North Atlantic Current variability through marine isotope stage M2 (circa 3.3 Ma) during the mid-Pliocene
Journal
Paleoceanography
Journal Volume
24
Journal Issue
4
Date Issued
2009
Author(s)
Abstract
The mid-Pliocene was an episode of prolonged global warmth and strong North Atlantic thermohaline circulation, interrupted briefly at circa 3.30 Ma by a global cooling event corresponding to marine isotope stage (MIS) M2. Paleoceanographic changes in the eastern North Atlantic have been reconstructed between circa 3.35 and 3.24 Ma at Deep Sea Drilling Project Site 610 and Integrated Ocean Drilling Program Site 1308. Mg/Ca ratios and δ18O from Globigerina bulloides are used to reconstruct the temperature and relative salinity of surface waters, and dinoflagellate cyst assemblages are used to assess variability in the North Atlantic Current (NAC). Our sea surface temperature data indicate warm waters at both sites before and after MIS M2 but a cooling of ∼2-3°C during MIS M2. A dinoflagellate cyst assemblage overturn marked by a decline in Operculodinium centrocarpum reflects a southward shift or slowdown of the NAC between circa 3.330 and 3.283 Ma, reducing northward heat transport 23-35 ka before the global ice volume maximum of MIS M2. This will have established conditions that ultimately allowed the Greenland ice sheet to expand, leading to the global cooling event at MIS M2. Comparison with an ice-rafted debris record excludes fresh water input via icebergs in the northeast Atlantic as a cause of NAC decline. The mechanism causing the temporary disruption of the NAC may be related to a brief reopening of the Panamanian Gateway at about this time. Copyright 2009 by the American Geophysical Union.
Other Subjects
calcium; Deep Sea Drilling Project; dinoflagellate cyst; global climate; ice sheet; magnesium; marine isotope stage; Ocean Drilling Program; oceanic current; oxygen isotope; paleoceanography; planktonic foraminifera; Pliocene; reconstruction; sea surface temperature; thermohaline circulation; Atlantic Ocean; Atlantic Ocean (North)
Type
journal article