North Atlantic millennial-scale climate variability 910 to 790ka and the role of the equatorial insolation forcing

Patrizia Ferretti, Simon J. Crowhurst, Michael A. Hall, Isabel Cacho

Research output: Contribution to journalArticleResearchpeer-review

45 Citations (Scopus)


The Mid-Pleistocene transition (MPT) was the time when quasi-periodic (~100kyr), high-amplitude glacial variability developed in the absence of any significant change in the character of orbital forcing, leading to the establishment of the characteristic pattern of late Pleistocene climate variability. It has long been known that the interval around 900ka stands out as a critical point of the MPT, when major glaciations started occurring most notably in the northern hemisphere. Here we examine the record of climatic conditions during this significant interval, using high-resolution stable isotope records from benthic and planktonic foraminifera from a sediment core in the North Atlantic (Integrated Ocean Drilling Program Expedition 306, Site U1313). We have considered the time interval from late in Marine Isotope Stage (MIS) 23 to MIS 20 (910 to 790ka). Our data indicate that interglacial MIS 21 was a climatically unstable period and was broken into four interstadial periods, which have been identified and correlated across the North Atlantic region. These extra peaks tend to contradict previous studies that interpreted the MIS 21 variability as consisting essentially of a linear response to cyclical changes in orbital parameters. Cooling events in the surface record during MIS 21 were associated with low benthic carbon isotope excursions, suggesting a coupling between surface temperature changes and the strength of the Atlantic meridional overturning circulation. Time series analysis performed on the whole interval indicates that benthic and planktonic oxygen isotopes have significant concentrations of spectral power centered on periods of 10.7kyr and 6kyr, which is in agreement with the second and forth harmonic of precession. The excellent correspondence between the foraminifera δ18O records and insolation variations at the Equator in March and September suggests that a mechanism related to low-latitude precession variations, advected to the high latitudes by tropical convective processes, might have generated such a response. This scenario accounts for the presence of oscillations at frequencies equal to precession harmonics at Site U1313, as well as the occurrence of higher amplitude oscillations between the MIS22/21 transition and most of MIS 21, times of enhanced insolation variability.

Original languageEnglish
Pages (from-to)28-41
Number of pages14
JournalEarth and Planetary Science Letters
Issue number1-2
Publication statusPublished - Apr 2010
Externally publishedYes


  • Early Pleistocene
  • Foraminifera
  • Insolation
  • IODP
  • Millennial
  • North Atlantic
  • Site U1313
  • Stable isotopes

Cite this