Ice stream influence on West Greenland Ice Sheet dynamics during the Last Glacial Maximum

This paper investigates the processes governing bedrock bedform evolution in ice sheet and ice stream areas in central West Greenland, and explores the evidence for a cross‐shelf ice stream at the Last Glacial Maximum (LGM). To the east of Sisimiut the formation of streamlined bedforms with high elongation ratios and high bedform density has been controlled by geological structure and topography in slow‐flowing ice sheet areas. At the coast, the effects of regional flow convergence, caused by coastal fjord orientation, routed ice into the Sisimiut/Itilleq area where it formed an ice stream onset zone. This funnelled ice into an offshore trough (Holsteinsborg Dyb), resulting in a southwesterly regional ice flow direction and the formation of a topographically routed ice stream (Holsteinsborg Isbrae). To the south of this, striae and bedform evidence show that local valley glaciers initially flowed east to west across the coast, but were later redirected by the Itilleq Fjord ice which turned southwestward due to diffluent flow and deflection by Holsteinsborg Isbrae. Roches moutonnées in this area have low elongation ratios and high bedform density, but do not provide unequivocal support for ice streaming, as they are a product of both bedrock structure and changes in ice flow direction, rather than enhanced flow velocities. Cosmogenic surface exposure ages limit maximum ice sheet surface elevation to ca. 755–810 m above sea level in this region. Such ice thickness enabled Holsteinsborg Isbrae to reach the mid/outer continental shelf during the LGM, and to contribute to the formation of a trough mouth fan and the Outer Hellefisk moraines. Initial deglaciation across this region was driven by rising sea level and increasing air temperatures prior to the Bølling Interstadial at ca. 14.5 cal. ka BP. Between 12 and 10 cal. ka BP both increased air and ocean temperatures post the Younger Dryas, and peak sea‐level rise up to the marine limit, caused accelerated thinning and marginal retreat through calving, although dating evidence suggests ice streams remained along the inner shelf/coast boundary until at least ca. 10 cal. ka BP, their longevity maintained by increased ice thickness and ice discharge. Copyright © 2009 John Wiley & Sons, Ltd.     

青藏高原末次冰期最盛时的冰川与环境

在１６－３２ｋａＢｐ的末次冰期最盛时，青藏高原较现代降温７℃左右，降水为现代的０３－７０％。极地型冰川广泛分布，高原内部平衡线较下降值减至５００－３００ｍ以内，高原东部，南缘及西缘可能以亚极地型冰川为主，并有小部分温冰川，平衡线下降８００ｍ以至１００－１２００ｍ。初步统计，包括周围高山在内冰川面积在３５×１０＾４ｋｍ＾２左右，为现代冰川的７．５倍，冰储量相当于全海平面变化２４．２ｃｍ。其时，多年冻     

Permafrost at the time of the Last Glacial Maximum (LGM) in North America

This paper presents three maps that summarize current knowledge as to the extent of Past permafrost and Relict permafrost in North America at approximately the time of the Last Glacial Maximum (LGM; c. 25–17 ka BP) and during subsequent deglaciation until c. 10 ka BP. Analysis of the post‐1983 literature suggests that the extent of Past permafrost south of the LGM limit was broader in eastern North America and slightly narrower in the Interior Great Plains than previously mapped. The recognition and dating of Relict permafrost in the nonglaciated terrain of the northwestern Arctic suggests that permafrost may be of great antiquity and can persist under changing climatic conditions. The formation of permafrost features during deglaciation suggests that ice‐proximal climatic conditions remained cold at least long enough for short‐lived permafrost aggradation; a latitudinal gradient is evident in the timing of its development as the Laurentide Ice Sheet retreated.     

Support for the Innuitian Ice Sheet in the Canadian High Arctic during the Last Glacial Maximum

The extent of glacier ice in the Canadian High Arctic during the Last Glacial Maximum (LGM) has been debated for decades. One school proposed a regional Innuitian Ice Sheet whereas another proposed a smaller, non-contiguous Franklin Ice Complex. Research throughout western Nares Strait supports coalescent Innuitian and Greenland ice during the LGM, based on widespread glacial and marine deposits dated by ¹⁴C and amino acid analyses. This coalescence likely promoted a vigorous regional ice flow westward across Ellesmere Island to Eureka Sound. Post-glacial emergence in Eureka Sound suggests a former ice thickness at least as great as that in Nares Strait (≥ 1 km). Recently, independent field studies elsewhere in the High Arctic also support an Innuitian Ice Sheet during the LGM. Collectively, these studies resolve a long-standing debate, and initiate new opportunities concerning the reconstruction of high-latitude palaeoenvironmental and palaeoclimatic change. © 1998 John Wiley & Sons, Ltd.     

The Scandinavian Ice Sheet: from MIS 4 to the end of the Last Glacial Maximum

Lambeck, K., Purcell, A., Zhao, J. & Svensson, N‐O. 2010 (April): The Scandinavian Ice Sheet: from MIS 4 to the end of the Last Glacial Maximum. Boreas, Vol. 39, pp. 410–435. 10.1111/j.1502‐3885.2010.00140.x. ISSN 0300‐9483. Glacial rebound modelling, to establish constraints on past ice sheets from the observational evidence of palaeo‐shoreline elevations, is well established for the post‐ Last Glacial Maximum (post‐LGM) period, for which the observational evidence is relatively abundant and well distributed spatially and in time. This is particularly the case for Scandinavia. For the earlier part of the glacial cycle this evidence becomes increasingly sparse and uncertain such that, with the exception of the Eemian period, there are very few, if any, direct sea‐level indicators that constrain any part of the Scandinavian Ice Sheet evolution before the LGM. Instead, we assume that ice‐sheet basal conditions during Marine Isotope Stage 3 (MIS 3) are the same as those for the LGM, focus on establishing these conditions from the rebound analysis for the LGM and Lateglacial period, and then extrapolate to the earlier period using observationally constrained locations of the ice margins. The glacial rebound modelling and inversion follow previously established formulations, with the exception that the effects of water loading from proglacial lakes that form within the Baltic Basin and elsewhere have been included. The data set for the inversion of the sea‐ and lake‐level data has been extended to include marine‐limit data in order to extend the observational record further back in time. The result is a sequence of time slices for the Scandinavian Ice Sheet from the time of MIS 4 to the Lateglacial that are characterized by frozen basal conditions until late in the LGM interval when rapid thinning occurred in the eastern and southern sectors of the ice sheet. The primary function of these models is as an interpolator between the fragmentary observational constraints and to produce quantitative models for the glaciation history with predictive capabilities, for example regarding the evolution of the Baltic Basin.     

A model for Holocene retreat of the West Antarctic Ice Sheet

Marine ice sheets are grounded on land which was below sea level before it became depressed under the ice-sheet load. They are inherently unstable and, because of bedrock topography after depression, the collapse of a marine ice sheet may be very rapid. In this paper equations are derived that can be used to make a quantitative estimate of the maximum size of a marine ice sheet and of when and how rapidly retreat would take place under prescribed conditions. Ice-sheet growth is favored by falling sea level and uplift of the seabed. In most cases the buttressing effect of a partially grounded ice shelf is a prerequisite for maximum growth out to the edge of the continental shelf. Collapse is triggered most easily by eustatic rise in sea level, but it is possible that the ice sheet may self-destruct by depressing the edge of the continental shelf so that sea depth is increased at the equilibrium grounding line.Application of the equations to a hypothetical “Ross Ice Sheet” that 18,000 yr ago may have covered the present-day Ross Ice Shelf indicates that, if the ice sheet existed, it probably extended to a line of sills parallel to the edge of the Ross Sea continental shelf. By allowing world sea level to rise from its late-Wisconsin minimum it was possible to calculate retreat rates for individual ice streams that drained the “Ross Ice Sheet.” For all the models tested, retreat began soon after sea level began to rise (～15,000 yr B.P.). The first 100 km of retreat took between 1500 and 2500 yr but then retreat rates rapidly accelerated to between 0.5 and 25 km yr^?1, depending on whether an ice shelf was present or not, with corresponding ice velocities across the grounding line of 4 to 70 km yr^?1. All models indicate that most of the present-day Ross Ice Shelf was free of grounded ice by about 7000 yr B.P. As the ice streams retreated floating ice shelves may have formed between promontories of slowly collapsing stagnant ice left behind by the rapidly retreating ice streams. If ice shelves did not form during retreat then the analysis indicates that most of the West Antarctic Ice Sheet would have collapsed by 9000 yr B.P. Thus, the present-day Ross Ice Shelf (and probably the Ronne Ice Shelf) serves to stabilize the West Antarctic Ice Sheet, which would collapse very rapidly if the ice shelves were removed. This provides support for the suggestion that the 6-m sea-level high during the Sangamon Interglacial was caused by collapse of the West Antarctic Ice Sheet after climatic warming had sufficiently weakened the ice shelves. Since the West Antarctic Ice Sheet still exists it seems likely that ice shelves did form during Holocene retreat. Their effect was to slow and, finally, to halt retreat. The models that best fit available data require a rather low shear stress between the ice shelf and its sides, and this implies that rapid shear in this region encouraged the formation of a band of ice with a preferred crystal fabric, as appears to be happening today in the floating portions of fast bounded glaciers.Rebound of the seabed after the ice sheet had retreated to an equilibrium position would allow the ice sheet to advance once more. This may be taking place today since analysis of data from the Ross Ice Shelf indicates that the southeast corner is probably growing thicker with time, and if this persists then large areas of ice shelf must become grounded. This would restrict drainage from West Antarctic ice streams which would tend to thicken and advance their grounding lines into the ice shelf.     

Volume of Antarctic Ice at the Last Glacial Maximum, and its impact on global sea level change

The volume of Antarctic ice at the Last Glacial Maximum is a key factor for calculating the past contribution of melting ice sheets to Late Pleistocene global sea level change. At present, there are large uncertainties in our knowledge of the extent and thickness of the formerly expanded Antarctic ice sheets, and in the timing of their release as meltwater into the world’s oceans. This paper reviews the four main approaches to determining former Antarctic ice volume, namely glacial geology, glacio-isostatic studies, glaciological modelling, and ice core analysis and attempts to reconcile these to give a ‘best estimate’ for ice volume. In the Ross Sea there was a major expansion of grounded ice at the Last Glacial Maximum, accounting for 2.3–3.2 m of global sea level. At some time in the Weddell Sea a large grounded ice sheet corresponding to c. 2.7 m of global sea level extended to the shelf break. However, this ice expansion has not yet been confidently dated and may not relate to the Last Glacial Maximum. Around East Antarctica there was thickening and advance offshore of ice in coastal regions. Ice core evidence suggests that the interior of East Antarctica was either close to its present elevation or thinner during the last glacial so the effect of East Antarctica on sea level depends on the net balance between marginal thickening and interior thinning. Suggested East Antarctic contributions vary from a 3–5.5 m lowering to a 0.64 m rise in global sea level. The Antarctic Peninsula ice sheet thickened and extended offshore at the Last Glacial Maximum, with a sea level equivalent contribution of c. 1.7 m. Thus, the Antarctic ice sheets accounted for between 6.1 and 13.1 m of global sea level fall at the Last Glacial Maximum. This is substantially less than has been suggested by most previous studies but the maximum figure matches well with one modelling estimate. The timing of Antarctic deglaciation is not well known. In the Ross Sea, terrestrial evidence suggests deglaciation may have begun at c. 13,000 yr BP¹ but that grounded ice persisted until c. 6,500 yr BP. Marine evidence suggests the western Ross Sea was deglaciated by c. 11,500 yr BP. Deglaciation of the Weddell Sea is poorly constrained. Grounded ice in the northern Antarctic Peninsula had retreated by c. 13,000 yr BP, and further south deglaciation occurred sometime prior to c. 6,000 yr BP. Many parts of coastal East Antarctica apparently escaped glaciation at the LGM, but in those areas that were ice-covered deglaciation was underway by 10,000 yr BP. With existing data, the timing of deglaciation shows no firm relation to northern hemisphere-driven sea level rise. This is probably due partly to lack of Antarctic dating evidence but also to the combined influence of several forcing mechanisms acting during deglaciation.     

LGM热带西太平洋硅藻席古生产力定量评估

巨型"树荫种"硅藻在成层化大洋中通过"秋季倾泻"勃发模式向深部大洋输出的有机碳通量等于甚至超过"春季勃发"硅藻, 其在第四纪全球气候转型、大洋碳储库演变中的重要地位最近才予以重视.作为大洋碳循环系统的重要参数, 生产力无疑成为探索这一作用的有效窗口.以东菲律宾海的Ethmodiscus rex硅藻席(LDM, laminated diatom mats)岩心WPD-03为材料, 以opal、TOC、bio-Ba等生源组分数据为基础, 运用前人建立的各种生产力经验公式, 试图估算LGM(last glacial maximum)热带西太平洋LDM的古生产力状况.结果显示, LDM沉积期初级生产力、有机碳雨率和埋藏生产力估算合理, 平均分别为248.42 g·m-2·a-1、61.93 g·m-2·a-1和5.27 g·m-2·a-1.估计的初级生产力与代表高生产力的世界大洋各上涌海区可比, 纠正了成层化大洋生产力低下的传统观点, 支持巨型"树荫种"硅藻对大洋有机碳生产与输出的充分贡献.然而, 估算的输出生产力明显不合理, 表明利用基于真光层建立的生产力模型评估次表层水中的巨型"树荫种"硅藻时应格外谨慎, 加强了区别对待"深部"生产力和"表层"生产力的重要性.LGM热带西太平洋LDM的高生产力状况与风尘硅输入的E. rex勃发条件以及还原的沉积环境相一致.      

Modelling Last Glacial Maximum ice cap with the Parallel Ice Sheet Model to infer palaeoclimate in south-west Turkey

Modelling palaeoglaciers in mountainous terrain is challenging due to the need for detailed ice flow computations in relatively narrow and steep valleys, high-resolution climate estimations, knowledge of pre-ice topography, and proxy-based palaeoclimate forcing. The Parallel Ice Sheet Model (PISM), a numerical model that approximates glacier sliding and deformation to simulate large ice sheets such as Greenland and Antarctica, was recently adapted to alpine environments. In an attempt to reconstruct the climate conditions during the Last Glacial Maximum (LGM) on Mount Dedegöl in SW Turkey, we used PISM and explored palaeoglacier dynamics at high spatial resolution (100 m) in a relatively small domain (225 km²). Palaeoice-flow fields were modelled as a function of present temperature and precipitation. Nine different palaeoclimate simulations were run to reach the steady-state glacier extents and the modelled glacial areas were compared with the field-based and chronologically well-established ice extents. Although our results provide a non-unique solution, best-fit scenarios indicate that the LGM climate on Mount Dedegöl was between 9.2 and 10.6 °C colder than today, while precipitation levels were the same as today. More humid (20% wetter) or arid (20% drier) conditions than today bring the palaeotemperature estimates to 7.7–8.8 or 11.5–13.2 °C lower than present, respectively.     

Signature and timing of the Kattegat Ice Stream: onset of the Last Glacial Maximum sequence at the southwestern margin of the Scandinavian Ice Sheet

At the end of the Middle Weichselian (30–25 ka BP) a glacier advance from southern Norway, termed the Kattegat Ice Stream, covered northern Denmark, the Kattegat Sea floor and the Swedish West Coast during onset of the Last Glacial Maximum (LGM) at the southwest margin of the Scandinavian Ice Sheet. The lithostratigraphic unit deposited by the ice stream is the till of the Kattegat Formation (Kattegat till). Because morphological features have been erased by later glacial events, stratigraphic control and timing are decisive. The former ice stream is identified by the dispersal of Oslo indicator erratics from southern Norway and by glaciodynamic structures combined with glaciotectonic deformation of subtill sediments. Ice movement was generally from northerly directions and the flow pattern is fan-shaped in marginal areas. To the east, the Kattegat Ice Stream was flanked by passive glaciers in southern Sweden and its distribution was probably governed by the presence of low permeability and highly deformable marine and lacustrine deposits. When glaciers from southern Norway blocked the Norwegian Channel, former marine basins in the Skagerrak and Kattegat experienced glaciolacustrine conditions around 31–29 ka BP. The Kattegat Ice Stream became active some time between 29 ka BP and 26 ka BP, when glaciers from the Oslo region penetrated deep into the shallow depression occupied by the Kattegat Ice Lake. Deglaciation and an interlude with periglacial and glaciolacustrine sedimentation lasted until c. 24–22 ka BP and were succeeded by the Main Glacier Advance from central Sweden reaching the limit of Late Weichselian glaciations in Denmark around 22–20 ka BP, the peak of the LGM. This was followed by deglaciation and marine inundation in the Kattegat and Skagerrak around 17 ka BP.     

Sea-level history of the Gulf of Mexico since the Last Glacial Maximum with implications for the melting history of the Laurentide Ice Sheet

Sea-level records from the Gulf of Mexico at the Last Glacial Maximum, 20 ka, are up to 35 m higher than time-equivalent sea-level records from equatorial regions. The most popular hypothesis for explaining this disparity has been uplift due to the forebulge created by loading from Mississippi River sediments. Using over 50 new radiocarbon dates as well as existing published data obtained from shallow-marine deposits within the northern Gulf of Mexico and numerical models simulating the impact of loading due to the Mississippi Fan and glacio-hydro-isostasy, we test several possible explanations for this sea-level disparity. We find that neither a large radiocarbon reservoir, sedimentary loading due to the Mississippi Fan, nor large-scale regional uplift can explain this disparity. We do find that with an appropriate model for the Laurentide Ice Sheet, the observations from the Gulf of Mexico can be explained by the process of glacio-hydro-isostasy. Our analysis suggests that in order to explain this disparity one must consider a Laurentide Ice Sheet reconstruction with less ice from 15 ka to its disappearance 6 ka and more ice from the Last Glacial Maximum to 15 ka than some earlier models have suggested. This supports a Laurentide contribution to meltwater pulse 1-A, which could not have come entirely from its southern sector.     

末次冰盛期气候反馈特征研究

末次冰盛期（Last Glacial Maximum,简称LGM）被认为是较适合用来估算气候系统响应对辐射强迫变化的古气候区间之一。理解LGM时期气候反馈过程有助于进一步限定气候敏感度的范围。本研究利用辐射核方法和参加第三次古气候模式比较计划（Paleoclimate Modelling Intercomparison Project Phase Ⅲ,简称PMIP3）的8个耦合模式资料,对比研究了LGM时期与abrupt4xCO₂（4CO₂）情景下的气候反馈特征。结果表明：全球平均而言,不同情景下温度反馈、水汽反馈和反照率反馈的强度存在显著差异,然而这一关系并不存在于云反馈过程中,这可能与情景间/模式间云反馈的不确定性相联系;在不同情景下,不同反馈过程强度也存在明显空间差异。温度反馈过程的差异主要来源于LGM时期大陆冰盖强迫引起的温度变化的高度空间不均一性和海陆分布改变引起的热带对流活动的变化;水汽反馈变化可能与海陆分布变化引起的沃克环流变化以及全球降温相联系;大陆冰盖和海冰存在是导致LGM时期地表反照率反馈增加的主要原因;而云反馈的差异可能与低云云量和模式间不确定性有关。LGM时期单独强迫数值试验将有助于进一步厘清不同气候状态下气候反馈过程差异的原因。

     

The First Discovered Last Glacial Maximum (LGM) Event in the Middle and Lower Region of the Yongding River Basin,Southern Beijing Plain

正Objective LGM is a critical climate period in the late Quaternary and is the most recent extreme cold event.Clark et al.(2009)used 4271 14C records and 475 cosmogenic nuclide datings to define LGM be in 26.5–19.0 ka BP.LGM age often changes with time in different regions(Mix et al.,2001;Zhang Zhigang et al.,2015).However,LGM has not been described to date in the Beijing region.During our field work in 2015–2017,LGM event stratigraphy was     

Maximum extent and readvance dynamics of the Irish Sea Ice Stream and Irish Sea Glacier since the Last Glacial Maximum

The BRITICE-CHRONO Project has generated a suite of recently published radiocarbon ages from deglacial sequences offshore in the Celtic and Irish seas and terrestrial cosmogenic nuclide and optically stimulated luminescence ages from adjacent onshore sites. All published data are integrated here with new geochronological data from Wales in a revised Bayesian analysis that enables reconstruction of ice retreat dynamics across the basin. Patterns and changes in the pace of deglaciation are conditioned more by topographic constraints and internal ice dynamics than by external controls. The data indicate a major but rapid and very short-lived extensive thin ice advance of the Irish Sea Ice Stream (ISIS) more than 300 km south of St George's Channel to a marine calving margin at the shelf break at 25.5 ka; this may have been preceded by extensive ice accumulation plugging the constriction of St George's Channel. The release event between 25 and 26 ka is interpreted to have stimulated fast ice streaming and diverted ice to the west in the northern Irish Sea into the main axis of the marine ISIS away from terrestrial ice terminating in the English Midlands, a process initiating ice stagnation and the formation of an extensive dead ice landscape in the Midlands.     

Predicted relative sea-level changes (18,000 years B.P. to present) caused by late-glacial retreat of the Antarctic Ice Sheet

Predictions of global changes in relative sea level caused by retreat of the Antarctic Ice Sheet from its 18,000 yr B.P. maximum to its present size are calculated numerically. When combined with the global predictions of relative sea-level change resulting from retreat of the Northern Hemisphere ice sheets, the results may be compared directly to observations of sea-level change on the Antarctic continent as well as at distant localities. The comparison of predictions to the few observations of sea-level change on Antarctica supports the view that the Antarctic Ice Sheet was larger 18,000 years ago than at present. The contribution of the Antarctic Ice Sheet to the total eustatic sea-level rise is assumed to be 25 m (25% of the assumed total eustatic rise). If as little as 0.7 m of this 25-m rise occurred between 5000 yr B.P. and the present, few mid-oceanic islands would emerge. If the Antarctic Ice Sheet attained its present dimensions by 6000 yr B.P., however, and if the volume of the ocean has remained constant for the past 5000 years, numerous islands throughout the Southern Hemisphere would emerge. It is suggested that a thorough study of Pacific islands, believed by some to have slightly emerged shorelines of Holocene age, would yield useful information about ocean volume changes during the past 5000 years, and hence on the glacial history of the Antarctic Ice Sheet.     

Radiocarbon constraints on the age of the maximum advance of the British–Irish Ice Sheet in the Celtic Sea

Reconstructions of the British–Irish Ice Sheet (BIIS) during the Last Glacial Maximum (LGM) in the Celtic Sea and southern Ireland have been hampered by a paucity of well-dated stratigraphic records. As a result, the timing of the last advance of the largest outlet of the BIIS, the Irish Sea Ice Stream, to its maximum limit in the Celtic Sea has been variously proposed as being pre-last glaciation, Early Devensian and LGM. The Irish Sea Till was deposited by the Irish Sea Ice Stream during its last advance into the Celtic Sea. We present 26, stratigraphically well constrained, new AMS radiocarbon dates on glacially transported marine shells from the Irish Sea Till in southern Ireland, which constrain the maximum age of this advance. The youngest of these dates indicate that the BIIS advanced to its overall maximum limit in the Celtic Sea after 26,000–20,000 ¹⁴C yr BP, thus during the last glaciation. The most extensive phase of BIIS growth therefore appears to have occurred during the LGM, at least along the Celtic Sea and Irish margins. These data further demonstrate that the uppermost inland glacial tills, from the area of supposed “older drift” in southern Ireland, a region previously regarded as having been unglaciated during the LGM also date from the last glaciation. Thus most of southern Ireland was ice covered at the LGM. Advance of the BIIS to its maximum southern limit in the Celtic Sea may have been a short-lived glaciodynamic response facilitated by subglacial bed conditions, rather than a steady-state response to climate forcing alone.     

A splendid book on the West Antarctic Ice Sheet

Book reviewed in this article:
Van der Veen, C. J. & Oerlemans, J. (eds.) 1986: Dynamics of the West Antarctic Ice Sheet.     

Palaeo-ice streaming in the central sector of the British—Irish Ice Sheet during the Last Glacial Maximum: evidence from the northern Irish Sea Basin

Late Devensian glacial sediments and landforms of the Isle of Man record the advance and deglacial signature of the central sector of the British-Irish Ice Sheet. Evidence from the area, gathered from striae, erratic trains and drift limits, show ice was routed over and around the island in two flow phases post-36 kyr BP. In the south of the island, streamlined depositional bedforms with low elongation ratios suggest low ice-flow velocities resulting from one or more of (i) the up-ice location of the island within a regional onset zone, (ii) flow retardation of ice interacting with the margins of the island and (iii) localized drainage of the deforming bed. The deglacial landform assemblage of lateral marginal sandurs and drainage diversions, coupled with a lack of dead-ice features, suggests ice did not downwaste in situ but retreated intact along the coastal margins as Manx Upland ice thinned. In the north of the island, however, the Bride Moraine complex indicates a change in deglacial ice-sheet dynamics, with temporary re-advance and marginal oscillation causing proglacial tectonism and thrusting of the glacial sediment pile, possibly during the Killard Point Stadial event (18.8-16.4 cal. kyr BP). From a basin-wide perspective, the Irish Sea Basin sector of the British-Irish Ice Sheet had many of the characteristics of an ice stream, such as a zone of flow convergence up-ice, a grounding line in the southern Celtic Sea and recessional limits characterized by proglacially tectonized and thrust dead-ice landscapes indicative of a rapidly oscillating ice margin.     

Chronology of the Last Glacial Maximum in the Salzach palaeoglacier area (Eastern Alps)

A chronostratigraphy based on luminescence data was established at a key loess profile (Duttendorf) in the northern alpine foreland of Austria. The data help to constrain the timing and duration of the Last Glacial Maximum (LGM) in the area of one of the largest east Alpine piedmont glaciers, the Salzach palaeoglacier. Climate deterioration and maximum advance of this glacier were coeval with the beginning of the main loess accumulation phase in the glacier forefield at ～29–30 ka. A late LGM‐outwash gravel layer deposited on top of the loess profile marks the end of the LGM glacier activity at ～20 ka. The geomorphological setting around the loess profile provides evidence of a major glacier oscillation during the course of the LGM, a phenomenon qualitatively known from other alpine palaeoglaciers but never interpreted in terms of palaeoclimate. A LGM glacier oscillation similar to that of the Salzach palaeoglacier was reported recently from the south Alpine Tagliamento palaeoglacier, suggesting a common forcing. The onset of loess deposition at Duttendorf and the tentatively contemporal advance of the Salzach palaeoglacier reflect, as do other data, the drastic cooling in Europe as a result of Heinrich event 3. The first glacier maximum is not well constrained in the study area but a correlation with the better dated Tagliamento amphitheatre suggests a possible response to Heinrich 2. The second re‐advance occurred synchronously (within dating uncertainties) in both palaeoglaciers forefields (at ～21 ka) but the forcing mechanism remains unknown. Copyright © 2011 John Wiley & Sons, Ltd.