ALBERT

Description: McMurdo Sound sea ice can generally be partitioned into two regimes: (1) a stable fast-ice cover, forming south of approximately 77.6∘ S around March–April and then breaking out the following January–February, and (2) a more dynamic region north of 77.6∘ S that the McMurdo Sound and Ross Sea polynyas regularly impact. In 2019, a stable fast-ice cover formed unusually late due to repeated break-out events. We analyse the 2019 sea-ice conditions and relate them to a modified storm index (MSI), a proxy for southerly wind events. We find there is a strong correlation between the timing of break-out events and several unusually large MSI events.

Description: Icequakes are the result of processes occurring within the ice mass or between the ice and its environment. Studying icequakes provides a unique view on ice dynamics, specifically on the basal conditions. Changes in conditions due to environmental or climate changes are reflected in icequakes. Counting and characterizing icequakes is thus essential to monitor them. Most of the icequakes recorded by the seismic station at the Belgian Princess Elisabeth Antarctica Station (PE) have small amplitudes corresponding to maximal displacements of a few nanometres. Their detection threshold is highly variable because of the rapid and strong changes in the local seismic noise level. Therefore, we evaluated the influence of katabatic winds on the noise measured by the well-protected PE surface seismometer. Our purpose is to identify whether the lack of icequake detection during some periods could be associated with variations in the processes generating them or simply with a stronger seismic noise linked to stronger wind conditions. We observed that the wind mainly influences seismic noise at frequencies greater than 1 Hz. The seismic noise power exhibits a bilinear correlation with the wind velocity, with two different slopes at a wind velocity lower and greater than 6 m s−1 and with, for example at a period of 0.26 s, a respective variation of 0.4 dB (m −1 s) and 1.4 dB (m −1 s). These results allowed a synthetic frequency and wind-speed-dependent noise model to be presented that explains the behaviour of the wind-induced seismic noise at PE, which shows that seismic noise amplitude increases exponentially with increasing wind speed. This model enables us to study the influence of the wind on the original seismic dataset, which improves the observation of cryoseismic activity near the PE station.

Description: Severe winter windstorms have become an increasingly common occurrence over recent decades in northwestern Europe. Although there exists considerable uncertainty, storminess is projected to increase in the future. On centennial to millennial time scales in particular, the mechanisms forcing storminess remain unsettled. We contribute to available palaeostorm records by reconstructing changes over the last 6670 years using a coastal peat sequence retrieved from the ombrotrophic Laphroaig bog on Islay, southwestern Scotland. We use a combination of ash content, grain size and elemental chemistry to identify periods of greater storminess, which are dated to 6605, 6290–6225, 5315–5085, 4505, 3900–3635, 3310–3130, 2920–2380, 2275–2190, 2005–1860, 1305–1090, 805–435 and 275 cal. a BP. Storm signals in the first half of the record up to ~3000 cal. a BP are mainly apparent in the grain‐size changes. Samples from this time period also have a different elemental signature than those later in the record. We speculate that this is due to receding sea levels and the consequent establishment of a new sand source in the form of dunes, which are still present today. The most significant events and strongest winds are found during the Iron Ages Cold Epoch (2645 cal. a BP), the transition into, and in the middle of, the Roman Ages Warm Period (2235 and 1965 cal. a BP) and early in the Little Ice Age (545 cal. a BP). The Laphroaig record generally agrees with regionally relevant peat palaeostorm records from Wales and the Outer Hebrides, although the relative importance of the different storm periods is not the same. In general, stormier periods are coeval with cold periods in the region as evidenced by parallels with increased ice‐rafted debris in the North Atlantic, highlighting that sea‐ice conditions could impact future storminess and storm track position.

Description: Holocene sedimentation patterns and environmental development in Aarhus Bay, Denmark, were reconstructed based on proxy analyses of two sediment cores (M1 and M5). Together, the two cores offer an opportunity to examine the history of the area during the past c. 10 000 years. The investigation consisted of acoustic mapping and multi‐proxy analyses of the sediment cores including macrofossils, sediment physical properties, sediment accumulation rates, grain size, and X‐ray fluorescence elemental counts. Radiocarbon dating of the two sediment successions revealed that they cover the periods c. 10 000–3700 cal. a BP (M1) and c. 4400 cal. a BP to the present (M5). The data from the M1 site indicate the presence of a near‐shore lake environment between c. 10 000 and 9000 cal. a BP. The first intrusion of marine water into the area is dated to c. 9000 cal. a BP. In the following c. 1300 years, brackish‐water conditions prevailed in the area characterized by a mixture of taxa from marine, limnic and terrestrial habitats, reflecting a shallow estuarine environment. Around 7700 cal. a BP full marine conditions were established, accompanied by a marked increase in sedimentation rates. The changes to full marine conditions and higher sedimentation rates are probably due to a significant sea‐level rise leading to flooding of former land areas and intensified erosion. A subsequent distinct decrease in sedimentation rates around 6350 cal. a BP is presumably linked to a previously documented sea‐level drop about this time. Continuous sedimentation ceased around 3700 cal. a BP in the central part of the bay, most probably due to a major sea‐level lowering involving widespread erosion. In the eastern and deeper part of the bay, sedimentation continued until today. Fully marine conditions prevailed there for at least the last 4400 years.

Description: 〈b〉Simulated single-layer forest canopies delay Northern Hemisphere snowmelt〈/b〉〈br〉 Markus Todt, Nick Rutter, Christopher G. Fletcher, and Leanne M. Wake〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-270,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 Vegetation is often represented by a single layer in global land models. Studies have found deficient simulation of thermal radiation beneath forest canopies when represented by single-layer vegetation. This study corrects thermal radiation in forests for a global land model using single-layer vegetation in order to assess the effect of deficient thermal radiation on snow cover and snowmelt. Results indicate that single-layer vegetation causes snow in forests being too cold and melting too late.

Description: 〈b〉Brief Communication: Early season snowpack loss and implications for oversnow vehicle recreation travel planning〈/b〉〈br〉 Benjamin J. Hatchett and Hilary G. Eisen〈br〉 The Cryosphere, 13, 21-28, https://doi.org/10.5194/tc-13-21-2019, 2019〈br〉 We examine the timing of early season snowpack relevant to oversnow vehicle (OSV) recreation over the past 3 decades in the Lake Tahoe region (USA). Data from two independent data sources suggest that the timing of achieving sufficient snowpack has shifted later by 2 weeks. Increasing rainfall and more dry days play a role in the later onset. Adaptation strategies are provided for winter travel management planning to address negative impacts of loss of early season snowpack for OSV usage.

Description: 〈b〉Greenland Ice Sheet late-season melt: Investigating multi-scale drivers of K-transect events〈/b〉〈br〉 Thomas J. Ballinger, Thomas L. Mote, Kyle Mattingly, Angela C. Bliss, Edward Hanna, Dirk van As, Melissa Prieto, Saeideh Gharehchahi, Xavier Fettweis, Brice Noël, Paul C. J. P. Smeets, Mads H. Ribergaard, and John Cappelen〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-285,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 Studies have questioned links between Arctic marginal sea open water duration and Greenland Ice Sheet (GrIS) surface balance changes, namely melt events. Through analyses involving observations and climate models, we show that late summer through autumn “unseasonal” melt events are primarily driven by the northward movement of warm, moist air masses across the western ice sheet edge, while near-surface, off-ice winds block heat transfer off nearby Baffin Bay.

Description: 〈b〉Distributed Temperature Profiling System Provides Spatially Dense Measurements and Insights about Permafrost Distribution in an Arctic Watershed〈/b〉〈br〉 Emmanuel Léger, Baptiste Dafflon, Yves Robert, Craig Ulrich, John E. Peterson, Sébastien Biraud, Vladimir E. Romanovsky, and Susan S. Hubbard〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-264,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉Soil temperature has been recognized as a property that strongly influences a myriad of hydro-biogeochemical processes, as well as containing important information on the properties modulating the soil thermal flux. In spite of its importance, our ability to acquire soil temperature data with high spatial and temporal resolution and coverage is limited, because of the high cost of equipment, the difficulties of deployment, and the complexities of data management. Here we propose a new strategy that we call Distributed Temperature Profiling (DTP), which consists of cheap, low-impact, low-power, vertically resolved temperature probes that independently and autonomously record soil temperature. We developed a prototype DTP system for characterizing and monitoring near-surface thermal properties, using an unprecedented number of laterally and vertically distributed temperature measurements. The DTP system was tested in an Arctic ecosystem near Nome, AK, to identify near-surface permafrost distribution and various thermal regimes in a discontinuous permafrost environment during the summer time. Results show that the DTP system enabled successful acquisition of vertically resolved profiles of summer soil temperature over the top 0.8 m at numerous locations. DTP also enabled high resolution identification and lateral delineation of near-surface permafrost locations from surrounding zones with no permafrost or deep permafrost table locations overlain by a perennially thawed layer. The DTP strategy overcomes some of the limitations associated with – and complements the strengths of – borehole-based soil temperature sensing as well as Fiber-Optic Distributed Temperature Sensing (FO-DTS) approaches. Combining DTP data with co-located topographic and vegetation maps obtained using Unmanned Aerial Vehicle (UAV) and Electrical Resistivity Tomography (ERT) data allowed us to identify correspondences between surface and subsurface property distribution, and in particular between topography, vegetation, shallow soil properties, and near-surface permafrost. Finally, the results highlight the considerable value of the newly developed DTP strategy for investigating the significant variability and complexity of subsurface thermal and hydrological regimes in discontinuous permafrost regions.〈/p〉

Description: Quaternary fluvial succession of the Jászság Basin (Hungary) was investigated, challenging the stratigraphical potential of ‘early postglacial fluvial magnetic susceptibility episodes' recognized earlier in the Körös Basin. Low field magnetic susceptibility (MS) was measured in four boreholes from the basin centre and margins, representing channel and flood‐plain environments. Statistical distributions of MS data contain significant sets of outliers, regardless of facies conditions. The downhole distribution of these outliers produces magnetic susceptibility cycles. Supported by magnetic susceptibility cycles, high‐resolution facies correlations were performed reflecting a steady palaeohydrographical situation in the area, with a trunk river to the southeast and tributaries to the northwest. SEM‐EDX data revealed that ferromagnetic grains are responsible for the outlying MS values. The heterogeneous association of magnetite indicates a catchment area with volcanic and metamorphic rocks, while the group of small (〈5 μm) magnetite octahedrons originated from nearby rhyolitic tuff formations. Magnetic grains were transported along channel belts, while small (〈2 μm) magnetic particles were floated onto flood‐plains attached to clays. Climatic control is indicated by peaks at ~100 ka frequency in spectra of MS records and was also detected in palaeosol development and in flood frequency using the spectra of measured colour (~100 ka) and logged resistivity (~100 ka, ~41 ka), respectively. The climate‐dependent MS signal traceable far into the basin in both channel and flood‐plain environments can be summoned when the Quaternary fluvial succession of the Pannonian Basin is investigated, assuming some sources of magnetite in the catchment areas. According to the concept of ‘fluvial magnetic susceptibility episodes’, the early postglacial escape and spreading of the magnetite fraction control the MS signal that can support mapping of the unconformable Quaternary base and building of high‐resolution models of aquifers.

Description: Nares Strait, a major connection between the Arctic Ocean and Baffin Bay, was blocked by coalescent Innuitian and Greenland ice sheets during the last glaciation. This paper focuses on the events and processes leading to the opening of the strait and the environmental response to establishment of the Arctic‐Atlantic throughflow. The study is based on sedimentological, mineralogical and foraminiferal analyses of radiocarbon‐dated cores 2001LSSL‐0014PC and TC from northern Baffin Bay. Radiocarbon dates on benthic foraminifera were calibrated with ΔR = 220±20 years. Basal compact pebbly mud is interpreted as a subglacial deposit formed by glacial overriding of unconsolidated marine sediments. It is overlain by ice‐proximal (red/grey laminated, ice‐proximal glaciomarine unit barren of foraminifera and containing 〉2 mm clasts interpreted as ice‐rafted debris) to ice‐distal (calcareous, grey pebbly mud with foraminifera indicative of a stratified water column with chilled Atlantic Water fauna and species associated with perennial and then seasonal sea ice cover) glacial marine sediment units. The age model indicates ice retreat into Smith Sound as early as c. 11.7 and as late as c. 11.2 cal. ka BP followed by progressively more distal glaciomarine conditions as the ice margin retreated toward the Kennedy Channel. We hypothesize that a distinct IRD layer deposited between 9.3 and 9 (9.4–8.9 1σ) cal. ka BP marks the break‐up of ice in Kennedy Channel resulting in the opening of Nares Strait as an Arctic‐Atlantic throughflow. Overlying foraminiferal assemblages indicate enhanced marine productivity consistent with entry of nutrient‐rich Arctic Surface Water. A pronounced rise in agglutinated foraminifers and sand‐sized diatoms, and loss of detrital calcite characterize the uppermost bioturbated mud, which was deposited after 4.8 (3.67–5.55 1σ) cal. ka BP. The timing of the transition is poorly resolved as it coincides with the slow sedimentation rates that ensued after the ice margins retreated onto land.

Description: Only a few chronological constraints on Lateglacial and Early Holocene glacier variability in the westernmost Alps have hitherto been obtained. In this paper, moraines of two palaeoglaciers in the southern Écrins massif were mapped. The chronology of the stabilization of selected moraines was established through the use of 10Be cosmic ray exposure (CRE) dating. The equilibrium line altitude (ELA) during moraine deposition was reconstructed assuming an accumulation area ratio (AAR) of 0.67. Ten pre‐Little Ice Age (LIA) ice‐marginal positions of the Rougnoux palaeoglacier were identified and seven of these have been dated. The 10Be CRE age of a boulder on the lowermost sampled moraine indicates that the landform may have been first formed during a period of stable glaciers at around 16.2±1.7 ka (kiloyears before AD 2017) or that the sampled boulder experienced pre‐exposure to secondary cosmic radiation. The moraine was re‐occupied or, alternatively, shaped somewhat before 12.2±0.6 ka when the ELA was lowered by 230 m relative to the LIA ELA. At least six periods of stable ice margins occurred thereafter when the ELA was 220–160 m lower than during the LIA. The innermost dated moraine stabilized at or before 10.9±0.7 ka. Three 10Be CRE ages from a moraine of the Prelles palaeoglacier indicate a period of stationary ice margins at or before 10.9±0.6 ka when the ELA was lowered by 160 m with respect to the end of the LIA. The presented 10Be CRE ages are in good agreement with those of moraines that have been attributed to the Egesen stadial. Assuming unchanged precipitation, summer temperature in the southern Écrins massif at ~12 ka must have been at least 2 °C lower relative to the LIA.

Description: Glacial lake outburst floods occurred frequently during the last deglaciation of the Laurentide Ice Sheet. Within the Interior Plains, these floods carved large spillway systems; however, due to a lack of abundant sediment, deposits within prairie spillways are rarely preserved. Here, we present geomorphic and sedimentary evidence and hydraulic modelling of the eastern Beaver River Spillway, formed by the catastrophic drainage of the ice‐dammed glacial Lake Algar, in north central Alberta. During this flood, coarse‐grained sediment eroded from local till formed large pendant bars. Within the first ~50 km of the spillway (Reach 1), pendant bars contain downstream orientated foresets overlain by horizontally bedded coarser gravels. The remaining pendant bars (Reach 2), present downflow of a moraine barrier, differ, comprising massive, matrix‐supported, inversely graded gravels capped by a boulder layer. We use a HEC‐GeoRAS/HEC‐RAS system in conjunction with palaeostage indicators to estimate the steady‐state water surface elevation. Modelling results show that peak discharge within Reach 1 of the eastern Beaver River Spillway was approximately 14 000–21 000 m3 s−1. For Reach 2, 30 km downstream, the peak discharge was estimated at 23 000–40 000 m3 s−1 (nbulked 18 000–26 000 m3 s−1). The downstream discharge increase, consistent with the sedimentary change in pendant bar deposits, is attributed to sediment bulking of the flood flow. This provides the opportunity to observe a range of flow conditions, and associated sedimentology, from a single flood event. The reconstructed flow conditions, coupled with lake volume estimates from the ponding above the moraine barrier suggest a minimum flow duration of 3–5 days.

Description: The azimuth of imbrication of minimum magnetic susceptibility axes in the youngest loess from Ukraine defines prevailing wind directions during aeolian sedimentation. It changes along the studied sections. These changes can be directly correlated with the fluctuations of the Fennoscandian Ice Sheet. The northern and northeastern winds noted in the loess succession separated by a period when southwestern to southeastern winds were predominant may be correlated with two main phases of ice‐sheet advance during the Last Glacial Maximum. The ice‐sheet advances towards the areas of loess deposition generated katabatic winds that influenced aeolian sedimentation in the periglacial zone. A period of relatively stable wind directions during a younger phase of the Last Glacial Maximum was interrupted by periods with more chaotic wind regime most probably caused by fluctuations of the Fennoscandian Ice Sheet during its retreat from the peri‐Baltic part of Europe. These intervals occur where initial soils developed. The distribution of anisotropy of magnetic susceptibility axes defined along the periglacial loess sections from central and eastern Europe can serve to constrain fluctuations of the Fennoscandian Ice Sheet.

Description: Understanding resource utilization and economic diversification amongst Holocene hunter‐gatherers in southern Brazil requires in‐depth taphonomic analysis of faunal assemblages. Three Early to Late Holocene archaeological sites (Garivaldino, Pilger and Sangão) in Rio Grande do Sul State, southern Brazil, revealed large assemblages of small mammal (˂1 kg) remains, composed mainly of rodents. To appreciate depositional processes of fauna in relation to human consumption, taphonomic attributes and processes were evaluated. The results indicated that the remains accumulated through different antemortem taphonomic pathways, apparently linked to the size and natural history of the species represented. The small‐ and medium‐sized (〈150 g) cricetid rodents (e.g. Pseudoryzomys simplex and Sooretamys angouya) were represented by a low proportion of teeth with lightly digestive corrosion suggesting that they were derived from the predatory activity of owls, possibly Tyto alba. In contrast, large‐sized cricetids (〉150 g; Kunsia tomentosus, Gyldenstolpia sp. and Holochilus sp.), and several caviomorph rodents with aggregated spatial distributions (Echimyidae (†Dicolpomys fossor, Phyllomys sp., †Clyomys riograndensis and †Euryzygomatomys mordax), Caviidae (Cavia sp.) and Ctenomyidae (Ctenomys sp.)) showed evidence of thermoalteration patterns and cut marks on bones, suggesting human exploitation. A postmortem depositional environment was deduced from dendritic and branched patterns of rootlet etching, apparent mostly at Garivaldino and Pilger. Polished areas and holes on bone surfaces, and impregnation of manganese showed moderate (Sangão) or low (Garivaldino and Pilger) incidence, pointing to water transport under moderate (Pilger) and low (Garivaldino and Sangão) energy over short distances. The results obtained here provide the first clear evidence of early human exploitation of small mammals in southern Brazil, suggesting a diversification of economies. In addition, as several of the recorded rodents are today regionally or biologically extinct, a preliminary discussion about the potential impact of humans on this process is provided.

Description: The Göschenertal (Göschenen valley) is the type locality of the so‐called Göschenen Cold Phases I (~3–2.3 ka) and II (~1.8–1.1 ka). According to earlier studies, these Late Holocene climatic cooling periods were characterized by changes in vegetation and pronounced glacier advances. As a peculiarity, the Göschenen Cold Phase I was thought to be connected to a local surge‐type advance of the Chelengletscher (Chelen glacier) – an exceptional event of unparalleled dimension in the European Alps. Based on cosmogenic 10Be exposure ages from moraine boulders, we investigated the local glacier chronology. In contrast to former research, moraines at different positions within the Göschenen valley (central Swiss Alps) have been dated to the Younger Dryas and the Early Holocene. This questions the applicability of palaeo‐Equilibrium Line Altitude (ELA) calculations for stadial attributions without additional numerical age constraints. Furthermore, we have found compelling evidence that the proposed non‐climatic glacier advance attributed to the Göschenen Cold Phase I did not occur. The present results, along with a reappraisal of the original study, question the scientific reliability and the glaciological definition of the Göschenen Cold Phases as glacier advances that clearly exceeded the Little Ice Age positions. While our data do not exclude potential changes in climate and vegetation, we nonetheless show that the Göschenen Cold Phases are not suitable as reference stadials in the system of Alpine Holocene glacier fluctuations.

Description: Pronounced climatic warming associated with the Late Weichselian Pleniglacial‐to‐Lateglacial transition caused considerable environmental changes throughout the former periglacial zones (in Europe ~53°–46°N). During permafrost degradation and subsequent ground subsidence (i.e. thermokarst processes), the landscape changed rapidly. In this study we investigated a flat mid‐altitude area in south Bohemia, Czech Republic, lying close to the southern limit of the Weichselian permafrost. We discovered palaeo‐lake basins with sedimentary infillings up to 11 m in depth. According to radiocarbon and palynostratigraphical dating, these basins were formed at the onset of the Late Pleniglacial‐to‐Lateglacial transition, whereas the smaller depressions were formed later. We suggest that the basins resulted from thermal and fluvio‐thermal erosion of the former permafrost and represent remnants of discontinuous gullies and possibly collapsed frost mounds (pingo/lithalsa scars). The formation of this a fossil thermokarst landscape was climatically driven and multiple phased, with the major phase during the climatic warming and wetting at the onset of GI‐1e (Bølling) and the minor phase during GI‐1c (Allerød). This study enhances knowledge of the palaeogeography of the former European periglacial zone by showing that Late Pleistocene thermokarst activity could have had a significant impact on the evolution of the landscape of at least some regions of central Europe along the southern limit of the continuous permafrost zone. The research also points to a similar history for the physical transformation of the landscape of the former European periglacial zone and current thermokarst landscapes and could be a valuable source of information with respect to the future transformation of the Arctic under conditions of ongoing global warming.

Description: Recent LiDAR surveys have revealed that on postglacially uplifting coasts of Estonia rhythmic coastal landforms (beach ridge sequences and foredune plains) occur to a considerable extent. We studied four of them to reveal age and periodicity in these multiple ridge systems and discussed their genesis in the Subatlantic (semi‐continental) conditions of the Baltic Sea area. Using recent models of Fennoscandian uplift due to glacial isostatic adjustment (GIA), we constructed Holocene apparent sea level curves for the study sites at Õngu, Mänspe, Haldi and Keibu; converted distance–height shore profiles into time series (including corrections on shore profile non‐linearity and variations in GIA‐eustasy balance); and analysed the patterns using spectral analysis. It was suggested that due to non‐tidal conditions, relatively low‐energy hydrodynamic forcing and small aeolian contribution, the ridges mark ancient shorelines. They are relatively modest in height (mostly 0.2–1 m), form regular and extensive (up to 150 ridges) patterns, and date back to ~9000 years before present. We studied 〈5‐ka‐old sections. The mean ridge spacing varied, depending also on coastal slope, between 21 and 39 m. Both simple counting and spectral analysis involved some specific limitations, yet the estimates for typical spacing were alike, at 32 (±5) years. The regular nature of the low‐ridge patterns originated from relative sea level lowering and gradual sediment accretion/erosion. However, the progradation was rather uplift‐ than accretion‐driven and the stepwise process in ridge formation was probably not autocyclic. It was governed or modulated by quasi‐periodic 25–40 year cyclicity in local wave forcing, relative sea level variations and wind conditions. Being most likely connected to the North Atlantic Oscillation, the quasi‐regular, decadal‐scale, similarly phased variations may magnify each other's effect on the westerly exposed coasts of Estonia. Additionally, some other (e.g. event‐driven) mechanisms may also be present.

Description: The aim of this contribution is to describe a femur (MCRS 199) assigned to Nothrotheriops sp. from the Late Pleistocene of Santa Fe Province (Argentina), and discuss the implications of this find in the context of the dispersal of ground sloths during the Great American Biotic Interchange. The specimen MCRS 199 is smaller than the femora referred to the North American species Nothrotheriops texanus and Nothrotheriops shastensis but shares several features with these species: (i) shape and position of the greater trochanter, (ii) development of the lesser trochanter, (iii) presence of connection between the third trochanter and the ectepicondyle, (iv) distal third of the femur wider, with ML/DW index of 1.93, and (v) location and relationship of the distal condyles. These similarities allow us to assign MCRS 199 to Nothrotheriops sp. The record of Nothrotheriops sp. from Santa Fe Province chronologically coincides with the earliest records of Nothrotheriops shastensis suggesting a broad geographical distribution of Nothrotheriops during the Late Pleistocene, ranging from 33–36°N (e.g. states of California and Arizona, USA) to 31°S (northern Salado River, Santa Fe Province, Argentina). Thus, Nothrotheriops have dispersed from North America (where Nothrotheriops has early records, Calabrian–Middle Pleistocene) to South America where localities bearing Nothrotheriops are Late Pleistocene in age. In addition, once in South America and probably during the Middle Pleistocene, Nothrotheriops probably gave rise to its sister taxon, Nothrotherium, with records from the Middle Pleistocene (e.g. 223 ka BP, northeastern Brazil) to the Late Pleistocene (e.g. 15 ka BP).

Description: Prehistoric settlements are usually perceived as being in opposition to the natural development of the landscape. Indeed, for woodland snail assemblages in anthropogenic landscapes in central Europe, considerable impoverishment is typical. However, it remains unclear whether this has been caused by humans only or also by climate effects. From an archaeological point of view, the Moravian Karst is one of the classic prehistorical locations in central Europe, but with a more humid climate than the previously studied anthropogenic areas. To learn more about coexistence of humans and natural forests during the Lateglacial and Holocene, we analysed 11 mollusc successions covering this entire area, a unique data set for such a relatively small area. These mollusc successions show several specific features compared to the standard development known from other mid‐European areas. One is that although the Moravian Karst is not far from the Western Carpathians, Carpathian species appeared relatively late, only during the second half of the Holocene climatic optimum. Similarly, some western European and Alpine elements appeared later than expected. In contrast to this, however, a number of forest species with central European range appeared relatively early during the Lateglacial or Early Holocene. Two even survived the Last Glacial Maximum in the Moravian Karst. This would suggest an early occurrence of forest patches in a mosaic landscape. Humans have apparently inhabited this area since the Lateglacial amongst islands of forests, which later changed during the Boreal and then the climatic optimum into humid canopy forests. Thus, a mosaic of anthropogenic and natural habitats persisting in close vicinity was possible in rugged and humid landscapes practically until the Industrial Revolution.

Description: Boreas, Volume 48, Issue 2, Page i-iv, April 2019.

Description: Regional‐scale, high‐resolution terrain data permit the study of landforms across south‐central Ontario, where the bed of the former Laurentide Ice Sheet is well exposed and passes downflow from irregular topography on Precambrian Shield highlands to flat‐lying Palaeozoic carbonate bedrock, and thick (50 to 〉200 m) unconsolidated sediment substrates. Rock drumlins and megagrooves are eroded into bedrock and mega‐scale glacial lineations (MSGL) occur on patchy streamlined till residuals in the Algonquin Highlands. Downflow, MSGL pass into juxtaposed rock and drift drumlins on Palaeozoic bedrock and predominantly till‐cored drumlins in areas of thick drift. The Lake Simcoe Moraines, now traceable for more than 80 km across the Peterborough drumlin field (PDF), form a distinct morphological boundary: downflow of the moraine system, drumlins are larger, broader and show no indication of subsequent reworking by the ice, whereas upflow of the moraines, a higher degree of complexity in bedform pattern and morphology is distinguished. Discrete radial and/or cross‐cutting flowset terminate at subtle till‐cored moraine ridges downflow of local topographic lows, indicating multiple phases of late‐stage ice flow with strong local topographic steering. More regional‐scale flow switching is evident as NW‐orientated bedforms modify drumlins south of the Oak Ridges Moraine, and radial flowset emanate from areas within the St. Lawrence and Ottawa River valleys. Most of the drumlins in the PDF formed during an early, regional drumlinization phase of NE–SW flow that followed the deposition of a thick regional till sheet. These were subsequently modified by local‐scale, topographically controlled flows that terminate at till‐cored moraines, providing evidence that the superimposed bedforms record dynamic ice (re)advances throughout the deglaciation of south‐central Ontario. The patterns and relationships of glacial landform distribution and characteristics in south‐central Ontario hold significance for many modern and palaeo‐ice sheets, where similar downflow changes in bed topography and substrate lithology are observed.

Description: Ten monitoring sites were established in 1986 near the Scottbreen and Renardbreen glaciers (Bellsund, Spitsbergen) in order to determine the rates of gelifluction on raised marine terraces and on talus cones, accumulation on talus cones, and movement of the protalus rampart. The measurements were performed in 1987, 2007 and 2016. The results obtained revealed a very slow rate of changes on the surface of the analysed area. During 30 years, only one out of 84 points where the gelifluction rate was measured was displaced by 15 cm down‐slope. The maximal annual and average gelifluction rates were calculated at 0.5 cm and 0.18 cm a−1, respectively. Several measurement points did not change their position over the observation period. As shown by the observations, the gelifluction rate largely does not depend on slope inclination. Studies of talus cones allowed the level of cone increment to be determined as 314.3 kg of scree per square metre. Analysis of factors influencing the rate of mass movement allowed for correlation of the small‐scale gelifluction movement at the analysed sites with the general trends of climate warming. In this part of the Arctic, these trends are manifested by soil desiccation. It appears that slope processes depend on very local topoclimatic factors. Analysis of the obtained data with regard to palaeogeographical and climatic investigations suggests that the ice segregation forms on raised marine terraces developed during the last Holocene cooling, i.e. the Little Ice Age.

Description: Boreas, Volume 48, Issue 2, Page 269-272, April 2019.

Description: Here we investigate, for the first time, the use of optically stimulated luminescence (OSL) for dating cobbles from the body of successive beach ridges and compare cobble surface‐derived ages to standard quartz OSL ages from sand. Between four and eight cobbles and sand samples (age control) were dated with the luminescence method, taken from the modern beach and from beach ridges on the south and north extremes of a prograding spit on the westernmost coast of Lolland, Denmark. Luminescence‐depth profiles perpendicular to the surfaces of the cobbles show that the feldspar infrared signals stimulated at 50 °C were fully reset to various depths into the cobbles prior to final deposition; as a result, the equivalent doses determined from close to the surface of such cobbles can be used to calculate burial ages. Beach‐ridge burial ages given by the average of ages of individual cobbles taken from the same site are consistent, within errors, with the ages derived from the sand samples. Cobble‐ and sand‐derived ages show that the southernmost beach ridge at Albuen was formed around 2 ka ago, indicating that this sandy spit is younger than other coastal systems in Denmark. The agreement between ages derived from clasts and from standard quartz OSL in this study confirms that, even in the absence of sandy sediments, we can reliably date sites using OSL by targeting larger clasts. In addition, the record of prior light exposure contained in the shape of the cobbles’ luminescence‐depth profile removes one of the major uncertainties (i.e. the degree of signal reset prior to burial) in the luminescence dating of high latitude sites.

Description: This article reports on an Early Saalian proglacial lake formed between the Scandinavian Ice Sheet and the front of the Sudeten Mountains, Poland. Sediments investigated at Mysłów point to a transition from glacifluvial to glaciolacustrine environments. The bulk of the sediments was deposited in deep‐water Gilbert‐type deltas (A–E complexes). A delta plain (topset) gradually passes into a subaerial plateau and then a clastic shoreline and the subaquatic slope of a prograding delta (foreset). The glaciolacustrine lithofacies represent a number of lake‐basin environments, from marginal subaqueous slopes to distal parts of a subaqueous fan. Glaciolacustrine and glaciodeltaic deposits locally reach ˜50–70 m in thickness. Analyses of A–E complexes indicate that the lake existed for more than 130 years and that its origin and evolution were closely connected with the ice front. This case study records lake sedimentation at an ice‐sheet margin with cohesionless gravity flows, turbidity currents, debris‐avalanching and, to a much lesser degree, parapelagic suspension fall‐out and ice‐raft dumping. In the initial stage, the lake extended more than 10 km to the south, and the deposition was relatively slow. In the second stage, recession of the ice sheet caused rapid growth of a delta. The third and ultimate stage coincided with the final glacial recession, with rapid deposition occurring only on the lake bottom. The model of the glaciolacustrine environment presented here may also be applicable to many other proglacial lakes in mountain areas.

Description: In earlier studies, the topography and melting dynamics of ice‐cored ridges within marginal zones of the Pleistocene ice sheets were routinely reconstructed based only on conceptual and qualitative models supported by geomorphological, sedimentological and palaeogeographical studies. Here, a novel approach based on detailed structural analysis of two collapse structures affecting Pleistocene kame deposits is presented. The high regularity of the geometry of synclines and related strain fields as well as the patterns of subsidence of the folded strata are all interpreted as evidence of topography of ice‐cored ridges and their melting dynamics. The topography is described in terms of elongation, orientation and cross‐sectional shape of ice‐cored ridges. In turn, the melting dynamics are assessed based on a semi‐quantitative model of different relative rates of backwasting and downwasting. The topography of ice‐cored ridges, derived independently from the morphology of the related supraglacial landforms, is interpreted as an effect of ablation controlled by debris bands within parent ice. The reconstructed ice‐cored ridges are considered to represent the second‐order topographic features within a wide ice‐cored depression. The sedimentary evolution of collapse structures expressed as migration of their hinges/depocentres provides new semi‐quantitative insight into melting dynamics of ice showing the predominance of backwasting over downwasting. This evolution concerns the final stage of de‐icing, which was probably preceded by lowering of the ice‐cored topography and progressive formation of the ice‐cored ridges.

Description: This article presents a new comprehensive assessment of the Holocene hydrological variability of Lake Ladoga, northwest Russia. The reconstruction is based on oxygen isotopes of lacustrine diatom silica (δ18Odiatom) preserved in sediment core Co 1309, and is complemented by a diatom assemblage analysis and a survey of modern isotope hydrology. The data indicate that Lake Ladoga has existed as a freshwater reservoir since at least 10.8 cal. ka BP. The δ18Odiatom values range from +29.8 to +35.0‰, and relatively higher δ18Odiatom values around +34.7‰ between c. 7.1 and 5.7 cal. ka BP are considered to reflect the Holocene Thermal Maximum. A continuous depletion in δ18Odiatom since c. 6.1 cal. ka BP accelerates after c. 4 cal. ka BP, indicating Middle to Late Holocene cooling that culminates during the interval 0.8–0.2 cal. ka BP, corresponding to the Little Ice Age. Lake‐level rises result in lower δ18Odiatom values, whereas lower lake levels cause higher δ18Odiatom values. The diatom isotope record gives an indication for a rather early opening of the Neva River outflow at c. 4.4–4.0 cal. ka BP. Generally, overall high δ18Odiatom values around +33.5‰ characterize a persistent evaporative lake system throughout the Holocene. As the Lake Ladoga δ18Odiatom record is roughly in line with the 60°N summer insolation, a linkage to broader‐scale climate change is likely.

Description: Seismostratigraphical studies of the 11.8‐km2‐large and ~140‐m‐deep Lake Bolshoye Shchuchye, Polar Ural Mountains, reveal up to 160‐m‐thick acoustically laminated sediments in the lake basin. Using a dense grid of seismic lines, the spatial and temporal distributions of the sedimentary history have been reconstructed. Three regional seismic horizons have been identified and correlated with the well‐dated 24‐m‐long sediment core retrieved from the lake. Isopach maps constructed from the seismic data show four phases of sedimentation. A contour map of the deepest regional seismic reflector represents the earliest hemipelagic sedimentation in the lake. Three contour maps represent time intervals covering the last 23 cal. ka based on the well‐dated core stratigraphy from the lake. The detailed time constraints on the upper stratigraphical units in the lake allow calculation of the lake's development in terms of sediment fluxes and the denudation rates from the Last Glacial Maximum (LGM) to the present. The sedimentation in Lake Bolshoye Shchuchye has been dominated by hemipelagic processes during at least the last 24 cal. ka BP only locally interrupted by delta progradation and slope processes. A major shift in the sediment accumulation at c. 18.7 cal. ka BP is interpreted to mark the end of the local glacial maximum, greatly reduced denudation and the onset of the deglaciation period; this also demonstrates how fast the glaciers melted and possibly disappeared at the end of the LGM. The denudation rate during the Holocene is only a fifth of the LGM rate. The age of the oldest stratified sediments in Lake Bolshoye Shchuchye is not well constrained, but estimated as c. 50–60 ka.

Description: To assess the reliability of arboreal phytoliths for differentiating vegetation types in temperate forest regions, we systematically analysed arboreal leaf phytoliths from 72 arboreal plants and 49 modern soils from three forest types in northeast China. The arboreal leaf phytolith production and morphotypes were highly variable between species. The arboreal leaf phytolith assemblages could clearly distinguish between broadleaf and coniferous species, but they were much less successful in differentiating broadleaved trees into subtaxa. Coniferous leaf morphotypes were successfully used to differentiate coniferous trees into families and subtaxa, especially in the Pinaceae. Two diagnostic broadleaved and six coniferous phytolith morphotypes were recognized within the modern soil beneath forest ecosystems. These arboreal phytoliths comprised up to 10–15% of the total soil phytoliths, and were dominated by coniferous types. Arboreal phytolith concentrations and phytolith assemblages in the soils fluctuated substantially amongst the three forest types. Soil arboreal phytolith assemblages were successfully used to differentiate samples from Larix mixed forest, broadleaf forest and Pinus koraiensis mixed forest. In addition, the arboreal index quantitatively distinguished the three forest types, with B/BE values 〈0.4 for Larix mixed forest samples, values from 0.4 to 0.6 for broadleaf forest samples, and values from 0.6 to 0.9 for P. koraiensis mixed forest. Thus, our surface soil arboreal phytolith assemblages and arboreal index are a useful reference for differentiating forest ecotypes, and they also provide reliable analogues for arboreal phytoliths from palaeoecological contexts in temperate forest regions.

Description: A multi‐channel, high‐resolution seismic reflection survey using a Micro‐GI airgun was carried out in the framework of the Russian‐German project PLOT (Paleolimnological Transect) on Lake Levinson‐Lessing, Taymyr Peninsula, in 2016. In total, ~70 km of seismic reflection profiles revealed in unprecedented detail the glacial and postglacial sedimentary infill of the lake basin. Five main seismic units have been recognized and interpreted as glacial (Unit V), subglacial and proglacial (Unit IV), marine (Unit III), fluvial‐lacustrine (Unit II) and lacustrine (Unit I) sediments. Of particular significance are imbricated, south‐orientated structures present in the southernmost part of the lake basin within Unit V and a large topographic ridge recognized in front of those structures. We interpret these structures as push moraines and an end moraine, respectively, left by the glacier after its retreat. The depositional pattern of the units above the moraines documents past lake‐level fluctuations. We interpret Unit IV, Unit III and Unit I as highstand deposits, and Unit II as lowstand deposits. Gas‐charged sediments dominate the northern part of the lake basin, whilst they occur only sporadically and in limited spatial extent in the central and southern parts of the lake. In the latter areas, the seismic and echo‐sounder data suggest recent tectonic activity. Our study contributes to the reconstruction of environmental conditions in the Taymyr Peninsula directly following the Early Weichselian deglaciation and shows that deep tectonic lake basins affected by several glaciations can preserve important palaeoenvironmental records, which contributes significantly to our understanding of palaeoenvironmental changes in the Taymyr Peninsula and the central Russian Arctic.

Description: Calcareous root tubes (CRTs) contain abundant information about palaeoenvironmental conditions and have been used for palaeoenvironmental studies in the desert hinterlands of arid regions. However, as subclasses of CRTs, calcareous sheaths and rhizocretions are formed by different processes, and it remains unclear whether these differences produce variations in the chemical element composition. Furthermore, it remains uncertain whether variations in chemical element concentrations amongst different subclasses of the CRTs can affect palaeoenvironmental reconstructions. In this study, we collected 54 CRT samples from the Tengger Desert of northwestern China. All samples were dated by accelerator mass spectrometry (AMS) 14C dating, and the chemical element composition and concentration differences of the two CRT subclasses were determined using X‐ray fluorescence spectrometry. The CRT samples were dated to the Holocene. The calcareous sheath and rhizocretion samples contained varying concentrations of the same chemical elements. The rhizocretions had high concentrations of mobile elements (Ca, Mg and Sr) and P, whereas the calcareous sheaths had high concentrations of stable elements, including Al, Si, Ti, Zr, Rb and Ba. These differences were due to the different formation processes of the two subclasses of CRTs. Moreover, the Sr/Ca and Mg/Ca ratios in the calcareous sheaths were higher than those in the rhizocretions from the same period, but these ratio differences had little effect on palaeo‐effective moisture reconstructions at the millennial scale during the Holocene. The reconstructions were not influenced by the various CRT subclasses. The Holocene millennial‐scale moisture changes in the Tengger Desert revealed by the Sr/Ca and Mg/Ca ratios showed that there was an arid period during the Early Holocene, a humid period during the Middle Holocene and a humid to arid period during the Late Holocene.

Description: Cave bears (Ursus spelaeus) are an iconic component of the European late Quaternary Ice Age megafauna. Recent demographic analyses based on cave bear mtDNA sequences and refined radiocarbon dating indicate that cave bear population size and genetic diversity started to decline some 50 kilo years ago (kya). Hence, neither the coldest phase of the last glaciation (started some 24 kya), nor the colonization of Europe by Palaeolithic hunters (started some 45 kya) coincides with the beginning of population decline. Here, we reconstructed cave bear climatic niche evolution through time. Then, we performed spatially explicit population viability analyses to assess cave bear demographics through time in response to climatic changes, human effects on bear survival and their combination. We found that climate change was responsible for a 10‐fold decrease in cave bear population size after 40 kya. However, climate change on its own could not explain U. spelaeus extinction at 24 kya. Additional negative effects consistent with human population expansion are required to explain both U. spelaeus' retreat from eastern Europe since 40 kya and its final extinction.

Description: The study presents the first description and analysis of ostracod records from three sites cored in different parts of the Baltic Sea during the IODP Expedition 347, Baltic Sea Paleoenvironment. Our data present the first high‐resolution ostracod records from the Late Weichselian and Holocene sediments collected across the Baltic Sea Basin. Using published data on modern ostracod species ecology of the Baltic Sea, we were able to provide ostracod‐based palaeoreconstructions of the history of the region. The stratigraphical framework for the sites is based on radiocarbon‐based age models. The three studied sites reveal different ostracod assemblage successions that reflect environmental changes in the study area. Site M0060, located in the Kattegat area, contains the oldest ostracod assemblages that document a marine environment with very high sedimentation rates during the most recent deglaciation. Between ~13 000 and 7500 cal. a BP a modern‐like near‐shore environment developed. Site M0059 in the southwestern Baltic Sea, Little Belt area, contains assemblages reflecting the transition from a freshwater lake to the brackish Littorina Sea between ~7500 and 7300 cal. a BP. Site M0063 is the deepest location in the central Baltic, Landsort Deep, and yielded very limited ostracod data, but comparison with our organic carbon data allowed us to distinguish the Yoldia Sea, Ancylus Lake and Littorina Sea intervals. The ostracod record correlates well with the organic carbon record with alternation between periods of hypoxia and periods of low oxygen that still supported ostracods.

Description: Rock‐Eval pyrolysis provides a quick, relatively inexpensive means of characterizing organic‐rich strata, and has been used for decades to understand global petroleum systems. Although designed to characterize ancient kerogens, pyrolysis is increasingly being used to understand Holocene systems as well. The ability of this technique to distinguish between types of preserved organic matter is useful in characterizing climatic evolution, particularly in systems sensitive to climatic fluctuation such as isolated fens and bogs. Cores collected from the Tokewanna and Garden Basin Cattail fens in central/eastern Utah exhibit variability of organic source, with the mixture of terrestrial and algal sources varying through time, as shown through the hydrogen index (HI) and oxygen index pyrolysis parameters. A sediment core was collected at each fen, and 176 samples were taken from the cores at 6‐cm intervals. Total organic carbon (TOC) for all samples ranges from 1.3 to 44.2%, with an average of 18.2% TOC. Samples range from 84 to 687 HI, equivalent to Type I (lacustrine algal) to Type III (terrestrial) organic material (OM). Variability in HI response represents mixing of the two OM sources, and the relative amount of aqueous organic input can be estimated through time based on age‐calibrated HI curves at the two sites. The balance of organic input serves as an accurate, high‐resolution proxy for climate, and calibration with palynological data near both sites confirms patterns shown by pyrolysis, showing the utility of this method in quickly, affordably and accurately characterizing Holocene sediments for use in understanding palaeoclimate.

Description: The new pollen record from the upper 12.75 m of a sediment core obtained in Lake Ladoga documents regional vegetation and climate changes in northwestern Russia over the last 13.9 cal. ka. The Lateglacial chronostratigraphy is based on varve chronology, while the Holocene stratigraphy is based on AMS 14C and OSL dates, supported by comparison with regional pollen records. During the Lateglacial (c. 13.9–11.2 cal. ka BP), the Lake Ladoga region experienced several climatic fluctuations as reflected in vegetation changes. Shrub and grass communities dominated between c. 13.9 and 13.2 cal. ka BP. The increase in Picea pollen at c. 13.2 cal. ka BP probably reflects the appearance of spruce in the southern Ladoga region at the beginning of the Allerød interstadial. After c. 12.6 cal. ka BP, the Younger Dryas cooling caused a significant decrease in spruce and increase in Artemisia with other herbs, indicative of tundra‐ and steppe‐like vegetation. A sharp transition from tundra‐steppe habitats to sparse birch forests characterizes the onset of Holocene warming c. 11.2 cal. ka BP. Pine forests dominated in the region from c. 9.0 to 8.1 cal. ka BP. The most favourable climatic conditions for deciduous broad‐leaved taxa existed between c. 8.1 and 5.5 cal. ka BP. Alder experiences an abrupt increase in the local vegetation c. 7.8 cal. ka BP. The decrease in tree pollen taxa (especially Picea) and the increase in herbs (mainly Poaceae) probably reflect human activity during the last 2.2 cal. ka. Pine forests have dominated the region since that time. Secale and other Cerealia pollen as well as ruderal herbs are permanently recorded since c. 0.8 cal. ka BP.

Description: We present a high‐resolution reconstruction of the vegetation and climate dynamics during the penultimate interglacial, corresponding with Marine Isotope Stage (MIS) 7, based on detailed palynological analyses of lacustrine sediments from Lake El'gygytgyn, northeastern Siberia. The analysed sediments were deposited between 246 and 181 ka ago (late MIS 8 to early MIS 6.6). The interglacial vegetation was characterized by herb and shrub (mainly alder and birch) dominated plant communities. Pollen‐based biome reconstruction shows a dominance of the tundra (TUND) biome, thus indicating rather open vegetation. Warmer intervals (MIS 7.5, 7.3 and 7.1) were marked by an increase in the cold deciduous forest (CLDE) biome scores and a synchronous decrease in the cold steppe (STEP) biome scores. The thermal maximum occurred during MIS 7.1, as indicated by the highest CLDE biome scores occurring in this period, and lasted ~10 ka, possibly favoured by the high precession‐related summer insolation and the legacy of the preceding mild and dry stadial (MIS 7.2). In contrast, MIS 7.3 and 7.5 were characterized by shorter durations (~4 ka) and lower summer temperatures. The preceding cold glacial and stadial (MIS 8 and 7.4, respectively) might have led to an extensive distribution of permafrost that hindered vegetation development during the subsequent warm intervals. MIS 7.4 and 6.6 were cold and wet, probably triggered by low obliquity values and coevally low precession‐related summer insolation. As a result, these periods were marked by significantly reduced summer temperatures and an enhanced snow‐ice albedo feedback. The obtained reconstructions provide potential scenarios for future climate changes and allow a better understanding of the relationship between vegetation, climate and external/internal forcings in the high latitudes.

Description: By applying advanced spatial statistical methods, spatial taphonomy complements the traditional taphonomic approach and enhances our understanding of biostratinomic and diagenetic processes. In this study, we elaborate on a specific aspect – spatial anisotropy – of taphonomic processes. We aim to unravel the taphonomic history of the Early Pleistocene vertebrate assemblage of Tsiotra Vryssi (Mygdonia Basin, Greece). Circular statistics are used for the fabric analysis of elongated elements; geostatistics (directional variograms), wavelet and point pattern analyses are applied for detecting anisotropy at the assemblage level. The anisotropy of magnetic susceptibility (AMS) of sedimentary magnetic minerals is also investigated. The results, integrated with preliminary remarks about the differential preservation of skeletal elements, sedimentological and micromorphological observations, suggest multiple dispersion events and recurrent spatial re‐arrangement of a lag, (peri)autochthonous assemblage, consistent with the cyclical lateral switching of a braided fluvial system. Furthermore, this study offers a contribution to the building of a spatial taphonomic referential framework for the interpretation of other fossil vertebrate assemblages, including archaeo‐palaeontological ones.

Description: 〈b〉On the timescales and length scales of the Arctic sea ice thickness anomalies: a study based on 14 reanalyses〈/b〉〈br〉 Leandro Ponsoni, François Massonnet, Thierry Fichefet, Matthieu Chevallier, and David Docquier〈br〉 The Cryosphere, 13, 521-543, https://doi.org/10.5194/tc-13-521-2019, 2019〈br〉 The Arctic is a main component of the Earth's climate system. It is fundamental to understand the behavior of Arctic sea ice coverage over time and in space due to many factors, e.g., shipping lanes, the travel and tourism industry, hunting and fishing activities, mineral resource extraction, and the potential impact on the weather in midlatitude regions. In this work we use observations and results from models to understand how variations in the sea ice thickness change over time and in space.

Description: 〈b〉Brief communication: Evaluation and inter-comparisons of Qinghai–Tibet Plateau permafrost maps based on a new inventory of field evidence〈/b〉〈br〉 Bin Cao, Tingjun Zhang, Qingbai Wu, Yu Sheng, Lin Zhao, and Defu Zou〈br〉 The Cryosphere, 13, 511-519, https://doi.org/10.5194/tc-13-511-2019, 2019〈br〉 Many maps have been produced to estimate permafrost distribution over the Qinghai–Tibet Plateau. However the evaluation and inter-comparisons of them are poorly understood due to limited in situ measurements. We provided an in situ inventory of evidence of permafrost presence or absence, with 1475 sites over the Qinghai–Tibet Plateau. Based on the in situ measurements, our evaluation results showed a wide range of map performance, and the estimated permafrost region and area are extremely large.

Description: 〈b〉Impact of assimilating sea ice concentration, sea ice thickness and snow depth in a coupled ocean–sea ice modelling system〈/b〉〈br〉 Sindre Fritzner, Rune Graversen, Kai H. Christensen, Philip Rostosky, and Keguang Wang〈br〉 The Cryosphere, 13, 491-509, https://doi.org/10.5194/tc-13-491-2019, 2019〈br〉 In this work, a coupled ocean and sea-ice ensemble-based assimilation system is used to assess the impact of different observations on the assimilation system. The focus of this study is on sea-ice observations, including the use of satellite observations of sea-ice concentration, sea-ice thickness and snow depth for assimilation. The study showed that assimilation of sea-ice thickness in addition to sea-ice concentration has a large positive impact on the coupled model.

Description: 〈b〉Hydrologic Diversity in Glacier Bay Alaska: Spatial Patterns and Temporal Change〈/b〉〈br〉 Ryan L. Crumley, David F. Hill, Jordan P. Beamer, and Elizabeth Holzenthal〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2019-1,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 In this study we investigate the historical (1980–2015) and forecast (2070–2099) components of freshwater runoff to Glacier Bay, Alaska using a modeling approach. We find that many of the historically snow-dominated watersheds in Glacier Bay National Park and Preserve may transition towards rainfall-dominated hydrographs in a future scenario in which CO〈sub〉2〈/sub〉 emissions are not mitigated. The changes in timing and volume of freshwater entering Glacier Bay will affect bay ecology and hydrochemistry.

Description: 〈b〉Robust uncertainty assessment of the spatio-temporal transferability of glacier mass and energy balance models〈/b〉〈br〉 Tobias Zolles, Fabien Maussion, Stephan Peter Galos, Wolfgang Gurgiser, and Lindsey Nicholson〈br〉 The Cryosphere, 13, 469-489, https://doi.org/10.5194/tc-13-469-2019, 2019〈br〉 A mass and energy balance model was subjected to sensitivity and uncertainty analysis on two different Alpine glaciers. The global sensitivity analysis allowed for a mass balance measurement independent assessment of the model sensitivity and functioned as a reduction of the model free parameter space. A novel approach of a multi-objective optimization estimates the uncertainty of the simulated mass balance and the energy fluxes. The final model uncertainty is up to 1300 kg m〈sup〉−3〈/sup〉 per year.

Description: 〈b〉Four decades of Antarctic surface elevation changes from multi-mission satellite altimetry〈/b〉〈br〉 Ludwig Schröder, Martin Horwath, Reinhard Dietrich, Veit Helm, Michiel R. van den Broeke, and Stefan R. M. Ligtenberg〈br〉 The Cryosphere, 13, 427-449, https://doi.org/10.5194/tc-13-427-2019, 2019〈br〉 We developed an approach to combine measurements of seven satellite altimetry missions over the Antarctic Ice Sheet. Our resulting monthly grids of elevation changes between 1978 and 2017 provide unprecedented details of the long-term and interannual variation. Derived mass changes agree well with contemporaneous data of surface mass balance and satellite gravimetry and show which regions were responsible for the significant accelerations of mass loss in recent years.

Description: 〈b〉Two-dimensional Inversion of wideband spectral data from the Capacitively Coupled Resistivity method – First Applications in periglacial environments〈/b〉〈br〉 Jan Mudler, Andreas Hördt, Anita Przyklenk, Gianluca Fiandaca, Pradip Kumar Maurya, and Christian Hauck〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-288,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 The Capacitively Coupled Resistivity method (CCR) enables the determination of frequency dependent electrical parameters of the subsurface. CCR is well suited for the application in cryospheric areas because it provides logistical advantages regarding the coupling on hard surfaces and highly resistive grounds. With our new spectral two-dimensional inversion, we can identify subsurface structures based on full spectral information. We show first results of the Inversion method on the field scale.

Description: 〈b〉Brief communication: Analysis of organic matter in surface snow by PTR-MS – implications for dry deposition dynamics in the Alps〈/b〉〈br〉 Dušan Materić, Elke Ludewig, Kangming Xu, Thomas Röckmann, and Rupert Holzinger〈br〉 The Cryosphere, 13, 297-307, https://doi.org/10.5194/tc-13-297-2019, 2019〈br〉 〈p〉The exchange of organic matter (OM) between the atmosphere and snow is poorly understood due to the complex nature of OM and the convoluted processes of deposition, re-volatilisation, and chemical and biological processing. OM that is finally retained in glaciers potentially holds a valuable historical record of past atmospheric conditions; however, our understanding of the processes involved is insufficient to translate the measurements into an interpretation of the past atmosphere. This study examines the dynamic processes of post-precipitation OM change at the alpine snow surface with the goal of interpreting the processes involved in surface snow OM.〈/p〉

Description: 〈b〉Modelling the Antarctic Ice Sheet across the Mid Pleistocene Transition – Implications for Oldest Ice〈/b〉〈br〉 Johannes Sutter, Hubertus Fischer, Klaus Grosfeld, Nanna B. Karlsson, Thomas Kleiner, Brice Van Liefferinge, and Olaf Eisen〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2019-24,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 The Antarctic Ice Sheet may have played an important role in moderating the transition between warm and cold climate epochs over the last million of years. We find that the Antarctic Ice Sheet grew considerably about 0.9 Myr ago, a time when ice age/warm age cycles changed from a 40 000 to a 100 000 yr periodicity. Our findings also suggest that ice as old as 1.5 Myr still exists at the bottom of the East Antarctic ice sheet despite the major climate reorganizations in the past.

Description: 〈b〉The vertical structure of precipitation at two stations in East Antarctica derived from micro rain radars〈/b〉〈br〉 Claudio Durán-Alarcón, Brice Boudevillain, Christophe Genthon, Jacopo Grazioli, Niels Souverijns, Nicole P. M. van Lipzig, Irina V. Gorodetskaya, and Alexis Berne〈br〉 The Cryosphere, 13, 247-264, https://doi.org/10.5194/tc-13-247-2019, 2019〈br〉 Precipitation is the main input in the surface mass balance of the Antarctic ice sheet, but it is still poorly understood due to a lack of observations in this region. We analyzed the vertical structure of the precipitation using multiyear observation of vertically pointing micro rain radars (MRRs) at two stations located in East Antarctica. The use of MRRs showed the potential to study the effect of climatology and hydrometeor microphysics on the vertical structure of Antarctic precipitation.

Description: 〈b〉Recent changes in pan-Antarctic surface snowmelt detected by AMSR-E and AMSR2〈/b〉〈br〉 Lei Zheng, Chunxia Zhou, Tingjun Zhang, Qi Liang, and Kang Wang〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-279,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 Snowmelt plays a key role in mass and energy balance in polar regions. In this study, we report on the spatial and temporal variations of the surface snowmelt over the Antarctic sea ice and ice sheet (pan-Antarctic) based on AMSR-E and AMSR2. Overall, the pan-Antarctic surface snowmelt showed a trend toward later melt onset during the 2002–2017 period. The decreasing surface snowmelt on the Antarctic ice sheet was very likely linked with the enhancing summer Southern Annular Mode.

Description: 〈b〉Water tracks intensify surface energy and mass exchange in the Antarctic McMurdo Dry Valleys〈/b〉〈br〉 Tobias Linhardt, Joseph S. Levy, and Christoph K. Thomas〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2019-8,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 We measured sensible, latent and soil heat fluxes along with radiation in the McMurdo Dry Valleys, Antarctica, at a water track and at predominant dry soils, serving as reference. We found a distinct impact of water tracks on surface energy and mass exchange which suggests that water tracks may serve as an indicator of change in the McMurdo Dry Valleys.

Description: 〈b〉Brief communication: Rapid machine-learning-based extraction and measurement of ice wedge polygons in high-resolution digital elevation models〈/b〉〈br〉 Charles J. Abolt, Michael H. Young, Adam L. Atchley, and Cathy J. Wilson〈br〉 The Cryosphere, 13, 237-245, https://doi.org/10.5194/tc-13-237-2019, 2019〈br〉 We present a workflow that uses a machine-learning algorithm known as a convolutional neural network (CNN) to rapidly delineate ice wedge polygons in high-resolution topographic datasets. Our workflow permits thorough assessments of polygonal microtopography at the kilometer scale or greater, which can improve understanding of landscape hydrology and carbon budgets. We demonstrate that a single CNN can be trained to delineate polygons with high accuracy in diverse tundra settings.

Description: 〈b〉Estimation of turbulent heat flux over leads using satellite thermal images〈/b〉〈br〉 Meng Qu, Xiaoping Pang, Xi Zhao, Jinlun Zhang, Qing Ji, and Pei Fan〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-262,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 Can we ignore the contribution of small ice leads when estimating the turbulent heat flux? Combining bulk formulae and a fetch-limited model with surface temperature from MODIS and Landsat-8 Thermal Infrared Sensor (TIRS) images, we found small leads account for 25 % of the turbulent heat flux, due to its large total area. Estimated turbulent heat flux is larger from TIRS than that from MODIS with a coarser resolution, and larger using fetch-limited model than that using bulk formulae.

Description: 〈b〉Automatically delineating the calving front of Jakobshavn Isbræ from multi-temporal TerraSAR-X images: a deep learning approach〈/b〉〈br〉 Enze Zhang, Lin Liu, and Lingcao Huang〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2019-14,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 Conventionally, calving front positions have been manually delineated from remote sensing images. We design a novel method to automatically delineate the calving front positions of Jakobshavn Isbræ based on deep learning, the first of this kind for Greenland outlet glaciers. We generate high temporal resolution (about two measurements every month) calving fronts. Demonstrating through this successful case study on Jakobshavn Isbræ, our methodology can be applied to many other tidewater glaciers.

Description: 〈b〉IcePAC – a probabilistic tool to study sea ice spatio-temporal dynamics: application to the Hudson Bay area〈/b〉〈br〉 Charles Gignac, Monique Bernier, and Karem Chokmani〈br〉 The Cryosphere, 13, 451-468, https://doi.org/10.5194/tc-13-451-2019, 2019〈br〉 The IcePAC tool is made to estimate the probabilities of specific sea ice conditions based on historical sea ice concentration time series from the EUMETSAT OSI-409 product (12.5 km grid), modelled using the beta distribution and used to build event probability maps, which have been unavailable until now. Compared to the Canadian ice service atlas, IcePAC showed promising results in the Hudson Bay, paving the way for its usage in other regions of the cryosphere to inform stakeholders' decisions.

Description: 〈b〉Spatio-temporal variability and decadal trends of snowmelt processes on Antarctic sea ice observed by satellite scatterometers〈/b〉〈br〉 Stefanie Arndt and Christian Haas〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2019-27,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉The timing and intensity of snowmelt processes on sea ice are key drivers determining the seasonal sea-ice energy and mass budgets. In the Arctic, satellite passive microwave and radar observations have revealed a trend towards an earlier snowmelt onset during the last decades, which is an important aspect of Arctic amplification and sea ice decline. Around Antarctica, snowmelt on perennial ice is weak and very different than in the Arctic, with most snow surviving the summer.〈/p〉 〈p〉Here we compile time series of snowmelt-onset dates on seasonal and perennial Antarctic sea ice from 1992 to 2014/15 using active microwave observations from European Remote Sensing Satellite (ERS-1/2), Quick Scatterometer (QSCAT) and Advanced Scatterometer (ASCAT) radar scatterometers. We define two snowmelt transition stages: A weak backscatter rise indicating the initial warming and metamorphism of the snowpack (pre-melt), followed by a rapid backscatter rise indicating the onset of thaw-freeze cycles (snowmelt).〈/p〉 〈p〉Results show large interannual variability with an average pre-melt onset date of 29 November and melt onset of 10 December, respectively, on perennial ice, without any significant trends over the study period, consistent with the small trends of Antarctic sea ice extent. There was a latitudinal gradient from early snowmelt onsets in mid-November in the northern Weddell Sea to late (end-December) or even absent snowmelt conditions in the southern Weddell Sea.〈/p〉 〈p〉We show that QSCAT Ku-band (13.4 GHz signal frequency) derived pre-melt and snowmelt onset dates are earlier by 25 and 11 days, respectively, than ERS and ASCAT C-band (5.6 GHz) derived dates. This offset has been considered when constructing the time series. Snowmelt onset dates from passive microwave observations (37 GHz) are later by 13 and 5 days than those from the scatterometers, respectively.〈/p〉 〈p〉Based on these characteristic differences between melt onset dates observed by different microwave wavelengths, we developed a conceptual model which illustrates how the evolution of seasonal snow temperature profiles affects different microwave bands with different penetration depths. These suggest that future multi-frequency active/passive microwave satellite missions could be used to resolve melt processes throughout the vertical snow column.〈/p〉

Description: 〈b〉Moisture transport in observations and reanalyses as a proxy for snow accumulation in East Antarctica〈/b〉〈br〉 Ambroise Dufour, Claudine Charrondière, and Olga Zolina〈br〉 The Cryosphere, 13, 413-425, https://doi.org/10.5194/tc-13-413-2019, 2019〈br〉 The East Antarctic Ice Sheet is thicker and larger than its western counterpart. Whether it gains or loses mass depends in part on the snowfall but this is difficult to measure and model inside the continent. Fortunately, the weather balloons launched from a network of stations along the coast provide an indirect estimate. Indeed, they track the water vapour that will eventually precipitate inland. It turns out there has been no consistent change in moisture transport from 1980 to 2017.

Description: 〈b〉Crystallographic preferred orientations of ice deformed in direct-shear experiments at low temperatures〈/b〉〈br〉 Chao Qi, David J. Prior, Lisa Craw, Sheng Fan, Maria-Gema Llorens, Albert Griera, Marianne Negrini, Paul D. Bons, and David L. Goldsby〈br〉 The Cryosphere, 13, 351-371, https://doi.org/10.5194/tc-13-351-2019, 2019〈br〉 Ice deformed in nature develops crystallographic preferred orientations, CPOs, which induce an anisotropy in ice viscosity. Shear experiments of ice revealed a transition in CPO with changing temperature/strain, which is due to the change of dominant CPO-formation mechanism: strain-induced grain boundary migration dominates at higher temperatures and lower strains, while lattice rotation dominates at other conditions. Understanding these mechanisms aids the interpretation of CPOs in natural ice.

Description: 〈b〉Assessment of the Greenland ice sheet–atmosphere feedbacks for the next century with a regional atmospheric model coupled to an ice sheet model〈/b〉〈br〉 Sébastien Le clec'h, Sylvie Charbit, Aurélien Quiquet, Xavier Fettweis, Christophe Dumas, Masa Kageyama, Coraline Wyard, and Catherine Ritz〈br〉 The Cryosphere, 13, 373-395, https://doi.org/10.5194/tc-13-373-2019, 2019〈br〉 Quantifying the future contribution of the Greenland ice sheet (GrIS) to sea-level rise in response to atmospheric changes is important but remains challenging. For the first time a full representation of the feedbacks between a GrIS model and a regional atmospheric model was implemented. The authors highlight the fundamental need for representing the GrIS topography change feedbacks with respect to the atmospheric component face to the strong impact on the projected sea-level rise.

Description: 〈b〉Change detection of bare-ice albedo in the Swiss Alps 〈/b〉〈br〉 Kathrin Naegeli, Matthias Huss, and Martin Hoelzle〈br〉 The Cryosphere, 13, 397-412, https://doi.org/10.5194/tc-13-397-2019, 2019〈br〉 The paper investigates the temporal changes of bare-ice glacier surface albedo in the Swiss Alps between 1999 and 2016 from a regional to local scale using satellite data. Significant negative trends were found in the lowermost elevations and margins of the ablation zones. Although significant changes of glacier ice albedo are only present over a limited area, we emphasize that albedo feedback will considerably enhance the rate of glacier mass loss in the Swiss Alps in the near future.

Description: 〈b〉Validation of the sea ice surface albedo scheme of the regional climate model HIRHAM–NAOSIM using aircraft measurements during the ACLOUD/PASCAL campaigns〈/b〉〈br〉 Evelyn Jäkel, Johannes Stapf, Manfred Wendisch, Marcel Nicolaus, Wolfgang Dorn, and Annette Rinke〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-266,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 The sea ice surface albedo parameterization of a coupled regional climate model was validated against aircraft measurements performed in May/June 2017 north of Svalbard. The albedo parameterization was run offline from the model using the measured parameters surface temperature and snow depth to calculate the surface albedo and the individual fractions of the ice surface subtypes. An adjustment of the variables and additionally accounting for cloud cover reduced the root mean squared error.

Description: 〈b〉Global glacier volume projections under high-end climate change scenarios〈/b〉〈br〉 Sarah Shannon, Robin Smith, Andy Wiltshire, Tony Payne, Matthias Huss, Richard Betts, John Caesar, Aris Koutroulis, Darren Jones, and Stephan Harrison〈br〉 The Cryosphere, 13, 325-350, https://doi.org/10.5194/tc-13-325-2019, 2019〈br〉 We present global glacier volume projections for the end of this century, under a range of high-end climate change scenarios, defined as exceeding 2 °C global average warming. The ice loss contribution to sea level rise for all glaciers excluding those on the peripheral of the Antarctic ice sheet is 215.2 ± 21.3 mm. Such large ice losses will have consequences for sea level rise and for water supply in glacier-fed river systems.

Description: 〈b〉Quantifying the light absorption and source attribution of insoluble light-absorbing particles on Tibetan Plateau glaciers between 2013 and 2015〈/b〉〈br〉 Xin Wang, Hailun Wei, Jun Liu, Baiqing Xu, Mo Wang, Mingxia Ji, and Hongchun Jin〈br〉 The Cryosphere, 13, 309-324, https://doi.org/10.5194/tc-13-309-2019, 2019〈br〉 A large survey on measuring optical and chemical properties of insoluble light-absorbing impurities (ILAPs) from seven glaciers was conducted on the Tibetan Plateau (TP) during 2013–2015. The results indicated that the mixing ratios of black carbon (BC), organic carbon (OC), and iron (Fe) all showed a tendency to decrease from north to south, and the industrial pollution (33.1 %), biomass and biofuel burning (29.4 %), and soil dust (37.5 %) were the major sources of the ILAPs on the TP.

Description: 〈b〉Subglacial hydrological control on flow of an Antarctic Peninsula palaeo-ice stream〈/b〉〈br〉 Robert D. Larter, Kelly A. Hogan, Claus-Dieter Hillenbrand, James A. Smith, Christine L. Batchelor, Matthieu Cartigny, Alex J. Tate, James D. Kirkham, Zoë A. Roseby, Gerhard Kuhn, Alastair G. C. Graham, and Julian A. Dowdeswell〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-273,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 We present high-resolution bathymetry data that provide the most complete and detailed imagery of any Antarctic paleo-ice stream bed. These data show how subglacial water was delivered to and influenced the dynamic behavior of the ice stream. Our observations provide insights relevant to understanding the behavior of modern ice streams and forecasting the contributions that they will make to future sea-level rise.

Description: 〈b〉Estimation of the Antarctic surface mass balance using the regional climate model MAR (1979–2015) and identification of dominant processes〈/b〉〈br〉 Cécile Agosta, Charles Amory, Christoph Kittel, Anais Orsi, Vincent Favier, Hubert Gallée, Michiel R. van den Broeke, Jan T. M. Lenaerts, Jan Melchior van Wessem, Willem Jan van de Berg, and Xavier Fettweis〈br〉 The Cryosphere, 13, 281-296, https://doi.org/10.5194/tc-13-281-2019, 2019〈br〉 Antarctic surface mass balance (ASMB), a component of the sea level budget, is commonly estimated through modelling as observations are scarce. The polar-oriented regional climate model MAR performs well in simulating the observed ASMB. MAR and RACMO2 share common biases we relate to drifting snow transport, with a 3 times larger magnitude than in previous estimates. Sublimation of precipitation in the katabatic layer modelled by MAR is of a magnitude similar to an observation-based estimate.

Description: 〈b〉Simulated retreat of Jakobshavn Isbræ during the 21st century〈/b〉〈br〉 Xiaoran Guo, Liyun Zhao, Rupert Gladstone, Sainan Sun, and John C. Moore〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2019-7,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉The early in the 21st century retreat of Jakobshavn Isbræ, one of Greenland's largest outlet glaciers, into its over-deepened bedrock trough was accompanied by acceleration to unprecedented ice-stream speeds. Such dramatic changes suggested the possibility of substantial mass loss over the rest of this century. Using a three-dimensional ice-sheet model with parameterizations to represent the effects of ice mélange buttressing, crevasse-depth-based calving and submarine melting, we can reproduce its recent evolution. The model can accurately replicate its inter-annual variations in grounding line and terminus position, including new modes of seasonal fluctuations that emerged after arriving at the over-deepened basin and the disappearance of a persistent floating ice shelf. The shear margin induced decreases in ice viscosity we simulate are particularly important in reproducing the large observed inter-annual changes in terminus velocity. We use this model to project Jakobshavn's evolution over this century when forced by the IPCC RCP4.5 climate scenario and simulated by ocean temperatures from 7 Earth System Models along with surface runoff derived from RACMO. In our simulations, Jakobshavn's grounding line continues to retreat ~ 18.5 km by the end of this century with total mass loss of ~ 2030 Gt (5.6 mm sea-level-rise equivalent). Despite the relative success of the model in simulating the recent behavior of the glacier, the model does not simulate winter calving events that have become relatively more important.〈/p〉

Description: 〈b〉Responses of sub-ice platelet layer thickening rate and frazil-ice concentration to variations in ice-shelf water supercooling in McMurdo Sound, Antarctica〈/b〉〈br〉 Chen Cheng, Adrian Jenkins, Paul R. Holland, Zhaomin Wang, Chengyan Liu, and Ruibin Xia〈br〉 The Cryosphere, 13, 265-280, https://doi.org/10.5194/tc-13-265-2019, 2019〈br〉 The sub-ice platelet layer (SIPL) under fast ice is most prevalent in McMurdo Sound, Antarctica. Using a modified plume model, we investigated the responses of SIPL thickening rate and frazil concentration to variations in ice shelf water supercooling in McMurdo Sound. It would be key to parameterizing the relevant process in more complex three-dimensional, primitive equation ocean models, which relies on the knowledge of the suspended frazil size spectrum within the ice–ocean boundary layer.

Description: 〈b〉Past and future dynamics of the Brunt Ice Shelf from seabed bathymetry and ice shelf geometry〈/b〉〈br〉 Dominic A. Hodgson, Tom A. Jordan, Jan De Rydt, Peter T. Fretwell, Samuel A. Seddon, David Becker, Kelly A. Hogan, Andrew M. Smith, and David G. Vaughan〈br〉 The Cryosphere, 13, 545-556, https://doi.org/10.5194/tc-13-545-2019, 2019〈br〉 The Brunt Ice Shelf in Antarctica is home to Halley VIa, the latest in a series of six British research stations that have occupied the ice shelf since 1956. A recent rapid growth of rifts in the Brunt Ice Shelf signals the onset of its largest calving event since records began. Here we consider whether this calving event will lead to a new steady state for the ice shelf or an unpinning from the bed, which could predispose it to accelerated flow or collapse.

Description: 〈b〉Uncertainty in predicting the Eurasian snow: Intercomparison of land surface models coupled to a regional climate model〈/b〉〈br〉 Da-Eun Kim and Seon Ki Park〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2019-15,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 An accurate prediction of the Eurasian snow is essentially important in predicting the climate and weather phenomena in Asia. Regional climate models are mostly coupled with several land surface models (LSMs) in which the land surface process parameters are calculated under their own physical principles and parameterization schemes. We show that prediction of the Eurasian snow cover is sensitive to the choice of LSMs coupled to regional climate models, and hence the future climate projections.

Description: 〈b〉Apparent discrepancy of Tibetan ice core δ〈sup〉18〈/sup〉O records may be attributed to misinterpretation of chronology〈/b〉〈br〉 Shugui Hou, Wangbin Zhang, Hongxi Pang, Shuangye Wu, Theo M. Jenk, and Margit Schwikowski〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-295,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 The apparent discrepancy between the Holocene δ〈sup〉18〈/sup〉O records of the Guliya and the Chongce ice cores may be attributed to a possible misinterpretation of the Guliya ice core chronology.

Description: 〈b〉Development of physically based liquid water schemes for Greenland firn-densification models〈/b〉〈br〉 Vincent Verjans, Amber Leeson, C. Max Stevens, Michael MacFerrin, Brice Noël, and Michiel R. van den Broeke〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2019-21,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 Firn models rely on empirical approaches for representing the percolation and refreezing of meltwater through the firn column. We develop liquid water schemes of different levels of complexities for firn models and compare their performances with respect to observations of density profiles from Greenland. Our results demonstrate that physically advanced water schemes do not lead to better agreement with density observations. Uncertainties in other processes contribute more to model discrepancy.

Description: A sudden release of large volumes of water during a glacier outburst flood (GLOF) is a major hazard worldwide. Here, we identify the sedimentary signature of glacial and non‐glacial processes, including GLOFs, based on lacustrine sediments from the distal glacier‐fed Lake Buarvatnet in western Norway. Historically documented GLOFs in 2002 CE and during the 1980s CE are identified in the 210Pb‐ and 14C‐dated sediments. These events have the same sedimentary signature as 12 earlier events throughout the Holocene interpreted to represent previous GLOFs in the catchment. The GLOFs are interpreted to have occurred during periods when the glacier extent was similar to the modern positions, and the events are thus used to pinpoint past positions of the glacier terminus and, hence, the equilibrium line altitudes (ELAs). The results indicate that the glacier Svartenutbreen, located at the eastern part of Folgefonna, had a similar size in 2002 CE as c. 8200–8300 cal. a BP, corresponding to the 8.2 ka event in the North Atlantic region. The regrowth of Sørfonna after the Holocene Thermal Optimum occurred at c. 6900 cal. a BP and Svartenutbreen was at modern size and extent in the periods c. 6400, c. 5450, c. 4850, c. 3850, c. 3550 and c. 1650 cal. a BP. Since 1650 cal. a BP, we infer that the glacier was larger than the 2002 CE glacier extent until 1910 CE when a GLOF occurred. Svartenutbreen has been retreating since 1910 CE, which led to the ice damming of the two historical GLOFs in the 1980s and 2002 CE separated by a glacier advance in the 1990s CE. The findings are discussed and compared to other regional glacier reconstructions in Norway, and emphasize the value of identifying and utilizing GLOFs as an indicator of past ELA variability.

Description: 〈b〉Shear failure of weak snow layers in the first hours after burial〈/b〉〈br〉 Benjamin Reuter, Neige Calonne, and Ed Adams〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-268,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 Storm snow instabilities often crest during storms which hampers field experiements. Yet, layers of nature-like snow can be created in the lab. We shear tested samples containing typical storm snow and other weak layers. Failure was consistently located in the weak layer and ocurred after linear elastic-perfectly plastic deformation. Measurements of shear modulus and fracture toughness indicate that surface hoar and precipitation particles are equally fragile in the first hours after burial.

Description: 〈b〉Definition differences and internal variability affect the simulated Arctic sea ice melt season〈/b〉〈br〉 Abigail Smith and Alexandra Jahn〈br〉 The Cryosphere, 13, 1-20, https://doi.org/10.5194/tc-13-1-2019, 2019〈br〉 Here we assessed how natural climate variations and different definitions impact the diagnosed and projected Arctic sea ice melt season length using model simulations. Irrespective of the definition or natural variability, the sea ice melt season is projected to lengthen, potentially by as much as 4–5 months by 2100 under the business as usual scenario. We also find that different definitions have a bigger impact on melt onset, while natural variations have a bigger impact on freeze onset.

Description: 〈b〉Warming of SE Greenland shelf waters in 2016 primes large glacier for runaway retreat〈/b〉〈br〉 Suzanne L. Bevan, Adrian J. Luckman, Douglas I. Benn, Tom Cowton, and Joe Todd〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-260,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 Kangerdlugssuaq Glacier in Greenland retreated significantly in the early 2000s and typified the response of calving glaciers to climate change. Satellite images show that it has recently retreated even further. The current retreat follows the appearance of extremely warm surface waters on the continental shelf during the summer of 2016 which likely entered the fjord and caused the rigid mass of sea-ice and icebergs, that normally inhibits calving, to melt and break up.

Description: 〈b〉Arctic sea-ice-free season projected to extend into autumn〈/b〉〈br〉 Marion Lebrun, Martin Vancoppenolle, Gurvan Madec, and François Massonnet〈br〉 The Cryosphere, 13, 79-96, https://doi.org/10.5194/tc-13-79-2019, 2019〈br〉 The present analysis shows that the increase in the Arctic ice-free season duration will be asymmetrical, with later autumn freeze-up contributing about twice as much as earlier spring retreat. This feature is robustly found in a hierarchy of climate models and is consistent with a simple mechanism: solar energy is absorbed more efficiently than it can be released in non-solar form and should emerge out of variability within the next few decades.

Description: 〈b〉Brief communication: Supraglacial debris-cover changes in the Caucasus Mountains〈/b〉〈br〉 Levan G. Tielidze, Tobias Bolch, Roger D. Wheate, Stanislav S. Kutuzov, Ivan I. Lavrentiev, and Michael Zemp〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-259,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 Debris cover on glaciers can significantly alter melt, and hence, glacier mass balance and runoff. Debris coverage typically increases with shrinking glaciers. Here, we present data on debris cover and its changes for 559 glaciers located in different regions of the Greater Caucasus mountains based on 1986, 2000 and 2014 Landsat and SPOT images. Over this time period, the total glacier area decreased from 691.5 km〈sup〉2〈/sup〉 to 590.0 km〈sup〉2〈/sup〉 (0.52 % yr〈sup〉−1〈/sup〉). Thereby, the debris covered area increased from ~ 11 to ~ 24 % on the northern, and from ~ 4 to 10 % on the southern macro-slope between 1986 and 2014. Overall, we found 18 % debris cover for the year 2014. With the glacier shrinkage, debris-covered area and the number of debris-covered glaciers increased as a function of elevation, slope, aspect, glacier morphological type, Little Ice Age moraines, and lithology.

Description: 〈b〉Brief communication: Pancake ice floe size distribution during the winter expansion of the Antarctic marginal ice zone〈/b〉〈br〉 Alberto Alberello, Miguel Onorato, Luke Bennetts, Marcello Vichi, Clare Eayrs, Keith MacHutchon, and Alessandro Toffoli〈br〉 The Cryosphere, 13, 41-48, https://doi.org/10.5194/tc-13-41-2019, 2019〈br〉 Existing observations do not provide quantitative descriptions of the floe size distribution for pancake ice floes. This is important during the Antarctic winter sea ice expansion, when hundreds of kilometres of ice cover around the Antarctic continent are composed of pancake floes (〈i〉D〈/i〉 = 0.3–3 m). Here, a new set of images from the Antarctic marginal ice zone is used to measure the shape of individual pancakes for the first time and to infer their size distribution.

Description: 〈b〉Version 2 of the EUMETSAT OSI SAF and ESA CCI sea-ice concentration climate data records〈/b〉〈br〉 Thomas Lavergne, Atle Macdonald Sørensen, Stefan Kern, Rasmus Tonboe, Dirk Notz, Signe Aaboe, Louisa Bell, Gorm Dybkjær, Steinar Eastwood, Carolina Gabarro, Georg Heygster, Mari Anne Killie, Matilde Brandt Kreiner, John Lavelle, Roberto Saldo, Stein Sandven, and Leif Toudal Pedersen〈br〉 The Cryosphere, 13, 49-78, https://doi.org/10.5194/tc-13-49-2019, 2019〈br〉 The loss of polar sea ice is an iconic indicator of Earth’s climate change. Many satellite-based algorithms and resulting data exist but they differ widely in specific sea-ice conditions. This spread hinders a robust estimate of the future evolution of sea-ice cover. In this study, we document three new climate data records of sea-ice concentration generated using satellite data available over the last 40 years. We introduce the novel algorithms, the data records, and their uncertainties.

Description: 〈b〉Distinguishing ice-rich and ice-poor permafrost to map ground temperatures and -ice content in the Swiss Alps〈/b〉〈br〉 Robert Kenner, Jeannette Noetzli, Martin Hoelzle, Hugo Raetzo, and Marcia Phillips〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-235,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 A new countrywide permafrost distribution map of Switzerland is presented. Zone 1 indicates ground temperatures and zone 2 excess ground ice which is located outside of zone 1. By distinguishing ice-poor and ice-rich permafrost we achieved a clear improvement in the cartographic representation of commonly occurring permafrost-free elevational belts which are bordered above and below by permafrost. The reproduction of such permafrost gaps allowed a higher accuracy and unambiguity of the map.

Description: 〈b〉The optical characteristics and sources of chromophoric dissolved organic matter (CDOM) in seasonal snow of northwestern China〈/b〉〈br〉 Yue Zhou, Hui Wen, Jun Liu, Wei Pu, Qingcai Chen, and Xin Wang〈br〉 The Cryosphere, 13, 157-175, https://doi.org/10.5194/tc-13-157-2019, 2019〈br〉 We first investigated the optical characteristics and potential sources of chromophoric dissolved organic matter (CDOM) in seasonal snow over northwestern China. The abundance of CDOM showed regional variation. At some sites strongly influenced by local soil, the absorption of CDOM cannot be neglected compared to black carbon. We found two humic-like and one protein-like fluorophores in snow. The major sources of snow CDOM were soil, biomass burning, and anthropogenic pollution.

Description: 〈b〉Thermal conductivity of firn at Lomonosovfonna, Svalbard, derived from subsurface temperature measurements〈/b〉〈br〉 Sergey Marchenko, Gong Cheng, Per Lötstedt, Veijo Pohjola, Rickard Pettersson, Ward van Pelt, and Carleen Reijmer〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-294,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 Thermal conductivity (〈i〉k〈/i〉) of firn at Lomonosovfonna, Svalbard, is estimated using measured temperature evolution and density. The optimized 〈i〉k〈/i〉 values (0.2–1.6 W/(m K)) increase downwards and over time and are most sensitive to systematic errors in measured temperature values and their depths, particularly in the lower part of the profile. Compared to density-based parameterizations our 〈i〉k〈/i〉 values are consistently larger, suggesting a faster conductive heat exchange in firn.

Description: 〈b〉Evaluating the destabilization susceptibility of active rock glaciers in the French Alps〈/b〉〈br〉 Marco Marcer, Charlie Serrano, Alexander Brenning, Xavier Bodin, Jason Goetz, and Philippe Schoeneich〈br〉 The Cryosphere, 13, 141-155, https://doi.org/10.5194/tc-13-141-2019, 2019〈br〉 This study aims to assess the occurrence of rock glacier destabilization in the French Alps, a process that causes a landslide-like behaviour of permafrost debris slopes. A significant number of the landforms in the region were found to be experiencing destabilization. Multivariate analysis suggested a link between destabilization occurrence and permafrost thaw induced by climate warming. These results call for a regional characterization of permafrost hazards in the context of climate change.

Description: 〈b〉Rapid decline of Arctic sea ice volume: Causes and consequences〈/b〉〈br〉 Jean-Claude Gascard, Jinlun Zhang, and Mehrad Rafizadeh〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2019-2,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 4 comments)〈br〉 From ERA Interim surface air temperature reanalysis, we estimated Freezing Degrees Days (FDD) over the whole Arctic Ocean during the freezing period each year for the past 40 years. We deduced sea ice growth from FDD that we compared with model (PIOMAS) and satellite (Cryosat-2) estimations. The warming of the Atmosphere and the vertical heat fluxes from the Ocean are contributing to the Arctic sea ice rapid decline. A disappearance of Arctic sea ice in summer is predictable within 15 years.

Description: 〈b〉Scaling of instability time-scales of Antarctic outlet glaciers based on one-dimensional similitude analysis〈/b〉〈br〉 Anders Levermann and Johannes Feldmann〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-252,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 1 comment)〈br〉 Using scaling analysis we propose that all potential marine ice-sheet instabilities in Antarctica will be slower than the currently observed instability in Amundsen Sea Sector.

Description: 〈b〉Characterizing the behaviour of surge- and non-surge-type glaciers in the Kingata Mountains, eastern Pamir, from 1999 to 2016〈/b〉〈br〉 Mingyang Lv, Huadong Guo, Xiancai Lu, Guang Liu, Shiyong Yan, Zhixing Ruan, Yixing Ding, and Duncan J. Quincey〈br〉 The Cryosphere, 13, 219-236, https://doi.org/10.5194/tc-13-219-2019, 2019〈br〉 We highlight 28 glaciers in the Kingata Mountains, among which 17 have changed markedly over the last decade. We identify four advancing and 13 surge-type glaciers. The dynamic evolution of the surges is similar to that of Karakoram, suggesting that both hydrological and thermal controls are important for surge initiation and recession. Topography seems to be a dominant control on non-surge glacier behaviour. Most glaciers experienced a significant and diverse change in their motion patterns.

Description: 〈b〉Converting Snow Depth to Snow Water Equivalent Using Climatological Variables〈/b〉〈br〉 David F. Hill, Elizabeth A. Burakowski, Ryan L. Crumley, Julia Keon, J. Michelle Hu, Anthony A. Arendt, Katreen Wikstrom Jones, and Gabriel J. Wolken〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-286,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 We present a new statistical model for converting snow depths to water equivalent. The only variables required are snow depth, day of year, and location. We use the location to look up climatological parameters such as mean annual precipitation and temperature characteristics. The model is simple by design so that it can applied to depth measurements anywhere, anytime. The model is shown to perform better than other widely used approaches.

Description: 〈b〉Sensitivity of active-layer freezing process to snow cover in Arctic Alaska〈/b〉〈br〉 Yonghong Yi, John S. Kimball, Richard H. Chen, Mahta Moghaddam, and Charles E. Miller〈br〉 The Cryosphere, 13, 197-218, https://doi.org/10.5194/tc-13-197-2019, 2019〈br〉 To better understand active-layer freezing process and its climate sensitivity, we developed a new 1 km snow data set for permafrost modeling and used the model simulations with multiple new in situ and P-band radar data sets to characterize the soil freeze onset and duration of zero curtain in Arctic Alaska. Results show that zero curtains of upper soils are primarily affected by early snow cover accumulation, while zero curtains of deeper soils are more closely related to maximum thaw depth.

Description: 〈b〉Brief communication: Full-field deformation measurement for uniaxial compression of sea ice by using the digital image correlation method〈/b〉〈br〉 Anliang Wang, Zhijun Wei, Xiaodong Chen, Shunying Ji, Yu Liu, and Longbang Qing〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-263,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 We applied digital images to measuring the full-field deformation of sea ice in the mechanical experiment. The characteristics of failure mode, nonlinear behavior and crack propagation are all captured by the strain field of specimens. To our knowledge, this is the first attempt to experimentally capture sequential full-field deformations in the mechanical properties of sea ice. This achievement will extend the ability to further explore the complex mechanical behaviors of sea ice.

Description: 〈b〉Multisensor validation of tidewater glacier flow fields derived from SAR intensity tracking〈/b〉〈br〉 Christoph Rohner, David Small, Daniel Henke, Martin P. Lüthi, and Andreas Vieli〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-278,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 The recent increase in ice flow and calving rates of ocean-terminating glaciers contributes substantially to the mass loss of the Greenland ice sheet. Using in situ reference observations, we validate the satellite-based method of iterative offset tracking of Sentinel-1A data for deriving flow-speeds. Our investigations highlight the importance of spatial resolution near the fast-flowing calving front, resulting in significantly higher ice velocities compared to large scale operational products.

Description: 〈b〉Permafrost distribution and conditions at the headwalls of two receding glaciers (Schladminger and Hallstadt glaciers) in the Dachstein Massif, Northern Calcareous Alps, Austria〈/b〉〈br〉 Matthias Rode, Harald Schnepfleitner, Oliver Sass, Andreas Kellerer-Pirklbauer, and Christoph Gitschthaler〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-281,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉Permafrost distribution in rockwalls surrounding receding glaciers is an important factor for rock slope failure and rockwall retreat. The Northern Calcareous Alps of the Eastern European Alps form a geological and climatological transition zone between the Alpine Foreland and the Central Alps. Some of highest summits of this area are located in the Dachstein Massif (47°28'32'' N, 13°36'23'' E) in Austria reaching up to 2995 m a.s.l. Occurrence, thickness and thermal regime of permafrost at this partly glaciated mountain massif are scarcely known and related knowledge is primarily based on regional modeling approaches. We applied a multi method approach with continuous ground surface and near-surface temperature monitoring, measurement of bottom temperature of the winter snow cover, electrical resistivity tomography/ERT, airborne photogrammetry, topographic maps, visual observations and field mapping for permafrost assessment. Our research focused on steep rockwalls consisting of massive limestone above several receding glaciers exposed to different slope aspects at elevations between c.2600–2700 m a.s.l. We aimed to quantify distribution and conditions of bedrock permafrost particularly at the transition zone between the present glacier surface and the adjacent rockwalls. 〈/p〉 〈p〉 Low ground temperature data suggest that permafrost is mainly found at cold, north exposed rockwalls. At southeast exposed rockwalls permafrost is only expected in very favourable cold conditions at shadowed higher elevations (2700 m a.s.l.). ERT measurements reveal high resistivities (〉 30.000 ohm.m) at ≥ 1.5 m depth at north-exposed slopes (highest measured resistivity values 〉 100 kohm.m). Based on laboratory studies and additional measurements with small scale ERT, these values indicate permafrost existence. Such permafrost bodies were found in the rockwalls at all measurement sites independent of investigated slope orientation. ERT data indicate large permafrost bodies at north exposed sites whereas discontinuous permafrost bodies prevail at northwest and northeast facing rockwalls. In summary, permafrost distribution and conditions around the headwalls of the glaciers of the Dachstein Massif is primarily restricted to the north exposed sector, whereas at the south exposed sector permafrost is restricted to the summit region.〈/p〉

Description: 〈b〉initMIP-Antarctica: An ice sheet model initialization experiment of ISMIP6〈/b〉〈br〉 Hélène Seroussi, Sophie Nowicki, Erika Simon, Ayako Abe Ouchi, Torsten Albrecht, Julien Brondex, Stephen Cornford, Christophe Dumas, Fabien Gillet-Chaulet, Heiko Goelzer, Nicholas R. Golledge, Jonathan M. Gregory, Ralf Greve, Matthew J. Hoffman, Angelika Humbert, Philippe Huybrechts, Thomas Kleiner, Eric Larour, Gunter Leguy, William H. Lipscomb, Daniel Lowry, Matthias Mengel, Mathieu Morlighem, Frank Pattyn, Anthony J. Payne, David Pollard, Stephen Price, Aurélien Quiquet, Thomas Reerink, Ronja Reese, Christian B. Rodehacke, Nicole-Jeanne Schlegel, Andrew Shepherd, Sainan Sun, Johannes Sutter, Jonas Van Breedam, Roderik S. W. van de Wal, Ricarda Winkelmann, and Tong Zhang〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-271,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉Ice sheet numerical modeling is the best approach to estimate the dynamic contribution of Antarctica to sea level rise over the coming centuries. The influence of initial conditions on ice sheet model simulations, however, is still unclear. To better understand this influence, an initial state intercomparison exercise (initMIP) has been developed to compare, evaluate, and improve initialization procedures and estimate their impact on century-scale simulations. initMIP is the first set of experiments of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6), which is the primary Coupled Model Intercomparison Project Phase 6 (CMIP6) activity focusing on the Greenland and Antarctic Ice Sheets. Following initMIP-Greenland, initMIP-Antarctica has been designed to explore uncertainties associated with model initialization and spin-up and to evaluate the impact of changes in external forcings. Starting from the state of the Antarctic ice sheet at the end of the initialization procedure, three forward experiments are each run for 100 years: a control run, a run with a surface mass balance (SMB) anomaly, and a run with a basal melting anomaly beneath floating ice. This study presents the results of initMIP-Antarctica from 25 simulations performed by 16 international modeling groups. The submitted results use different initial conditions and initialization methods, as well as ice flow model parameters and reference external forcings. We find a good agreement among model responses to the SMB anomaly, but large variations in responses to the basal melting anomaly. These variations can be attributed to differences in the extent of ice shelves and their upstream tributaries, the numerical treatment of grounding line, as well as the initial ocean conditions applied, suggesting that ongoing efforts to better represent ice shelves in continental-scale models should continue.〈/p〉

Description: 〈b〉New insight from CryoSat-2 sea ice thickness for sea ice modelling〈/b〉〈br〉 David Schröder, Danny L. Feltham, Michel Tsamados, Andy Ridout, and Rachel Tilling〈br〉 The Cryosphere, 13, 125-139, https://doi.org/10.5194/tc-13-125-2019, 2019〈br〉 This paper uses sea ice thickness data (CryoSat-2) to identify and correct shortcomings in simulating winter ice growth in the widely used sea ice model CICE. Adding a model of snow drift and using a different scheme for calculating the ice conductivity improve model results. Sensitivity studies demonstrate that atmospheric winter conditions have little impact on winter ice growth, and the fate of Arctic summer sea ice is largely controlled by atmospheric conditions during the melting season.

Description: 〈b〉Contributions of advection and melting processes to the decline in sea ice in the Pacific sector of the Arctic Ocean〈/b〉〈br〉 Haibo Bi, Qinghua Yang, Xi Liang, and Haijun Huang〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2019-11,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 The Arctic sea ice extent is diminishing, which is deemed as an immediate response to a warmer earth. However, quantitative estimate about the contribution due to transport and melt to the sea ice loss is still in vague. This study mainly utilizes satellite observations to quantify the dynamic and thermodynamic aspects of ice loss for a nearly 40 years (1979–2016). In addition, the potential impacts on ice reduction due to different atmospheric circulation pattern is highlighted.

Description: 〈b〉Sensitivity of centennial mass loss projections of the Amundsen basin to the friction law〈/b〉〈br〉 Julien Brondex, Fabien Gillet-Chaulet, and Olivier Gagliardini〈br〉 The Cryosphere, 13, 177-195, https://doi.org/10.5194/tc-13-177-2019, 2019〈br〉 Here, we apply a synthetic perturbation to the most active drainage basin of Antarctica and show that centennial mass loss projections obtained through ice flow models depend strongly on the implemented friction law, i.e. the mathematical relationship between basal drag and sliding velocities. In particular, the commonly used Weertman law considerably underestimates the sea-level contribution of this basin in comparison to two water pressure-dependent laws which rely on stronger physical bases.

Description: 〈b〉On the multi-fractal scaling properties of sea ice deformation〈/b〉〈br〉 Pierre Rampal, Véronique Dansereau, Einar Olason, Sylvain Bouillon, Timothy Williams, and Abdoulaye Samaké〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-290,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 In this article, we look at how the Arctic sea ice cover, as a solid body, behaves on different temporal and spatial scales.We show that the numerical model neXtSIM that uses a new approach to simulate the mechanics of sea ice is reproducing the characteristics of how sea ice deforms as observed by satellite.We discuss the importance of this model performance in the context of simulating climate processes taking place in polar regions,like the exchange of energy between the ocean and atmosphere.

Description: 〈b〉The role of debris cover in the evolution of Zmuttgletscher, Switzerland, since the end of the Little Ice Age〈/b〉〈br〉 Nico Mölg, Tobias Bolch, Andrea Walter, and Andreas Vieli〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-292,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 Debris can partly protect glaciers from melting. But many debris-covered glaciers change similar to debris-free glaciers. To better understand the debris influence we investigated 150 years of development of Zmuttgletscher in Switzerland. We found an increase of debris extent over time and a link to glacier flow velocity changes. We also found an influence of debris on the melt locally, but only a small volume change reduction over the whole glacier, also because of the influence of ice cliffs.

Description: 〈b〉Differential InSAR for tide modelling in Antarctic ice-shelf grounding zones〈/b〉〈br〉 Christian T. Wild, Oliver J. Marsh, and Wolfgang Rack〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-269,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 In Antarctica, ocean tides control the motion of ice sheets near the coastline as well as melt rates underneath the floating ice. By combining the spatial advantage of rare but highly accurate satellite images with the temporal advantage of tide-prediction models, vertical displacement of floating ice due to ocean tides can now be predicted accurately. This allows the detailed study of ice-flow dynamics in areas that matter the most to the stability of Antarctica's ice sheets.

Description: 〈b〉Arctic freshwater fluxes: sources, tracer budgets and inconsistencies〈/b〉〈br〉 Alexander Forryan, Sheldon Bacon, Takamasa Tsubouchi, Sinhué Torres-Valdés, and Alberto C. Naveira Garabato〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-247,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 We compare contol-volume and geochemical tracer-based methods of estimating the Arctic Ocean freshwater budget and find both methods in good agreement. Inconsistencies arise from the distinction between "Atlantic" and "Pacific" waters in the geochemical calculations. The definition of Pacific waters is particularly problematic, due to the non-conservative nature of the nutrients underpinning the definition and the low salinity characterising waters entering the Arctic through Bering Strait.

Description: 〈b〉Observation of the process of snow accumulation on the Antarctic Plateau by time lapse laserscanning〈/b〉〈br〉 Ghislain Picard, Laurent Arnaud, Romain Caneil, Eric Lefebvre, and Maxim Lamare〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2019-4,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 To study how snow accumulates in Antarctica, we use daily surface elevation recorded by an automatic laserscanner. We show that new snow often accumulates in thick patches covering a small fraction of the surface. Most patches are removed by erosion within weeks, implying that only a few contribute to the snowpack. The result is a great heterogeneity on the surface and in the snowpack. These findings are important for surface mass and energy balance, photochemistry and ice core interpretation.

Description: 〈b〉The evolution of snow bedforms in the Colorado Front Range and the processes that shape them〈/b〉〈br〉 Kelly Kochanski, Robert S. Anderson, and Gregory E. Tucker〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-293,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 Wind-blown snow does not lie flat. It forms dunes, ripples, and anvil-shaped sastrugi. These features ornament much of the snow on Earth, and change the snow's effects on polar climates, but they have rarely been studied. We spent three winters watching snow move through the Colorado Front Range. We present our findings, including the first time-lapse videos of snow dune and sastrugi growth, here.