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Analysing abrupt climate change using varved sediments

Innovative Varve Analysis

The Greenland ice-core records have demonstrated that pronounced, decadal-scale climate shifts occurred during the last glacial cycle. In order to establish high-resolution regional correlations, palaeoclimatic records obtained from marine and terrestrial sedimentary environments need to be obtained that are of comparable temporal resolution. The only sediment records that will normally enable this degree of age precision to be achieved are annually-laminated (varved) deposits. The CQR have an established record of analysing these varved sediment records from both cold-climate and temperate environments. To undertake this work we combine comprehensive fieldwork using industrial-scale coring rigs alongside detailed analysis of sediments using: thin section micromorphology, micro-xrf core scanning, palaeoecology, grain size analysis, and Electron microscopy. Using these techniques, the CQR team able to identify, define and count annual sediment layers with very high precision, and to cross-validate the results obtained by different analysts.

Clastic varves and the Last Glacial to interglacial Transition

In lakes that occur in extremely cold environments, the sediments laid down in winter contrast markedly with those that accumulate in summer.  In the summer, the lake surface is not frozen, so that the water can be agitated by surface winds, internal currents, inflowing streams and other processes.  Very fine particles (clays, fine silts) are constantly kept in suspension, but coarser material (e.g. sand) will sink to the bottom of the lake.  In the winter when the lake surface is frozen, the lake is protected from these influences, the water is stilled, and fine material can then sink.  The end result is a series of laminations of contrasting particle size, with coarser summer and finer winter layers.  Annual layers can therefore be identified as lamination couplets (varves), their number providing an estimate of the duration of the period over which the varves accumulated.

Varved sediment sequences which span the LGIT have been investigated in a number of sites in continental Europe, Scandinavia and Greenland, where they can be used for dating purposes (varve chronology).  Although records of varved sediments have been reported from sites in Britain, and a few examined quite closely, very feww robust varve chronologies have ever been developed for the period 16 to 8 ka BP. We are the first group to undertake this work , and our ongoing research focusses on deposits that accumulated in Scotland where ice-dammed lakes were formed by the advance of glacier ice during the Loch Lomond or Younger Dryas Stadial (c. 12.9-11.5 ka BP), the last occasion when glaciers existed in the British Isles.  Two of these, Glen Roy-Glen Spean and to the south-east of Loch Lomond were studied as part of the NERC-funded RAPID programme.

Biochemical varves and previous Interglacials

Biochemical varves form as a result of seasonal changes in bio-productivity and water chemistry, and are characterised by the growth and deposition of microscopic organisms and the biologically driven precipitation of minerals such as carbonate. They typically form during warm climate intervals, known as interglacials, and allow us to reconstruct the climates and environments of the current warm episode and past interglacials that may act as analogues for the future (Candy et al., 2013).

Understanding the dynamics of landscape response to abrupt climate change has major implications for society, because such events are thought to have contributed to the demise of human settlements in the past (e.g. Orlove, 2005), and are likely to occur in the future (e.g. Williams, 2009). Investigating the impacts of abrupt events during the Holocene is problematic because humans are modifying the landscape, potentially masking the impact of these events. By applying thin section analysis to produce a varve chronology, and stable isotopes as a proxy for temperature, to the study of interglacials (e.g. MIS 11) that are suggested to be analogous to the current interglacial (Berger and Loutre, 2003), it is possible to construct high-resolution records of how climate varies and evolves during a Holocene-like interglacial, but without the impact of Humans.

Orlove, B., 2005. Environmental Science and Policy 8, 589-600.

Berger, A., Loutre, M.F. (2003). Geophysical Monograph Series 137, 17-26.

Candy, I. et al., 2013. Earth Science Reviews

Orlove, B., 2005. Environmental Science and Policy 8, 589-600.

Williams, P.D., 2009. International Journal of Green Economics 3 (1), 63-76.


Recent Publications

Palmer et al (2008) Annually laminated Late Pleistocene sediments from Llangorse Lake, South Wales, UK: a chronology for the pattern of ice wastage.Proceedings of the Geologists Association, 119, 3-4, 245-258.

Palmer et al (2010) Annually resolved events of Younger Dryas glaciation in Lochaber (Glen Roy and Glen Spean), Western Scottish Highlands. Journal of Quaternary Science, 25, 4, 581-596. Doi: 10.1002/jqs1370

MacLeod et al (2011) Timing of glacier response to Younger Dryas climatic cooling in Scotland. Global and Planetray Change, 79, 3-4, 264-274. Doi: 10.1016/j.gloplacha.2010.07.006

Palmer et al (2012) Evidence for phase-locked changes in climate between Scotland and Greeland during GS-1 (younger Dryas) using micromorphology of glaciolacsutrine varves from Glen Roy. Quaternary Science Reviews, 36, 114-123. Doi:10.016/j.quascirev.2011.12.003

CQR Varve team

Dr Adrian Palmer

Dr Alison MacLeod

Dr Ian Candy

Dr Simon Blockley

Gareth Tye

Jenifer Sherriff

Jacob Bendle







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