Centre for Ice, Cryosphere, Carbon and Climate (iC3). Closing large-scale uncertainty in Polar ice sheet impacts on the global carbon cycle

Poster presentation at the International UK Arctic Conference, Cambridge, UK, 11.09.23 - 13.09.23: https://www.bas.ac.uk/event/uk-arctic-science-conference-2023/

The build-up, configuration, and dynamical sensitivity of the Eurasian ice-sheet complex to Late Weichselian climatic and oceanic forcing

The Eurasian ice-sheet complex (EISC) was the third largest ice mass during the Last Glacial Maximum (LGM), after the Antarctic and North American ice sheets. Despite its global significance, a comprehensive account of its evolution from independent nucleation centres to its maximum extent is conspicuously lacking. Here, a first-order, thermomechanical model, robustly constrained by empirical evidence, is used to investigate the dynamics of the EISC throughout its build-up to its maximum configuration. The ice flow model is coupled to a reference climate and applied at 10 km spatial resolution across a domain that includes the three main spreading centres of the Celtic, Fennoscandian and Barents Sea ice sheets. The model is forced with the NGRIP palaeo-isotope curve from 37 ka BP onwards and model skill is assessed against collated flowsets, marginal moraines, exposure ages and relative sea-level history. The evolution of the EISC to its LGM configuration was complex and asynchronous; the western, maritime margins of the Fennoscandian and Celtic ice sheets responded rapidly and advanced across their continental shelves by 29 ka BP, yet the maximum aerial extent (5.48 × 106 km2) and volume (7.18 × 106 km3) of the ice complex was attained some 6 ka later at c. 22.7 ka BP. This maximum stand was short-lived as the North Sea and Atlantic margins were already in retreat whilst eastern margins were still advancing up until c. 20 ka BP. High rates of basal erosion are modelled beneath ice streams and outlet glaciers draining the Celtic and Fennoscandian ice sheets with extensive preservation elsewhere due to frozen subglacial conditions, including much of the Barents and Kara seas. Here, and elsewhere across the Norwegian shelf and North Sea, high pressure subglacial conditions would have promoted localised gas hydrate formation

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)

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)

Advances in understanding subglacial meltwater drainage from past ice sheets

Meltwater drainage beneath ice sheets is a fundamental consideration for understanding ice–bed conditions and bed-modulated ice flow, with potential impacts on terminus behavior and iceshelf mass balance. While contemporary observations reveal the presence of basal water movement in the subglacial environment and inferred styles of drainage, the geological record of former ice sheets, including sediments and landforms on land and the seafloor, aids in understanding the spatiotemporal evolution of efficient and inefficient drainage systems and their impact on ice-sheet behavior. We highlight the past decade of advances in geological studies that focus on providing process-based information on subglacial hydrology of ice sheets, how these studies inform theory, numerical models and contemporary observations, and address the needs for future research

Morphological evidence for marine ice stream shutdown, central Barents Sea

The authors would like to thank NERC Oil and Gas CDT for the funding and support. We would also like to thank MAREANO (www.mareano.no) and EMODnet Bathymetry Consortium 2016 (http://www.emodnet-bathymetry.eu) for providing bathymetric data. We would like to thank Sarah Greenwood and two anonymous reviewers whose comments helped us to improve the manuscript.Peer reviewedPublisher PD

Structural and fluid-migration control on hill-hole pair formation: Evidence from high-resolution 3D seismic data from the SW Barents Sea

Hill-hole pairs are subglacial landforms consisting of thrust-block hills and associated source depressions. Formed by evacuation of material where ice sheets have been locally frozen to the substrate, they give insights into paleo-ice-sheet dynamics. The aim of this study was to document the relationships between ancient hill-hole pairs identified on a buried glacial unconformity with the structure of the underlying sedimentary deposits, and then to determine if the basin geology and glacial fluid migration pathways promoted local subglacial freeze-on during the hill-hole pair formation. The study is based on seismic geomorphological interpretation of four high-resolution 3D seismic cubes covering an area of 800 km2 in the SW Barents Sea, and fluid seepage data from 37 gravity cores. The seismic datasets allowed the identification of 55 hill-hole pairs along the buried unconformity. The hills are characterized by chaotic to homogenous seismic facies forming up to 19 m high mounds, each covering areas of 2000–644,000 m2. The holes form depressions between 1 and 44 m deep and 2000–704,000 m2 in areal extent, which cut into preglacial Mesozoic bedrock and later infilled by glacial till. The holes are often found above fault terminations. High-amplitude reflections identified along the faults and in the strata below the holes are interpreted as shallow gas migrating upward towards the glacial unconformity. Geochemical data of the seabed sediment cores further indicates an association between hill-hole pair occurrence and present-day thermogenic hydrocarbon seepage. The hill-hole pairs geometries were also used to identify five paleo-ice-flow directions along the glacial unconformity. These ice flows exhibit polythermal regimes, and four of them are parallel to ice-stream flow sets interpreted from glacial lineations. The integrated interpretation supports localized fault-related basal freezing of the Barents Sea Ice Sheet which resulted in the formation of hill-hole pairs when the ice sheet moved. In this context, the faults functioned as migration pathways for deep thermogenic fluids, possibly sourced from leaking Jurassic reservoirs.>p> This study highlights the importance of the underlying geology for ice-sheet dynamics: While hill-hole pairs above glacial till appear to be commonly associated with dispersed gas hydrates, hill-hole pairs above bedrock additionally indicate a link to underlying fault systems and hydrocarbon reservoirs. Freeze-on of underlying bedrock to the basal ice along the strike of faults in sedimentary bedrock explains deeper hill-hole pairs with smaller extents along the glacial unconformity compared to areally larger but shallow hill-hole pairs detected above glacial till on modern seabeds. Such close association between paleo-thermogenic gas seepage and the location of hill-hole pairs strongly support that hill-hole pairs are excellent markers revealing exit points of fluid migration pathways in petroleum system models

The role of ocean and atmospheric dynamics in the marine-based collapse of the last Eurasian Ice Sheet

Information from former ice sheets may provide important context for understanding the response of today’s ice sheets to forcing mechanisms. Here we present a reconstruction of the last deglaciation of marine sectors of the Eurasian Ice Sheet, emphasising how the retreat of the Norwegian Channel and the Barents Sea ice streams led to separation of the British-Irish and Fennoscandian ice sheets at c. 18.700 and of the Kara-Barents Sea-Svalbard and Fennoscandian ice sheets between 16.000 and 15.000 years ago. Combined with ice sheet modelling and palaeoceanographic data, our reconstruction shows that the deglaciation, from a peak volume of 20 m of sea-level rise equivalent, was mainly driven by temperature forced surface mass balance in the south, and by Nordic Seas oceanic conditions in the north. Our results highlight the nonlinearity in the response of an ice sheet to forcing and the significance of ocean-ice-atmosphere dynamics in assessing the fate of contemporary ice sheets

Distinct modes of meltwater drainage and landform development beneath the last Barents Sea ice sheet

The flow of glacial ice is impacted by basal meltwater drainage systems that fluctuate on a continuum from distributed, high-pressure environments to channelized, lower pressure networks. Understanding the long-term development of dominant drainage modes and impacts on ice flow and landform development is a crucial step in predicting palaeo and contemporary ice-mass response to changes in climate. The spatial and temporal scales at which different drainage modes operate are largely unknown, and the geomorphological legacy of subglacial meltwater networks that evolve over a glaciation provide composite records of drainage system development. Here, we use high-resolution bathymetric data from shallow banks in the central Barents Sea to map the geomorphological imprint of meltwater drainage beneath the collapsing marine-based Barents Sea Ice Sheet (BSIS). We observe a succession of distinct meltwater landforms that provide relative timing constraints for subglacial drainage modes, indicating that extensive networks of channelized drainage were in operation during deglaciation. Interlinked basins and channels suggest that meltwater availability and drainage system development was influenced by filling and draining cycles in subglacial lakes. Networks of eskers also indicate near-margin meltwater conduits incised into basal ice during late-stage deglaciation, and we suggest that these systems were supplemented by increased inputs from supraglacial melting. The abundance of meltwater during the late stages of BSIS deglaciation likely contributed to elevated erosion of the sedimentary substrate and the mobilisation of subglacial sediments, providing a sediment source for the relatively abundant eskers found deposited across bank areas. A newly discovered beaded esker system over 67 km long in Hopendjupet constrains a fluctuating, but generally decelerating, pace of ice retreat from ∼1,600 m a−1 to ∼620 m a−1 over central Barents Sea bank areas during a 91-year timespan