Similar rates of modern and last-glacial ocean thermohaline circulation inferred from radiochemical data

Today, the ocean thermohaline circulation transports half of the ²³¹Pa produced by radioactive decay in the Atlantic Ocean water column to the Southern Ocean. This export respectively imparts low and high ²³¹Pa/²³⁰Th ratios to the surface sediments of these oceans. Ocean sediments from the Last Glacial Maximum bear a similar isotopic fingerprint, implying that advection of North Atlantic Deep/Intermediate Water into the Circumpolar Deep Water of the Southern Ocean occurred at a similar - or slightly higher - rate during the last glacial period.