Remote sensing of glacier change (1965 - 2021) and identification of surge-type glaciers on Severnaya Zemlya, Russian High Arctic

Glaciers in the Russian High Arctic have undergone accelerated mass loss due to atmospheric and oceanic warming in the Barents-Kara Seas region. Most studies have concentrated on the western Barents-Kara sector, despite evidence of accelerating mass loss as far east as Severnaya Zemlya. However, long-term trends in glacier change on Severnaya Zemlya are largely unknown and this record may be complicated by surge-type glaciers. Here, we present a long-term assessment of glacier change (1965-2021) on Severnaya Zemlya and a new inventory of surge-type glaciers using declassified spy-satellite photography (KH-7/9 Hexagon) and optical satellite imagery (ASTER, Sentinel-2A, Landsat 4/5 TM & 8 OLI). Glacier area reduced from 17,053 km2 in 1965 to 16,275 in 2021 (-5%; mean: -18%, max: -100%), with areal shrinkage most pronounced at land-terminating glaciers on southern Severnaya Zemlya, where there is a recent (post-2010s) increase in summer atmospheric temperatures. We find that surging may be more widespread than previously thought, with three glaciers classified confirmed as surge-type, eight as likely to have surged and nine as possible, comprising 11% of Severnaya Zemlya’s 190 glaciers (37% by area). Under continued warming, we anticipate accelerated retreat and increased likelihood of surging as basal thermal regimes shift

Backarc basin and ocean island basalts in the Narooma Accretionary Complex, Australia: setting, geochemistry and tectonics

The Cambrian-Ordovician Wagonga Group contains basalts at Melville Point and Barlings Beach, 20 km south of Batemans Bay, New South Wales. At Melville Point, the succession has basal altered basalts overlain by chert and interbedded siliceous mudstone of the Wagonga Group, in turn overlain by turbidites and chert of the Adaminaby Group with a latest Cambrian to earliest Ordovician age. By contrast, at Barlings Beach, basalt is associated with highly disrupted chert (tectonic mélange), various slivers of mudstone and turbidites, and turbidites of the Adaminaby Group. Immobile elements in the basalts show consistent patterns that allow the magmatic affinity and tectonic setting to be determined in spite of pervasive hydrothermal alteration and subsequent lower greenschist facies metamorphism that accompanied strong folding and multiple foliation development. The Melville Point basalts show Ti/V ratios transitional between arc and MORB and therefore may have formed in either a forearc or backarc basin setting. However, these rocks have higher Ti/V ratios, LREE, Th and Nb than found in forearc basalts and are therefore considered to have formed in a backarc basin setting. In contrast to Melville Point, most basalts at Barlings Beach have a geochemical signature distinctive of ocean island settings like those reported from elsewhere in the Wagonga Group. We believe these rocks developed in a Cambrian backarc basin setting. In the Early to Middle Ordovician, much of the ocean basin was inundated by quartzose turbidites followed by basin destruction with accretion/underplating at a Late Ordovician-early Silurian Benambran subduction zone and formation of the Narooma Accretionary Complex

Characteristics and formation of bedrock mega-grooves (BMGs) in glaciated terrain: 1 - morphometric analyses

Bedrock mega-grooves (BMGs) are subglacial landforms of erosion that occur in glaciated terrain in various geological and (palaeo)glaciological settings. Despite a significant literature on BMGs, no systematic morphometric analysis of these landforms has been undertaken. This is a necessary step towards exploring BMG formation and has been successfully applied to other subglacial landforms of similar magnitude (e.g. mega-scale glacial lineations (MSGLs) and drumlins). In this study, BMGs from ten locations across the world are systematically mapped, sampled and measured. Based on the 10th–90th percentile of the aggregated global population (n = 1242), BMGs have lengths of 224–2269 m, widths of 21–210 m, depths of 5–15 m, elongation ratios of 5:1–41:1, and the spacing between adjacent grooves is 35–315 m. Frequency distributions for all metrics are unimodal, strongly suggesting that the sampled BMGs form a single landform population. This establishes the BMG as a geomorphic entity, distinctive from other subglacial landforms. The variability of the metrics and their correlations between and within sites most likely reflect site-specific geological characteristics. At sites which have been associated with fast-ice flow, BMGs display the largest dimensions (especially in terms of length, depth and width) but lowest elongation ratios, whereas BMGs formed under a primary geological control occupy smaller size ranges and have higher elongation ratios. Morphometrically, BMGs and MSGLs plot as different populations, with BMGs being on average 4 × shorter, 3.5 × narrower, 3.5 × more closely spaced and about 2 × deeper. It is suggested that future research focuses on numerical modelling experiments to test rates of erosion in different bedrock lithologies under varying glaciological conditions, and on adding to the body of existing field-derived empirical observations. The latter remains key to validating geological controls over BMG formation and assessing the efficiency of erosion mechanisms

Twenty-first century response of Petermann Glacier, northwest Greenland to ice shelf loss

Ice shelves restrain flow from the Greenland and Antarctic ice sheets. Climate-ocean warming could force thinning or collapse of floating ice shelves and subsequently accelerate flow, increase ice discharge, and raise global mean sea levels. Petermann Glacier (PG), northwest Greenland, recently lost large sections of its ice shelf, but its response to total ice shelf loss in the future remains uncertain. Here, we use the ice flow model Úa to assess the sensitivity of PG to changes in ice shelf extent, and to estimate the resultant loss of grounded ice and contribution to sea level rise. Our results have shown that under several scenarios of ice shelf thinning and retreat, removal of the shelf will not contribute substantially to global mean sea level (< 1 mm). We hypothesise that grounded ice loss was limited by the stabilization of the grounding line at a topographic high approximately 12 km inland of its current grounding line position. Further inland, the likelihood of a narrow fjord that slopes seawards suggests that PG is likely to remain insensitive to terminus changes in the near future

Introduction: Processes and Palaeo-Environmental Changes in the Arctic from Past to Present (PalaeoArc) special issue

PalaeoArc (Processes and Palaeo-Environmental Changes in the Arctic: From Past to Present) is an international network research programme, the aim of which is to understand and explain the climatically induced environmental changes in the Arctic that have taken place throughout the Quaternary and continue in the present-day (see http://www.palaeoarc.no/). This network builds on and extends the impressive legacy of previous palaeo-Arctic network programs and projects extending back to the 1980s. This began with the “Polar North Atlantic Margins—Late Cenozoic Evolution” project (PONAM: 1990–1994; Hjort and Persson 1994; Landvik and Salvigsen 1995; Elverhøi et al. 1998), which was followed by the “Quaternary Environment of the Eurasian North” project (QUEEN: 1996–2002; e.g., Larsen, Funder, and Thiede 1999; Thiede et al. 2001, 2004; Kjær et al. 2006). These were then followed by the “Arctic Palaeoclimate and Its Extremes” project (APEX: 2004–2012; Jakobsson et al. 2008, 2010, 2014) and the “Palaeo-Arctic Spatial and Temporal Gateways” project (PAST Gateways: 2012–2018; Ó Cofaigh et al. 2016, 2018). The latest incarnation of the network—PalaeoArc—was conceived at the final meeting of the PAST Gateways project in Durham, UK, in April 2019, when a new international steering committee was appointed to organize a series of activities and annual conferences for the following six years (2019–2024). The new international network held its first meeting in Poznań (20–24 May 2019), hosted by the Faculty of Geographical and Geological Sciences, Adam Mickiewicz University, Poznań (see Lyså et al. 2019), comprising the usual mix of talks, posters, discussions, workshops, and a field excursion. The network planned to organize a conference hosted by the Department of Earth Sciences at the University of Pisa in May 2020, but this had to be postponed due to the COVID-19 pandemic and was eventually held online in May 2021, endorsed by the International Arctic Science Council, Italian Geological Society, and Italian Association for the Study of the Quaternary. The meeting proved incredibly popular and was “attended” by over 250 Arctic scientists from twenty-six different countries over a four-day period, allowing glacial and marine geologists, palaeoceanographers, palaeoecologists, and specialists in permafrost and numerical modeling to discuss records of Arctic environmental change over decadal to millennial timescales. The collection of articles in this special issue stems from this second PalaeoArc International Conference and encompasses the diverse range of topics presented at the meeting, each of which addresses the overarching aims of PalaeoArc (detailed below). The third international PalaeoArc conference took place (in person) in Rovaniemi in August 2022. The network has been extended for a year, with further meetings planned in Akureyri (2023), Stockholm (2024), and Tromsø (2025)

Extensive and anomalous grounding line retreat at Vanderford Glacier, Vincennes Bay, Wilkes Land, East Antarctica

Wilkes Land, East Antarctica, has been losing mass at an accelerating rate over recent decades in response to enhanced oceanic forcing. Overlying the Aurora Subglacial Basin, it has been referred to as the ‘weak underbelly’ of the East Antarctic Ice Sheet and is drained by several major outlet glaciers. Despite their potential importance, few of these glaciers have been studied in detail. This includes the six outlet glaciers which drain into Vincennes Bay, a region recently discovered to have the warmest intrusions of modified Circumpolar Deep Water (mCDW) ever recorded in East Antarctica. Here, we use remotely sensed optical imagery, differential satellite aperture radar interferometry (DInSAR) and datasets of ice surface velocity, ice surface elevation and grounding line position, to investigate ice dynamics between 1963 and 2022. Decadal trends in frontal position are observed across the Vincennes Bay outlet glaciers, potentially correlated to variations in sea ice production. Ice surface velocities were generally stable between 2000 and 2021, with some fluctuations measured across the grounding line of Bond East Glacier. Changes in ice surface elevation were spatially variable, but a clear and consistent thinning trend was measured at Vanderford Glacier between 2003 and 2020. Enhanced rates of ice thinning were seen across each of the Vanderford, Adams, Anzac, and Underwood Glaciers between 2017 and 2020. Most importantly, our results confirm extensive grounding line retreat at Vanderford Glacier, measured at 18.6 km between 1996 and 2020. Such rapid grounding line retreat (0.8 km yr-1) is consistent with the notion that warm mCDW is able to access deep cavities formed below the Vanderford Ice Shelf, driving high rates of basal melting. With a retrograde slope observed inland along the Vanderford Trench, such oceanic forcing may have significant implications for the future stability of Vanderford Glacier

Introduction: Processes and Palaeo-Environmental Changes in the Arctic from Past to Present (PalaeoArc) special issue

PalaeoArc (Processes and Palaeo-Environmental Changes in the Arctic: From Past to Present) is an international network research programme, the aim of which is to understand and explain the climatically induced environmental changes in the Arctic that have taken place throughout the Quaternary and continue in the present-day (see http://www.palaeoarc.no/). This network builds on and extends the impressive legacy of previous palaeo-Arctic network programs and projects extending back to the 1980s. This began with the “Polar North Atlantic Margins—Late Cenozoic Evolution” project (PONAM: 1990–1994; Hjort and Persson 1994; Landvik and Salvigsen 1995; Elverhøi et al. 1998), which was followed by the “Quaternary Environment of the Eurasian North” project (QUEEN: 1996–2002; e.g., Larsen, Funder, and Thiede 1999; Thiede et al. 2001, 2004; Kjær et al. 2006). These were then followed by the “Arctic Palaeoclimate and Its Extremes” project (APEX: 2004–2012; Jakobsson et al. 2008, 2010, 2014) and the “Palaeo-Arctic Spatial and Temporal Gateways” project (PAST Gateways: 2012–2018; Ó Cofaigh et al. 2016, 2018). The latest incarnation of the network—PalaeoArc—was conceived at the final meeting of the PAST Gateways project in Durham, UK, in April 2019, when a new international steering committee was appointed to organize a series of activities and annual conferences for the following six years (2019–2024). The new international network held its first meeting in Poznań (20–24 May 2019), hosted by the Faculty of Geographical and Geological Sciences, Adam Mickiewicz University, Poznań (see Lyså et al. 2019), comprising the usual mix of talks, posters, discussions, workshops, and a field excursion. The network planned to organize a conference hosted by the Department of Earth Sciences at the University of Pisa in May 2020, but this had to be postponed due to the COVID-19 pandemic and was eventually held online in May 2021, endorsed by the International Arctic Science Council, Italian Geological Society, and Italian Association for the Study of the Quaternary. The meeting proved incredibly popular and was “attended” by over 250 Arctic scientists from twenty-six different countries over a four-day period, allowing glacial and marine geologists, palaeoceanographers, palaeoecologists, and specialists in permafrost and numerical modeling to discuss records of Arctic environmental change over decadal to millennial timescales. The collection of articles in this special issue stems from this second PalaeoArc International Conference and encompasses the diverse range of topics presented at the meeting, each of which addresses the overarching aims of PalaeoArc (detailed below). The third international PalaeoArc conference took place (in person) in Rovaniemi in August 2022. The network has been extended for a year, with further meetings planned in Akureyri (2023), Stockholm (2024), and Tromsø (2025)

Seasonal evolution of supraglacial lakes on an East Antarctic outlet glacier

Supraglacial lakes are known to influence ice melt and ice flow on the Greenland ice sheet and potentially cause ice shelf disintegration on the Antarctic Peninsula. In East Antarctica, however, our understanding of their behavior and impact is more limited. Using >150 optical satellite images and meteorological records from 2000 to 2013, we provide the first multiyear analysis of lake evolution on Langhovde Glacier, Dronning Maud Land (69°11′S, 39°32′E). We mapped 7990 lakes and 855 surface channels up to 18.1 km inland (~670 m above sea level) from the grounding line and document three pathways of lake demise: (i) refreezing, (ii) drainage to the englacial/subglacial environment (on the floating ice), and (iii) overflow into surface channels (on both the floating and grounded ice). The parallels between these mechanisms, and those observed on Greenland and the Antarctic Peninsula, suggest that lakes may similarly affect rates and patterns of ice melt, ice flow, and ice shelf disintegration in East Antarctica