Atlantic overturning responses to obliquity and precession over the last 3 Myr

This study analyzes 39 Atlantic and seven Pacific benthic δC records to characterize obliquity and precession responses in Atlantic overturning since 3 Ma. Regional benthic δC stacks are also analyzed. A major transition in orbital responses is observed at 1.5–1.6 Ma coincident with the first glacial shoaling of Northern Component Water. Since ∼1.5 Ma, the phases of Atlantic benthic δC records from 2300 to 4000 m depth lag maximum obliquity by 59 (6.7 kyr) and June perihelion precession forcing by 133 (8.5 kyr). Comparison with North Atlantic sea surface temperature suggests that these orbital responses (particularly precession) in middle deep Atlantic δC are associated with changes in ocean heat transport and overturning rates. The mid-Pleistocene transition had little effect on the obliquity and precession phases of benthic δC but did result in a ∼50% decrease in the obliquity power of middle deep Atlantic δC at 0.6 Ma.