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Quantifying Arctic responses to past climate change

Final Report Summary - QUARCTIC (Quantifying Arctic responses to past climate change)

Project objectives summary:

(a) examine sedimentary sequences throughout the Northern Hemisphere for the presence of far-travelled volcanic ashes (tephras);
(b) use these tephras as precise isochrons (timelines) to link together distant sequences and thereby assess the relative timings of past environmental changes;
(c) extract remains of environmentally sensitive chironomid (midge) head capsule from sequence sediments and assess feasibility of reconstructing palaeotemperatures.

A description of the work performed since the beginning of the project:

(a) sediment cores from study sites in northern Russia and North America have been examined for the presence of volcanic ash isochrons and chironomid head capsules;
(b) detected ash layers have been geochemically characterised and correlated with their volcanic sources as well as those documented in literature sources. Chironomid head capsules are similarly distinctive and capable of taxonomic identification.

A description of the main results achieved:

(a) Ash shards have been detected in lake sites in the northern Urals. The estimated age and Icelandic-type morphology of one layer suggests a correlation with the Vedde Ash (ca. 12 200 years BP). Analytical laboratory time scheduled for November 2012 is expected to confirm this. This would increase the detected range of this important and widespread stratigraphic marker layer by approximately 2 500 km, and lies approximately 3 600 km from its source volcano. Numerous and well-preserved chironomid (midge) fossil head capsules have been found in conjunction with the ashes in these lakes.

(b) Numerous ash layers have been detected at sites in north-eastern North America - including a Holocene mire and a Lateglacial lake site. Analysis of the layers reveals they derive from a number of North American sources (Alaska and Cascades Mountains, approximatly 5 000 - 6 000 km distant) rather than the relatively closer Icelandic sources. The detection of so many ash isochrons, many of which also occur in the Greenland ice-core stratigraphy, will allow precise age control for palaeoenvironmental study in this region which was subject to a number of climatic perturbations from North Atlantic current changes and glacial meltwater outflows. It is additionally anticipated that this tephrostratigraphic framework will be applicable throughout the majority of North America. Tephrochronology has seen surprisingly little application in this region and offers the researcher with an excellent opportunity to explore the geographic and temporal expansion of the technique, as well as furthering his own research and potentially offering future career prospects.

(c) A fortuitous discovery during this North-American research was the existence of a tephra of Alaskan origin in north-western Europe (British Isles, Germany) as well as the Greenland ice-cores. This discovery allows for the correlation of this tephra isochron across an area extending from the northeast Pacific Ocean, the North American continent, the Atlantic Ocean and into Europe. Ongoing work with international collaborators is expected to detect further trans-continental and trans-Atlantic ultra-distal tephras and form the basis of an ultra-distal chronological framework linking both sides of the Atlantic.

Final results and their potential impact and use (including the socio-economic impact and the wider societal implications of the project so far):

- The final results of this project have been to highlight the usefulness of far-travelled volcanic ashes as high-precision chronological marker layers within sedimentary sequences. In particular, the results highlight the degree to which fine ash particles can travel in the atmosphere to become deposited many thousands of kilometres from source. This has introduced the technique to new geographic areas where ash deposition was hitherto thought unlikely or of limited use only.

- This geographic extension and enhanced awareness and potential of the technique will contribute to the accuracy and precision of past environmental change reconstructions. The improved understanding of timings and causes of such events will then be of use in modelling the future impacts of possible anthropogenic environmental changes. The development of a Trans-Atlantic tephra framework, in particular, will be useful as it straddles the mid-Atlantic region of oceanic circulation which is widely seen as a principle driver of past and future climate change.

- Recent disruption by volcanic eruptions highlights the vulnerability of modern transport infrastructures to such events. Data provided through this project should prove useful in predicting the frequency and magnitude of inevitable future disruptions and hazard mitigation measures, e.g. eruption source frequency, ash cloud direction, ash particle sizes and concentrations. Project findings suggest that there is potential for trans-Atlantic socio-economic disruption resulting from future large-scale North American eruptions.