Sea Levels: 
(Sfx: crashing waves) 
     THE LEVEL OF THE ATLANTIC OCEAN IS ABOUT 50 CENTIMETERS LOWER THAN THE
PACIFIC OCEAN, AND THE MEDITERRANEAN SEA IS ABOUT 100 CENTIMETERS EVEN LOWER
THAN THAT. WE TREAT SEA LEVEL AS IF IT IS A FIXED CONSTANT -- WE EVEN MEASURE THE
HEIGHTS OF MOUNTAINS AND THE DEPTHS OF VALLEYS AS  RELATIVE TO SEA LEVEL.'  BUT
WHEN SCIENTISTS AVERAGE OUT THE TIDES AND WAVES OF THE DIFFERENT OCEANS, THE
FACT IS THAT THEY EACH HAVE A UNIQUE LEVEL.  THAT'S BECAUSE OCEANS AROUND THE
WORLD CONTAIN DIFFERENT AMOUNTS OF SALT, SAYS GRAHAM GIESE, AN
OCEANOGRAPHER AT WOODS HOLE OCEANOGRAPHIC INSTITUTE.  THE SALTINESS OF A
PARTICULAR OCEAN DEPENDS ON

     Giese: "the evaporation that takes place there as opposed to the freshwater
input, say from rivers or rain that replenishes water."

     THE CONCENTRATIONS NEVER EVEN OUT BECAUSE WATER CIRCULATES BETWEEN
THE OCEANS VERY SLOWLY.  SALTIER WATER IS HEAVIER, SO SALTIER OCEANS SETTLE MORE
UNDER THEIR OWN WEIGHT AND TEND TO HAVE LOWER SEA LEVELS.   WE DON'T NOTICE
THIS SEA LEVEL VARIABILITY IN OUR EVERYDAY LIVES, SINCE WE USUALLY ONLY SEE ONE
OCEAN AT A TIME, BUT THE EFFECT IS NOTICABLE.   YOU CAN SEE IT WHERE THE ATLANTIC
OCEAN HITS THE MEDITERRANEAN SEA --THE WATER FROM THE ATLANTIC STREAMS
STEADILY INTO THE MEDITERRANEAN AS IF IT WERE FLOWING DOWN A HILL.

     Giese: "there is a net motion of water ... because the Mediterranean sea is lower
than the Atlantic ocean that it opens into."

      SO THE NEXT TIME SOMEONE MATTER-OF-FACTLY TELLS YOU YOU'RE A CERTAIN
NUMBER OF FEET ABOVE SEA LEVEL, YOU MIGHT JUST WANT TO ASK WHICH SEA'S LEVEL
THEY'RE TALKING ABOUT!  

(Sfx: Surf music)