The full programme book (PDF) - Royal Geographical Society

T2
Towards a Greenland tephra lattice: a detailed framework from four ice-cores
spanning 25-45 ka
A.J. Bourne 1 *, E. Cook 1 , S.M. Davies 1 , P.M. Abbott 1 , A.J. Griggs 1 , M. Chapman 2 , I.R.
Hall 3 , J. Scourse 4 , J.P Steffensen 5 , A. Svensson 5
1 Department of Geography, College of Science, Swansea University, Singleton Park, Swansea, SA2
8PP
2 School of Environmental Sciences, University of East Anglia (UEA), Norwich, NR4 7TJ
3 School of Earth, Ocean, and Planetary Sciences, Cardiff University, Main Building, Park Place, Cardiff,
CF10 3YE
4 School of Ocean Sciences, Bangor University, Menai Bridge, Anglesey, LL59 5AB
5 Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30, DK-
2100 Copenhagen, Denmark
The TRACE project aims to utilise tephrochronology to facilitate the high-precision
correlation of palaeoclimatic archives preserving a record of the rapid climate changes that
characterised the North Atlantic region during the last glacial period. The synchronisation
of the Greenland ice-cores to North Atlantic marine records will allow the determination of
lead/lag relationships between the atmospheric and oceanic systems over these climatic
events and permit an assessment of potential causal mechanisms. Initial investigations
have focused on the period between 25-45 ka b2k in four deep ice cores from Greenland.
Within this time period 34 tephra layers were identified in NGRIP, 24 tephra layers were
identified in NEEM, 25 tephra layers were identified in GRIP and 20 tephra layers were
identified in DYE-3. The majority of tephras are basaltic and are predominantly tholeiitic in
composition indicating a source from the rift zones of Iceland, with the Grimsvötn and
Kverkfjöll systems the most likely sources. Two non-basaltic horizons appear to have a
source from outside Iceland.
Tephra layers that fall between Greenland Interstadial 8 and 9 (13 in NGRIP, 7 in NEEM,
12 in GRIP and 7 in DYE-3) have been shown to all fall within the compositional envelope
of the Faroe Marine Ash Zone III tephra layer, which has implications for the use of this
tephra layer as a marine-ice synchronisation point (Bourne et al., 2013). Early
comparisons of the ice core layers to North Atlantic marine records highlight four potential
common tephra horizons, within GS-3 (29,130 ± 456 a b2k), GS-9 (38,300 ± 703 a b2k),
GS-10 (40,220 ± 792 a b2k) and GS-12 (43,680 ± 877 a b2k). Other potential correlations
throughout the period are being explored. We explore all these potential correlations and
compare the climatic changes preserved within these cores as constrained by these
tephra horizons.
Ongoing work on the ice will allow an assessment of the Icelandic volcanic frequency
during the last glacial period as well as the relationship between volcanic eruptions
preserved in the ice and climate changes.
Keywords: tephra; Greenland; North Atlantic; synchronisation.