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RAPID Climate Change

NERC RAPID Climate Change thematic programme, project NE/C509158/1 :  ‘Precise chronology of the timing of changes in behaviour of the North Atlantic THC and their forcing effects, 16-8 ka BP’

The project is concerned with an important transitional period (the Last Glacial-Interglacial Transition: LGIT) which spans the final stages of ice-sheet glaciation in Britain and the early phase of the present interglacial.  This period, between c 16 and 8 ka BP, witnessed a number of abrupt and pronounced climatic changes throughout the North Atlantic region and elsewhere, events which are clearly reflected in, and precisely dated by, the Greenland ice-core records.  The overall aim of our project is to test the extent to which the impacts of those abrupt events, as experienced in the British Isles and environs, were the direct consequence of changes in North Atlantic THC.  To do this, we need to demonstrate the precise temporal relationships between North Atlantic THC changes on the one hand, and marked changes in environmental conditions in the British Isles on the other.  This is something which is presently difficult to achieve at better than centennial precision, because of a number of technical difficulties that compromise radiocarbon dating, the principal geochronological method employed for this time period.

Our project is exploring the potential of three methods which, in combination, may lead to significant improvement in the precision and accuracy with which we can date climatic events, and synchronise the proxy-climate records obtained from marine and terrestrial contexts, and from ice cores: these are varve chronology, tephrochronology and new statistical approaches to age modeling.  The key outcomes to emerge so far are outlined below.


A regional varve chronology for the Lochaber district has been constructed which spans 515 years (Roy and Spean lake systems) while an embryonic chronology for Glacial Lake Blane spanning 295 years has been defined.

The Lochaber series of varves show decadal-scale variations in internal composition and structure that match climatic variations reflected in the Greenland ice-core record.  We believe that the Greenland ice and sedimentation in ice-dammed lakes in Scotland were responding to a common climate forcing factor – perhaps decadal migrations of the North Atlantic Polar Front, or variations in solar radiation output.

Counting of the varves and comparison of these laminated sequences with the Greenland records enables us to date events in Scotland with a remarkable degree of precision.  For example, the records show that the varves in the Glen Roy-Glen Spean area accumulated over a period of 515 years between 12,119 and 11,506 years ago, and that the glacier ice that impounded the lakes in Glens Roy and Spean reached their maximum extent ca. 840 years after the onset of a major cooling episode which, according to the Greenland ice-core records, commenced around 11,797 years ago.

The onset of climate warming and melting of the ice that impounded the lakes in Glen Roy is dated to 11,570, which is very close to the age of the onset of the present interglacial in the Greenland ice-core records, again suggesting that Greenland and Scotland were dancing to the same climatic tune.

Volcanic glass shards, originating from volcanoes on Iceland (see below), have been found in the varved sediments. This is a very important discovery for it will enable us to validate the above conclusions, and to synchronise the Scottish records with those in the North Atlantic, mainland Europe and Greenland more precisely.

The Croftamie sequence provides an important test of numerical models of the timing of the last glacier ice advance in Scotland, and of the rate of response to climatic triggers, such as changes in the North Atlantic THC


Discovery of important new cryptotephras in sites in the British Isles (Pyne-O-Donnell et al., 2007, 2008) which fall within the period of interest to our project (Figure 7).

Discovery of non-visible, discrete cryptotephra layers of probable Icelandic origin in marine basins in the Labrador Sea and in the vicinity of the Laurentian Fan, as well as in other parts of the North Atlantic (Figure 8). These tephra layers were probably disseminated by icebergs or melting sea ice, and hence provide important information on the conditions in, and circulation of, the North Atlantic during the study period.

Extension of the distribution of one of the most important ash beds, the Vedde Ash (dated to c. 12.0 k cal yrs BP), across Europe to sites in southern Germany and Switzerland, the most southerly finds so far (Blockley et al., 2007), and to Lake Yamozero on the Timan Ridge in northern Russia. This is 1200 km beyond the previous most easterly find (St. Petersburg area), and 3,000 km from the source volcano, Katla, in southern Iceland.

The use of tephrochronology to provide a more precise chronology of the retreat of the last British ice sheet.

Discovery of the first cryptotephras in varved records in the British Isles (see ‘varve chronology’ above).

Age modelling

An extensive radiocarbon dating programme at Croftamie has allowed revision of the timing of maximum ice extent at the type-site for the Loch Lomond Readvance (equivalent to the Younger Dryas).

Research in Southern Europe has indicates that the onset and termination of abrupt climate events may be asynchronous with Greenland.


The Royal Holloway RAPID team

Professor John Lowe

Dr Simon Blockley

Dr Adrian Palmer

Dr Sean Pyne O’Donnell

Dr Alison MacLeod










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