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Holocene environmental and climate change on the Tibetan Plateau is intensively studied and discussed with the aim to better understand the factors controlling the hydrology of individual river catchments and especially the availability of water which is of utmost significance for the communities downstream in times of rapid climate change. Thus, a late glacial and Holocene sediment record from Lake Heihai in the Kunlun-Pass region was investigated using ostracod and geochemical analyses. Cold and dry conditions were inferred between ca. 12.9 and 12.3 cal ka BP and higher temperatures before and afterwards. The cold spell probably corresponds to the Younger Dryas (YD) event in the North Atlantic region. Warmer and wetter conditions with highest lake levels and decreased lake-water salinity were recorded from ca. 10.8 to 7.0 cal ka BP when the summer monsoon was strengthened. The cold 8.2 cal ka BP event is not significantly recorded in the region probably due to the predominance of the summer monsoon over the westerlies. A declined lake level and increased lake-water salinity as the result of cold and dry conditions are inferred from ca. 7.0 to 4.5 cal ka BP when the strengthening of the mid-latitude westerly circulation probably triggered glacier advances in the catchment. An even lower lake level existed during cold conditions with glacier advances from ca. 4.5 to 1.2 cal ka BP. The level of Lake Heihai rose again after ca. 1.2 cal ka BP due to warmer conditions, causing the retreat of glaciers and higher runoff. Our record from the Kunlun Pass region provides further evidence for the catchment-specific response of hydrographical systems which are partly controlled by glaciers as major water sources. [ABSTRACT FROM AUTHOR]

[Display omitted] With ongoing global warming and permafrost thawing, weathering processes will change on the Yukon River, with risks for water quality and ecosystem sustainability. Here, we explore the relationship between weathering processes and permafrost cover using elemental concentration and strontium and lithium isotopic data in the dissolved load of 102 samples collected during the summer across most major tributaries of the Yukon River. The Yukon River basin is dominated by silicate weathering with a high contribution from young volcanic rock units. In glaciated mountainous zones, we observe higher carbonate weathering contribution, low Li/Na ratios and low δ 7Li values (<15‰). In these areas, the high denudation rate and high supply of fresh minerals associated with alpine glaciers favor congruent silicate weathering, and sulfide oxidation accelerates carbonate weathering. In floodplains covered by continuous permafrost, we observe a high carbonate weathering contribution, relatively high Li/Na ratios, and low δ 7Li values (∼18‰). We argue that the minimal water–rock interactions in this setting inhibit silicate weathering and favor congruent weathering of easily weatherable minerals (i.e., carbonates). Conversely, in areas with discontinuous or sporadic permafrost, we observe a dominance of silicate weathering, with higher and more variable Li/Na ratios and high δ 7Li values (11–33‰). In this setting, longer water–rock interactions combined with the high supply of fresh minerals from mountain zones favor more incongruent weathering. The unique history of Pleistocene glaciations on the Yukon River basin also influences weathering processes. Many areas of the basin were never glaciated during the Pleistocene, and rivers draining those regions have higher δ 7Li values suggesting more incongruent weathering associated with deeper flow paths and longer water residence time in the regolith. Our work underlines that water–rock interactions, including active layer weathering and groundwater inputs, are highly dependent on climate conditions and glacial processes across the Yukon River basin, with key implications for future water quality in this warming basin. [ABSTRACT FROM AUTHOR]

• The glacier area retreat rate in the Chinese Altay Mountains is 0.55% a-1 during 1990–2021. • Glaciers in the Chinese Altay Mountains experienced a more intense retreat in 2000-2009. • Solar radiation and summer temperature have important effects on glacier retreat. Melting glaciers have changed the spatial–temporal distribution of water resources in inland river basins and are one of the important inducements of extreme hydrological events. Most previous studies on glacier changes in the Chinese Altay Mountains have focused on the period 1960–2011; however, there is a lack of glacier data reflecting recent changes (1990–2021) over the past decades, and the response of glaciers to regional climate change is still unclear. In this study, Landsat images and the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) were used to map glacier outlines from 1990 to 2021 for the whole region and its surrounding areas, and the impacts of temperature, precipitation, and solar radiation variation on glacier retreat were investigated. The results indicate that (1) the glacier area retreat rate of 0.55 %∙a-1 in the Chinese Altay Mountains during 1990–2021 is obviously lower than the glacier area shrinkage rate of 0.75 %∙a-1 from 1960 to 2009, and the retreat rate of glacier volume is 0.60 %∙a-1. (2) More than 80 % of the total glacier area located at elevation ranged from 2600 to 3400 m, and the greatest glacier area loss occurred within the elevation range of 2800–3000 m. Although the glacier area was retreating in all orientations, the south-facing glacier has the largest retreat rate. (3) The rate of change of glacier area was −1.26 %∙a-1, −0.71 %∙a-1 and −0.51 %∙a-1 in the Haba sub-basin, Sawir Mountains region, and Burqin sub-basin, respectively. (4) Owing to the slowdown in the warming rate since 1990, the glacier shrinkage rate was moderate during 1990–2021 compared to the 1960 s–1980 s, and contribution of the increase of solar radiation (35.72 %) and summer temperature (25.3 %) to glacier retreat from 1990 to 2021 were more prominent than other climate factors. [ABSTRACT FROM AUTHOR]

Well-dated and highly resolved paleoclimate records from high latitudes allow for a better understanding of past climate change. Lake sediments are excellent archives of environmental change, and can record processes occurring within the catchment, such as the growth or demise of an upstream glacier. Here we present a Holocene-length, multi-proxy lake sediment record from proglacial lake Gjøavatnet on the island of Amsterdamøya, northwest Svalbard. Today, Gjøavatnet receives meltwater from the Annabreen glacier and contains a record of changes in glacier activity linked to regional climate conditions. We measured changes in organic matter content, dry bulk density, bulk carbon isotopes, elemental concentrations via Itrax core-scanning, and diatom community composition to reconstruct variability in glacier extent back through time. Our reconstruction indicates that glacially derived sedimentation in the lake decreased markedly at ∼11.1 cal kyr BP, although a glacier likely persisted in the catchment until ∼8.4 cal kyr BP. During the mid-Holocene (∼8.4–1.0 cal kyr BP) there was significantly limited glacial influence in the catchment and enhanced deposition of organic-rich sediment in the lake. The deposition of organic rich sediments during this time was interrupted by at least three multi-centennial intervals of reduced organic matter accumulation (∼5.9–5.0, 2.7–2.0, and 1.7–1.5 cal kyr BP). Considering our chronological information and a sedimentological comparison with intervals of enhanced glacier input, we interpret these intervals not as glacial advances, but rather as cold/dry episodes that inhibited organic matter production in the lake and surrounding catchment. At ∼1.0 cal kyr BP, input of glacially derived sediment to Gjøavatnet abruptly increased, representing the rapid expansion of the Annabreen glacier. [ABSTRACT FROM AUTHOR]

Numerical glacier models applied to moraine chronologies provide an opportunity to quantify past climate change. Here we apply a two-dimensional coupled mass balance – ice flow model to well-dated moraine sequences deposited by former alpine glaciers at two central Patagonian sites: Cerro Riñón (43.97°S, 71.64°W) and Río Tranquilo (47.50°S, 72.38°W), to reconstruct the local temperatures during both the Antarctic Cold Reversal (14.7–13 ka) and the Younger Dryas (12.9–11 ka). Modelled temperature anomalies during the Antarctic Cold Reversal are −2.6 ± 0.4 °C at 44°S, and −2.9 ± 0.6 °C at 47°S. At both locations this cold event is followed by temperature increases of +0.6–0.7 °C or precipitation reductions of c. 20% to drive glacier retreat to moraines deposited during Younger Dryas time. The consistent climatic anomalies between these two latitudes suggest this region of Patagonia was responding to a common climatic event. Further, the late-glacial temperature anomalies found here compare well to those determined by similar glacier modelling techniques in New Zealand, at 43–44° S. These results support a trans-Pacific response throughout the southern mid to high latitudes (43–47° S) during the ACR that is best explained by a northward expansion of the south westerly winds. • Glacier modelling reconstructs Patagonian temperatures during late-glacial. • Cooling of −2.7 to −2.9 ° C below modern during the Antarctic Cold Reversal. • Warming of +0.6 ° C from the Antarctic Cold Reversal into the Younger Dryas period. • Climate trends parallel New Zealand glaciers implicating southern westerly winds. [ABSTRACT FROM AUTHOR]

Glacial changes during the Little Ice Age (LIA) in the Himalayan Mountains are important for understanding changes in the monsoonal and westerly climate of the so-called ‘the Third Pole’. However, knowledge of these changes and their dynamics remains limited because of the region's geographical inaccessibility, in addition to geopolitical reasons. In this study, we used high resolution three-dimensional images from Google Earth to identify lateral and terminal moraines as delineators of paleoglacier boundaries, and mapped the boundaries of both modern and LIA glaciers. ArcGIS 9.3 software was applied to map data and to calculate glacier lengths and areas; modern glacier surface elevation data were derived from SRTM (Shuttle Radar Topography Mission) records. Three methods, the toe-to-headwall altitude ratio (THAR), the toe-to-summit altitude method (TSAM), and the toe-to-ridge altitude method (TRAM) were used to estimate equilibrium line altitude (ELA). The transient snowlines (TSL) of ninety-one modern glaciers were acquired using Landsat 8 OLI images in late summer to evaluate the reliability of the calculated ELAs. Our results showed that the total length and total area of two hundred and twenty glaciers in the central and western Himalaya (CWH) had decreased respectively by 35% and 31% since the LIA. The TRAM method was the preferred method for the reconstruction of ELAs. The mean depression of ELAs from the LIA to the first decade of the 21st Century, as reconstructed using the TRAM method, was 123 m. The ELA depression and rate of change of glacier length and glacier area displayed generally increasing trends from west to east along the central and western Himalaya, suggesting that the moisture was most likely transported from an easterly direction. These changes were more intensive on southern than northern slopes, suggesting that southerly and westerly precipitation likely increased over the same period. We speculated that the CWH had been influenced by both the Indian Summer Monsoon (ISM) and Westerlies since the LIA. ISM moisture, as in modern times, was the main factor controlling the distribution of glaciers during the LIA. Further, precipitation carried by the Westerlies likely intensified along southerly pathways along the CWH during the LIA. [ABSTRACT FROM AUTHOR]

Rapid shrinkage and dramatic volume loss of the glaciers on Mt. Bogda in the eastern Tianshan Mountains have resulted in water shortages in the surrounding arid regions of China. Understanding ice thickness and its variation is important to the analysis of changes in glacial volume, which are directly related to regional hydrology and water resources. Fan-shaped Diffluence Glacier and Heigou Glacier No. 8 are located on the northern and southern slopes of Mt. Bogda, respectively. In this paper, the spatial distribution of the ice thickness of these two glaciers and the changes in their area and volume are discussed based on a 2009 survey result and comparison to previous investigations. The mean ice thickness of the tongue of Fan-shaped Diffluence Glacier was about 82.3 m and the calculated ice volume was 385.2 × 10 6 m 3 in 2009. It had thinned by 14 ± 8 m (0.30 ± 0.17 m a − 1 ) from 1962 to 2009, equivalent to an ice volume loss of 65.5 ± 37.4 × 10 6 m 3 . The mean ice thickness of the tongue of Heigou Glacier No. 8 was 58.7 m and the calculated ice volume was 115.1 × 10 6 m 3 in 2009. The tongue of Heigou Glacier No. 8 thinned by 13 ± 6 m (0.57 ± 0.26 m a − 1 ) from 1986 to 2009, which corresponds to an ice volume loss of 25.5 ± 11.8 × 10 6 m 3 . The greater thinning and retreat of Heigou Glacier No. 8 than those of Fan-shaped Diffluence Glacier is partially due to topographic characteristics. The difference can be attributed mainly to the greater increase in temperature on the southern slope than on the northern slope. [ABSTRACT FROM AUTHOR]

• Pir Panjal Range, an active mountain, has been home to large glaciers in the past. • Cirques are the dominant glacial geomorphic features present in the range. • Morphometry helps to identify the plausible causes of varied cirque geometry. • NE-facing cirques are the best developed in the Pir Panjal Range. Cirques are prominent features of alpine glacial landscapes, and they often form as a result of the glacial climate and follow the general aspect of the mountain ranges on which these develop. The role of controlling factors on the development of 143 cirques located in the Pir Panjal Range (PPR), NW Himalaya was investigated using morphometric analyses. The PPR, trending SE to NW, is of Pliocene to Quaternary age and largely deglaciated, except a few small debris-covered cirque glaciers. The role played by glaciers in sculpting the geomorphology of the PPR is evident from the presence of various erosional and depositional glacial landforms. The NE-, NW-, SW- and SE-oriented cirques account for ∼44%, ∼35%, ∼16% and 5% of the cirques investigated, respectively. In comparison to the NW cirques, the NE-oriented cirques are deeper, longer and more circular. Regardless of the dominant aspect or slope of the mountain range the trend of geological structures can influence the direction of erosion and define the shape and direction of cirque development. The cirque morphometry analyses described in this research back up the combined influence of climate and topography, on cirque development in the PPR. The study, which is first of its kind in the Himalaya, adds to the body of knowledge about uplift-driven climate change and explains the topographic and glacial geomorphic evolution in the PPR. [ABSTRACT FROM AUTHOR]

The hydrological conditions during the Last Glacial Maximum in the Eastern Mediterranean have long been debated. In particular, very little is known about the development of high-altitude glaciers in this region. In the present study, morphological and sedimentological evidence, such as U-shape valleys, glacial cirques, and morainic ridges, are used to identify past glaciers on the western slopes of Mount Lebanon, which is by far the highest topography along the eastern Mediterranean coast (3088 m a.s.l.). The geometry of three paleo-glaciers is reconstructed: one 8-km-long glacial tongue stretching from the highest peak down to an elevation of about 2000 m a.s.l., and two small glacial cirques located at about 2300 m a.s.l. The age of maximum glacier advance is constrained from a 10-m-deep 36Cl depth-profile within the diamicton of one terminal moraine, and yields an early LGM timing (between 25.4 ± 3.1 ka and 31.2 ± 4.5 ka), which agrees with the chronology of the last maximum glacier extension in the Eastern Mediterranean. The three glaciers together form a consistent group, compatible with an Equilibrium Line Altitude (ELA) at 2400 m estimated using the Accumulation Area Ratio method. A degree-day model is further used to infer the temperature and precipitation conditions required to depress the LGM ELA to 2400 m. Our results suggest that the observed glacier extent is compatible with early LGM paleo-temperature records of the area only under the condition of decreased precipitation relative to modern times. These findings thus support an early LGM climate of the Levant region that was drier than today. • First evidence of LGM glaciers in the southeastern Mediterranean (Mount Lebanon; 34.25°N) are provided. • The geometry of three glaciers is reconstructed and constrains the LGM Equilibrium Line Altitude at about 2400 m a.s.l. • Glacial and climate modeling indicates a drier LGM climate than today. [ABSTRACT FROM AUTHOR]

Abstract: This review summarises landform records and published age-estimates (largely based upon tephrochronology) to provide an overview of glacier fluctuations upon the Kamchatka Peninsula during the Holocene and, to a lesser degree, earlier phases of glaciation. The evidence suggests that following deglaciation from the Last Glacial Maximum (LGM), the peninsula experienced numerous phases of small-scale glacial advance. During the Late Glacial, moraine sequences appear to reflect the former presence of extensive glaciers in some parts of the peninsula, though little chronological control is available for deposits of this period. During the Holocene, the earliest and most extensive phase of advance likely occurred sometime prior to c. 6.8ka, when glaciers extended up to 8km beyond their current margins. However, these deposits lack maximum age constrains, and pre-Holocene ages cannot be discounted. Between c. 6.8ka and the onset of ‘Neoglaciation’ c. 4.5ka, there is little evidence of glacial advance upon the peninsula, and this period likely coincides with the Holocene climatic optimum (or ‘hypsithermal’). Since c. 4.5ka, numerous moraines have been deposited, likely reflecting a series of progressively less extensive phases of ice advance during the Late Holocene. The final stage of notable ice advance occurred during the Little Ice Age (LIA), between c. 1350 and 1850 C.E., when reduced summer insolation in the Northern Hemisphere likely coincided with solar activity minima and several strong tropical volcanic eruptions to induce widespread cooling. Following the LIA, glaciers upon the peninsula have generally shown a pattern of retreat, with accelerated mass loss in recent decades. However, a number of prominent climatically and non-climatically controlled glacial advances have also occurred during this period. In general, there is evidence to suggest that millennial scale patterns in the extent and timing of glaciation upon the peninsula (encompassing much of the last glacial period) are governed by the extent of ice sheets in North America. Millennial-to-centennial scale fluctuations of Kamchatkan glaciers (encompassing much of the Holocene) are governed by the location and relative intensity of the Aleutian Low and Siberian High pressure systems. Decadal scale variations in glacier extent and mass balance (particularly since the LIA) are governed by inter-decadal climatic variability over the North Pacific (as reflected by the Pacific Decadal Oscillation), alongside a broader trend of hemispheric warming. [Copyright &y& Elsevier]

Abstract: Fully understanding the timing and climate of Last Glacial Maximum (LGM) is still lack in the head of the Tashkurgan Valley, northwest Tibetan Plateau (TP). The recent improvements in cosmogenic 10Be exposure dating and glacier modeling present an opportunity to estimate the LGM climatic conditions. In the paper, we investigated the moraines and used the 10Be exposure dating on the moraine boulders to constrain the timing of the LGM, the Kuzigun glacial stage in the head of the Tashkurgan Valley. Then, we used a coupled mass-balance and ice-flow model to quantify the paleoclimate from past glacier extents constrained by mapped and dated Kuzigun glacial moraines in the area. We showed that the glaciers terminated at an elevation of 4100–4200 m asl during the Kuzigun glacial stage and the glacial stage occurred during or slightly before 15–23 ka, corresponding to the timing of the global LGM. The modeled mass balances indicated that present-day equilibrium line altitude (ELA) ranges from 5150 to 5250 m asl, and LGM ELA is between 4550 and 4600 m asl in the area, suggesting an ELA lowering of ∼600 m during the LGM. Model results suggested that the temperature during the LGM in the head of the Tashkurgan Valley is 5–8 °C colder than today, considering a 30–70% reduction in precipitation compared to today. The paleoclimate estimates are generally consistence with previous studies that showed the LGM climate was colder and drier than today on the TP. [Copyright &y& Elsevier]

Abstract: Results from cryogenic column experiments are compared with the geochemical data collected in the Canadian and Fennoscandian Shields over the past 25years to investigate the relative influence of the glacial–interglacial cycle; specifically, the impact of continental glaciers, permafrost, and methane hydrate, on the evolution of groundwater from crystalline shield environments. Several different geochemical indicators of freezing processes (either glacial or permafrost-related) were utilized: comparisons of Na/Cl and Br/Cl ratios, δ18O and δ2H values, and δ18O values and Cl− concentration. During freezing, fluids with different dominant cations follow distinctly different linear trends when Na/Cl and Br/Cl ratios are compared. Significantly, none of the freezing trends follows the trend hypothesized by for the evolution of seawater chemistry during freezing. Intrusion of glacial meltwater and in situ freezing (i.e., permafrost formation) result in a similar end-member when comparing δ18O values and Cl− concentration. The geochemical influence of a freezing process on fresh, brackish, and some saline fluids was identified at some, but not all Canadian Shield sites, regardless of site location with respect to modern-day permafrost. Appreciably, physical and geochemical data do not support the formation of brines through any freezing process in the Canadian and Fennoscandian Shields, as hypothesized by . Rather, on all diagnostic freezing plots, brines are an end-member, indicating a different evolutionary pathway. Significant depletions in 18O with respect to modern precipitation, an indication of either glacial meltwater or a freezing process, were identified at depths of up to 1km at some sites in the Canadian Shield, and to shallower depths in the Fennoscandian Shield. The potential of this fluid to reach such depths could be attributable to artificial gradients and mixing, glacial recharge, permafrost or paleo-permafrost formation, or methane hydrate or paleo-methane hydrate formation. At most locations it was not possible to distinguish between the different scenarios using the current geochemical database. [Copyright &y& Elsevier]

Abstract: We present constraints on the chronology, palaeogeography and palaeoclimatic implications for western Europe of Middle and Late Pleistocene glaciation in the Ariège catchment, north-eastern Pyrenees. Based on 37 cosmogenic 10Be exposure ages obtained from moraines and glacially scoured bedrock exposures, we have dated six regional glacial stades. The chronology emphasises several conclusions that are new to the region: (i) in the Pyrenees, the global LGM occurred several thousands of years after the maximum ice extent of the Würmian glaciation; (ii) almost full glacier extent occurred again during the global LGM, but only in the eastern Pyrenees; (iii) valley glaciers such as in the Ariège trunk valley attained lengths of ~25km during the Oldest Dryas Stadial. The cosmogenic exposure ages additionally provide the first direct evidence of ~10km-scale fluctuations of ice-front positions during the Late Pleistocene glacial cycle, probably at the time of Marine Isotope Stage 3, as well as rare insights into Middle Pleistocene ice-margin positions. Compared with existing evidence of glacial palaeogeography in other catchments of the Pyrenan range, the data also reveal a sharp contrast in relative ice extent between the glacierized catchments of the eastern Pyrenees (Ariège, Carol–Malniu, Têt), where Würmian MIE and LGM ice fronts reached similar positions, and the rest of the range, where ice fronts at the time of the MIS 2 and global LGM palaeotemperature minima lagged far behind the Würmian MIE terminal moraines. We ascribe this non-uniform behaviour among catchments to non-uniform palaeoclimatic conditions along the strike of the Pyrenees. A range of palaeoenvironmental proxies reviewed in the literature highlight a sharp difference in sea-surface temperatures between the warmer Western Mediterranean and the cooler Bay of Biscay. The consequences of such an E–W temperature gradient on weather patterns during the global LGM are compatible with a strengthening of Mediterranean low-pressure systems (particularly the semi-permanent Balearic Low) generating greater precipitation over the eastern Pyrenees compared to Atlantic weather systems further west. [Copyright &y& Elsevier]

Abstract: The biogeochemical cycling and isotopic fractionation of calcium during the initial stages of weathering were investigated in an alpine soil chronosequence (Damma glacier, Switzerland). This site has a homogeneous silicate lithology and minimal biological impacts due to sparse vegetation cover. Calcium isotopic compositions, obtained by TIMS using a 43Ca–46Ca double spike, were measured in the main Ca pools. During this very early stage of weathering, the young soils which have formed were indistinguishable to the rocks from which they were derived and stream water was also within error of the average rock. This lack of variation indicates that the dissolution of the bulk silicate rock does not strongly fractionate Ca isotopes. The only Ca pool which was strongly fractionated from bulk rock was vegetation, which exhibited an enrichment of light Ca isotopes. Significant Ca isotope fractionation between bulk rock and the dissolved flux of Ca is likely to only occur where the Ca biogeochemical cycle is dominated by secondary processes such as biological cycling, adsorption and secondary mineral precipitation. [ABSTRACT FROM AUTHOR]

Abstract: The chronology of late-glacial and Holocene ice fluctuations in East Greenland is important for documenting glacier response to climate change and for determining the mechanisms behind abrupt climate switches. Raised marine sediments and landforms suggest culmination of the late-glacial Milne Land Stade in Schuchert Dal alongside Scoresby Sund before ∼11,900–12,300calyr B.P. Ice in Schuchert Dal apparently receded during the later part of the Younger Dryas, consistent with the idea that this period was characterized by strong seasonality. A stillstand or slight readvance probably interrupted overall recession just prior to 11,000calyr B.P. In many locations, ice was back close to present positions by the start of the Holocene. The most extensive glacier advance of the Holocene occurred during the Little Ice Age and was restricted to within a few kilometers of present-day ice margins. [ABSTRACT FROM AUTHOR]

Abstract: With the increasing use of digital elevation models in palaeo-glacier reconstructions and the availability of freeware spreadsheets the Area-Altitude Balance Ratio (AABR) and Balance Ratio (BR) methods are becoming increasingly used in palaeo-glacier reconstruction for estimating Equilibrium Line Altitudes (ELA) and subsequently deriving quantitative estimates of palaeo-climate. While there are many data detailing contemporary Accumulation Area Ratios, there are still only a few studies that have established, from contemporary environments, AABR/BR ratios. Publicly available glacier mass balance (World Glacier Monitoring Service, US Geological Survey, and Norwegian Water Directorate) and spatial extent datasets provided the basis for this research. From a time series of mass balance, regressing specific net balance against ELA allows the zero net balance ELA to be identified. Once the zero balance ELA is established, the glacier hypsometry above and below the ELA is defined. The AABR/BR is calculated by using (the right hand side) the following: where, bnab and bnac are the net mass balance gradients in the ablation and accumulation zones respectively, and are the area-weighted mean altitudes of the accumulation and ablation areas respectively and Aac and Aab are the areas of the accumulation and ablation areas respectively. AABRs are calculated for a suite of glaciers located across a range of climatic zones and glacier types, with Antarctica being excluded. The following “representative” AABRs are found: a global AABR=1.75±0.71; Mid-latitude maritime=1.9±0.81; High-latitude=2.24±0.85; North America – West Coast=2.09±0.93; North America – Eastern Rockies=1.11±0.1; Canadian Arctic=2.91±0.35; Svalbard=2.13±0.52; Western Norway=1.5±0.4; European Alps=1.59±0.6; Central Asia=1.75±0.56; Kamchatka=3.18±0.16. This study provides an empirically derived dataset characterising AABR ratios which may be used for ELA estimation in palaeo-glacier reconstructions and for palaeo-climate quantification. [Copyright &y& Elsevier]

Abstract: This special issue presents a collection of papers that address a wide range of important challenges and exciting advances in the field of glacial landscape evolution. Primarily, these papers reflect persistent uncertainty that surrounds the mechanisms and timescales of glacial landscape evolution. For example, estimates of the duration of glacial occupancy required for the evolution of characteristic glacial valley forms from previously fluvial landscapes range from 100 kyrs for landscapes beneath large ice sheets (Jamieson et al.) to ~400–600 kyrs for glaciated alpine terrains (Brook et al.). Further, the mechanisms of glacial erosion are debated through analyses of the importance of ice thickness (Brocklehurst et al.; van der Beek and Bourbon), ice surface steepness (Vieira) and, in the case of large ice sheets, the co-evolution of ice sheet thermal regime, dynamics, and subglacial topography (Kleman et al.; Swift et al.). Debate concerning the potential climatic impacts of landscape evolution in alpine terrains is represented by van der Beek and Bourbon, who infer a significant increase in relief as a direct result of glacial erosion, and by Brocklehurst et al. and Heimsath and McGlynn, who demonstrate respectively that glacial relief production can be surprisingly modest and that rates of glacial erosion may be lower than those for fluvial incision. Further confirmation that valleys beneath large ice sheets evolve through selective linear erosion comes from studies that have combined geomorphological evidence with cosmogenic nuclide (Briner et al.) and apatite (U–Th)/He thermochronometry (Swift et al.), and the resulting style of landscape evolution is demonstrated by the antiquity of fjords in East Greenland (Swift et al.) and of deep erosion zones and thick drift covered zones in Fennoscandia (Kleman et al.), although the location of areal scouring zones may be subject to major alteration during single glacial events (Kleman et al.). Another set of papers shows that analyses of glacial lineation systems continue to provide important data on the dynamics of glacial landscape evolution, whether the lineations are formed underneath ice streams (Bradwell et al.; Andreassen et al.) or not (Jansson and Glasser), and whether they indicate intricate patterns of landscape modification (Andreassen et al.) or preservation (Jansson and Glasser). The final three papers address rarely-reported issues relating to landscapes of glacial deposition, including moraine degradation (Putkonen et al.), proglacial hydrogeology (Robinson et al.), and the evolution of hummocky-till topography (Clayton et al.). [Copyright &y& Elsevier]

Abstract: In this paper, we describe mapping of palaeo-ice streams in the Foxe/Baffin sector of the Laurentide Ice Sheet by means of geomorphological interpretation of high-resolution satellite images. Our interpretations were guided by a glaciological inversion scheme, aided by digital elevation models, publicly available sonar surveys and field studies. As a result, we produced a map depicting the location, geometry and relative temporal changes of palaeo-ice streams and analysed their palaeoglaciological implications for the Foxe/Baffin sector. We conclude that in the period between the Last Glacial Maximum and approximately 7.0kyrBP, the Foxe/Baffin sector was largely drained by topographically controlled outlet glaciers and ice streams, which were organized in a relatively stable pattern. During this time, large areas of Melville Peninsula and central Baffin Island were subject to cold-based conditions. Between 7.0 and 6.0kyrBP, the Foxe/Baffin sector collapsed catastrophically in the Foxe Basin, after which its remnant portion became confined to Baffin Island. During this collapse, rapid successions of small transient ice streams occurred along wide, loosely defined topographical corridors in two sectors of Baffin Island. The presently available landform archive on emerged land is not sufficient to conclusively support the existence of fully scaled ice streams along the whole length of Hudson Strait. As an alternative solution, we propose that topographically controlled ice streams might have occurred along the deepest parts of Hudson Strait, with attendant cold-based ice zones on marginal areas and islands at the head of the strait. [Copyright &y& Elsevier]

Abstract: To elucidate the way in which past climatic changes are encoded magnetically by wind-blown silt, we have investigated two stratigraphic sections in the Chinese Loess Plateau (Xiagaoyuan, in the cool, dry western plateau and Houzhuang, in the warmer, wetter central plateau). In view of the anticipated importance of magnetic particle size, we have determined grain-size distributions from >50 μm down to ∼10 nm by sequential sieving, sedimentation and centrifugation of typical loess and palaeosol material from the two sites. For the essentially unaltered loess, the main susceptibility contribution lies in the 20–50 μm fraction, with only ∼20% of the signal residing in the &#60;2 μm fraction. In the well-developed palaeosol, ∼60% of the susceptibility comes from the &#60;2 μm fraction, with a strong peak in the 0.1–0.4 μm fraction. Low-temperature experiments confirm this magnetic enhancement, and also exhibit Verwey transitions characteristic of magnetite. Magnetic hysteresis parameters show simple relationships to susceptibility, which can be interpreted in terms of a uniform mineral ingredient which increases in amount as pedogenesis intensifies. Beryllium-10 content was determined for a profile spanning palaeosol S1 (corresponding to oxygen isotope stage 5) at Houzhuang, and a peak value of 4.8×108 atoms/g was observed, almost identical to that found by other workers for the same horizon at Luochuan. A similar profile at Xiagaoyuan reveals three peaks corresponding to palaeosols S1S1 (2.6×108 atoms/g), S1S2 (3.3×108 atoms/g) and S1S3 (3.3×108 atoms/g). Conversion of these concentrations into 10Be fluxes indicates low dust accumulation during warmer climate episodes. At these times pedogenic susceptibility enhancement is favoured, the amounts of which imply palaeoprecipitation slightly higher than today for S1S3 at Xiagaoyuan, but somewhat lower than today for S1 at Houzhuang. [Copyright &y& Elsevier]

Beginning in 1995, a large outlet glacier of the Sermersauq Ice Cap on Disko Island surged 10.5 km downvalley to within 10 km of the head of the fjord, Kuannersuit Sulluat, reaching its maximum extent in summer 1999 before beginning to retreat. Sediment discharge to the fjord increased from 13×103 t day−1 in 1997 to 38×103 t day−1 in 1999. CTD results, sediment traps and cores from the 2000 melt season document the impact of the surge on the glacimarine environment of the fjord. Within 4 km of the inflow sedimentation rates increased by 30 times over those before the surge, reaching an estimated maximum value of 29 cm a−1 (up to 4.2 mm day−1 between 24 July and 9 September 2000). Fine-grained deposits from suspension in the water column displayed diurnal laminations in response to the interaction of tidal cycles with the sediment plume; these are not found in the sediments deposited before surging. Thin beds of sandy turbidites from turbidity currents originating from slope failures on the delta front occurred at about 20 day intervals during the melt season. Each of these effects was limited to within several kilometres of the point of inflow, but provide a unique signal significantly different from those generated by normal hydroclimatically induced events. [Copyright &y& Elsevier]

A mechanism is presented for subaerial calving of ice slabs and subaqueous calving of ice ledges from ice walls and ice shelves in lacustrine and marine glacial environments. The calving rate is equated with the maximum forward velocity of slab-bending at the time of calving. The rate of slab calving above water is shown to control the rate of block calving from ice ledges below water. Slabs theoretically calve along surface crevasses that are at a distance behind the calving front of about one-tenth the subaerial height of the ice wall or ice shelf. Blocks theoretically calve along bottom crevasses when subaqueous ice ledges produced by subaerial slab calving approach one-half of the ice thickness below water. These calculations are supported by studies of a calving ice wall on Deception Island, Antarctica, and by observations of calving from ice walls along the Antarctic Peninsula, from the Ross and Getz Ice Shelves in Antarctica, from large tabular icebergs in the Ross and Amundsen Seas of Antarctica, from Jakobshavns Isbrae in Greenland, and from tidewater glaciers in Alaska, Greenland, and Svalbard. Calving bays accelerate the retreat of Quaternary ice sheets along lacustrine and marine ice margins at the termination of Quaternary glaciation cycles. Rapid calving retreat causes sudden outbursts of icebergs from marine ice streams and meltwater from ice-dammed lakes, events that may trigger abrupt climatic changes. In the case of the Laurentide Ice Sheet, retreat of a calving bay along Hudson Strait would not only be accompanied by an iceberg outburst into the North Atlantic, the calving bay could also continue into Hudson Bay and carve out the heart of the Laurentide Ice Sheet itself, thereby terminating the last cycle of Quaternary glaciations. [Copyright &y& Elsevier]

Late Pleistocene glaciation of Australia was restricted to the Snowy Mountains and the Tasmanian highlands. Glaciers were most extensive in Tasmania where ice caps formed on the Central Plateau and West Coast Ranges, and systems of valley and cirque glaciers formed on surrounding mountains. To investigate the timing of maximum glacier advance during the Last Glacial Maximum (LGM), we dated boulders on 18 moraines in 8 glaciated areas using cosmogenic 36Cl and 10Be. We sampled moraines deposited by cirque and valley glaciers, in a range of climate types and lithologies over a 7° latitudinal and a 1430 m altitudinal transect. Exposure ages for LGM moraine boulders group tightly in the range 17–20 ka. Boulders from the Hamilton moraine, often treated as the LGM type moraine, range in age from ∼190–350 ka, indicating that it was deposited well before the last glaciation. Collectively, the exposure ages show that southeastern Australia was glaciated briefly during and after the LGM, and deglaciated well before the Holocene. Ice retreated from the terminal moraines after the period of coldest sea-surface temperatures in the southwest Pacific Ocean. No evidence was found for readvance of glaciers during the Antarctic Cold Reversal or the Younger Dryas period. [Copyright &y& Elsevier]

The most recent maximum in global ice volume occurred around 23,000 to 19,000 years ago, during Marine Isotope Stage 2 (MIS 2; ∼29-14 ka) according to benthic δ18O and sea level records. However, evidence from cosmogenic surface exposure dating indicates that world-wide many glacier systems of different sizes as well as portions of some ice sheets were more extensive during MIS 4 (∼71-57 ka) and MIS 3 (∼57-29 ka) than they were during MIS 2. This discrepancy between global ice volume and ice extent must be explained in order to understand Earth's recent paleoclimate history. Here, we review MIS 4 moraine chronologies based on 10Be exposure dating, and we describe additional paleoclimate proxy records that indicate similar magnitudes of cooling during MIS 4 and MIS 2. While certain regions may have benefited from a wetter MIS 4 relative to MIS 2, it is unlikely that precipitation alone can explain more extensive glaciation on a global scale between 71 and 57 ka. Our review supports the hypothesis that the discrepancy between ice volume and ice extent during MIS 4 can be attributed to the growth of the North American ice sheets (and perhaps other northern ice sheets). Glaciers ultimately respond to changes in climate, however, large northern ice sheets also were affected by factors involving topography, isostacy, and glaciologic and mass balance dynamics. Given these feedbacks, the North American ice sheets' dominant role in global ice volume, sea level, and benthic δ18O signals might therefore result in a skewed picture of global climate. If maximum global ice volume during MIS 2 is mainly a function of North American ice sheet volume and not necessarily directly connected to global temperatures, then other records with extremes during MIS 2, such as dust and CO 2 , could be primarily reflecting ice volume change. • MIS 4 moraine chronologies in many locations suggest a possible collective advance of glaciers due to global cooling. • It is difficult to explain MIS 4 glacier extents if one assumes that global mean temperature followed a 'sawtooth' pattern. • Records displaying the 'sawtooth' pattern might be reflecting global ice volume rather than climate. • Obliquity causes symmetrical changes in insolation in both hemispheres and may still drive glacial climate. [ABSTRACT FROM AUTHOR]

• We introduce a new valley network parameter accounting for elevation-drainage area distribution. • We develop a new 1D model for coupled glacial-fluvial topography in steady state. • Tectonics and climate control the shape of both glacial and fluvial topography. • Temperate glaciers erode more efficiently than rivers for typical parameter sets. • The influence of tectonics and climate on glacial relief is compatible with the glacial buzzsaw. Studies on relief and hypsometry in glaciated mountain ranges have recognized the equilibrium line altitude of glaciers as a major control on mountain height. This has led to the belief that, in contrast to fluvial topography, glacial topography is limited by climate, with tectonics playing a secondary role. This concept is known as the glacial buzzsaw. However, the understanding of controls on glacial relief has remained mainly qualitative, in part because a reference scenario for glacial landscape evolution — a glacial topographic steady state linked to the base level by a fluvial topographic steady-state downstream of the glacier terminus - and its dependencies have not yet been defined. Here we define such a reference and compare steady state longitudinal profiles in a coupled system of glacial and fluvial erosion that involves both tectonics and climate. Our model is based on the stream power law for fluvial erosion, the shallow ice approximation in combination with a glacial erosion rule, and an empirically determined drainage area-flow length relationship for both rivers and glaciers. Further, we introduce a new approach to incorporate dendritic glacier network structures into the one-dimensional model. Modeling of coupled glacial-fluvial steady-state profiles with empirical glacial and fluvial erosion parameters shows that the difference between glacial and fluvial relief depends on climate, tectonics and the applied erosion laws. Our results imply that glacial erosion can typically balance tectonic uplift rates at lower relief and topographic slopes than fluvial erosion. This steady state equivalent of the glacial buzzsaw effect suggests that glaciers may indeed be more efficient erosional agents than rivers increasing erosion in a cooling climate. [ABSTRACT FROM AUTHOR]