The full programme book (PDF) - Royal Geographical Society

T2
Tracing and constraining key tephras between 29.2 – 11.1 ka b2k within the NEEM,
NGRIP and GRIP ice core records
Eliza Cook* 1 , S.M. Davies 1 , P.M. Abbott 1 , A.J, Bourne 1 , M. Bigler 2 , I.K. Seirstad 3 , A.
Svensson 3 , S.O. Rasmussen 3 , J.P. Steffensen 3
1 Department of Geography, College of Science, Swansea University, Swansea
2 Physics Institute, Climate and Environmental Physics and Oeschger Centre for Climate Change
Research, University of Bern, Sidlerstrasse 5, CH-3012, Bern, Switzerland
3 Ice and Climate group, Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30, DK-2100
Copenhagen, Denmark
This project aims to improve the European tephrochronological framework for the last
glacial-interglacial transition (LGIT) between 29.2 and 11.10 ka b2k through the
identification and characterisation of tephra layers within the NEEM, NGRIP and GRIP icecore
records from Greenland. Prior to this study, just 16 tephra horizons had been
identified within this interval in Greenland. Here we outline the discovery of a further 64
new tephra horizons in the 3 deep ice-cores from Greenland, with 23 identified in NEEM,
24 in GRIP and 17 in NGRIP. Iceland is the dominant source of tephra, although one
horizon is far travelled and represents the first Kamchatka-Kurile island arc tephra to be
identified in Greenland ice.
Tephras are identified in the ice by adoption of a new low-resolution screening approach
for NEEM via the continuous flow analysis system (CFA). A high-resolution sampling
strategy was devised based on the results of the former and was successful in identifying
many previously unknown tephra horizons at a 3-20cm resolution. Horizons found in
NEEM were then traced in GRIP and NGRIP.
The key highlights of this work include:
1. 20 new tie-points have been established between GRIP and NGRIP between
GS-2 and GS-5.
2. 9 tie-points have been established between NEEM and either NGRIP or GRIP.
These include the Vedde ash (12,171 ± 57 yr b2k), a NGRIP Katla horizon that falls within
GS-5 and dated to 29,130 ± 456 yr b2k, a basaltic horizon within the cold GI-1d episode
and three isochrons in the poorly resolved GS-2b/a interval, promoting confident matching
and timescale transfer between cores.
3. A dacitic horizon detected in NEEM during GS-3 has a potential Kamchatka-
Kurile island provenance; providing an opportunity to examine synchronicity of North
Atlantic/North West Pacific climate records during the glacial maximum.
4. Two Borrobol-Penifiler type horizons have been found in GRIP and one in
NGRIP, during GI-1e.
The discovery of new inter-core tie points provides a test of the matching/synchronisation
approach used for the transferral of the GICC05 timescale from NGRIP to other Greenland
ice-cores as well as providing individual timescale transfer points e.g. Rasmussen et al.,
2013. Ongoing geochemical analysis will focus on extending these tephra isochrons to
terrestrial and marine sequences.
KEYWORDS: tephra horizons; isochrons; Greenland ice-cores; Iceland; last glacialinterglacial
transition