Lateglacial and early Holocene palaeoclimatic reconstruction based on glacier fluctuations and equilibrium‐line altitudes at northern Folgefonna,Hardanger, western Norway

Northern Folgefonna (c. 23 km²), is a nearly circular maritime ice cap located on the Folgefonna Peninsula in Hardanger, western Norway. By combining the position of marginal moraines with AMS radiocarbon dated glacier‐meltwater induced sediments in proglacial lakes draining northern Folgefonna, a continuous high‐resolution record of variations in glacier size and equilibrium‐line altitudes (ELAs) during the Lateglacial and early Holocene has been obtained. After the termination of the Younger Dryas (c. 11 500 cal. yr BP), a short‐lived (100–150 years) climatically induced glacier readvance termed the ‘Jondal Event 1’ occurred within the ‘Preboreal Oscillation’ (PBO) c. 11 100 cal. yr BP. Bracketed to 10 550–10 450 cal. yr BP, a second glacier readvance is named the ‘Jondal Event 2’. A third readvance occurred about 10 000 cal. yr BP and corresponds with the ‘Erdalen Event 1’ recorded at Jostedalsbreen. An exponential relationship between mean solid winter precipitation and ablation‐season temperature at the ELA of Norwegian glaciers is used to reconstruct former variations in winter precipitation based on the corresponding ELA and an independent proxy for summer temperature. Compared to the present, the Younger Dryas was much colder and drier, the ‘Jondal Event 1’/PBO was colder and somewhat drier, and the ‘Jondal Event 2’ was much wetter. The ‘Erdalen Event 1’ started as rather dry and terminated as somewhat wetter. Variations in glacier magnitude/ELAs and corresponding palaeoclimatic reconstructions at northern Folgefonna suggest that low‐altitude cirque glaciers (lowest altitude of marginal moraines 290 m) in the area existed for the last time during the Younger Dryas. These low‐altitude cirque glaciers of suggested Younger Dryas age do not fit into the previous reconstructions of the Younger Dryas ice sheet in Hardanger. Copyright © 2005 John Wiley & Sons, Ltd.     

The Younger Dryas glaciation in the southeastern Monadhliath Mountains,Scotland: glacier reconstruction and palaeoclimate implications

Geomorphological mapping of locally nourished glaciers was conducted in four glens in the southeastern Monadhliath Mountains, Scotland. Three glaciers are interpreted to be of Younger Dryas age based on geomorphological similarity to features in other Scottish upland areas known to have been glaciated during the Younger Dryas, and on comparison to adjacent ice‐free areas in the lower glens where landform‐sediment assemblages typically reflect peri/paraglacial readjustment during the stadial. Here we reconstruct Younger Dryas glacier termini based on moraine alignments and associated geomorphological and sedimentological evidence. An adjacent wide plateau area at high altitude may have permitted extensive ice accumulation, but no unequivocal geomorphological signature is evident. To establish upper glacier limits, a series of ice profiles are modelled. The results yield a range of realistic glacier configurations bracketed between two distinct scenarios: a valley glaciation with the glaciers' upper limit on the plateau edge, and a low‐domed icecap centred on the plateau with ice flowing radially into the lower glens. Reconstructed equilibrium‐line altitudes are 795 m a.s.l. for the valley‐glacier scenario and 894 m a.s.l. for the icecap scenario. Calculated mean ablation‐season temperatures at the ELA are 1.2°C and 0.4°C for the valley‐glacier and the icecap scenario, respectively, from which we infer mean annual precipitation rates between 323 and 520 mm a^?1. Palaeoclimate results indicate a stadial climate in central Scotland 65–79% more arid than at present, comparable to that of western Norway for the stadial and to the present‐day Canadian Arctic.     

Topographic controls on plateau icefield recession: insights from the Younger Dryas Monadhliath Icefield,Scotland

Plateau icefields are a common form of mountain ice mass, frequently found in mid‐latitude to high‐arctic regions and increasingly recognized in the Quaternary record. Their top‐heavy hypsometry makes them highly sensitive to changes in climate when the equilibriaum line altitude (ELA) lies above the plateau edge, allowing ice to expand significantly as regional ELAs decrease, and causing rapid recession as climate warms. With respect to future climate warming, it is important to understand the controls on plateau icefield response to climate change in order to better predict recession rates, with implications for water resources and sea‐level rise. Improving knowledge of the controls on glacier recession may also enable further palaeoclimatic information to be extracted from the Quaternary glacial record. We use the distribution of moraines to examine topographic controls on Younger Dryas icefield recession in Scotland. We find that overall valley morphology influences the style of recession, through microclimatic and geometric controls, with bed gradient affecting moraine spacing. Ice mass reconfiguration may occur as recession progresses because ice divide migration could alter the expected response based on hypsometric distribution. These results add to a growing body of research examining controls on glacier recession and offer a step towards unravelling non‐linear ice mass behaviour. Copyright © 2019 John Wiley & Sons, Ltd.     

The last Welsh Ice Cap: Part 2 – Dynamics of a topographically controlled icecap

During the Last Glacial Maximum, the British–Irish Ice Sheet was dominated by a number of accumulation centres, including a terrestrially based, semi‐independent icecap centred on Wales. The dynamics of this Welsh Ice Cap (WIC) over the last glacial period are still relatively poorly understood, with few studies taking into consideration the dynamic evolution of the icecap as a whole. Here we contrast results from two modelled reconstructions of the WIC in conjunction with the wider glacial geomorphological record to elucidate understanding of its form, extent and dynamics. Model output was analysed to yield zones of high basal motion and the spatial distribution of potential glacial erosion. We conclude that coherent flowsets of streamlined bedforms are linked to fast‐flowing outlets dominated by basal sliding. Large‐scale changes in dynamics are discussed, with a number of possible major advances proposed over the glacial cycle. Maximum ice thicknesses of ～1200 m in Mid Wales indicate that all mountain summits were probably ice‐covered during the Last Glacial Maximum, even if it was with a thin protective mantle of cold‐based ice, leading to landscape preservation of these upland zones. The distribution, dynamism and landscape modification related to the WIC are further discussed at the regional scale. Model predictions of glacier distribution through the Younger Dryas stadial accord well with geologically reconstructed limits at this time.     

Pre-Younger Dryas resurgence of the southwestern margin of the Cordilleran ice sheet, British Columbia, Canada

Clague, J. J., Mathewes, R. W., Guilbault, J.-P., Hutchinson, I. & Ricketts, B. D. 1997 (September): Pre-Younger Dryas resurgence of the southwestern margin of the Cordilleran ice sheet, British Columbia, Canada. Boreas , Vol. 26, pp. 261–278. Oslo. ISSN 0300–9483.
A lobe of the Cordilleran ice sheet readvanced into the central Fvaser Lowland, southwestern British Columbia, Canada, on at least two occasions near the end of the last glaciation. This ice also flowed into the previously deglaciated, lower reaches of mountain valleys adjacent to the Fraser Lowland and into Washington state. The first of these advances occurred before about 11900 BP and ended with glacier retreat and the establishment of lodgepole pine forest on newly deglaciated terrain. Parts of this forest were overridden by ice during a second advance, shortly after 11300 BP. The younger advance is most likely older than the Younger Dryas Chronozone (11000–10000 BP) and may correlate with an intra-Allerad cooling event (the Killarney-Gerzensee oscillation). The older advance may have occurred during the Oldest Dryas or Older Dryas cold period. Non-climatic factors could also be involved, as emergence of the Fraser Lowland before the older advance greatly reduced or eliminated calving at the glacier margin and thus altered the mass balance of the ice lobe.     

Stratigraphical signatures of glacier activity,marine processes and a possible tsunami in the Leirfjorden fjord‐valley system,north Norway

An integrated interpretation of on‐ and offshore stratigraphical records at Leirfjorden, north Norway, reveals new aspects of the area's palaeoenvironmental history. The study is based on marine sparker data and well‐exposed sections on land that were analysed for their sediment facies, mineralogy and fossil assemblages. Existing research and new radiocarbon dates provide a chronological framework for the interpretation. The late Younger Dryas Nordli substage type locality in the Leirfjorden catchment is revised and found to reflect local glacial activity, maybe a collapse of stagnant ice rather than glacier advance, while late Younger Dryas to Preboreal glacier re‐advances south of Leirfjorden and near Ranfjorden are here named the Bardal substage. The stratigraphical record includes pre‐Younger Dryas, valley‐crossing, glacial striae and old till with provenance of resistant bedrock typical of more elevated mountain areas. It differs from younger till units representing topographically controlled glacier movement. Part of the Leirfjorden fjord‐valley system is located between the main glacial and fluvial drainage paths affecting the sediment supply. As a result, highstand deposits are indistinct and fluvial sediments form only a minor part of the forced‐regressive systems tract. Instead, the valley fill overlying till and subtill sediments is dominated by the deglacial transgressive tract and a forced‐regressive systems tract with composite marine deposits and various marine erosion surfaces. A special event bed is interpreted as a possible tsunami deposit caused by seismicity and/or mass‐wasting in the fjord following glacier retreat. The study highlights the stratigraphical complexity of interconnected fjord and sound systems in a low accretion setting.     

Exposure age dating and Equilibrium Line Altitude reconstruction of an Egesen moraine in the Maritime Alps, Italy

Four boulder samples from the Piano del Praiet frontal moraine in the Gesso della Barra Valley (Maritime Alps) have been ¹⁰Be dated. The results give a weighted mean age of 11 340±370 (870) yr, constraining the frontal moraine to the Egesen glacial stadial, during the Younger Dryas cold phase. By applying the same ¹⁰Be production rate to other Egesen moraines previously dated in the Alps, we obtain similar ages for all of them. This suggests a synchroneity of the Egesen deglaciation in the European Alps at the end of the Younger Dryas. From the palaeoshape of the Egesen glacier, reconstructed by means of geomorphological mapping, an Equilibrium Line Altitude depression (δELA) of −520 to −530 m, with respect to the present-day ELA, and of −260 to −320 m, with respect to the Little Ice Age ELA, has been calculated. Comparison with other Alpine sector δELAs indicates that the Maritime Alps experienced humid climatic conditions during the Younger Dryas.     

The glacial geomorphology of the Loch Lomond (Younger Dryas) Stadial in Britain: a review

This paper systematically reviews the glacial geomorphological evidence of the Loch Lomond Stadial (LLS; Younger Dryas) glaciation in Britain (12.9–11.7 ka). The geomorphology of sub‐regions within Scotland, England and Wales is assessed, providing the most comprehensive synthesis of this evidence to date. The contrasting nature of the evidence at the local scale is reviewed and conceptual themes common to multiple sub‐regions are examined. Advancements in glaciological theory, mapping technologies, numerical modelling and dating have been applied unevenly to localities across Britain, inhibiting a holistic understanding of the extent and dynamics of the LLS glaciation at a regional scale. The quantity and quality of evidence is highly uneven, leading to uncertainties regarding the extent of glaciation and inhibiting detailed analysis of ice dynamics and chronology. Robust dates are relatively scarce, making it difficult to confidently identify the limits of LLS glaciers and assess their synchroneity. Numerical models have allowed the glacier–climate relationships of the LLS to be assessed but have, thus far, been unable to incorporate local conditions which influenced glaciation. Recommendations for future research are made that will allow refined reconstructions of the LLS in Britain and contribute to a more comprehensive understanding of glacier–climate interactions during the Younger Dryas.     

The Younger Dryas climatic conditions in the Za Mnichem Valley (Polish High Tatra Mountains) based on exposure‐age dating and glacier‐climate modelling

Cosmogenic ³⁶Cl was measured in bedrock and moraine boulders in the Za Mnichem Valley (High Tatra Mountains). The post‐LGM deglaciation of the study area occurred about 15.9 ka ago. The northernmost part of the valley slopes was ice‐free around 15 ka ago. The terminal moraine on the valley threshold was finally stabilized 12.5 ka ago during the Younger Dryas cold event (Greenland Stadial 1). At that time, the Za Mnichem glacier was 1.3 km long and had an area of 0.57 km². The AAR equilibrium line of the glacier was located at 1990 m a.s.l., which corresponds to an ELA depression of ～500 m compared to today. The mean summer temperature was colder by 4°–4.5°C than the present‐day temperature. The mean annual temperature was colder by 6°C than today. Such conditions suggest a decrease of the annual precipitation by ～15–25% compared with the present‐day annual average. These data indicate a probable uniform temperature change across central and western Europe, with the precipitation being the most significant factor affecting the mass balance of mountain glaciers. The spatial distribution of balance data suggests increasing continentality towards the east during the Younger Dryas.     

Calendar year age estimates of Allerød–Younger Dryas sea‐level oscillations at Os,western Norway

A detailed shoreline displacement curve documents the Younger Dryas transgression in western Norway. The relative sea‐level rise was more than 9 m in an area which subsequently experienced an emergence of almost 60 m. The sea‐level curve is based on the stratigraphy of six isolation basins with bedrock thresholds. Effort has been made to establish an accurate chronology using a calendar year time‐scale by ¹⁴C wiggle matching and the use of time synchronic markers (the Vedde Ash Bed and the post‐glacial rise in Betula (birch) pollen). The sea‐level curve demonstrates that the Younger Dryas transgression started close to the Allerød–Younger Dryas transition and that the high stand was reached only 200 yr before the Younger Dryas–Holocene boundary. The sea level remained at the high stand for about 300 yr and 100 yr into Holocene it started to fall rapidly. The peak of the Younger Dryas transgression occurred simultaneously with the maximum extent of the ice‐sheet readvance in the area. Our results support earlier geophysical modelling concluding a causal relationship between the Younger Dryas glacier advance and Younger Dryas transgression in western Norway. We argue that the sea‐level curve indicates that the Younger Dryas glacial advance started in the late Allerød or close to the Allerød–Younger Dryas transition. Copyright © 2004 John Wiley & Sons, Ltd.     

An ice cap landsystem for palaeoglaciological reconstructions: characterizing the Younger Dryas in western Scotland

This paper reviews the contrasting behaviours of ice caps and icefields, defines a generic landsystem model that can effectively discriminate between them, and applies the model to landform-sediment assemblages in an area of western Scotland. Such a model is necessary, since many palaeoenvironmental inferences from formerly glaciated terrains are based on the geometry, extent and dynamics of reconstructed ice masses. The validity of these glacier reconstructions is dependent on the accurate initial interpretation of relict landforms and sediments, and their inter-relationships. A new landsystems model is presented here, in which individual geological and geomorphological elements are checked against a set of eight theoretical diagnostic criteria that characterize the style of former glaciation. When applied to a 1200 km² area of the western Scottish Highlands, the landsystem tool predicts (1) an extensive Younger Dryas ice cap with a maximum surface elevation of 900 m above sea level, implying colder or wetter conditions than previously thought, and (2) the survival of an independent mountain icefield in part of the area during deglaciation. Glaciological theory, proxy palaeoenvironmental data and established glacier-climate-topography relationships support these predictions, thereby giving credibility to the landsystem methodology as a generic tool for palaeoglaciological reconstructions.     

Multiple re‐advances of a Lake Vättern outlet glacier during Fennoscandian Ice Sheet retreat,south‐central Sweden

Lake Vättern represents a critical region geographically and dynamically in the deglaciation of the Fennoscandian Ice Sheet. The outlet glacier that occupied the basin and its behaviour during ice‐sheet retreat were key to the development and drainage of the Baltic Ice Lake, dammed just west of the basin, yet its geometry, extent, thickness, margin dynamics, timing and sensitivity to regional retreat forcing are rather poorly known. The submerged sediment archives of Lake Vättern represent a missing component of the regional Swedish deglaciation history. Newly collected geophysical data, including high‐resolution multibeam bathymetry of the lake floor and seismic reflection profiles of southern Lake Vättern, are used here together with a unique 74‐m sediment record recently acquired by drill coring, and with onshore LiDAR‐based geomorphological analysis, to investigate the deglacial environments and dynamics in the basin and its terrestrial environs. Five stratigraphical units comprise a thick subglacial package attributed to the last glacial period (and probably earlier), and an overlying >120‐m deglacial sequence. Three distinct retreat–re‐advance episodes occurred in southern Lake Vättern between the initial deglaciation and the Younger Dryas. In the most recent of these, ice overrode proglacial lake sediments and re‐advanced from north of Visingsö to the southern reaches of the lake, where ice up to 400 m thick encroached on land in a lobate fashion, moulding crag‐and‐tail lineations and depositing till above earlier glacifluvial sediments. This event precedes the Younger Dryas, which our data reveal was probably restricted to north‐central sectors of the basin. These dynamics, and their position within the regional retreat chronology, indicate a highly active ice margin during deglaciation, with retreat rates on average 175 m a^?1. The pronounced topography of the Vättern basin and its deep proglacial‐dammed lake are likely to have encouraged the dynamic behaviour of this major Fennoscandian outlet glacier.     

Late-glacial cirque glaciation in parts of western Norway

Younger Dryas cirque glaciers are known to have existed beyond the Scandinavian Ice Sheet in parts of western Norway. At Kråkenes, on the outermost coast, a cirque glacier formed and subsequently wasted away during the Younger Dryas. No glacier existed there during the Allerød. Large cirque moraines, some with marine deltas and associated fans, extend into the western part of Sykkylvsfjorden. Comparison with existing late-glacial sea-level curves shows that the uppermost marine sediment in these features was deposited well above Younger Dryas sea-level, demonstrating that the cirques were occupied by glaciers before the Younger Dryas. During the Younger Dryas the cirque glaciers expanded, and some advanced across the deltas, depositing till and supplying the sediment to form lower-level fans and deltas controlled by Younger Dryas sea level. The extent of the Younger Dryas advance of some of the glaciers was, at least in part, controlled by grounding on material deposited before the Younger Dryas. The depositional history of the glacial–marine deposits in the Sykkylven area indicates that cirque glaciers existed throughout Late-glacial time and only expanded during the Younger Dryas. The sediment sequence in glacial lakes beyond cirque moraines and reconstructions of glacier equilibrium lines indicate that this was true for most cirques in western Norway. Only on the outermost coast were new glaciers formed in response to Younger Dryas climate cooling. © 1998 John Wiley & Sons Ltd.     

Glaciers and climate in Pacific Far NE Russia during the Last Glacial Maximum

A combined geomorphological–physical model approach is used to generate three‐dimensional reconstructions of glaciers in Pacific Far NE Russia during the global Last glacial Maximum (gLGM). The horizontal dimensions of these ice masses are delineated by moraines, their surface elevations are estimated using an iterative flowline model and temporal constraints upon their margins are derived from published age estimates. The equilibrium line altitudes (ELAs) of these ice masses are estimated, and gLGM climate is reconstructed using a simple degree–day melt model. The results indicate that, during the gLGM, ice masses occupying the Pekulney, Kankaren and Sredinny mountains of Pacific Far NE Russia were of valley glacier and ice field type. These glaciers were between 7 and 80 km in length, and were considerably less extensive than during pre‐LGM phases of advance. gLGM ice masses in these regions had ELAs of between 575 ± 22 m and 1035 ± 41 m (above sea level) – corresponding to an ELA depression of 350–740 m, relative to present. Data indicate that, in the Pekulney Mountains, this ELA depression occurred because of a 6.4°C reduction in mean July temperature, and 200 mm a^?1 reduction in precipitation, relative to present. Thus reconstructions support a restricted view of gLGM glaciation in Pacific Far NE Russia and indicate that the region's aridity precluded the development of large continental ice sheets. Copyright © 2011 John Wiley & Sons, Ltd.     

Evaluating Younger Dryas glacier reconstructions in part of the western Scottish Highlands: a combined empirical and theoretical approach

Current understanding of the Younger Dryas (Loch Lomond Stadial) ice cap in Scotland is dominated by reconstructions derived solely from field evidence. We use an area in the western Scottish Highlands to evaluate three examples of this approach by comparing the proposed glacier reconstructions with new empirical data and the predictions of a high-resolution numerical model. Particular emphasis is placed on accurately determining the maximum surface altitude attained by the ice cap, dominant palaeo-iceflow directions and the style of ice-cap recession. By combining new geomorphological and sedimentological data with model predictions, we present a revised interpretation of the build-up and decay of Loch Lomond Stadial ice in the study area - one that suggests a maximum ice-surface altitude of c. 900 m a.s.l., east and southeastward iceflow and active recession of a dynamic margin. Good agreement between the new field-based interpretation and the predictions of the numerical model validates the latter and by implication extends confidence in its veracity beyond the study area.     

A test of the englacial thrusting hypothesis of ''hummocky'' moraine formation: case studies from the northwest Highlands, Scotland

The melt-out of material contained within englacial thrust planes has been proposed to result in the formation of stacked moraine sequences with characteristic proximal rectilinear slopes. This model has been applied to explain the formation of Scottish Younger Dryas ice-marginal ('hummocky') moraines on the basis of these morphological characteristics. However, no sedimentological data exist to support this proposal. This article reviews hitherto proposed models of 'hummocky' moraine formation and presents detailed geomorphological and sedimentological results from the NW Scottish Highlands with the aims of reconstructing the dynamics of Younger Dryas glaciers and of testing the applicability of the englacial thrusting model. Exposures demonstrate that moraines represent terrestrial ice-contact fans throughout, with a variety of postdepositional deformation structures being identified in most cases, indicating that glacier retreat was incremental and oscillatory; proximal rectilinear slopes are interpreted as ice-contact faces formed after ice support was withdrawn during retreat. This evidence strongly suggests a temperate glacier regime and short glacier response times similar to those in present-day SW Norway or Iceland. It contradicts the thrusting model and the proposal that Svalbard might form a suitable analogue for Younger Dryas moraines in Scotland.     

Deglaciation of western Central Norway

The glacier movements and corresponding ice margins in Central Norway during Younger Dryas and Preboreal are reconstructed. Scattered, older marginal deposits are difficult to correlate. Raised beach features indicate that the deep fjords became ice-free at an early stage due to calving. In Møre og Romsdal county the glacier front lay at the fjord heads during Younger Dryas, with extensive local glaciation in the intervening mountain areas, and a limit of glaciation 500–600 m lower than the present. In certain places local moraines older than Younger Dryas have been preserved. Autochthonous block fields are widespread in the mountains of Møre og Romsdal. The lower limit of block fields lies at c. 500 m above sea level on the outermost coast and rises to c. 1500 m above sea level in the interior fjord country. No erratics, striation or lateral moraines from the inland ice have been found above this limit. Its gradient, which in outer fjord districts is about 1%, seems to indicate the ice surface at the last maximum of Weichsel glaciation.     

Lateglacial and early Holocene dynamics of adjacent valley glaciers in the Western Swiss Alps

The Alps play a pivotal role for glacier and climate reconstructions within Europe. Detailed glacial chronologies provide important insights into mechanisms of glaciation and climate change. We present 26 ¹⁰Be exposure dates of glacially transported boulders situated on moraines and ice‐moulded bedrock samples at the Belalp cirque and the Great Aletsch valley, Switzerland. Weighted mean ages of ～10.9, 11.1, 11.0 and 9.6 ka for the Belalp, on up to six individual moraine ridges, constrain these moraines to the Egesen, Kartell and Schams stadials during Lateglacial to early Holocene times. The weighted mean age of ～12.5 ka for the right‐lateral moraine of the Great Aletsch correlates with the Egesen stadial related to the Younger Dryas cooling. These data indicate that during the early Holocene between ～11.7 and ～9.2 ka, glaciers in the Swiss Alps seem to have been significantly affected by cold climatic conditions initiated during the Younger Dryas and the Preboreal Oscillation. These conditions resulted in glacier margin oscillations relating to climatic fluctuations during the second phase of the Younger Dryas – and continuing into Boreal times – as supported by correlation of the innermost moraine of the Belalp Cirque to the Schams (early) Holocene stage. Copyright © 2011 John Wiley & Sons, Ltd.     

Chronology of glaciation and deglaciation during the Loch Lomond (Younger Dryas) Stade in the Scottish Highlands: implications of recalibrated 10Be exposure ages

Considerable uncertainty surrounds the timing of glacier advance and retreat during the Younger Dryas or Loch Lomond Stade (LLS) in the Scottish Highlands. Some studies favour ice advance until near the end of the stade (c. 11.7 ka), whereas others support the culmination of glacier advance in mid‐stade (c. 12.6–12.4 ka). Most published ¹⁰ Be exposure ages reported for boulders on moraines or deglacial sites post‐date the end of the LLS, and thus appear to favour the former view, but recalibration of 33 ¹⁰ Be ages using a locally derived ¹⁰ Be production rate and assuming rock surface erosion rates of zero to 1 mm ka^?1 produces exposure ages 130–980 years older than those originally reported. The recalibrated ages are filtered to exclude anomalous data, and then employed to generate aggregate probability density distributions for the timing of moraine deposition and deglaciation. The results suggest that the most probable age for the timing of the deposition of the sampled outermost moraines lies in the interval 12.4–12.1 ka or earlier. Deglacial ages obtained for sites inside Loch Lomond Stadial glacier limits imply that glaciers at some or all of the sampled sites were retreating prior to 12.1 ka. Use of aggregated data does not exclude the possibility of asynchronous glacier behaviour at different sites, but confirms that some glaciers reached their maximum limits and began to retreat several centuries before the rapid warming that terminated the LLS at 11.7–11.6 ka, consistent with the retrodictions of recent numerical modelling experiments and with geomorphological evidence for gradual oscillatory ice‐margin retreat under stadial conditions.     

Correlation of Swedish glacial varves with the Greenland (GRIP) oxygen isotope record

A mean varve thickness curve has been constructed for a part of the Swedish varve chronology from the northwestern Baltic proper. The mean varve thickness curve has been correlated with the δ¹⁸O record from the GRIP ice-core using the Younger Dryas–Preboreal climate shift. This climate shift was defined by pollen analyses. The Scandinavian ice-sheet responded to a warming at the end of the Younger Dryas, ca. 10995 to 10700 clay-varve yr BP. Warming is recorded as a sequence of increasing mean varve thickness and ice-rafted debris suggesting intense calving of the ice front. The Younger Dryas–Preboreal climatic shift is dated to ca. 10650 clay-varve yr BP, about 40 yr after the final drainage of the Baltic Ice Lake. Both the pollen spectra and a drastic increase in varve thickness reflect this climatic shift. A climate deterioration, correlated with the Preboreal oscillation, is dated to ca. 10440 to 10320 clay-varve yr BP and coincides with the brackish water phase of the Yoldia Sea stage. The ages of the climatic oscillations at the Younger Dryas–Preboreal transition show an 875 yr discrepancy compared with the GRIP record, suggesting a large error in the Swedish varve chronology in the part younger than ca. 10300 clay-varve yr BP. Copyright © 1999 John Wiley & Sons, Ltd.