Download ocean currents and weather

OCEAN CURRENTS AND WEATHER
OCEAN CURRENTS AND WEATHER
OCEAN CURRENTS AND WEATHER
(MOVEMENT OF AIR CURRENTS) ARE
CONNECTED.
WIND INFLUENCES OCEAN CURRENTS.
OCEAN CURRENTS INFLUENCE WEATHER.
BOTH ARE DRIVEN BY THE UNEVEN
HEATING OF THE EARTH’S SURFACE BY
THE SUN.
THERE ARE TWO KINDS OF OCEAN CURRENTS:
1. SURFACE CURRENTS - USUALLY LIMITED TO
THE TOP 400 METERS OF THE OCEAN - MAKE
UP ABOUT 10% OF THE WATER IN THE OCEAN
2. DEEP CURRENTS - MAKE UP 90% OF THE
WATER IN THE OCEANS - DRIVEN BY DENSITY
DIFFERENCES AND GRAVITY
WHAT DRIVES SURFACE CURRENTS?
1. SOLAR HEATING - THE SUN HEATS THE WATER
ALONG THE EQUATOR. THIS CAUSES THE
WATER TO EXPAND. THE WATER ALONG THE
EQUATOR IS ABOUT 8 CM HIGHER THAN IN
THE MIDDLE LATITUDES. THIS CAUSES A
SLIGHT RISE, AND WATER WANTS TO FLOW
DOWN THAT RISE.
2. WIND - THE FRICTION OF THE WIND BLOWING
ON THE WATER WILL TEND TO PUSH THE
WATER IN THE DIRECTION THE WIND IS
BLOWING. WIND BLOWING ON THE SURFACE
OF THE OCEAN FOR 10 HOURS WILL MOVE
THE WATER AT 2% OF THE WIND SPEED.
WATER PILES UP IN THE DIRECTION THE
WIND IS BLOWING.
3. GRAVITY - WATER WANTS TO FLOW DOWN
HILL AGAINST THE PRESSURE GRADIENT.
4. CORIOLIS FORCE - THE CORIOLIS FORCE
TURNS THE CURRENTS TO THE RIGHT IN THE
NORTHERN HEMISPHERE AND TO THE LEFT
IN THE SOUTHERN HEMISPHERE.
ALL OF THESE FORCES COMBINE TO FORM
CIRCULAR CURRENTS CALLED GYRES.
THE NORTH ATLANTIC GYRE IS DIVIDED INTO 4
CONNECTED CURRENTS - THE NORTH
EQUATORIAL CURRENT, THE GULF STREAM, THE
NORTH ATLANTIC CURRENT, AND THE CANARY
CURRENT.
THIS SHOWS THE COMPLEXITY OF THE EARTH’S
MAJOR OCEAN CURRENTS. THE PICTURE ALSO
SHOWS THAT ALTHOUGH THE OCEANS HAVE
DIFFERENT NAMES, THEY ARE ALL CONNECTED.
THE GULF STREAM ACTUALLY BEGINS OFF THE
COAST OF AFRICA AS THE NORTH EQUATORIAL
CURRENT.
PART OF THIS CURRENT FLOWS INTO THE
CARIBBEAN, THROUGH THE YUCATAN
CHANNEL, INTO THE GULF OF MEXICO, AND
THEN THROUGH THE STRAITS OF FLORIDA.
THE WATER IS RESTRICTED AS IT FLOWS
THROUGH THE STRAITS OF FLORIDA AND
BUILDS UP QUITE A BIT OF FORCE (LIKE
PUTTING YOUR THUMB OVER THE END OF A
HOSE).
ITS VELOCITY REACHES AROUND 6 KNOTS AT
THIS POINT.
THE GULF STREAM WAS DISCOVERED BY JUAN PONCE DE LEON IN
1513 AND WAS USED BY THE SPANISH IN SAILING BACK TO
EUROPE.
LATER, IN 1768, BENJAMIN FRANKLIN (THEN POSTMASTER
GENERAL) TRIED TO CONSTRUCT A MAP OF THE GULF STREAM SO
THAT COLONIAL SHIPS COULD USE IT TO THEIR ADVANTAGE IN
SAILING THE ATLANTIC.
THE GULF STREAM PARALLELS THE COAST
OF THE U.S. UNTIL IT GETS TO CAPE
HATTERAS.
THEN, IT MOVES OUT TO SEA, CONTINUES TO
MOVE IN A NORTHERLY DIRECTION.
IT SPLITS INTO SEVERAL CURRENTS, THE
LARGEST OF WHICH IS THE NORTH ATLANTIC
CURRENT. THIS FEEDS ALONG THE
WESTERN COAST OF EUROPE.
WHAT DOES THE GULF STREAM DO?
1. IT MOVES WARM WATER ALONG THE WEST
COAST OF EUROPE. THE WINDS BLOWING OFF
THIS WARM WATER MAKE EUROPE MUCH
WARMER THAN IT WOULD BE. FOR EXAMPLE,
THE AVERAGE LOW IN LONDON IN DECEMBER
IS 42o F, WHILE THE AVERAGE LOW IN ST.
JOHN’S NEWFOUNDLAND IS 27o F.
2. IT STRENGTHENS HURRICANES AND CHANGES
WEATHER.
3. IT ADDS TO THE DIVERSITY OF OCEAN LIFE.
FOR EXAMPLE, THE WATERS OFF
MASSACHUETS ARE MUCH MORE DIVERSE
BECAUSE OF THE WARM CURRENTS.
WHAT WOULD HAPPEN IF THE GULF STREAM
SHUT DOWN?
WHAT WOULD HAPPEN IF THE GULF STREAM
SHUT DOWN?
EUROPE WOULD GET COLDER.
SCIENTIST THINK THIS IS WHAT HAPPENED
ABOUT 12,000 YEARS AGO.
AT THE END OF THE LAST ICE AGE,
TEMPERATURES WERE WARMING, AND ICE
WAS MELTING. THEN, THERE WAS A “LITTLE ICE
AGE.” EUROPE GOT MUCH COLDER FOR
SEVERAL HUNDRED YEARS.
SO MUCH FRESH WATER WAS RELEASED INTO
THE NORTH ATLANTIC THAT THE GULF STREAM
STOPPED.
OCEAN CURRENTS ARE DRIVEN IN PART BY WIND
AND IN PART BY DIFFERENCES IN DENSITY.
COLDER WATER IS DENSER THAT WARM WATER.
WATER WITH A HIGHER SALINE CONTENT (MORE
SALT) IS DENSER.
AS THE WARM GULF STREAM MOVES NORTH,
EVAPORATION IS OCCURING, SO THE WATER
BECOMES SALTIER. THE WATER IS ALSO
COOLING.
IT EVENTUALLY REACHES A POINT WHERE IT IS
ACTUALLY DENSER THAN THE SURROUNDING
WATER, AND IT SINKS AND BECOMES A DEEP
WATER CURRENT.
AS THE GULF STREAM MOVES NORTH, IF IT
WERE DILUTED WITH FRESH WATER, IT WOULD
NOT BE DENSE ENOUGH TO SINK, AND
CIRCULATION WOULD STOP.
THIS IS WHAT SCIENTISTS THINK HAPPENED
APPROXIMATELY 12,000 YEARS AGO.
COULD THIS HAPPEN AGAIN?
OCEAN GYRES ARE NOTORIOUS
COLLECTION SPOTS FOR TRASH WASHED
INTO THE OCEAN.
MUCH OF THIS IS PLASTIC DEBRIES OF
VARIOUS TYPES.
AS PLASTIC WEATHERS, IT CAN BREAK INTO
VERY SMALL FRAGMENTS WHICH
RESEMBLE PLANKTON AND CAN BE
INGESTED BY SMALLER MARINE
CREATURES.
THE NORTH PACIFIC GYRE HAS GOTTEN
THE MOST ATTENTION, AS IT PROBABLY
CONTAINS THE MOST TRASH.
http://mindfully.org/Plastic/Ocean/Moore-TrashedPacificNov03.htm
THIS IS AN ARTICLE BY CHARLES MOORE WHO
WAS ONE OF THE FIRST PEOPLE TO CALL
ATTENTION TO THE NORTH PACIFIC GYRE.
PLASTIKI, A 60 FT. SAILING CATAMARAN WAS
BUILT TO CALL ATTENTION TO THE PROBLEMS
OF PLASTIC WASTE IN THE OCEANS.
THE HULL IS MADE OUT OF 13,000 PRESSURIZED 2
L PLASTIC BOTTLES.