The formation of a geometrical ridge network by the surge-type glacier Kongsvegen,Svalbard

Traditionally, geometrical ridge networks are interpreted as the product of the flow of subglacial sediment into open basal crevasses at the cessation of a glacier surge (‘crevasse-fill’ ridges). They are widely regarded as a characteristic landform of glacier surges. Understanding the range of processes by which these ridge networks form is therefore of importance in the recognition of palaeosurges within the landform record. The geometrical ridge network at the surge-type glacier Kongsvegen in Svalbard, does not form by crevasse filling. The networks consist of transverse and longitudinal ridges that can be seen forming at the current ice margin. The transverse ridges form as a result of the incorporation of basal debris along thrust planes within the ice. The thrusts were apparently formed during a glacier surge in 1948. Longitudinal ridges form through the meltout of elongated pods of debris, which on the glacier surface are subparallel to the ice foliation and pre-date the surge. This work adds to the range of landforms associated with glacier surges.     

Imaging glacial sediment inclusions in 3‐D using ground‐penetrating radar at Kongsvegen,Svalbard

The quiescent‐phase surge‐type glacier, Kongsvegen, flows confluent with the continuously fast‐flowing Kronebreen in northwestern Spitsbergen. The lower regions of Kongsvegen overlie glaciomarine sediments, which have been incorporated into the ice during multiple surge events. The resulting englacial structures are exposed at the surface and on a cliff section. These structures have variously been interpreted as thrusts, formed by compression, or sediment‐filled crevasses, formed by extension. We collected a grid of closely spaced ground‐penetrating radar profiles in the area adjacent to the cliff section. Several structures were imaged in 3‐D, including a strong subhorizontal basal reflector, which was underlain by a second, weaker subhorizontal reflector. The basal reflector was occasionally reverse faulted, suggesting compression. Clear englacial features extended upwards from it, dipping up‐glacier at angles of <40° and steepening towards the glacier surface; they had complex geometries that changed rapidly cross‐glacier. The structures were orientated at ～30° to ice flow, suggesting modification by lateral compression from Kronebreen. Some of these englacial structures clearly crossed the basal reflector. We conclude that the englacial features imaged are not likely to be derived from crevasse filling and were probably formed by thrusting. The results contribute to our understanding of surge initiation and termination processes, and interpretation of features in the palaeorecord. Copyright © 2009 John Wiley & Sons, Ltd.     

The landform and sediment assemblage produced by a tidewater glacier surge in Kongsfjorden,Svalbard

This paper describes the landform and sediment assemblage produced by a surge (in 1948) of the Kongsvegen/Kronebreen tidewater glacier complex in northwest Spitsbergen. The main geomorphological products of this advance are two large thrustmoraine complexes on opposite sides of the fjord, and a system of geometrical ridges revealed on glacier decay. The thrust-moraines are composed largely of diamicton, sandy and muddy gravel, gravelly sand, sand and mud, with minor laminites. All of these appear to be derived from the fjord floor and represent both fine fjord basin sediments and coarse grounding-line fan deposits. Thrusting was the principal mode of emplacement of the sediment onto the adjacent land areas during the 1948 advance. However, the geomorphology of the thrust-moraine complexes on either side of the fjord is quite different, reflecting a transpressive regime on the southwest side (mainly long ridges) and a normal compressive regime on the northeast side (short ridges and pinnacles of a ‘hummocky’ nature). The advance which produced the moraine complex has previously been attributed to a surge of Kongsvegen, but the glaciological and geomorphological evidence suggests that the advance involved both Kongsvegen and Kronebreen. Comparison of the landform assemblage produced by this event with that produced by other tidewater glacier surges demonstrates the diverse range of landform assemblages associated with glacier surges, or other episodes of rapid flow, within glaciomarine environments.     

Moraine development at a small High‐Arctic valley glacier: Rieperbreen,Svalbard

Ice‐cored lateral and frontal moraine complexes, formed at the margin of the small, land‐based Rieperbreen glacier, central Svalbard, have been investigated through field observations and interpretations of aerial photographs (1936, 1961 and 1990). The main focus has been on the stratigraphical and dynamic development of these moraines as well as the disintegration processes. The glacier has been wasting down since the ‘Little Ice Age’ (LIA) maximum, and between 1936 and 1990 the glacier surface was lowered by 50–60 m and the front retreated by approximately 900 m. As the glacier wasted, three moraine ridges developed at the front, mainly as melting out of sediments from debris‐rich foliation and debris‐bands formed when the glacier was polythermal, probably during the LIA maximum. The disintegration of the moraines is dominated by wastage of buried ice, sediment gravity‐flows, meltwater activity and some frost weathering. A transverse glacier profile with a northward sloping surface has developed owing to the higher insolation along the south‐facing ice margin. This asymmetric geometry also strongly affects the supraglacial drainage pattern. Lateral moraines have formed along both sides of the glacier, although the insolation aspect of the glacier has resulted in the development of a moraine 60 m high along its northern margin. Copyright © 2001 John Wiley & Sons, Ltd.     

近50年来北极斯瓦尔巴地区冰川物质平衡变化特征

利用长时间序列的冰川物质平衡资料,详细分析了北极斯瓦尔巴地区冰川的物质平衡变化特征以及气候因子对物质平衡的影响。结果表明：近50年来斯瓦尔巴地区冰川物质平衡变化主要呈负平衡、零平衡/略微增长两种状态。冰川净平衡一般为负值,年际变化波动幅度较大且呈负平衡趋势,累积物质平衡表现出长期稳定的负平衡增长态势。除Kongsvegen冰川外,其他冰川不存在短期内的平衡波动。季节变化表现为夏季消融、冬季积累,且夏季消融比冬季积累波动更大,冰川净平衡与夏季消融保持同步变化趋势。冰川净平衡与平衡线高度（ELA）呈负相关（平均相关系数为-0.89）,与积累区面积比率（AAR）呈正相关（平均相关系数为0.84）,该地区大多数冰川AAR减小,说明冰川物质补给处于劣势,冰川物质平衡向负平衡发展。夏季气温升高是斯瓦尔巴地区冰川表面物质加速亏损的直接原因。     

Formation and disintegration of a high-arctic ice-cored moraine complex, Scott Turnerbreen, Svalbard

Englacial debris structures, morphology and sediment distribution at the frontal part and at the proglacial area of the Scott Turnerbreen glacier have been studied through fieldwork and aerial photograph interpretation. The main emphasis has been on processes controlling the morphological development of the proglacial area. Three types of supraglacial ridges have been related to different types of englacial debris bands. We suggest that the sediments were transported in thrusts, along flow lines and in englacial meltwater channels prior to, and during a surge in, the 1930s, before the glacier turned cold. Melting-out of englacial debris and debris that flows down the glacier front has formed an isolating debris cover on the glacier surface, preventing further melting. As the glacier wasted, the stagnant, debris-covered front became separated from the glacier and formed icecored moraine ridges. Three moraine ridges were formed outside the present ice-front. The further glacier wastage formed a low-relief proglacial area with debris-flow deposits resting directly on glacier ice. Melting of this buried ice initiated a second phase of slides and debris flows with a flow direction independent of the present glacier surface. The rapid disintegration of the proglacial morphology is mainly caused by slides and stream erosion that uncover buried ice and often cause sediments to be transported into the main river and out of the proglacial area. Inactive stream channels are probably one of the morphological elements that have the best potential for preservation in a wasting ice-cored moraine complex and may indicate former ice-front positions.     

Surge dynamics of Aavatsmarkbreen,Svalbard, inferred from the geomorphological record

This study investigated the surge dynamics of Aavatsmarkbreen, a glacier in Svalbard and its geomorphological impact based on remote sensing data and field observations. The main objective was to analyse and classify subglacial and supraglacial landforms in the context of glacial deformation and basal sliding over a thin layer of thawed, water‐saturated deposits. The study also focused on the geomorphological evidence of surge‐related sub‐ and supraglacial crevassing and glacier front fracturing. From 2006 to 2013, the average recession of Aavatsmarkbreen was 363 m (52 m a⁻¹). A subsequent surge during 2013–2015 resulted in a substantial advance of the glacier front of over 1 km and an increase in its surface area of more than 2 km². The surface of Aavatsmarkbreen was severely fractured. Significant ice‐flow acceleration was noted whereby the highest surface velocity reached 4.9 m day⁻¹. The ephemeral water‐escape structures and mini‐flutings on the fine‐grained till surface that formed during the surge are indicative of high subglacial pore‐water pressure and enhanced basal sliding. Two genetic types of clast pavements occur in the marginal zone of Aavatsmarkbreen. The results of this study will help to constrain glaciological and geomorphological processes involved in surge phenomena. Understanding the scale and effects of these processes provides insight into the behaviour of fast‐flowing glaciers and ice streams and reveals their relationships with external factors.     

Holocene glacial evolution of Mohnbukta in eastern Spitsbergen

Submarine geomorphology is one of the main tools for understanding past fluctuations of tidewater glaciers. In this study we investigate the glacial history of Mohnbukta, on the east coast of Spitsbergen, Svalbard, by combining multibeam‐bathymetric data, marine sediment cores and remote sensing data. Presently, three tidewater glaciers, Heuglinbreen, Königsbergbreen and Hayesbreen calve into Mohnbukta. Hayesbreen surged at the end of the Little Ice Age, between 1901 and 1910. The submarine landform assemblage in Mohnbukta contains two large transverse ridges, interpreted as terminal moraines, with debrisflow lobes on their distal slopes and sets of well‐preserved geometric networks of ridges, interpreted as crevasse‐squeeze ridges inshore of the moraines. The arrangement of crevasse‐squeeze ridges suggests that both landform sets were produced during surge‐type advances. The terminus position of the 1901–1910 Hayesbreen surge correlates with the inner (R.2) terminal moraine ridge suggesting that the R.1 ridge formed prior to 1901. Marine sediment cores display ¹⁴C ages between 5700–7700 cal. a BP derived from benthic foraminifera, from a clast‐rich mud unit. This unit represents pre‐surge unconsolidated Holocene sediments pushed in front of the glacier terminus and mixed up during the 1901 surge. An absence of retreat moraines in the deeper part of the inner basin and the observation of tabular icebergs calving off the glacier front during retreat suggest that the front of Hayesbreen was close to flotation, at least in the deeper parts of the basin. As the MOH15‐01 core does not penetrate into a subglacial till and the foraminifera in the samples were well preserved, the R.1 ridge is suggested to have formed prior to the deposition of the foraminifera. Based on these data we propose that a surge‐type advance occurred in Mohnbukta in the early Holocene, prior to 7700 cal. a BP, which in turn indicates that glaciers can switch to and from surge mode.     

Sedimentology of a debris‐rich,perhumid valley glacier margin in the Rakaia Valley,South Island,New Zealand

The sedimentology and stratigraphy of a multi‐phase glaciation sequence dating to Marine Isotope Stage 6 in the Rakaia Valley, South Island, New Zealand, is presented. This outcrop presents an example of the depositional signature of an end member of temperate valley glaciation, where voluminous sediment supply in a tectonically active setting combines with high annual temperatures and low seasonality to generate significant year‐round glacifluvial activity. Such glacial systems produce geological–climatic units that are dominated by thick sequences of aggradational gravels and proglacial lake sediments trapped behind outwash heads during deglaciation. At Bayfields Cliff, outwash sequences record an oscillating glacier margin marked by a sequence of glacier‐fed, Gilbert‐type deltas. The deltas are cut by numerous small‐scale, syndepositional, normal faults indicating both loss of glacier support and melt‐out of buried ice. A larger‐scale thrust fault system reflects late‐stage ice overrun. Braid plain gravels and chaotic disturbed glacial lake sediments are also recorded. A notable feature of these systems is the virtual absence of till in an environment with much other evidence for proximal ice. Cumulatively we regard these sediment–landform associations as diagnostic of debris‐laden, perhumid, temperate valley glacier systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Structure and composition of a tidewater glacier push moraine, Svalbard, revealed by DC resistivity profiling

A push moraine deposited by the surging tidewater glacier Paulabreen (Svalbard) was investigated using 2D resistivity profiling. Six longitudinal and transverse profiles were obtained on the moraine and the resistivities were compared with data from three boreholes. Four profiles indicate that the inner part of the moraine is ice-cored and that the buried glacier ice is more than 30 m thick. A transverse profile shows evidence of basal crevasses near the former glacier margin. Three profiles cross the former glacier margin and onto a proglacial plain which dips slightly away from the former glacier margin. Low resistivities were encountered where borehole and field observations indicate that the plain consists of marine muds with a high salt content. This landform has previously been interpreted as a slab of seabed pushed up in front of the surging glacier, possibly facilitated by permafrost in the seabed. We suggest, alternatively, that the landform originated from sediments extruded from below (or pushed in front of) the glacier at the surge terminus and deposited as a debrisflow. Ground penetrating radar can reveal small-scale structures, but larger structures and overall composition are better imaged by resistivity measurements.     

Svalbard glaciers re‐advanced during the Pleistocene–Holocene transition

Despite warming regional conditions and our general understanding of the deglaciation, a variety of data suggest glaciers re‐advanced on Svalbard during the Lateglacial–early Holocene (LGEH). We present the first well‐dated end moraine formed during the LGEH in De Geerbukta, NE Spitsbergen. This landform was deposited by an outlet glacier re‐advancing into a fjord extending 4.4 km beyond the late Holocene (LH) maximum. Comparing the timing of the De Geerbukta glacier re‐advance to a synthesis of existing data including four palaeoclimate records and 15 other proposed glacier advances from Svalbard does not suggest any clear synchronicity in glacial and climatic events. Furthermore, we introduce six additional locations where glacier moraines have been wave‐washed or cut by postglacial raised marine shorelines, suggesting the landforms were deposited before or during high relative sea‐level stands, thus exhibiting a similar LGEH age. Contrary to current understanding, our new evidence suggests that the LGEH glaciers were more dynamic, exhibited re‐advances and extended well beyond the extensively studied LH glacial expansion. Given the widespread occurrence of the LGEH glacier deposits on Svalbard, we suggest that the culmination of the Neoglacial advances during the Little Ice Age does not mark the maximum extent of most Svalbard glaciers since deglaciation; it is just the most studied and most visible in the geological record.     

青藏高原东南部贡嘎山海螺沟冰川冰下沉积物形成与变形

冰岩界面的冰川动力学是冰川系统的重要组成部分, 海螺沟冰川地处温暖湿润的海洋环境, 冰川运动速度较快, 冰川底部接近压融点, 是研究冰下过程的较理想地点. 在海螺沟冰川大型磨光面上浅显侵蚀坑内发现了碎屑物质. 对碎屑物质理化特征研究表明: 粒度特征、地球化学与石英砂SEM 分析表明沉积在冰岩界面上的物质来自于冰川底部的底碛层, 而不是冰上环境的产物. 偏光显微镜下观察到的冰下沉积物呈现出一系列塑性变形(微旋转、褶皱)和脆性变形(线性结构、支撑结构、断层)微观结构和构造. 两种变形结构的存在是碎屑物质在形成过程中其含水量波动情况的反映. 冰下碎屑物质是冰下融出、滞碛作用的共同产物. 在整个冰下碎屑物质形成与变形过程中, 由于冰下水系季节性变化带来的冰岩界面上冰川融水含量的波动起了决定性作用.     

The ice-dammed lakes of Ossian Sarsfjellet (Svalbard): their geomorphology and significance

The tidewater glacier complex of Kongsvegen/Kronebreen, at the head of Kongsfjorden in north-west Spitsbergen, has advanced rapidly several times since its Neoglacial maximum. Two such advances, 1869 and 1948, are well constrained in time and space and are widely interpreted as glacier surges. During the 1869 advance an ice-dammed lake formed on the western side of Ossian Sarsfjellet. This ice-dammed lake is associated with a thrust moraine complex. Four lake levels are identified, two of which are associated with rock-cut shorelines implying a degree of lake stability. The history of this lake, the nature of the ice dam and its relationship to the thrust moraine complex are discussed. The lake history spanning 28 to 35 years is used to assess the ice-marginal dynamics of the Kongsvegen/Kronebreen glacier. It is concluded that, contrary to previous suggestions, the rapid advance of this tidewater glacier may simply be an example of a non-climatic ice-marginal fluctuation, of the type common to tidewater glacier, as opposed to a glacier surge. A second ice-dammed lake, to the east of Ossian Sarsfjellet, formed sometime after 1869 as the ice retreated, and still exists today. This largely supraglacial lake is associated with a very different geomorphological assemblage, which has a poor long-term preservation potential. The geomorphological characteristics of the two lakes on Ossian Sarsfjellet are compared and used to discuss the problems associated with the recognition of ice-dammed lakes within the Pleistocene record. On the basis of the evidence presented here, ice-dammed lakes may be more common during deglaciation than currently suggested.     

Subglacial deformation at sub-freezing temperatures? Evidence from Hagafellsjökull-Eystri,Iceland

We report evidence of deformation at sub-freezing temperatures beneath Hagafellsjökull-Eystri, an Icelandic surge-type glacier. The bed of a piedmont lobe that advanced during the 1999 surge comprises deformed blocks of glacier ice set within frozen sediment. This material has also been injected through overlying ice to form a network of crevasse-squeeze ridges. This layer contains evidence for two phases of deformation under contrasting rheological conditions: (1) deformation under relatively warm conditions, when the blocks of glacier ice acted as competent clasts within an unfrozen deforming matrix and (2) subsequent deformation at sub-freezing temperatures when the ice blocks were attenuated into the surrounding frozen matrix along fractures and planar shears enriched with excess ice. This suggests that the basal thermal regime of the advancing ice margin changed from warm-based to cold-based during the surge event. The persistence and potential prevalence of subglacial sediment deformation at sub-freezing temperatures has fundamental implications for our understanding of the dynamic behaviour, sediment flux and geomorphic ability of cold-based glaciers.     

Sediment‐rich meltwater plumes and ice‐proximal fans at the margins of modern and ancient tidewater glaciers: Observations and modelling

Turbid meltwater plumes and ice‐proximal fans occur where subglacial streams reach the grounded marine margins of modern and ancient tidewater glaciers. However, the spacing and temporal stability of these subglacial channels is poorly understood. This has significant implications for understanding the geometry and distribution of Quaternary and ancient ice‐proximal fans that can form important aquifers and hydrocarbon reservoirs. Remote‐sensing and numerical‐modelling techniques are applied to the 200 km long marine margin of a Svalbard ice cap, Austfonna, to quantify turbid meltwater‐plume distribution and predict its temporal stability. Results are combined with observations from geophysical data close to the modern ice front to refine existing depositional models for ice‐proximal fans. Plumes are spaced ca 3 km apart and their distribution along the ice front is stable over decades. Numerical modelling also predicts the drainage pattern and meltwater discharge beneath the ice cap; modelled water‐routing patterns are in reasonable agreement with satellite‐mapped plume locations. However, glacial retreat of several kilometres over the past 40 years has limited build‐up of significant ice‐proximal fans. A single fan and moraine ridge is noted from marine‐geophysical surveys. Closer to the ice front there are smaller recessional moraines and polygonal sediment lobes but no identifiable fans. Schematic models of ice‐proximal deposits represent varying glacier‐terminus stability: (i) stable terminus where meltwater sedimentation produces an ice‐proximal fan; (ii) quasi‐stable terminus, where glacier readvance pushes or thrusts up ice‐proximal deposits into a morainal bank; and (iii) retreating terminus, with short still‐stands, allowing only small sediment lobes to build up at melt‐stream portals. These modern investigations are complemented with outcrop and subsurface observations and numerical modelling of an ancient, Ordovician glacial system. Thick turbidite successions and large fans in the Late Ordovician suggest either high‐magnitude events or sustained high discharge, consistent with a relatively mild palaeo‐glacial setting for the former North African ice sheet.     

Basal processes beneath an Arctic glacier and their geomorphic imprint after a surge, Elisebreen, Svalbard

The foreground of Elisebreen, a retreating valley glacier in West Svalbard, exhibits a well-preserved assemblage of subglacial landforms including ice-flow parallel ridges (flutings), ice-flow oblique ridges (crevasse-fill features), and meandering ridges (infill of basal meltwater conduits). Other landforms are thrust-block moraine, hummocky terrain, and drumlinoid hills. We argue in agreement with geomorphological models that this landform assemblage was generated by ice-flow instability, possibly a surge, which took place in the past when the ice was thicker and the bed warmer. The surge likely occurred due to elevated pore-water pressure in a thin layer of thawed and water-saturated till that separated glacier ice from a frozen substratum. Termination may have been caused by a combination of water drainage and loss of lubricating sediment. Sedimentological investigations indicate that key landforms may be formed by weak till oozing into basal cavities and crevasses, opening in response to accelerated ice flow, and into water conduits abandoned during rearrangement of the basal water system. Today, Elisebreen may no longer have surge potential due to its diminished size. The ability to identify ice-flow instability from geomorphological criteria is important in deglaciated terrain as well as in regions where ice dynamics are adapting to climate change.     

Climatic control of the surge periodicity of an Icelandic outlet glacier

Surging outlet glaciers are important in draining large ice caps, but the mechanisms controlling surge periodicities are poorly known. We investigated a sediment sequence from the glacier‐fed Lake Lögurinn in eastern Iceland, and our unique annually resolved data, based on sedimentary varves, imply that Eyjabakkajökull, an outlet glacier of Vatnajökull, began surging about 2200 cal a BP (before 1950 AD). Approximately 1700 cal a BP, the glacier started to surge at a uniform 34‐ to 38‐year periodicity that prevailed until the coldest part of the Little Ice Age when the periodicity almost halved to 21–23 years. Since the late 1800 s the surge periodicity of Eyjabakkajökull has returned to a longer period of 35–40 years. We suggest that surge periodicities of Eyjabakkajökull are forced by climatically driven mass balance changes, which may be a common forcing factor for similar surge‐type outlet glaciers. Copyright © 2011 John Wiley & Sons, Ltd.     

山东蒙山九龙潭冰川堆积“垄槽序列”的特征及演化过程研究——兼论冰川、泥石流堆积序列的差异性

中国东部中低山区是否存在第四纪冰川已经争议了一个世纪,作为东部地区冰川堆积重要依据的"泥砾"（冰碛）,一直被持非冰川观点者称作是泥石流沉积物。但是,由于冰川与泥石流的堆积过程之间存在本质差别,这必然在堆积体的特征上表现出专属性差异。因此建立冰川与泥石流在堆积特征与堆积过程上的专属性差异,在冰碛物的成因分析、冰碛堆积过程恢复上就有着重要意义。文章在对比分析了冰川堆积与泥石流堆积的过程差异的基础上,发现两类堆积体在平面与剖面上都存在明确的专属性差别。冰川冰碛在平面上形成专属性的垄槽序列,剖面上显示为无层理、混杂堆积状态。泥石流形成堆积扇,扇面上呈放射状垄岗堆积,剖面上表现为韵律序列。这是区别冰川与泥石流堆积体的本质所在。在此基础上,对蒙山九龙潭一带混杂堆积体进行调查与恢复,发现其具有典型的冰川成因垄槽序列特征,结合其剖面上表现为无层理、混杂堆积特征,从沉积序列与沉积过程的角度,佐证了蒙山九龙潭混杂堆积为第四纪冰川作用的事实。垄槽序列既是堆积物是否为冰川作用属性判断的专属性特征,也是恢复冰碛堆积体基本地貌特征与堆积过程的理论基础。     

Are there any relict rock glaciers in the British mountains?

The existence of a small population of ‘relict rock glaciers’ scattered across the main British mountain areas has previously been inferred from published cases of individual sites or local clusters. Discrete debris accumulations (DDAs) of widely differing character have been identified as ice‐debris landforms (whether ‘rock glaciers’ or ‘protalus lobes’) partly from morphological, sedimentological and topo‐locational evidence, but principally by analogy with both active and relict examples in present‐day arctic/alpine environments, with consequent palaeoclimate inferences. However, re‐interpretation of several supposed rock glaciers as rock slope failures has cast doubt on both the palaeoclimatic reconstructions and the origin of the remaining features. Issues of polygenesis and mimicry/equifinality have contributed to some previous misidentifications. We re‐evaluate the 28 candidate cases based on new field and image‐analysis evidence and place them on a continuum from no ice presence through passive ice presence and glacial shaping to emplacement onto glacier ice with consequent melt‐out topography. A null hypothesis approach (that there are no relict rock glaciers in the British mountains) is pursued, and the evidence indicates that none of the 28 cases clearly warrants classification as a relict rock glacier; their characteristics can be explained without recourse to any significant forward debris movement controlled or facilitated by incorporated or underlying ice as it deforms and melts out. However, only one‐third of the candidate DDAs are attributed in whole or part to rock slope failure (sensu stricto), with other debris sources including incremental rockfall, bedrock knolls with coarse debris veneer, protalus rampart and moraine. A few cases deserve more detailed investigation of their structure, morphology and sediments within a broader local glaciological/topographical context, with multitemporal/polygenetic evolution in mind. But it is for future researchers to demonstrate that deforming ice played an incontestable part in shaping these often enigmatic DDAs, given that other causes are simpler and commoner. Copyright © 2013 John Wiley & Sons, Ltd.     

High‐resolution proglacial lake records of pre‐Little Ice Age glacier advance,northeast Greenland

Understanding Arctic glacier sensitivity is key to predicting future response to air temperature rise. Previous studies have used proglacial lake sediment records to reconstruct Holocene glacier advance–retreat patterns in South and West Greenland, but high‐resolution glacier records from High Arctic Greenland are scarce, despite the sensitivity of this region to future climate change. Detailed geochemical analysis of proglacial lake sediments close to Zackenberg, northeast Greenland, provides the first high‐resolution record of Late Holocene High Arctic glacier behaviour. Three phases of glacier advance have occurred in the last 2000 years. The first two phases (c. 1320–800 cal. a BP) occurred prior to the Little Ice Age (LIA), and correspond to the Dark Ages Cold Period and the Medieval Climate Anomaly. The third phase (c. 700 cal. a BP), representing a smaller scale glacier oscillation, is associated with the onset of the LIA. Our results are consistent with recent evidence of pre‐LIA glacier advance in other parts of the Arctic, including South and West Greenland, Svalbard, and Canada. The sub‐millennial glacier fluctuations identified in the Madsen Lake succession are not preserved in the moraine record. Importantly, coupled XRF and XRD analysis has effectively identified a phase of ice advance that is not visible by sedimentology alone. This highlights the value of high‐resolution geochemical analysis of lake sediments to establish rapid glacier advance–retreat patterns in regions where chronological and morphostratigraphical control is limited.