Scientists from the Lamont Doherty Earth Observatory (LDEO) have provided new evidence that ocean circulation changes lagged behind, and were not the cause of, major climate changes at the beginning and end of the last ice age (short intervals known as glacial boundaries), according to a study published in the March 2005 issue of Science magazine.

Both ice sheet volume and the “global carbon budget,” the amount of carbon stored in deep ocean reservoirs compared to that on the earth’s surface, changed before ocean circulation patterns changed, according to evidence from deep sea cores taken from the South Atlantic. Thermohaline (heat and salt) ocean circulation changes were found to have occurred 1,000-3,000 years after carbon shifts in each case.

[www.ldeo.columbia.edu]

Notice the large drop in marine carbon isotopes 74,000 years ago (Toba?).