"EDML1": a chronology for the EPICA deep ice core from Dronning Maud Land, Antarctica, over the last 150 000 years

Abstract

Abstract. A chronology called EDML1 has been developed for the EPICA ice core from Dronning Maud Land (EDML). EDML1 is closely interlinked with EDC3, the new chronology for the EPICA ice core from Dome-C (EDC) through a stratigraphic match between EDML and EDC that consists of 322 volcanic match points over the last 128 ka. The EDC3 chronology comprises a glaciological model at EDC, which is constrained and later selectively tuned using primary dating information from EDC as well as from EDML, the latter being transferred using the tight stratigraphic link between the two cores. Finally, EDML1 was built by exporting EDC3 to EDML. For ages younger than 41 ka BP EDML1/EDC3 is based on dated volcanic events and on a match to the Greenlandic GICC05 time scale via 10Be and methane. The internal consistency between EDML1 and EDC3 is estimated to be typically ~6 years and always less than 450 years over the last 128 ka (always less than 130 years over the last 60 ka), which reflects an unprecedented synchrony of time scales. EDML1 ends at 150 ka BP (2417 m depth) because the match between EDML and EDC becomes ambiguous further down. This hints to a complex ice flow history for the deepest 350 m of the EDML ice core, which amongst other reasons may be caused by spatial variations of the geothermal heat flux.

Layer disturbances and the radio-echo free zone in ice sheets

“…The climate record is dated to 2417 m depth. However, Ruth et al (2007) report increasing difficulties in matching volcanic events with the Dome Concordia record below 1900 m depth. It is hypothesized that starting at 2050 m depth, complex flow history and increasing shear stress makes the climate record less reliable until dating is impossible below 2400 m (S. Faria, personal communication, 2009).…”

“…They dip slightly due to the inclination of the borehole. Crystals with diameters larger than 10 cm are present in the last interglacial (MIS5, ∼2300-2375 m, age-depth values are based on Ruth et al, 2007) and below ∼2600 m. A plot of mean crystal size is published by Weikusat et al (2009) in Fig. 2a.…”

Proxies and Measurement Techniques for Mineral Dust in Antarctic Ice Cores

“…Alternatively, total element ratios for upper continental crust could be used (Na/Ca ) 0.87) (42); and from high-resolution ice core data (Na/Ca) sol,dust ) 0.94 ( 0.07 is suggested (46 Compositional changes of the ice core dust over time can be identified by calculating ratios between different dust-related parameters on identical ice-core samples. Figure 5 shows time series of selected ratios on the common EDML1/EDC3 time scale (47,48): the recovery of ICP-MS measurements for sample preparation at pH 1 for Fe and Al, the Fe/Al ratio at pH 1, and the element ratios Si/Al and K/Al from PIXE. It is clearly noticeable that a regime-shift happens during the deglaciation.…”

Direct north-south synchronization of abrupt climate change record in ice cores using Beryllium 10

“…Although these data are being formally presented here for the first time, the position of this 10 Be peak in the EPICA core has been available for some time (Raisbeck et al, 2002), and has been used to help construct or support chronologies discussed in several papers of this special issue Ruth et al, 2007;Blunier et al, 2007;Loulergue et al, 2007) and elsewhere (EPICA Community Members, 2006;Jouzel et al, 2007).…”