Abstract
Abstract. Since its discovery in Greenland ice cores, the millennial scale climatic variability of the last glacial period has been increasingly documented at all latitudes with studies focusing mainly on Marine Isotopic Stage 3 (MIS 3; 28–60 thousand of years before present, hereafter ka) and characterized by short Dansgaard-Oeschger (DO) events. Recent and new results obtained on the EPICA and NorthGRIP ice cores now precisely describe the rapid variations of Antarctic and Greenland temperature during MIS 5 (73.5–123 ka), a time period corresponding to relatively high sea level. The results display a succession of abrupt events associated with long Greenland InterStadial phases (GIS) enabling us to highlight a sub-millennial scale climatic variability depicted by (i) short-lived and abrupt warming events preceding some GIS (precursor-type events) and (ii) abrupt warming events at the end of some GIS (rebound-type events). The occurrence of these sub-millennial scale events is suggested to be driven by the insolation at high northern latitudes together with the internal forcing of ice sheets. Thanks to a recent NorthGRIP-EPICA Dronning Maud Land (EDML) common timescale over MIS 5, the bipolar sequence of climatic events can be established at millennial to sub-millennial timescale. This shows that for extraordinary long stadial durations the accompanying Antarctic warming amplitude cannot be described by a simple linear relationship between the two as expected from the bipolar seesaw concept. We also show that when ice sheets are extensive, Antarctica does not necessarily warm during the whole GS as the thermal bipolar seesaw model would predict, questioning the Greenland ice core temperature records as a proxy for AMOC changes throughout the glacial period.
Highlights
Continental, marine and polar paleoclimate records preserve abundant evidence that a series of abrupt climate events at millennial scale occurred during the last glacial period (∼18– 110 thousand years before present, hereafter ka) with different expressions over the entire globe (Voelker, 2002)
Recent and new results obtained on the European Project for Ice Coring in Antarctica (EPICA) and NorthGRIP ice cores precisely describe the rapid variations of Antarctic and Greenland temperature during MIS 5 (73.5–123 ka), a time period corresponding to relatively high sea level
We present the most recent and accurate Greenland–Antarctica common dating over the last 123 ka using the NorthGRIP and EPICA ice cores
Summary
Continental, marine and polar paleoclimate records preserve abundant evidence that a series of abrupt climate events at millennial scale occurred during the last glacial period (∼18– 110 thousand years before present, hereafter ka) with different expressions over the entire globe (Voelker, 2002) These so-called “Dansgaard-Oeschger” (DO) events were first described and numbered in the deep Greenland ice cores from Summit back to 100 ka (72◦34 N, 37◦37 W, GISP2 and GRIP; Dansgaard et al, 1993; Grootes et al, 1993; GRIPmembers, 1993). Using the simplest possible model, Stocker and Johnsen (2003) successfully described the Antarctic millennial variability in response to the abrupt temperature changes in the north by involving a southern heat reservoir associated with AMOC variations Such an important role of the Southern Ocean for the bipolar seesaw mechanism is supported by marine records (Barker et al, 2009). Marine Isotopic Sub-stages 5d to 5c, 5c to 5b and 5b to 5a, respectively. 41 www.clim-past.net/6/345/2010/
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