Glacier Expansion Research Articles

Multiple independent records of local glacier variability on Nuussuaq, West Greenland, during the Holocene

The sensitivity of mountain glaciers to small-scale climate fluctuations makes records of their past extent among the best proxies for identifying spatio-temporal climate variability. Here we build on the few existing Holocene records of local glacier change in Greenland by using three independent geochronological methods—proglacial lake sediment analysis, cosmogenic 10Be surface-exposure dating, and in situ14C burial modeling—to reconstruct continuous records of Holocene glacier variability on Nuussuaq, West Greenland. 10Be ages of perched boulders indicate eastern Nuussuaq was deglaciated between ∼11.0 and 10.5 ka. Radiocarbon-dated sediments from two lakes on Nuussuaq contain mineral-rich layers between ∼9.6 and 9.0 and ∼8.7–8.0 cal ka BP that may be correlative with nearby ice sheet moraines deposited in the early Holocene. Multiple proxies for glacier size indicate frequent, high-amplitude glacier fluctuations superimposed on net glacier growth during the late Holocene, with significant ice expansion phases at ∼3.7 ka, 2.8 ka, and throughout the past ∼2 ka. Mean 10Be ages from five nested moraine crests confirm that local glacier extents on Nuussuaq culminated during both the Little Ice Age [∼1470 C.E. (n = 3) and 1750 C.E. (n = 3)] and the preceding centuries (∼520–1320 C.E.; n = 11). Results reveal that local glaciers on Nuussuaq episodically advanced and retreated at centennial timescales throughout the Holocene, most likely in response to regional climate changes in West Greenland superimposed on the progressive insolation-driven cooling trend in the Northern Hemisphere. Our new 10Be moraine chronologies coupled with other glacier-size proxies corroborate an emerging pattern of significant summer cooling and glacier expansion in the centuries prior to the Little Ice Age in the Arctic.

Paleo-shoreline changes in moraine dammed lake Khagiin Khar, Khentey Mountains, Central Mongolia

The formation and evolution of glacier moraine-dammed lakes are closely related to past glacier expansion and retreat. Geomorphic markers such as lacustrine terraces and beach ridges observed in these lakes provide important evidence for regional paleoenvironment reconstruction. We document the magnitude of paleo-shoreline fluctuations and timings of highstands of lake water by using cosmogenic 10Be surface exposure dating and optically stimulated luminescence (OSL) dating on samples collected from lacustrine sediment and bedrock strath in Lake Khagiin Khar. The lake was initially impounded by glacier moraine at the Global Last Glacial maximum (gLGM; 21–19 ka), and the lake reached its maximum paleo-shoreline level of 1840 m at sea level (a.s.l.). At that time, the stored lake water amount was up to seven times greater and the surface area was three times larger than the present values. The paleolake experienced higher shoreline levels at 1832, 1822, and 1817 m a.s.l. and reached the present lake level after 0.4 ka. We interpret that decrease in the paleolake level was caused by spillover. The increase in melt water after the gLGM and the Late Glacial exceeded the storage threshold of the lake, and the paleolake water overflowed across the lowest drainage divides. The lake spilled over across the lowest bedrock ridge at 15.9 ± 0.6 ka, and the outlet was incised since that time at a rate of 3.72 ± 0.15 mm/yr. The initial stream of the Khiidiin Pass River was disturbed by LGM moraine damming and was rerouted into the present course running through moraine after the spillover at 15.9 ± 0.6 ka.

Assessment of coastal vulnerability in Chabahar Bay due to climate change scenarios

Summary A substantial body of research has shown that two key factors of global sea level rise are thermal expansion and melting of land-based ice, glaciers and ice sheets. Moreover, climate change may result in changes to wind speeds and directions, consequently resulting in contributions to variations in wind-wave components, wave heights and directions. In this research, climate change scenarios were used to assess the coastal vulnerability to the Chabahar port area due to global sea level rise, significant wave height changes and tidal regime effects. These three items were calculated separately using numerical models and the impacts of possible climate change scenarios were applied to estimate possible changes to these items by 2100. Significant wave heights for 25, 50 and 100-year return periods were evaluated. Based on statistical analysis, the maximum significant wave heights for the A2 and A1B scenarios were estimated at approximately 13.7 and 7.6, respectively. Since the main aim of this research was to assess the coastal zones at higher flood risk, therefore the mean global sea level rise, extreme values of significant wave heights and tidal heights were investigated. The height of sea during sea storms and for the most extreme case was calculated as 17.3 m and 11.2 m for A2 and the A1B scenarios, respectively. According to output maps of inundation areas, large coastal zones in the Chabahar port area are at risk due to the sea storms and possible climate change.

Reconstruction of the Little Ice Age glaciers and equilibrium line altitudes in the Kodar Range, southeast Siberia

Little Ice Age (LIA), a time of global cooling widely manifested in the 14th-19th centuries, was characterized by worldwide expansion of mountain glaciers. Unfortunately, little is known about the LIA glacier changes in remote areas of continental Siberia. In this work we studied the evolution of the glaciers of the Kodar Range, southeast Siberia. These glaciers are mainly of small size (<0.5 km2), cirque and cirque-valley, with predominant northern and north-eastern aspects, located at elevations of 1900–2800 m a.s.l. Using field and satellite imagery data over the 2001–2013 period (Landsat ETM+, Cartosat-1, WorldView-2) we mapped the glaciers, equilibrium line altitudes (ELAs) and the LIA moraines. Modern ELAs vary from 1945 to 2615 m a.s.l. (mean value is 2286 ± 162 m) and demonstrate NNW to SSE increasing regional trend (from 2060 to 2430 m a.s.l.) with local ELA variability due to orography of ±114 m. The extents of the LIA glaciers were reconstructed from terminal moraines, located in front of the glacier termini. These moraines are of fresh morphology, non-vegetated, and locally dated by lichenometry at the mid-18th century. Since the LIA the total glacier area decreased from 19 km2 to 9 km2 (by 53%) and glacier termini retreated, on average, by 440 m. South and south-west facing glaciers shrunk 1.5–2 times stronger than those with northern and north-eastern aspects. Using the toe-to-headwall altitude ratio (THAR) and toe-to-summit altitude method (TSAM), the LIA ELAs were calculated. The LIA ELAs lowered, on average, by 40–60 m, while the ELA changes on south and south-west facing glaciers (mean value of 80–100 m) was 2–2.5 times greater than of the northern. ELA depression during the LIA corresponded to decrease in mean summer temperature of 0.9–1.1 °C (if precipitation was equal to the present). Temperature increase was mainly responsible for ELA rising since the LIA, however, the response of small glaciers could be modulated by other factors (e.g. local insolation or precipitation). Stronger reduction of the south and south-west facing Kodar glaciers can be explained by their greater sensitivity to both solar radiation and snow nourishment with southern cyclones and East Asian monsoon.

Evaluating Glacier Volume Changes since the Little Ice Age Maximum and Consequences for Stream Flow by Integrating Models of Glacier Flow and Hydrology in the Cordillera Blanca, Peruvian Andes

Evaluating the historical contribution of the volume loss of ice to stream flow based on reconstructed volume changes through the Little Ice Age (LIA) can be directly related to the understanding of glacier-hydrology in the current epoch of rapid glacier loss that has disquieting implications for a water resource in the Cordillera Blanca in the Peruvian Andes. However, the accurate prediction of the future glacial meltwater availability for the developing regional Andean society needs more extensive quantitative estimation from long-term glacial meltwater of reconstructed glacial volume. Modeling the LIA paleoglaciers through the mid-19th century (with the most extensive recent period of mountain glacier expansion having occurred around 1850 AD) in different catchments of the Cordillera Blanca allows us to reconstruct glacier volume and its change from likely combinations of climatic control variables and time. We computed the rate and magnitude of centennial-scale glacier volume changes for glacier surfaces between the LIA and the modern era, as defined by 2011 Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model Version 2 (GDEM V2) and 2008 Light Detection and Range (LiDAR) data. The model simulation showed good agreement with the observed geomorphic data and the volume and surface area (V-S) scaling remained within the 25% error range in the reconstructed simulation. Also, we employed a recently demonstrated approach (Baraër, M. et al.) to calculate meltwater contribution to glacierized catchment runoff. The results revealed multiple peaks of both mean annual and dry season discharge that have never been shown in previous research on the same mountain range.

Large observational bias on discharge in the Indus River since 1970s

The discharge of one of the world’s largest river - Indus River was reported to be increasing that was not supported by the Karakoram (KK) glacier expansion. A major hydrometric bias was ignored, which seemed similar to the montage that the Himalayan glaciers would disappear. This study proposed a framework for quantifying the bias resulting from inaccurate data affecting hydrologic studies on the Indus. We constructed a statistical model by converting the rating curves of rivers into air temperature (T) – discharge (Q) curves from an adjacent catchment in China where flow measurement was carried out using a standard method. We found that most flow data for the Indus were much greater than the error limits of T-Q curves estimated by daily data, a greater bias occurred in recent decades when discharge increased, the higher the flow was, the larger the bias was. The estimated mean annual and maximum monthly bias was 22.5% and 210%, respectively. These biases indicated that discharge increase in the Indus probably resulted from the large errors of hydrometrics without a scientific basis. We suggested a montage bias was needed in the hydrologic science of KK’s rivers that may strongly affect water resource management.

Dokriani glacier(Dingarh glacier) and its geological analysis

The study of geomorphological system not only gives information about environmental processes operating there but also relate them whith global environmental system. The geomorphological analysis of Dokriani glacier, Garhwal Himalaya shows five phases of glacial advancement and retreat in the form of well preserved lateral and terminal moraines. The observed retreat rate of glacier in last two decades is about 17.2 m/yr which represents its negative mass balance followed by change in snout position, area and surface height. The farthest glacier expansion of the valley represented as terminal moraine is situated at 8.3 km from present day snout. Whereas, the other sucsessive glacial stages has followed the similar fashion of glacial advancement due to climatic sensitiveness.

Holocene mountain glacier history in the Sukkertoppen Iskappe area, southwest Greenland

Mountain glaciers and ice caps (GIC) independent of the Greenland Ice Sheet respond rapidly to climate variations and records of their past extent provide information on the natural envelope of climate variability. Here, we use a multi-proxy approach that combines proglacial lake sediment analysis, cosmogenic nuclide surface-exposure dating (in situ10Be and 14C), and radiocarbon dating of recently ice-entombed moss to generate a centennial-scale record of Holocene GIC fluctuations in southwestern Greenland. Following local deglaciation ∼10-9 ka, sediments from proglacial Crash Lake record a glacier advance at ∼9 ka that is indistinguishable from nearby ice sheet moraines, implying a synchronous response of GIC and the Greenland Ice Sheet to a centennial-scale climate event. Following this local glacier advance, GIC experienced net recession until ∼4.6 ka. Radiocarbon ages of in situ moss (n = 29) and Crash Lake sediments reveal intervals of glacier expansion at ∼1.8, 1.2 and 0.7 ka that are superimposed on an overall trend of net glacier expansion throughout the late Holocene. In situ14C concentrations from bedrock adjacent to radiocarbon-dated moss samples further constrain the duration of ice cover through the Holocene in this region. We find that our glacier-size proxy records during the past ∼4 ka are broadly consistent with relatively lower temperatures recorded in GISP2 and occur during, or following, intervals of volcanic perturbations. Thus, we speculate that volcanic activity, although less frequent and intense than in the early Holocene and during the Little Ice Age, may have led to centennial-scale variability imprinted on net glacier expansion due to decreasing summer insolation through the late Holocene.

Late-glacial and Holocene history of the northeast Mediterranean mountain glaciers - New insights from in situ-produced 36Cl-based cosmic ray exposure dating of paleo-glacier deposits on Mount Olympus, Greece

In this study, we present a new glacial chronology based on 20 in situ-produced 36Cl-based cosmic ray exposure datings from moraine boulders and bedrock from the Throne of Zeus (TZ) and Megala Kazania (MK) cirques on Mount Olympus. The 36Cl derived ages of glacial landforms range from 15.6 ± 2.0 to 0.64 ± 0.08 ka, spanning the Late-glacial and the Holocene. The Late-glacial, recorded in both cirques, is partitioned in three distinct phases (LG1-3): an initial phase of moraine stabilization at 15.5 ± 2.0 ka with subsequent deglaciation starting at ∼14 ka (LG1), followed by a shift to marginal conditions for glaciation at 13.5 ± 2.0 ka (LG2), sustained by large amounts of wind-blown snow, despite regional warming. Glacial conditions returned at 12.5 ± 1.5 ka (LG3) and were characterized by low air temperatures and glacier shrinking. The Holocene glacial phases (HOL1-3) are recorded only in the MK cirque, likely due to its topographic attributes. An early Holocene glacier stillstand (HOL1) at 9.6 ± 1.1 ka follows the regional temperatures recovery. No glacier activity is observed during the mid-Holocene. The Late Holocene glacier expansions, include a moraine stabilization phase (HOL2) at 2.5 ± 0.3 ka, during wet conditions and solar insolation minima, while (HOL3) corresponds to the early part of the Little Ice Age (0.64 ± 0.08ka). Our glacial chronology is coherent with glacial chronologies from several cirques along the northeast Mediterranean mountains and in pace with numerous proxies from terrestrial and marine systems from the north Aegean Sea.

Global glacier dynamics during 100 ka Pleistocene glacial cycles

AbstractIce volume during the last ten 100 ka glacial cycles was driven by solar radiation flux in the Northern Hemisphere. Early minima in solar radiation combined with critical levels of atmospheric CO2drove initial glacier expansion. Glacial cycles between Marine Isotope Stage (MIS) 24 and MIS 13, whilst at 100 ka periodicity, were irregular in amplitude, and the shift to the largest amplitude 100 ka glacial cycles occurred after MIS 16. Mountain glaciers in the mid-latitudes and Asia reached their maximum extents early in glacial cycles, then retreated as global climate became increasingly arid. In contrast, larger ice masses close to maritime moisture sources continued to build up and dominated global glacial maxima reflected in marine isotope and sea-level records. The effect of this pattern of glaciation on the state of the global atmosphere is evident in dust records from Antarctic ice cores, where pronounced double peaks in dust flux occur in all of the last eight glacial cycles. Glacier growth is strongly modulated by variations in solar radiation, especially in glacial inceptions. This external control accounts for ~50–60% of ice volume change through glacial cycles. Internal global glacier–climate dynamics account for the rest of the change, which is controlled by the geographic distributions of glaciers.

Luminescence chronology and climatic implication of the late quaternary glaciation in the Nubra valley, Karakoram Himalaya, India

The present study investigates moraines, outwash gravel terraces, relict lake deposits and alluvial fans to reconstruct the pattern of glacier advances and associated climate variability in the Nubra Valley, Karakoram Himalaya, India. Optical chronologies obtained on stratigraphically constrained lateral moraines indicate that the oldest preserved record of glacier advance (Tirith-II) is dated to 60.4 ± 5.2 ka and corresponds to Marine Isotopic Stage-4 (MIS-4). During MIS-4, the Nubra valley was occupied by ~700 m thick ice cover that extended beyond the Nubra-Shyok confluence. It was followed by pulsating decrease in the ice-volume (vertical shrinking) with an insignificant lateral recession that continued until around 42.0 ± 3.0 ka (mid- MIS-3). The second major glacial advance (Tirith-I) is dated to 30 ± 2.5 ka (beginning of MIS-2) when the Siachen glacier reached up to the Nubra-Shyok confluence albeit, with lesser ice thickness (~300 m). The Tirith-I glacier advance continued to occupy the entire Nubra valley until around 18.2 ± 1.8 ka (Last Glacial Maximum). A deglaciation followed after 15.8 ± 1.6 ka and continued until the early Holocene (10.3 ± 1.3 ka). The third minor glacial advance-Siachen Glacial Advance (SGA) is dated to the mid-Holocene (6.8 ± 1.0/7.2 ± 1.4 ka) when the glacier extended below the Siachen glacier snout, whereas the youngest glacial expansion reached a few hundred meters below the present day snout and is dated between 1.0 ± 0.4 ka and 0.5 ± 0.2 ka.The study suggests that glacier advances were driven by a decrease in temperature with corresponding increase in the moisture contribution due to the enhanced mid-latitude westerlies during MIS-4, MIS-2, and the mid-Holocene. Within the age uncertainty, it can be suggested that the snout-proximal recessional moraines indicate marginal glacier expansion during the Little Ice Age (LIA). Following this, the glacier receded to its present position and seems to have stabilized since then. Unlike other Himalayan glaciers, the Siachen glacier does not show any alarming retreat after the LIA and is in conformity with recent observations suggesting that the glaciers in Karakoram region are either marginally advancing or stand still.

Trans-pacific glacial response to the Antarctic Cold Reversal in the southern mid-latitudes

Elucidating the timing and regional extent of abrupt climate events during the last glacial-interglacial transition (∼18–11.5 ka) is critical for identifying spatial patterns and mechanisms responsible for large-magnitude climate events. The record of climate change in the Southern Hemisphere during this time period, however, remains scarce and unevenly distributed. We present new geomorphic, chronological, and equilibrium line altitude (ELA) data from a climatically sensitive mountain glacier at Monte San Lorenzo (47°S), Central Patagonia. Twenty-four new cosmogenic 10Be exposure ages from moraines provide a comprehensive glacial record in the mid-latitudes of South America, which constrain the timing, spatial extent and magnitude of glacial fluctuations during the Antarctic Cold Reversal (ACR, ∼14.5–12.9 ka). Río Tranquilo glacier advanced and reached a maximum extent at 13.9 ± 0.7 ka. Three additional inboard moraines afford statistically similar ages, indicating repeated glacier expansions or marginal fluctuations over the ACR. Our record represents the northernmost robust evidence of glacial fluctuations during the ACR in southern South America, documenting not only the timing of the ACR maximum, but also the sequence of glacier changes within this climate event. Based on ELA reconstructions, we estimate a cooling of >1.6–1.8 °C at the peak of the ACR. The Río Tranquilo record along with existing glacial reconstructions from New Zealand (43°S) and paleovegetation records from northwestern (41°S) and central-west (45°S) Patagonia, suggest an uniform trans-Pacific glacier-climate response to an ACR trigger across the southern mid-latitudes. We posit that the equatorial migration of the southern westerly winds provides an adequate mechanism to propagate a common ACR signal across the Southern Hemisphere.

Onset and Evolution of Southern Annular Mode-Like Changes at Centennial Timescale

The Southern Westerly Winds (SWW) are the surface expression of geostrophic winds that encircle the southern mid-latitudes. In conjunction with the Southern Ocean, they establish a coupled system that not only controls climate in the southern third of the world, but is also closely connected to the position of the Intertropical Convergence Zone and CO2 degassing from the deep ocean. Paradoxically, little is known about their behavior since the last ice age and relationships with mid-latitude glacier history and tropical climate variability. Here we present a lake sediment record from Chilean Patagonia (51°S) that reveals fluctuations of the low-level SWW at mid-latitudes, including strong westerlies during the Antarctic Cold Reversal, anomalously low intensity during the early Holocene, which was unfavorable for glacier growth, and strong SWW since ~7.5 ka. We detect nine positive Southern Annular Mode-like events at centennial timescale since ~5.8 ka that alternate with cold/wet intervals favorable for glacier expansions (Neoglaciations) in southern Patagonia. The correspondence of key features of mid-latitude atmospheric circulation with shifts in tropical climate since ~10 ka suggests that coherent climatic shifts in these regions have driven climate change in vast sectors of the Southern Hemisphere at centennial and millennial timescales.

Volcanologic and petrologic evolution of Antuco-Sierra Velluda, Southern Andes, Chile

The Andean Southern Volcanic Zone comprises >30 active arc front volcanoes that grew over periods of hundreds of thousands of years. Quantifying the rates at which these volcanoes grow is key to appreciating geological hazards, clarifying petrologic evolution, and exploring possible relationships between volcanism, ice loading, and climate. The integration of precise geochronology and geologic mapping, together with new lava compositions and volume estimates, reveal the evolution of the Antuco-Sierra Velluda volcanic complex at 37.2°S. Thirty-one new 40Ar/39Ar age determinations illuminate a punctuated eruptive history that spans at least 430kyr. Sierra Velluda comprises ~130km3 and began to grow prior to 426.8ka. A lacuna in the volcanic record between 343.5 and 150.4ka coincides with glaciations associated with marine isotope stages (MIS) 10 and 8, although shallow intrusions were emplaced at 207.0 and 190.0ka. Antuco began to grow rapidly on the northeast flank of Sierra Velluda, erupting >60km3 of lava during three phases: (1) an early phase that began at 150.4ka, (2) a post-MIS 2 phase between 16.3 and 6.2ka, and (3) a post-sector collapse phase after 6.2ka. Volcanism has been continuous during the last 100kyr, with an average rate of cone growth during this period of ~0.46km3/kyr that has accelerated by about 50% during the past 6kyr.Whereas Sierra Velluda erupted basaltic andesitic to andesitic (53.5 to 58.7wt% SiO2) lavas, during the last expansion of glaciers between ~130 and 17ka, Early Antuco erupted a wider spectrum of lavas, ranging from basaltic andesite to dacite (52.0 to 64.5wt% SiO2). Notably, eruptions following the last glacial termination at 17ka produced basalts and basaltic andesites (50.9–53.7% SiO2), and following the 6.2ka cone collapse they have been exclusively olivine basalt (50.9–53.0% SiO2) with >5wt% MgO. Thermodynamic and trace element modeling suggests that lavas from Sierra Velluda and Early Antuco reflect extensive fractional crystallization of parental basaltic magmas with low water content (~1wt%) at pressures between 0.9 and 1.5kbar. In contrast, eruptions following rapid deglaciation tapped asthenospheric mantle-derived basalt that has been extensively modified by assimilation of partial melts of lower crustal rocks.

Climate evolution and forcing during the last 40 ka from the oscillations in Apennine glaciers and high mountain lakes, Italy

ABSTRACTThe results of studies carried out on the variations of glaciers and lakes in the higher Apennines during the last 40 ka are considered for correlation with some climate forcing agents, e.g. changes in insolation, variations in origin of the air masses carrying moisture and North Atlantic events, acting both at regional and hemispheric scales. The origin of air masses was assessed using the Apennine equilibrium line altitude pattern, the presence of a quartz‐rich loess in the former glacial environment and the sedimentation rate of Sahara quartz in maar lakes. Temperature and humidity variations have been deduced from glacier expansions and retreats and lake oscillations. The data discussed in the paper show that variations in insolation have driven climatic changes in the Apennines for most of the considered time span, producing gradual changes that took place during periods lasting several thousand years. However, during some periods, insolation seems to have been of minor importance compared to variations in frequency and intensity of southern air currents, and to the influence of North Atlantic events. The data, as a whole, allow us to highlight the climatic evolution of the high Apennine mountains during the last 40k cal a BP.

Late Holocene Glacier Dynamics in the Miyar Basin, Lahaul Himalaya, India

Detailed field mapping of glacial and paraglacial landforms and optical dating from these landforms are used to reconstruct the early Holocene glaciation in the semi-arid region of Miyar basin, Lahaul Himalaya. The study identifies three stages of glaciation, of decreasing magnitude and termed, from oldest to youngest, the Miyar stage (MR-I), Khanjar stage (KH-II), and Menthosa advance (M-III). The oldest glacial stage (MR-I) has been established on the basis of detailed geomorphological evidence such as U-shaped valley morphology, trimlines, and truncated spurs. It is speculated to be older than the global Last Glacial Maximum (gLGM) based on the magnitude of ΔELA (Equilibrium-Line Altitude, 606m). No evidence of glacier expansion recorded from the basin correlates with the period of the gLGM. The second stage (KH-II) is well represented by extensive depositional features such as lateral and terminal moraines, drumlins, and lacustrine fills that have been constrained within 10 ± 1 to 6.6 ± 1.0 ka (Optically stimulated luminescence—OSL—ages), dating it to the early Holocene advance following the Younger Dryas cooling event. Exceptionally young glacial records of expansion are limited within a few hundred meters of the present termini of tributary glaciers and correlates with the 18th-century cooling event. Records of this glacial advance, termed the Menthosa advance, are clearly noticed in some tributary valleys.

An Oldest Dryas glacier expansion on Mount Pelister (Former Yugoslavian Republic of Macedonia) according to 10 Be cosmogenic dating

We provide a geomorphological analysis of a glacial valley on Mount Pelister, in Macedonia. Three boulders from a frontal moraine were dated with the cosmogenic nuclide isotope 10 Be. The results demonstrate that the boulders have been exposed since 15.24 ± 0.85 ka. This age constrains the formation of the frontal moraine to the Oldest Dryas cold event. This age fits with that of other glacier deposits dated to the Older Dryas in the Alps, Balkans, Carpathians and Turkish mountains. The Pelister palaeoglacier has been reconstructed and its equilibrium line altitude extracted, returning a value of 2250 m a.s.l. This is in good agreement with the equilibrium line altitudes of most other reconstructed glaciers of the same age in the circum-Mediterranean mountains, demonstrating a comparable response to the Oldest Dryas event. Other palaeoenvironmental records near the Pelister mountain indicate that the Older Dryas was here characterized by a cold and remarkably dry event. The temporal relationship between Older Dryas glacier advances in the Balkan region and recorded changes in the Atlantic thermohaline circulation during the Laurentide Ice Sheet massive ice discharge (H1 event) confirms the strong climatic link between the pan-Mediterranean regions and the North Atlantic Ocean. Supplementary material: Geochemical laboratory results are available at http://doi.org/10.6084/m9.figshare.c.3830254

Recent Wetting and Glacier Expansion in the Northwest Himalaya and Karakoram

Hydroclimatic variability driven by global warming in the climatically vulnerable cold semi-arid to arid northwest (NW) Himalaya is poorly constrained due to paucity of continuous weather records and annually resolved proxies. Applying a network of annually resolved tree-ring-width chronologies from semi-arid region of Kishtwar, Jammu and Kashmir, India, we reconstructed April-May standardized precipitation index extending back to A.D. 1439 (576 years). The reconstructed series is featured by the most conspicuous long-term droughts during the 15th to early 17th centuries followed by a general wetting, with 1984–2014 being the wettest interval in the past 576 years. The data, consistent with other independently developed tree-ring-based hydrological records from cold semi-arid to arid NW Himalaya and Karakoram, point to an increased regional wetting in the recent decades. Such an increased wetting might have led to the anomalous behaviour of glaciers in the NW Himalaya and Karakoram in contrast to the general receding trends in the central and eastern Himalaya.

10Be exposure age chronology of the last glaciation of the Roháčská Valley in the Western Tatra Mountains, central Europe

10Be exposure ages from moraines and bedrock sites in the Roháčská Valley provide chronology of the last glaciation in the largest valley of the Western Tatra Mts., the Western Carpathians. The minimum apparent exposure age of 19.4±2.1ka obtained for the oldest sampled boulder and the mean age of 18.0±0.8ka calculated for the terminal moraine indicate that the oldest preserved moraine was probably deposited at the time of the global Last Glacial Maximum (LGM). The age of this moraine coincides with the termination of the maximum glacier expansion in other central European ranges, including the adjacent High Tatra Mts. and the Alps. The equilibrium line altitude (ELA) of the LGM glacier in the Roháčská Valley, estimated at 1400–1410m a.s.l., was 50–80m lower than in the eastern part of the range, indicating a positive ELA gradient from west to east among the north-facing glaciers in the Tatra Mts. Lateglacial glacier expansion occurred no later than 13.4±0.5ka and 11.9±0.5ka, as indicated by the mean exposure ages calculated for re-advance moraines. This timing is consistent with the exposure age chronology of the last Lateglacial re-advance in the High Tatra Mts., Alps and lower mountain ranges in central Europe. The ELA in the Roháčská Valley estimated at 1690–1770m a.s.l. in this period was located 130–300m lower than in the north-facing valleys in the High Tatra Mts. 10Be exposure ages obtained for a rock glacier constrains the timing of this landform stabilization in the Salatínska Valley and provides the first chronological evidence for the Lateglacial activity of rock glaciers in the Carpathians.

The Alpine LGM in the boreal ice-sheets game

New chronologic and stratigraphic constraints from the Garda morainic amphitheater define the extension of the last glaciation in the Adige-Sarca system and improve the Alpine LGM dataset. Together with the available chronology of the Rhine and Tagliamento systems, our results indicate a synchronous maximum culmination of Alpine glaciers during the LGM, which anticipated by about 3.5 ka the maximum extension of the Eurasian Ice Sheet (EIS). This is ascribed to the sensitivity of Alpine glaciers to the availability of moisture from southerly circulation, as recently documented by speleothem δ18O curve from Sieben Hengste (7 H). According to global circulation models, the waxing of the North American Ice Sheet (NAIS) at 26–23 ka pushed the North Atlantic jet stream southwards. This enhanced precipitation rates in southern Europe by advection of moisture from the Mediterranean Sea, triggering expansion of the Alpine glaciers. NAIS waning after 23 ka led to the gradual re-establishment of westerly circulation and renewal of a moisture supply to northern Europe, feeding the EIS to its maximum volume. Reduced supply of moisture from the Mediterranean Sea sealed the fate of the Alpine glaciers, which entered a final recessional phase after 22 ka and faded out after 17.5 ka.