THE world’s oceans may have become stagnant for several thousand years during
the last ice age, after their circulation system abruptly stopped. And thanks to
global warming it could happen again. So say researchers who studied a
half-metre chunk of stalactite hacked from a flooded cave on the island of Grand
Bahamas.
They looked at layers of calcium carbonate in the 45,000-year-old stalactite
to estimate prehistoric levels of carbon-14. This radioactive isotope is created
by cosmic rays bombarding the atmosphere. Levels usually remain fairly constant,
but knowing of any fluctuations allows archaeological remains to be accurately
carbon dated.
However,…
