photo © National Atomic Museum
photo © National Atomic Museum
Radioactive tritium became a perfect marker for tracking ocean water §. Scientists sampling North Atlantic water found that tritium released into the atmosphere before the 1962 nuclear test ban treaty, mixed downward by 1973. By 1980, the same tritium had moved into deep areas off Florida. The water had taken about 20 years to travel 3000 miles (4800 km) through the sea at an average speed of less than half a mile a day, about half the speed of a snail §.
Not all currents are predictable. Turbidity currents are submarine avalanches. Sediments settle and accumulate in shallow areas like the edges of the continental shelf and slope. Often triggered by an earthquake, they can spill down the continental slope into deep water. Fast turbidity currents carrying suspended sediments may spread over wide areas §.
Transatlantic telegraph cables snapped from north to south over thirteen hours in 1929, when an earthquake off New England sent sediments slumping and sliding. Scientists calculated that the resulting turbidity current traveled 25-35 miles per hour (40-55 kph), and covered an area slightly larger than Maine and Connecticut §.
Ocean Planet Exhibition Floorplan
gene carl feldman (gene@seawifs.gsfc.nasa.gov) (301) 286-9428 Judith Gradwohl, Smithsonian Institution (Curator/Ocean Planet)