• Biome
• type of plant and animal community that covers large geographic areas
• Global Environments
• distribution of biomes
• result of
• physical geography
• solar radiation
• global circulation patterns
• oceanic
• atmospheric

• Global Environments
• interdependent relationship between ocean and atmosphere
• same physical processes determine operation of both systems
• changes in ocean lead to long-term shifts in general circulation of atmosphere

• atmosphere and ocean together act like a global heat engine
• redistributing heat that reaches earth from sun

Solar Radiation

• Solar radiation
• warms earth’s surface
• drives circulation of oceans and atmosphere
• emitted by sun
• in form of radiant energy
• at same average rate in all directions
• received on earth’s surface
• in varying amounts, depending on
• distance
• duration of daylight
• angle at which sun’s rays impinge on surface
• variations in amount earth’s surface
• lead to uneven heating of atmosphere and oceans
• temperatures at equator higher than temperatures at poles
• drives interrelated patterns of circulation of oceans and atmosphere

Global Circulation Patterns - Atmospheric

• Global winds
• winds that blow steadily from specific directions over long distances
• produced by movement of air between equator and poles
• produces convection currents
• warm air rises at equator, air pressure is lower
• cold air sinks at poles, air pressure is higher

Fig. 17.2

• would blow in straight line from poles toward equator if earth did not rotate
• rotation of earth prevents winds from blowing in straight line
• as winds move, earth rotates from west to east under them
• making it seem as if winds have curved
• is known as Coriolis effect
• Coriolis effect
• Norhtern Hemisphere
• deflects winds to right of direction of travel
• Southern Hemisphere
• deflects winds to left of direction of travel
• patterns of calm areas and wind belts
• calm areas
• air moving vertically (rising or falling)
• doldrums
• horse latitudes
• wind belts
• air moving horizontally
• trade winds
• prevailing westerlies
• polar easterlies
• calm areas
• doldrums
• areas of steadily rising warm air near equator
• area of low pressure
• very little horizontal movement of air
• little to no wind
• horse latitudes
• areas of steadily sinking air
• warm air that rises at equator divides and flows N and S
• at ~30° N and S latitude, air stops moving toward poles, sinks
• area of high pressure
• very little horizontal movement of air
• little to no wind
• origin of name

• wind belts
• trade winds
• surface pressure differential between 30 ° N & S latitude and equator
• low pressure at equator
• high pressure at horse latitudes
• causes winds to blow from region of horse latitudes towards equator
• Northern Hemisphere (between ~30°N and equator)
• blow from northeast
• deflected right by Coriolis effect
• origin of name
• Southern Hemisphere (between ~30°S and equator)
• blow generally from southeast
• deflected left by Coriolis effect

• prevailing westerlies
• surface pressure differential between 30 ° N & S lat and 60 ° N & S lat
• low pressure at 60 ° N & S lat
• high pressure at 30 ° N & S lat
• causes winds to blow from region of
• 30 ° N to 60 ° N
• 30 ° S to 60 ° S

• so named because they blow from west to east
• Northern Hemisphere
• blow generally from southwest
• deflected right by Coriolis effect
• Southern Hemisphere
• blow generally from northwest
• deflected left by Coriolis effect

• polar easterlies
• cold air near poles sinks
• flows back toward lower latitudes
• Northern Hemisphere
• air flows from high pressure at north pole (90°N) to low pressure at 60 °N
• deflected to right by Coriolis effect
• Southern Hemisphere
• air flows from high pressure at north pole (90°S) to low pressure at 60 °S
• deflected to left by Coriolis effect
• meet the prevailing westerlies at ~ 60°N and S latitude
• a region called the polar front
• mixing of warm and cold air along polar front effect weather in US

Global Circulation Patterns - Oceanic

• The Oceans
• circulation
• El Nino
• tides
• Historical perspective
• early knowledge of ocean currents
• Pliny (~AD 50)
• Arabs (around 9th century)
• Benjamin Franklin (in 18th century)

• Matthew Fontaine Maury
• first to use large amounts of ocean data in a systematic study of surface currents
• from 1841 - 1853 he compiled data accumulated in thousands of old log books
• other involvements

• two types of circulation exist in oceans
• surface circulation
• horizontal movement of water
• driven by force of winds at water surface
• thermohaline circulation
• vertical movement of water
• driven by density differences resulting from variations in water
• temperature
• salinity

• Circulation patterns of oceans
• affected by four main factors
• wind acting on ocean surface
• containment of oceans within boundaries set by land masses
• earth’s rotation
• water density

• mechanics of ocean circulation patterns
• effect of wind
• wind exerts a push on water
• friction forces stronger in water than in air
• speed of water is only a fraction of that of wind
• response time of ocean currents to changes in atmospheric circulation is many months
• if earth was covered entirely with water
• winds would form well-defined belts
• ocean currents would move in distinct belts under influence of prevailing winds
• effect of continents
• presence of landmasses, modifies idealized oceanic circulation patterns
• since ocean current cannot leave its basin
• generalized circulation patterns in ocean basins tend to consist of closed loops called gyres

• effect of earth’s rotation
• due to rotation of earth
• objects moving in straight line along its surface are deflected
• as if a sidewise force were acting on it
• called the Coriolis effect
• always acts sidewise on objects moving horizontally on earth
• because earth spins to east, Coriolis effect causes a deflection
• to right of direction of motion in Northern Hemisphere
• to left of direction of motion in Southern Hemisphere
• effect water density
• density increases with
• increases in salinity
• increases in pressure
• decreases in temperature
• thermohaline circulation
• primarily a convection flow
• cold, dense waters from polar latitudes sink and move towards tropics
• replaced by warmer surface waters that originated in tropics

• Ocean surface circulation
• dominated by two huge surface gyres
• which move around subtropical zones of high pressure between 30° N & 30° S latitudes
• Northern Hemisphere gyre
• Southern Hemisphere gyre
• Northern Hemisphere gyre
• circulates in clockwise direction
• prevailing winds blow W to E due to earth’s eastward rotation are deflected to the right
• Southern Hemisphere gyre
• circulates in counterclockwise direction
• prevailing winds blow west to east due to earth’s eastward rotation are deflected to the left

• Principle oceanic surface currents
• tend to
• form loops of circulation marked by
• strong currents on perimeters
• relatively little movement internally
• move
• warm water poleward
• cold water toward tropics
• helps equalize distribution of heat
• western boundary currents
• eastern boundary currents
• equatorial currents
• polar circulation

• western boundary currents
• general northward current of warm equatorial water
• flow at west edge of ocean basins
• tend to be narrow, swift, deep flows with well-defined boundaries
• strong in Northern Hemisphere
• Gulf Stream in Atlantic Ocean
• Kuroshio (or Japanese) Current in Pacific Ocean
• weaker inSouthern Hemisphere
• Brazil Current in Atlantic Ocean
• West Australia Current in Pacific Ocean

• Gulf Stream
• warm northward current in north Atlantic Ocean
• runs from Cape Hatteras to near Grand Banks of Newfoundland
• reaches Europe near southern British Isles
• result, western Europe warmer and more temperate than eastern North American at similar latitudes

• Kuroshio Current
• warm northward current in northern Pacific Ocean
• runs along Japan northeast towards Alaska
• result, Alaska has a more temperate climate than would be expected based on latitude

• eastern boundary currents
• eastern sides of oceans
• broad, weak, shallow flows with poorly-defined boundaries
• force of wind and Coriolis effect combine at western continental seacoast
• cause warm surface water to move away from coast and out to sea
• deep cold water moves upward to replace water that blows seaward
• produces upwelling

• significance of upwelling
• brings deep, cool, nutrient-rich water to surface
• water rich in nutrients because of numerous creatures that die in surface waters and sink
• Peru (Humboldt) Current is an example
• flows northward along western coast of South America
• large amount of upwelling associated with this current
• upwelling provides nutrients for enough phytoplankton to support largest anchovy population in world
• anchovy fishery is one of largest industries in Peruvian economy

• equatorial currents
• confined mostly to surface
• warm, well-mixed surface layer
• sharp thermocline
• separates warm surface water from cold water below
• except at equator where mixing across thermocline occurs
• North Equatorial Current

• Equatorial Countercurrent

• South Equatorial Current

• polar circulation
• circulation differs at N vs S polar regions
• north polar region
• Arctic Ocean covered by pack ice
• sluggish counterclockwise drift
• deep cold water from Arctic Ocean is kept from mixing freely with that in Atlantic and Pacific Oceans
• south polar region
• water flows freely between Atlantic and Pacific Oceans
• Antarctic Circumpolar Current
• largest current in world
• circles Antarctica
• extends all way to bottom
• flows eastward

• El Nino
• name originally coined in late 1800s by Peruvian fishermen
• seasonal shift in current pattern off coast of Ecuador and Peru
• occurred around Chrsitmas time
• El Nino (Spanish for "Christ child)
• would replace cold, nutrient rich water with less productive, warm southward flowing water
• slightly reducing fish population
• giving fishermen some time off

• now refers to catastrophic version of original annual event
• part of phenomenon known as El Nino-Southern Oscillation (ENSO)
• continual but irregular cycle of shifts in ocean and atmospheric conditions that affect globe
• normally, Pacific Ocean is fanned by constantly blowing east-to-west trade winds
• push away the warm surface water along western coasts of Peru, Chile, Ecuador
• allows cold, nutrient-rich water from depths to well up (upwelling)
• warm water that was pushed away from coast "piles" up in western portion of Pacific Ocean
• results in waters of western Pacific Ocean being
• several degrees warmer
• about one meter higher
• than waters in eastern portion of Pacific

• if east-to-west trade winds slacken briefly
• warm water begins to slosh back across Pacific Ocean from west to east
• the warmer the eastern ocean gets, the warmer and lighter the air above it becomes
• thus, the more similar to air on western side
• reducing difference in pressure across ocean
• since a pressure difference is what makes wind blow, a lack thereof causes easterly trade winds to weaken
• continued reduction in winds allows warm water to continue its eastward advance
• end result is to shift weather systems of western Pacific Ocean about 6000km eastward
• tropical rainstorms usually drench Indonesia and Philippines
• when warm water moves east, so do clouds, leaving previously rainy Indonesia and Philippines in drought
• ecological effects during an El Nino
• in waters of Peru and northern Chile
• commercial fish stocks virtually disappear
• plankton decrease in abundance
• weather effects are propagated across world’s weather systems
• violent winter storms, flooding, on coast of California
• colder and wetter winters occur in Florida and along Gulf Coast
• American Midwest and Mid-east experience heavier than usual rains
• effects of El Nino are clear, trigger is not
• models suggest that type of climate change that triggers El Nino is chaotic
• wind and ocean currents return again and again to same condition but never in a regular pattern
• small nudges can send them off in many different directions

• noteworthy El Ninos
• 1982 - 1983: 2100 deaths, $13 billion in damages
• Austraila
• drought in sub-Saharan Africa
• southern Ecuador and northern Peru

• 1997 - 1998:
• California
• Florida
• Panama Canal
• Indonesia
• Tides
• another type of movement of ocean waters
• normally raise and lower the water level of a coast
• are significant
• geomorphically
• biologically
• geomorphic
• changes in water level expose different parts of coast to erosive action of waves
• biologic
• organisms living in areas subject to changes in water level must have adaptations to deal with alternating periods of submersion and exposure
• definition
• periodic rise and fall of Earth’s oceans
• caused by
• gravitational effects of sun & moon on oceans
• produce "bulges" of water
• magnitude of "bulges" is determined by varying and complex interactions resulting from relative positions of earth, moon and sun
• role of sun and moon
• sun’s gravitational pull on earth is less than 1/2 that of moon
• its significance on tides
• secondary to influence of moon
• strongest when sun aligns with moon and during equinoxes
• role of sun and moon
• moon’s gravitational pull on earth is ~ 2X that of sun
• it is primarily responsible for tides
• since moon’s distance from earth varies, so does its attractive forces
• characteristics
• frequency
• some areas
• 2 high tides each day
• only 1
• average interval between successive high tides is app. 12.5 hours
• time of day
• changes each day
• height
• typically 1 - 2 meters above average sea level
• varies with relative positions of earth, moon & sun
• influenced by local coastal topography

The end