Last Glacial Interglacial Cycle Research Articles

A revision of the British chronostratigraphy within the last glacial-interglacial cycle based on new evidence from Arclid, Cheshire UK

Of the 24 Greenland interstadials in the Last Glacial-interglacial cycle (LGIC) only five are conventionally recognised in Britain. This paper aims to improve understanding of the LGIC in Britain from a site at Arclid, Cheshire. Sediments were characterised and luminescence used to establish a chronology. This found that the Chelford Sand Formation spans 77-47 ka with sand deposited initially by aeolian but later by fluvial transportation. Coleoptera and Diptera from the basal peat lens provided a reconstruction for a heather-rich heathland environment grazed by large herbivores, with summer temperatures between 13 and 18 °C, and winter temperatures between −14 and 1 °C. Flies included the earliest records of the blood-sucking horsefly Haematopota pluvialis, and the soldierfly Chloromyia formosa. The overlying Stockport Sand Formation was deposited fluvioglacially between 47-41 ka with the upper Stockport Till formed by the advance of the last British icesheet after ∼33 ka. Stenothermic beetle analysis from Arclid indicate similarities with results from other British mid LGIC sites, some of which are at or beyond the limit of radiocarbon dating and may be of a similar age to Arclid. Basal organic sediments found at Arclid along with other reassigned sites are proposed as a new Arclid Interstadial. A revised British LGIC chronostratigraphy has the Wretton, Chelford and Brimpton Interstadials and the previously suggested but not widely recognised Cassington Interstadial. The Arclid Interstadial occurred after these, but prior to the Upton Warren Interstadial complex. This closes the previous gap in interstadials between the Brimpton Interstadial and the Upton Warren Interstadial complex within the British chronostratigraphy.

Simulations of the Northern Hemisphere through the last Glacial-interglacial cycle with a vertically integrated and a three-dimensional thermomechanical ice-sheet model coupled to a climate model

We present simulations of the Northern Hemisphere land ice through the last glacial-interglacial cycle with a vertically integrated ice-sheet model and a three-dimensional thermomechanical ice-sheet model. Both models are coupled asynchronously to the zonally averaged Louvain-la-Neuve climate model, which includes simplified treatments of the atmosphere, ocean and sea ice. The two-dimensional vertically integrated ice-sheet model, which contains no thermomechanical coupling, was developed in spherical coordinates (Marsiat, 1994). The three-dimensional thermomechanical ice-sheet model was developed using the two-dimensional vertically integrated model as source. We compare results of the vertically integrated with those of the thermomechanical ice-sheet model. in the thermomechanical model the deformation properties of ice depend on the temperature within the ice and the enhancement factor; the latter is introduced to model, in a simplified approach, the different flow properties of Pleistocene and Holocene ice due to varying dust content. The computations with the thermomechanical model show that the growth and decay of the Northern Hemisphere ice sheets can be modelled with a common enhancement factor for all ice sheets. It is shown that there are model set-ups for the thermomechanical model yielding temporal developments of the total ice volume comparable to those of the vertically integrated model. Furthermore, we demonstrate that for the coupled climate/cryosphere system the total ice volume depends considerably on the enhancement factor.