Moraine System Research Articles

Rapid deglaciation of the La Vega gorge (Sierra de Gredos, Iberian Peninsula) at the end of the global Last Glacial Maximum

AbstractPrevious studies from the Iberian Central System and other mountains of the Iberian Peninsula and Europe suggest that deglaciation in this area occurred at the end or immediately after the global Last Glacial Maximum (LGM, 26.5–19 ka). In this research, we investigate the timing and speed of deglaciation of the palaeoglacier in La Vega gorge (Iberian Central system) since the global LGM, dating the outer moraines, glacially polished bedrock and glaciofluvial deposits by means of in situ cosmogenic 10Be and optically stimulated luminescence. The results show that one intermediate arc located at the outer frontal moraine system has an age of ~21 ka, being consistent with the global LGM. Deglaciation began at ~21–19 ka, speeding up at ~19 ka. We estimate that around 4–5 km of the palaeoglacier receded in ~1–2 kyrs since ~19 ka, leaving La Vega gorge probably ice‐free at ~18 ka. Therefore, our data confirm that deglaciation in Sierra de Gredos began at the end of the global LGM, characterised by a rapid and massive retreat of glaciers.

Atmosphere–cryosphere interactions during the last phase of the Last Glacial Maximum (21 ka) in the European Alps

Abstract. Evidence that during the Last Glacial Maximum (LGM) glaciers extended well into the piedmont plains is still identifiable in the alpine foreland as a system of well-preserved moraines. Glaciers are strongly controlled by temperature and precipitation, and therefore, they are excellent indicators of climate change. Here, we use a regional climate model (RCM) to investigate some of the physical processes sustaining Alpine glaciers during the last phase of the LGM during Greenland Stadial 2 at 21 ka. We find a predominance of convection during summer and increased southwesterly stratiform precipitation over the southern Alps when compared to pre-industrial (PI) conditions. This precipitation pattern, along with lower temperatures, determined summer snowfall extending to low elevations, with a consequent substantial drop of the equilibrium line altitude (ELA), which is consistent with the estimated LGM glacier extent. Our RCM-based estimates of 21 ka ELA at the LGM yield excellent consistency with Alpine ELA reconstructions, further demonstrating the great potential of this technique for use in palaeoclimate studies.

Timing and extent of glaciation since the Last Glacial Maximum in the upper Kalguty basin, Russian Altai Mountains

ABSTRACTThe mountains systems of Central Asia are primary targets to study late Pleistocene climate evolution given their location at the crossroads of several atmospheric circulation systems. The timing of glacier extent during this period remains understudied, especially in the Altai Mountains. Here, we have reconstructed glacier extent during three main Late Pleistocene stadials in the upper Kalguty basin (south‐eastern Russian Altai) based on field‐based geomorphic analysis. Additionally, surface exposure dating with 10Be and 26Al at a key site was used to infer a minimum‐limiting age for the outermost well‐preserved Pleistocene frontal moraine system and to date the inception of glacier withdrawal. According to our data, around 20.6 ± 1.8 ka Kalguty Glacier was still 200 m thick at the key site, 10 km upstream of the outermost moraine, and the site was totally deglaciated shortly after 20.4 ± 0.4 ka. These results point to a rapid retreat of this low‐gradient valley glacier after its probably MIS 2 maximum which was prior to 21 ka and probably prior to 22.5 ka. Two other glacier stages have been identified upvalley, characterized by a depression of the equilibrium‐line altitude of 420 and 314 m with respect to the Little Ice Age, thus corresponding to Lateglacial advances. Our glacier reconstruction further provides a geomorphological and geochronological background to put into context archaeological findings in this area.

CAGE17-1-Leg 2 cruise report

From the afternoon of May 19th to the early morning of June 2nd 2017, CAGE-WP6 at the Department of Geology Uit, the Arctic University of Norway, arranged a scientific cruise aimed at investigating sediment cores and porewater, and water masses, at the western Svalbard margin, Fram Strait, East Greenland Ridge, and Storfjorden Trough, visiting methane seep sites off Vestnesa Ridge, and in Storfjorden Trough on R/V “Helmer Hanssen”. Investigated areas were (in order of visiting sites on the cruise): Prins Karls Forland (PKF) (overlap with ‘leg 1’ 17th to 19th of May – see Leg 1 report), southern Yermak Plateau, Vestnesa Ridge, East Greenland Ridge, Storfjorden Trough and Storfjorden.
 The scientific sampling was done within the framework of several ongoing projects at the Department of Geology, University of Tromsø: “CAGE – Centre for Arctic Gas Hydrate, Environment and Climate”-WP6: “Methane Release, Ocean Acidification and CO2”. Planned surveys north of Svalbard was abandoned due to extensive sea ice cover and the East Greenland Ridge was surveyed instead. Sea ice over outer Vestnesa prevented surveys there and Storfjorden trough was also completely covered, but the sea ice broke up towards the end of the cruise and thus could be surveyed during the very last part of the cruise.
 A total of 15 gravity cores (c. 60 m), and 20 CTD (conductivity-temperature-depth) casts were performed along the western Svalbard margin (Vestnesa and PKF and Yermak). Data were also collected at East Greenland Ridge and in Storfjorden Trough and Storfjorden, brine overflow was detected. The CTD casts and chirp- and multibeam lines from PKF May 17-19th are reported in the cruise report for Leg 1.
 Chirp profiles and multibeam lines were acquired during transits and in surveys (mapping of East Greenland Ridge, moraine systems and basins in Storfjorden Trough, active and inactive pockmarks at Vestnesa Ridge and over and to find potential core sites.
 The cruise may be known as: CAGE17_1_leg2

Mountain Landscape and Human Settlement in the Pindus Range: The Samarina Highland Zones of Western Macedonia, Greece

Past human mountain settlement patterns and resource and high-altitude landscape exploitation are underexplored research fields in archaeology. This study presents data gathered during more than 20 years of fieldwork in the Pindus range of Western Macedonia (Greece), focusing in particular on Holocene land use. The investigated territory is located around the Vlach town of Samarina. The area is partly bounded by Mounts Vasilitsa, Gurguliu, Bogdani and Anitsa, and their interconnecting watersheds between ca. 1400 and 2000 m a.s.l. This research led to the discovery of many sites and findspots of lithic and ceramic artefacts attributed to the Middle and Upper Palaeolithic, Mesolithic, Late Neolithic, Chalcolithic, Bronze Age, and several Historical periods. The radiocarbon results show an unexpected longue durée of Holocene human landscape use. The number of sites, their distribution, location, and subsistence strategies exhibit shifts between the Middle Palaeolithic and different periods of the Holocene, which are closely related to the exploitation of the mountain environment and its resources. Moreover, typical knapped stone artefacts have been used as a proxy for dating the glacial landforms which characterise the Samarina highland zone; we correlate them to the better-known moraine systems of Mount Tymphi in Epirus and contribute to the reconstruction of the Pleistocene glacial landscapes of the Pindus Range.

Deglacial dynamics of the Foxe–Baffin Ice Sheet, Frobisher Bay, Nunavut, Canada revealed by submarine landform mapping

ABSTRACTPrevious interpretation of the nature and distribution of subaerial glacial landforms established that Frobisher Bay in southeastern Baffin Island was glaciated in the Late Wisconsinan by ice flowing southeast from the Foxe–Baffin Ice Dome. New seafloor mapping within the bay has revealed submarine glacial landforms that are described and interpreted in the context of their subglacial, ice‐marginal, glaciomarine and marine process environments. Interpretation of the evidence confirms that ice occupied Frobisher Bay, flowing from the northwest to southeast, parallel to the orientation of the bay. Relatively rapid ice velocities are indicated by the presence of ice‐moulded bedrock and megaridges flanking a deep trough (>700 m) along the faulted southern flank of Frobisher Bay. In shallower regions, areal scouring and channelisation indicate the widespread presence of glacial ice. As ice retreated to the northwest towards the Foxe Ice Dome, De Geer and recessional moraines were deposited at the ice front. The latter correlate spatially with the extensive Frobisher Bay Moraine System on land. Two iceberg ploughmark populations are evident, with smaller relict features in shallow water in rare locations in the northwest of the bay, and larger relict and modern ploughmarks in deeper water in outer Frobisher Bay.

Evidence for an extensive ice shelf in northern Baffin Bay during the Last Glacial Maximum

The glaciological significance of ice shelves is relatively well established for the stability of modern ice sheets of Antarctica. Past ice shelves of the Arctic, however, are poorly documented while their role for the stability of former ice sheets remains mostly unknown. Here we present swath bathymetry data and seismostratigraphic profiles that reveal a large moraine system extending along the continental slope off Baffin Island, demonstrating that a 500-m thick ice shelf covered northern Baffin Bay during the last glacial episode. We suggest that this ice shelf had a profound impact on the stability of a series of major ice streams that drained the interior of the Laurentide, Innuitian and Greenland ice sheets. Climate warming and global sea-level rise in the early stage of deglaciation possibly contributed to a large-scale break-up of the ice shelf, which led to the destabilisation and reorganisation of tributary ice streams from these three ice sheets.

The Last Glacial Maximum and Deglacial History of the Seno Skyring Ice Lobe (52°S), Southern Patagonia

There are still many uncertainties about the climatic forcing that drove the glacier fluctuations of the Patagonian Ice Sheet (PIS, 38–55°S) during the last glacial period. A key source of uncertainty is the asynchrony of ice lobe fluctuations between the northern, central, and southern PIS. To fully understand the regional trends requires careful mapping and extensive geochronological studies. This paper presents geomorphological and geochronological reconstructions of the glacial and deglacial landforms formed during the last glacial period at the Seno Skyring lobe, southernmost Patagonia (52°S, 71°W). We present a detailed geomorphological map, where we identify two moraine systems. The outer and older is named Laguna Blanca (LB) and the inner Río Verde (RV). The LB moraines were built subaerially, whereas parts of the RV were deposited subaqueously under the palaeo lake Laguna Blanca, which developed during deglaciation. We conducted surface exposure 10Be dating methods on boulder samples collected from LB and RV glacial margins. The moraine LB III and LB IV formed at 26.3 ± 2.3 ka (n = 5) and 24.3 ± 0.9 ka (n = 3), respectively. For the inner RV moraine, we obtained an age of 18.7 ± 1.5 ka (n = 6). For the palaeo Laguna Blanca evolution, we performed 10Be exposure ages on shoreline berms and optically stimulated luminesce dating to constrain the lake levels, and 10Be depth profile dating on an outwash deposit formed by a partial lake drainage event, which occurred at 22 ± 3 ka. For the RV moraine deglaciation, we performed radiocarbon dating of basal sediments in a peat bog, which indicates that the glacier retreated from the terminal RV moraine by at least c. 16.4 cal kyr BP. Our moraine geochronology shows an asynchrony in the maximum extents and a different pattern of ice advances between neighbouring lobes in southern Patagonia. We speculate that this may be due, at least in part, to the interaction between topography and the precipitation carried by the southern westerly wind belt. However, we found broad synchrony of glacial readvances contemporaneous with the RV moraine.

Cosmogenic 10Be constraints on deglacial snowline rise in the Southern Alps, New Zealand

Geochronological dating of glacial landforms, such as terminal and lateral moraines, is useful for determining the extent and timing of past glaciation and for reconstructing the magnitude and rate of past climate changes. In the Southern Alps of New Zealand, well-dated glacial geomorphological records constrain the last glacial cycle across much of the Waitaki River basin (e.g. Ōhau, Pukaki, Tekapo) but its southern sector such as the Ahuriri River valley remains comparatively unconstrained. Recently, there has been debate on the scale and rapidity of mountain glacier retreat during the last glacial termination, particularly the 20–17 ka period in New Zealand. Missing from this debate is well-constrained equilibrium-line altitude (ELA) and associated temperature reconstructions, particularly over the period around 17 ka, which can help us to develop a more complete picture of how past temperature changes drove glacier retreat. Here we report the first glacial chronology dataset from the Last Glacial Maximum (LGM) and subsequent deglaciation from the Ahuriri River valley, Southern Alps, New Zealand (44°23′54″S, 169°39′48″E) based on 38 beryllium-10 (10Be) surface-exposure ages from terminal moraine systems and glaciated bedrock situated at the lower and middle sections of the valley. Our results show that the former Ahuriri Glacier reached its maximum extent at 19.8 ± 0.3 ka, which coincides with the global Last Glacial Maximum. By 16.7 ± 0.3 ka, the glacier had retreat ∼18 km up-valley suggesting at least ∼43% glacier-length loss relative to its full LGM extent. This deglaciation was accompanied by the formation of a shallow proglacial lake. Using the accumulation area ratio (AAR) method, we estimate that the ELA was lower than present by ∼880 m (∼1120 m a.s.l.) at 19.8 ± 0.3 ka, and ∼770 m lower (∼1230 m a.s.l.) at 16.7 ± 0.3 ka. Applying an estimate for temperature lapse rate, this ELA anomaly implies that local air temperature was 5 ± 1 °C colder than present (1981–2010) at 19.8 ± 0.3 ka, while it was 4.4 ± 0.9 °C colder at 16.7 ± 0.3 ka, assuming no change in precipitation. The substantial glacier retreat in response to a relatively small accompanying increases in ELA (110 m) and temperature (0.6 °C) may have been a result of the high glacier-length sensitivity of this glacier system due to its low gradient of former ice surface. Our low warming estimate differs markedly from other deglaciation studies, specifically from Rakaia River valley, which reports a much larger temperature increase at the onset of the last deglaciation. This precisely-dated moraine record along with reconstructed ELA as proxies for atmospheric conditions, provides new insight into post LGM glacier behaviour and climate conditions in New Zealand.

The Ticino-Toce glacier system (Swiss-Italian Alps) in the framework of the Alpine Last Glacial Maximum

We present a new glacier chronology from one of the major end moraine systems of the Southern Alps. Timing and extent of the Last Glacial Maximum (LGM) advance of the Ticino-Toce glacier were reconstructed in detail based on landform relationships and surface exposure dating. 10Be and 36Cl ages from 41 erratic boulders constrain the last maximum of the Ticino-Toce glacier to have lasted from 25.0 ± 0.9 ka to 19.9 ± 0.7 ka. Over this period of ca. 5000 years the Ticino-Toce glacier underwent only minor oscillations, during which the glacier front remained close to its LGM maximum position. Underpinned by our detailed geomorphological reconstruction, the ages further demonstrate that the Verbano piedmont lobe was significantly larger (about 200 km2) than shown on recent maps. A short-lived glacier readvance around 19.7 ± 1.1 ka terminated internal to the LGM maximum margins. Collapse of the Verbano lobe must have set in soon after and final withdrawal from the foreland occurred no later than 19 ka. The new Ticino-Toce chronology matches temporal constraints of major glacier systems emerging from adjacent Alpine accumulation areas. This points to in-phase glacier advances across the Western Alps, apart from the southwestern massifs for which a slightly earlier reaching of the Late Pleistocene maximum position of the Lyon lobe was shown recently. A two- potentially three-fold LGM advance structure with intervening retreat intervals, as reported for two major amphitheatres (Garda, Tagliamento) to the east is distinctly not supported by our data for the Ticino-Toce glacier. This contrast in glacier behaviour between the central and eastern Southern Alps is ascribed to shifting precipitation patterns after ca. 23–22 ka, away from southern to predominantly northwestern air flow and a greater independence of southerly moisture transport for the central Southern Alps.

Transient Electromagnetic (TEM) Surveys as a First Approach for Characterizing a Regional Aquifer: The Case of the Saint-Narcisse Moraine, Quebec, Canada

Geological contexts that lack minimal stratigraphic and piezometric information can be challenging to produce an initial hydrogeological map in remote territories. This study proposes an approach to characterize a regional aquifer using transient electromagnetic (TEM) surveys. Given the presence of randomly dispersed boreholes, the Saint-Narcisse moraine in the Mauricie region of Quebec (Canada) is an appropriate site for collecting the required geophysical data, correlating the stratigraphic and piezometric information, and characterizing regional granular aquifers in terms of stratigraphy, geometry, thickness, and extent. In order to use all TEM results (i.e., 47 stations) acquired in the moraine area, we also correlated 13 TEM stations, 7 boreholes, and 6 stratigraphic cross-sections to derive an empirical and local petrophysical relationship and to establish a calibration chart of the sediments. Our TEM data, combined with piezometric mapping and the sedimentary records from boreholes and stratigraphic cross-sections, revealed the compartmentalization of a multi-kilometer morainic system and indicated the presence of two large unconfined granular aquifers overlying the bedrock. These aquifers extend more than 12 km east to west across the study area and are between 25 and >94 m thick. The TEM method provides critical information on groundwater at a regional scale by acquiring information from multiple stations within a short time span to a degree not possible with other existing methodologies.

Disentangling the stratigraphic architecture of the Rivoli-Avigliana end moraine system (Western Alps, NW Italy)

ABSTRACT The Rivoli-Avigliana end moraine system (Italian Western Alps) hosts an important stratigraphic archive of Pleistocene glaciations. A new geological map provides a 3D architecture of the system that reveals a complex architecture of glacial, alluvial and lacustrine units. Six glacial units were recognized. During the deposition of the four older glacial units (Early-Middle Pleistocene) the morphology of the valley outlet had a different drainage pattern from the present, with the presence of large lakes. From the penultimate glaciation to the Last Glacial Maximum (LGM) the piedmont lobe was confined within the valley, never extending towards the alluvial Po Plain. The LGM is characterized by two glacial advances and four distinct recessional phases during the Lateglacial. The presence of a bedrock inselberg affected the flow of the glacier front, which should have had weak erosive strength as shown by the preservation of lacustrine deposits below the glacial units.

Cosmogenic nuclide inheritance in Little Ice Age moraines - A case study from Greenland

Cosmogenic exposure dating is one of the most widely used methods to constrain the deglaciation history of former glaciated areas. In Greenland, more than 1000 cosmogenic 10 Be exposure ages ( 10 Be ages) have been published within the last two decades. However, a recurring problem is that many of these studies have reported variable amounts of nuclide inheritance making the 10 Be ages too old and difficult to assess without large datasets or independent age control. In this study, we test the accuracy of 10 Be dating of Holocene moraines using independent age constraints from threshold lake records. In Kangerlussuaq, West Greenland, the 10 Be ages of the Ørkendalen moraine system are highly clustered with a mean age of 6.8 ± 0.3 ka (no outliers). In contrast, the nearby Little Ice Age (LIA) moraine yields scattered 10 Be ages ranging from 2.5 to 0.1 ka but with a mean of 0.18 ± 0.06 ka after excluding outliers which coincides with independent age constraints from threshold lakes and boulder kill dates. At Gletscherlukket, Southeast Greenland, the 10 Be ages of the LIA moraine range from 10.2 to 1.6 ka with a mean of 1.9 ± 0.2 ka after excluding outliers. This is ~1.7 ka older than recorded in the proglacial threshold lakes and suggests that all samples from this site contain a significant amount of nuclide inheritance. Our results are consistent with other reports of skewed 10 Be age distributions in LIA re-advance moraines and it probably reflects nuclide inheritance from exposure during the Holocene Thermal Maximum when the glaciers in Greenland were inside the LIA extent. In contrast, there is no evidence of nuclide inheritance in the Ørkendalen moraines, most likely because the glacial erosion was more intense prior to the formation of the moraines i.e. sometime between the advance phase during Last Glacial Maximum position and the subsequent lateglacial and Holocene deglaciation. Our results highlight a potential pitfall related to dating re-advance moraines using cosmogenic exposure dating and we recommend using a multi-method dating approach.

The submerged footprint of Perito Moreno glacier

Perito Moreno is the most famous calving glacier of the South Patagonia Icefield, the largest temperate glacier system of the Southern Hemisphere. Unlike most of the glaciers in the region that have strongly retreated in recent decades, the position of Perito Moreno glacier front remained relatively unchanged in the last century. However, earliest photographic documents show that, at the end of the nineteenth century, the front was ca. 800 m behind the current position. There is no reliable information about the positions of the Perito Moreno front in earlier times. Here we show evidence of two subaqueous moraine systems both in the Canal de Los Témpanos and in the Brazo Rico, the two arms of Lago Argentino along which Perito Moreno glacier has flowed over time. These moraines, identified for the first time in the Canal de Los Témpanos from bathymetric and high-resolution seismic profiles, mark the position of the largest glacier advance, tentatively correlated with the moraines of the “Herminita advance” identified and dated onland. We interpret these bedforms as the evidence of the most pronounced advance of Perito Moreno glacier during the mid-Holocene cooling event that characterized this sector of the Southern Hemisphere. This study highlights the importance of subaqueous glacial bedforms, representing decisive records of the glacial history and palaeoclimate, which could help unveiling the origin of the different behavior of glaciers like Perito Moreno that in a warming climate are relatively stable.

Climate sensitivity and geomorphological response of cirque glaciers from the late glacial to the Holocene, Sierra Nevada, Spain

Through a detailed geomorphological study, including thourough mapping of the geomorphic features as well as 10Be Cosmic-Ray Exposure (CRE) dating, the geomorphological evolution of the Mulhacén cirque since the maximum ice extent of the last glacial cycle until nowadays was determined. This glacial cirque is shaped on the northern face of the Mulhacén peak (3479 m a.s.l. 37°03′12″N/3°18′41″W), Sierra Nevada, southern Spain. It includes several depositional and erosional glacial landforms that allowed reconstructing its environmental evolution since the last glacial cycle. Furthermore, the sequence of glacial oscillations from this site was compared to that of other cirques of the massif, evidencing that: (i) new glaciers formed in these cirques during the Younger Dryas (YD), and (ii) disappeared at 11.7 ± 1.0 ka. Depending on the altitude, orientation and height of the cirque walls, the final deglaciation of the cirques generated a diversity of landscapes, including a wide range of glacial and periglacial landforms, such as polished surfaces, sequences of moraines, proto-rock glaciers or large rock glacier systems. No glaciers existed in the Sierra Nevada during the Middle Holocene. Only the cirques whose summits exceed 3300 m, are north-exposed and whose walls exceed 300 m high (i.e. Mulhacén and Veleta) hosted glaciers during Neoglacial phases, including the Little Ice Age (LIA) (approx. 1300–1850 CE). During these periods, climate oscillations favoured the formation of small glaciers in these cirques, which generated large moraine systems with either one polygenic ridge or a sequence of spaced frontal arcs. The existence of glaciers impeded the formation of permafrost-related landforms, such as rock glaciers and protalus lobes until the end of the LIA, when they started to form. These results are compared with the deglacial evolution in 55 cirques from Iberian mountains as well as from glacial cirques from other mid-latitude mountains and subpolar regions. The chronology of their deglaciation as well as the landforms generated during glacial retreat followed similar patterns, with no significant differences at regional scale. For each mountain range, the geomorphological diversity existing in each cirque depends on the local topographic characteristics although they formed during the same climatic phases.

Geology and Aquifer Sensitivity of Quaternary Glacial Deposits Overlying a Portion of the Mahomet Buried Bedrock Valley Aquifer System

To characterize the distribution of Holocene and Late Quaternary deposits and to assess the contamination potential of the Mahomet Aquifer, surficial geologic and aquifer sensitivity maps of the Gibson City East 7.5-Minute Quadrangle were created. Geologic data, extent, and thickness of the geologic materials were coupled with LiDAR topographic data and analyzed using ESRI’s ArcGIS 10.6.1. Aquifer sensitivity to contamination was calculated based on the depth to the first aquifer unit, aquifer thickness, and the lithology of the aquifer materials. The surficial geologic mapping identified five lithostratigraphic units: the Cahokia Formation, the Equality Formation, the Henry Formation, and the Yorkville and Batestown Members of the Lemont Formation. The southeast to northwest trending Illiana Morainic System is the most prominent feature in the study area and delineates the maximum extent of the glaciers during the Livingston Phase of glaciation. Postglacial deposits of the Cahokia Formation, alluvium, interfinger, and overlie with glacial outwash of the Henry Formation along channels and drainage ways downslope of the moraine. The areas of least sensitivity are located over the Illiana Morainic System, whereas the greatest potential to contamination occurs where the thickest deposits of the Henry Formation and Cahokia Formation lie at or just below the land surface.

A tree-ring δ18O series from southernmost Fuego-Patagonia is recording flavors of the Antarctic Oscillation

A 154 year-long, tree-ring based stable oxygen isotope time series (δ 18 O TRC ) of the evergreen southern beech ( Nothofagus betuloides ) was established for the southernmost part of Patagonia. The trees grew on the terminal moraine system of the Schiaparelli Glacier (54.4°S) within the windward and hyper-humid zone of the Austral Andes. The annually resolved δ 18 O TRC record spans the common period 1861–2015 and is based on the analysis of five individually analyzed tree individuals showing a significant mean interseries correlation ( r = 0.69). To date, this time series represents the worldwide southernmost chronology of tree-ring δ 18 O TRC . Variations of the δ 18 O TRC values are significantly correlated with hydroclimatic conditions, as derived from ERA-Interim reanalysis gridded data. Negative relationships between the δ 18 O TRC -series and relative humidity (r Oct-Feb = −0.62, p < 0.0001) or the amount of precipitation (r Jan-Feb = −0.52, p < 0.0001) can be observed for the austral spring and summer seasons. In contrast, a drier environment will increase the δ 18 O TRC as revealed by a positive influence of evaporation (r Sep-Feb = 0.44, p < 0.01), sea level pressure (r Oct-Feb = 0.56, p < 0.0001) or maximum temperature (r Oct-Feb = 0.43, p < 0.01). Spatial correlation maps indicate a strong supra-regional influence of climate variables on the chronology. The annular pressure seesaw, termed as Antarctic Oscillation (AAO), mostly influences climate variability within the Southern Hemisphere and is positively correlated with the δ 18 O TRC -chronology (r JF = 0.61, p < 0.0001). Since our chronology, as well as a neighboring δ 18 O TRC -chronology from the Perito Moreno Glacier (50°S), are showing a high correspondence in their sensitivities to climate variabilities and towards the AAO, we merged both time series into a mean chronology. This new regional mean δ 18 O TRC -chronology is highly sensitive to variations of the AAO ( r = 0.79, p < 0.0001)) and is tested for the suitability to reconstruct the AAO for the last 150 years. The reconstructed time series of the AAO reveals an increasing trend towards more positive index values, which is associated with an amplification in the amount of precipitation and wind speed in southernmost South America. • Southernmost existing tree-ring cellulose (δ 18 O TRC ) time series from the hyper-humid Austral Andes, Tierra del Fuego. • Highly significant hydroclimate imprints on δ 18 O TRC of the evergreen southern beech ( Nothofagus betuloides ). • Strong fingerprints of the Antarctic Oscillation (AAO) are reflected in δ 18 O TRC from Southern Patagonia. • Annual reconstruction of the Antarctic Oscillation based on tree-ring δ 18 O TRC since 1860.

Recent Climatic Mass Balance of the Schiaparelli Glacier at the Monte Sarmiento Massif and Reconstruction of Little Ice Age Climate by Simulating Steady-State Glacier Conditions

The Cordillera Darwin Icefield loses mass at a similar rate as the Northern and Southern Patagonian Icefields, showing contrasting individual glacier responses, particularly between the north-facing and south-facing glaciers, which are subject to changing climate conditions. Detailed investigations of climatic mass balance processes on recent glacier behavior are not available for glaciers of the Cordillera Darwin Icefield and surrounding icefields. We therefore applied the coupled snow and ice energy and mass balance model in Python (COSIPY) to assess recent surface energy and mass balance variability for the Schiaparelli Glacier at the Monte Sarmiento Massif. We further used COSIPY to simulate steady-state glacier conditions during the Little Ice Age using information of moraine systems and glacier areal extent. The model is driven by downscaled 6-hourly atmospheric data and high resolution precipitation fields, obtained by using an analytical orographic precipitation model. Precipitation and air temperature offsets to present-day climate were considered to reconstruct climatic conditions during the Little Ice Age. A glacier-wide mean annual climatic mass balance of −1.8 ± 0.36 m w.e. a − 1 was simulated between between April 2000 and March 2017. An air temperature decrease between −0.9 ° C and −1.7 ° C in combination with a precipitation offset of up to +60% to recent climate conditions is necessary to simulate steady-state conditions for Schiaparelli Glacier in 1870.

Morphometric and sedimentological characteristics of Late Holocene earth hummocks in the Zackenberg Valley (NE Greenland)

A multi-approach characterization of three earth hummock fields has been conducted to understand the morphometrical characteristics and distribution pattern of these periglacial features in the Zackenberg Valley, NE Greenland. Earth hummocks develop in poorly-drained areas affected by intense cryogenic conditions. An accurate analysis of the morphometrical properties of hundreds of earth hummocks distributed between different Early Holocene moraine systems of the eastern slope of the Zackenberg Valley reveals an important control of microtopography on their distribution. Sedimentological analysis of selected earth hummocks shows evidence of alternating organic-rich layers and mineral units. Radiocarbon dates of the basal organic layers in contact with the permafrost table yielded ages 615 ± 25 and 1755 ± 60 cal yr BP, with lower sedimentation rates over the last centuries when soil formation prevailed. Geochemical analysis of the soils (Glacic Reductaquic Cryosols) showed also significant differences in the properties and composition among the soils of the different fields of hummocks.

Timing of Little Ice Age maxima and subsequent glacier retreat in northern Troms and western Finnmark, northern Norway

ABSTRACT Glaciers are important indicators of climate change, and recent observations worldwide document increasing rates of mountain glacier recession. Here we present approximately 200 years of change in mountain glacier extent in northern Troms and western Finnmark, northern Norway. This was achieved through (1) mapping and lichenometric dating of major moraine systems within a subset of the main study area (the Rotsund Valley) and (2) mapping recent (post-1980s) changes in ice extent from remotely sensed data. Lichenometric dating reveals that the Little Ice Age (LIA) maximum occurred approximately 1814 (±41 years), which is before the early twentieth-century LIA maximum proposed on the nearby Lyngen Peninsula but younger than LIA maximum limits in southern and central Norway (mid-eighteenth century). Between LIA maximum and 1989, a small sample of measured glaciers (n = 15) shrank a total of 3.9 km2 (39 percent), and those that shrank by more than 50 percent are fronted by proglacial lakes. Between 1989 and 2018, the total area of glaciers within the study area (n = 219 in 1989) shrank by approximately 35 km2. Very small glaciers (<0.5 km2) show the highest relative rates of shrinkage, and 90 percent of mapped glaciers within the study area were less than 0.5 km2 in 2018.