 22.4 billion liters of water every day, just for drinking water for humans

� 69% of worldwide water use is for irrigation

� 15-35% of irrigation withdrawals unsustainable

� 22% of worldwide water use is industrial

Freshwater� Low concentrations of

salts

� Only 2.75% of the hydrosphere

� Most of that is frozen

� Fresh and unpolluted water accounts for 0.003% of total water available globally

Groundwater� Located in spaces

between particles of soil

� Deposits of groundwater are called aquifers

Watershed� A watershed is a geographic area in which all water

running off the land drains to a specific creek, river or stream

Watershed vs. Basin� A basin is a large-scale watershed, such as the St.

Lawrence River basin

Cryosphere� Water in the solid form

� Sea ice, lake and river ice

� Permafrost

� Snow cover

� Glaciers

� Ice caps and ice sheets •61 percent of all fresh water on the Earth is

held in the Antarctic ice sheet

•if melted, would cause sea levels to rise by

61.1 meters

Permafrost in Land Areas

� Regions in which soil water is permanently frozen constitute what is known as permafrost.

� Land areas in polar regions, such as Antarctica and Greenland, and the north slopes of Alaska and Siberia, have zones below their surfaces in which ground water remains frozen year-round.

Summary� The hydrosphere includes all water on Earth

� 97.2% of the hydrosphere is in the oceans

� Earth’s climate allows for solid, liquid, and vaporwater.

� Ocean basins cover 70% of the surface

� The oceans get deeper at the continental shelves

� The high heat capacity of of water buffers the Earth surface from large temperature changes

Summary� Ocean currents pull CO2 down to the deeper parts of

the oceans, and account for ¼ of the heat transport on Earth

� Differences in density (temperature and salinity) drive the Great Ocean Conveyor

� Last time the conveyor broke down there was an ice age (Panama closed off)

� Or the ice caps could melt, raising ocean levels

Summary� Oceans are the main reservoir of CO2, easily trapped

in cold, deep water

� Half of Earth’s oxygen comes from phytoplankton

� Tides are the rise and fall of sea levels caused by gravity

� Moon pulls the water up, opposite side has rebound bulge

� Sun and Moon’s gravity can combine to make spring and neap tides

Summary� Most water on Earth is salty, mostly NaCl

� Salinity measures saltiness – fresh, brackish, saline, and brine water

� Only 2.75% of the hydrosphere is freshwater

� Deposits of groundwater are called aquifers

Summary� A watershed is a geographic area in which all water

running off the land drains to a specific creek, river or stream

� A basin is a large-scale watershed

� The cryosphere is the term which collectively describes the portions of the Earth’s surface where water is in solid form,

� Permanently frozen ground is permafrost

Questions� How is the hydrosphere connected to the other “spheres”

we’ve seen in class? (Think in terms of climate change)

� Is fresh water a renewable resource? Explain your answer