ABSTRACT Benthic ecosystems are shaped by seafloor structure, yet linking geomorphology and biology across environmental gradients remains challenging. Here, we integrate seafloor imagery, multiscale bathymetry, and predictive modelling to quantify benthic biodiversity and its environmental drivers along the Powell Basin flank of the Antarctic Peninsula. Steep geomorphological landforms (terraces and steep slopes) hosted maximal densities and distinct communities, with significant enrichment of corals, sponges, ophiuroids, and sea pens. The marked congruence of slope across bathymetric resolutions enabled regional upscaling, estimating a standing stock of ∼96 billion individuals across 7,400 km² of the basin flank. Decadal oceanographic models indicate that benthic densities peak in cold bottom water below −0.15 °C. We identified four biodiversity hotspots (∼33 km 2 ) with slopes >35° and depths >1,700 m, with up to threefold higher densities. Hotspots align with the pathway of Weddell Sea Deep Water, where thermal decoupling between bottom and overlying waters indicates dynamic hydrography along steep, biodiverse terrain. Furthermore, contrasting sea-ice cover and stratification regimes suggest distinct cryo-pelagic-benthic coupling around hotspots. The concentration of biodiversity through seafloor geomorphology and ocean circulation bridges Antarctic benthic ecology from habitat to biogeography, with implications for monitoring change and guiding conservation in the warming Weddell Sea.

Ice shelves exert a buttressing effect on the Antarctic ice sheets that can reduce as basal melting drives their thinning and destabilization. This process is strongly affected by the depths and morphologies of the underlying cavity floors, which regulate ice-ocean interactions, but remain poorly constrained. We created a new model of the bathymetry beneath a section of the Ronne Ice Shelf downstream of the Evans Ice Stream by inversion of carefully selected airborne gravity data constrained by seismic and ice-penetrating radar depth references. The model reveals a deep, asymmetric and U-shaped trough aligned with the ice flow direction, reflecting glacial erosion and tectonic inheritance. The persistent retrograde slope of the seafloor potentially allows warm water intrusion from the open ocean up to the grounding line. Our model thus provides critical constraints for estimating basal melt rates and assessing ice shelf and ice sheet stability with regard to large-scale climate changes.

The Long-Term Ecological Research observatory HAUSGARTEN was established by the Alfred Wegener Institute for Polar and Marine Research (AWI) in the Fram Strait in summer 1999 to detect and track the impact of large-scale environmental changes on the marine ecosystem in the transition zone between the northern North Atlantic and the central Arctic Ocean. In this area, bathymetric data have been recorded with multibeam echosounders (MBES) during 44 research expeditions since 1984. Based on these data, we present a digital elevation model, geospatial derivatives and quantitative terrain descriptors for subsequent terrain analyses and habitat mapping. Heterogeneity of the bathymetric data, however, resulted in abundant small-scale artefacts in the digital elevation model and derived products that in some places overprint small seabed landforms. This heterogeneity is caused by the data collection with multibeam echosounders in differing technical stages over a period of four decades in different weather and ice conditions. Despite these technical limitations, the accumulated bathymetric data function as a vital physical baseline and environmental parameters for the HAUSGARTEN observatory that cannot be replicated by modern single-cruise surveys.

This paper presents new marine geophysical data and radiocarbon dated sediment cores to reconstruct the maximum extent of the Northeast Greenland Ice Stream (NEGIS) during the last glaciation and the timing of its initial retreat from the continental shelf. The NEGIS is the largest ice stream to drain the Greenland Ice Sheet (GrIS) today, and holds a sea-level equivalent of 1.1-1.4 m. It has undergone recent retreat but the longer-term history of NEGIS on the adjoining continental shelf is still relatively poorly constrained. Two cross-shelf bathymetric troughs, Westwind and Norske troughs, acted as pathways for offshore-flowing ice during the last glaciation but little is known about the acoustic stratigraphy, sedimentology and chronology of ice sheet retreat in the outer shelf sections of both troughs. Multibeam swath bathymetry and acoustic data from both troughs show flow parallel and flow transverse glacial landforms in the outer shelf sections of both troughs. Mega-scale glacial lineations in Westwind Trough record former streaming flow towards the shelf-edge. Grounding-zone wedges record episodic stabilisation during retreat from the shelf-edge. Sediment cores recovered subglacial tills and grounding-zone proximal sediments overlain by glacimarine sediments. The slope beyond Norske Trough is characterised by glacigenic debris flows typical of submarine slopes offshore of shelf-edge terminating palaeo-ice streams. Radiocarbon dates indicate that initial retreat of the ancestral NEGIS from the northeast Greenland shelf-edge was underway by 21.5-21.6 cal ka BP in Norske Trough and c. >= 19.0 cal ka BP in Westwind Trough. Retreat rates across the outer shelf were slow at 19-23 m a-1 but increased across the inner shelf. Our data provides the first direct chronological support for a shelf-edge terminating GrIS offshore of northeast Greenland during the last glacial maximum and demonstrates this sector of the GrIS underwent relatively early retreat from the shelf-edge.

We present Bedmap3, the latest suite of gridded products describing surface elevation, ice-thickness and the seafloor and subglacial bed elevation of the Antarctic south of 60 °S. Bedmap3 incorporates and adds to all post-1950s datasets previously used for Bedmap2, including 84 new aero-geophysical surveys by 15 data providers, an additional 52 million data points and 1.9 million line-kilometres of measurement. These efforts have filled notable gaps including in major mountain ranges and the deep interior of East Antarctica, along West Antarctic coastlines and on the Antarctic Peninsula. Our new Bedmap3/RINGS grounding line similarly consolidates multiple recent mappings into a single, spatially coherent feature. Combined with updated maps of surface topography, ice shelf thickness, rock outcrops and bathymetry, Bedmap3 reveals in much greater detail the subglacial landscape and distribution of Antarctica’s ice, providing new opportunities to interpret continental-scale landscape evolution and to model the past and future evolution of the Antarctic ice sheets.

Marine geophysical data combined with radiocarbon dated sediment cores provide a record of the advance and retreat of the ancestral Northeast Greenland Ice Stream (NEGIS) across the continental shelf offshore of NE Greenland during the last glaciation. Today, NEGIS is the largest ice stream to drain the Greenland Ice Sheet (GrIS), holding a sea-level equivalent of 1.1-1.4 m. However, the longer-term history of the ice stream, especially on the adjoining outer continental shelf has, to date, been poorly constrained. Streamlined subglacial landforms record grounded ice flow in the outer shelf section in cross shelf bathymetric troughs, with mega-scale glacial lineations recording former streaming flow towards the shelf edge. Flow transverse landforms in the form of downlow-tapering, sediment wedges occur at the shelf edge and on the outer-mid shelf of the bathymetric troughs. These landforms differ in their morphology from the classic ‘ramp-step’ form of typical grounding wedges but are similarly interpreted as a form of grounding-zone wedge in which sediment prograded and thinned away from the grounding-zone. The wedges record a shelf-edge terminating, grounded ancestral NEGIS, as well as the subsequent episodic retreat of the ice stream inshore during deglaciation. Beyond the shelf edge, glacigenic debris flows imaged on acoustic stratigraphic profiles and recovered in sediment cores document sediment delivery onto the slope; such deposits are typical of submarine slopes offshore of shelf-edge terminating palaeo-ice streams. On the outer shelf subglacial tills and grounding-zone proximal sediments overlain by deglacial stratified glacimarine sediments record ice stream advance and retreat in the troughs. Radiocarbon dates from glacimarine sediments in these cores indicate early deglaciation from the shelf edge but with relatively slow rates of subsequent ice-stream retreat across the outer shelf.

Abstract Knowledge about seafloor depth, or bathymetry, is crucial for various marine activities, including scientific research, offshore industry, safety of navigation, and ocean exploration. Mapping the central Arctic Ocean is challenging due to the presence of perennial sea ice, which limits data collection to icebreakers, submarines, and drifting ice stations. The International Bathymetric Chart of the Arctic Ocean (IBCAO) was initiated in 1997 with the goal of updating the Arctic Ocean bathymetric portrayal. The project team has since released four versions, each improving resolution and accuracy. Here, we present IBCAO Version 5.0, which offers a resolution four times as high as Version 4.0, with 100 × 100 m grid cells compared to 200 × 200 m. Over 25% of the Arctic Ocean is now mapped with individual depth soundings, based on a criterion that considers water depth. Version 5.0 also represents significant advancements in data compilation and computing techniques. Despite these improvements, challenges such as sea-ice cover and political dynamics still hinder comprehensive mapping.

Multibeam bathymetric and seismostratigraphic data collected in the Clyde fjord-cross-shelf trough system (eastern Baffin Island, Canadian Arctic Archipelago) display glacial landforms and depositional assemblages that enable the identification of the maximal extent of the Laurentide Ice Sheet (LIS) margin and delineating the patterns and controls on its subsequent retreat. Additionally, 10 new sediment cores – from which seven radiocarbon ages were acquired – allow the recognition of depositional processes. Results show that, during the Last Glacial Maximum, the LIS margin extended almost to the edge of the continental shelf. Early deglaciation of the trough was marked by an initial ice-shelf collapse and rapid retreat of the ice stream, as evidenced by the absence of ice marginal landforms and the presence of extensive iceberg ploughmarks across a large portion of the outer trough. It was followed by a slow retreat and successive stabilizations of the ice margin that led to the deposition of recessional moraines and grounding-zone wedges (GZWs). Deglaciation of the fjord in the early Holocene occurred in an episodic style, whereby rapid retreat was punctuated by relatively long standstills that enabled major moraine formation. Long-term stabilizations of the ice margin in the Clyde fjord-cross-shelf trough system are interpreted to coincide with major climatic cooling events, such as the Younger Dryas and early Holocene cold reversals. Ages derived from sediment cores and previous work suggest that higher retreat rates correspond with periods of significant global sea level rise, suggesting that oceanic forcing exerted a minor control on the deglaciation. GZWs and large moraine ridges are observed at pinning points in the trough and fjord, indicating that the location of ice margin stabilizations was influenced by topography. The reconstruction of the deglaciation of the Clyde fjord-cross-shelf trough system allows us to refine deglacial models for similar systems of northeastern Baffin Island, in particular beyond the coast and along the steeper section of the fjord where chronological gaps remained.

Ocean ecosystems are at the forefront of the climate and biodiversity crises, yet we lack a unified approach to assess their state and inform sustainable policies. This blueprint is designed around research capabilities and cross-sectoral partnerships. We highlight priorities including integrating basin-scale observation, modelling and genomic approaches to understand Atlantic oceanography and ecosystem connectivity; improving ecosystem mapping; identifying potential tipping points in deep and open ocean ecosystems; understanding compound impacts of multiple stressors including warming, acidification and deoxygenation; enhancing spatial and temporal management and protection. We argue that these goals are best achieved through partnerships with policy-makers and community stakeholders, and promoting research groups from the South Atlantic through investment and engagement. Given the high costs of such research (€800k to €1.7M per expedition and €30–40M for a basin-scale programme), international cooperation and funding are integral to supporting science-led policies to conserve ocean ecosystems that transcend jurisdictional borders.

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.

IBCSO v2 modified for technical validation. Cells and masks are modified for consistency of data sets for comparison calculations with SRTM15+. https://github.com/SeaBed2030/IBCSO_v2_Dorschel_et_al_2022/tree/main/COMPARISON

SRTM15+ south of 50°S modified for technical validation. Cells and masks are modified for consistency of data sets for comparison calculations with IBCSO v2. https://github.com/SeaBed2030/IBCSO_v2_Dorschel_et_al_2022/tree/main/COMPARISON

Prydz Bay lies at the terminus of one of East Antarctica's largest glacial systems and is a key region for understanding the response of the ice sheet to past and future environmental changes. In this study, we explore the dynamics and paleo-geometry of the ice sheet in eastern Prydz Bay, using a combination of bathymetric features on the seafloor to delineate past flow patterns, and cosmogenic nuclide dating of glacial deposits on land to constrain ice sheet terminus chronologies. Large streamlined bedforms on the sea floor record the existence of a primary ice stream in Svenner Channel, collecting ice from multiple tributary ice streams and discharging into the main trunk stream of the Lambert Glacier-Amery Ice Shelf system in Prydz Channel. The location and orientation of the north-eastern tributary to this ice stream also provide evidence for a substantial independent ice dome on the outer shelf at Four Ladies Bank. Exposure of ice-free areas at outer Rauer Group and Vestfold Hills indicates that grounding line retreat across eastern Prydz Bay was largely complete by similar to 14 ka BP, and the ice margin had retreated to within similar to 1 km of its present position by similar to 10 ka BP. Onshore moraines record periods of ice margin retreat during the middle (similar to 6 ka BP) and very late (similar to 0.5 ka BP) Holocene coinciding with local warm periods. Subsidence recorded in modern Global Navigation Satellite System (GNSS) observations suggests the regional ice sheet was smaller than at present in the period between the middle and very late Holocene advances. The unusually dynamic ice sheet behaviour in this area is attributed to the smooth, reverse-slope bed characteristics of eastern Prydz Bay, which enabled rapid retreat of the ice sheet margin several hundred kilometres during deglacial events. Crown Copyright (C) 2022 Published by Elsevier Ltd. All rights reserved.

The Southern Ocean surrounding Antarctica is a region that is key to a range of climatic and oceanographic processes with worldwide effects, and is characterised by high biological productivity and biodiversity. Since 2013, the International Bathymetric Chart of the Southern Ocean (IBCSO) has represented the most comprehensive compilation of bathymetry for the Southern Ocean south of 60°S. Recently, the IBCSO Project has combined its efforts with the Nippon Foundation – GEBCO Seabed 2030 Project supporting the goal of mapping the world’s oceans by 2030. New datasets initiated a second version of IBCSO (IBCSO v2). This version extends to 50°S (covering approximately 2.4 times the area of seafloor of the previous version) including the gateways of the Antarctic Circumpolar Current and the Antarctic circumpolar frontal systems. Due to increased (multibeam) data coverage, IBCSO v2 significantly improves the overall representation of the Southern Ocean seafloor and resolves many submarine landforms in more detail. This makes IBCSO v2 the most authoritative seafloor map of the area south of 50°S.

The Ekström Ice Shelf is one of numerous small ice shelves that fringe the coastline of western Dronning Maud Land, East Antarctica. Reconstructions of past ice-sheet extent in this area are poorly constrained, due to a lack of geomorphological evidence. Here, we present a compilation of geophysical surveys in front of and beneath the Ekström Ice Shelf, to identify and interpret evidence of past ice-sheet flow, extent and retreat. The sea floor beneath the Ekström Ice Shelf is dominated by an incised trough, which extends from the modern-day grounding line onto the continental shelf. Our surveys show that mega-scale glacial lineations cover most of the mouth of this trough, terminating 11 km away from the continental shelf break, indicating the most recent minimal extent of grounded ice in this region. Beneath the front ∼30 km of the ice shelf measured from the ice shelf edge towards the inland direction, the sea floor is characterised by an acoustically transparent sedimentary unit, up to 45 m thick. This is likely composed of subglacial till, further corroborating the presence of past grounded ice cover. Further inland, the sea floor becomes rougher, interpreted as a transition from subglacial tills to a crystalline bedrock, corresponding to the outcrop of the volcanic Explora Wedge at the sea floor. Ice retreat in this region appears to have happened rapidly in the centre of the incised trough, evidenced by a lack of overprinting of the lineations at the trough mouth. At the margins of the trough uniformly spaced recessional moraines suggest ice retreated more gradually. We estimate the palaeo-ice thickness at the calving front around the Last Glacial Maximum to have been at least 305 to 320 m, based on the depth of iceberg ploughmarks within the trough and sea level reconstructions. Given the similarity of the numerous small ice shelves along the Dronning Maud Land coast, these findings are likely representative for other ice shelves in this region and provide essential boundary conditions for palaeo ice-sheet models in this severely understudied region.

Abstract The Cape Darnley region in East Antarctica has been an area of scientific interest for a variety of disciplines over the last three decades. The recent acquisition of several high-resolution bathymetry datasets enabled the compilation of a detailed regional bathymetry grid. We present a high-resolution bathymetric compilation of the Cape Darnley region in East Antarctica, including areas of the Mac.Robertson Land shelf, slope and adjacent deep sea. A variety of data, single-beam and multibeam swath bathymetry and digitized depths from nautical charts were sourced from numerous institutions. The 100 m-resolution gridded bathymetric dataset improves previous bathymetric representations of the region and enables visualization of the seafloor morphology in unprecedented detail. The bathymetry grid has been constructed using a layered hierarchy approach based on the source of each dataset. This data compilation forms important baseline information for a range of scientific applications and end users including oceanographers, glacial modellers, biologists and geologists. The compilation will aid numerical modelling of ocean circulation, reconstruction of palaeo-ice streams and refinement of ice-sheet models.

The Ocean Floor Observation and Bathymetry System (OFOBS) is an underwater survey platform, which is designed and developed for research in the Polar Regions by the Alfred Wegener Institute (AWI). The tailored deep tow system brought a new perspective and clarity from Arctic Ocean by its optical and acoustic sensors. During the PS101 expedition at the Karasik seamount, OFOBS provides a novel picture of megafauna’s habitats. In this study, we develop a methodology to convert the imagery dataset to micro-bathymetry in order to provide primary data for object detection and habitat mapping which will provide a better understanding of arctic benthic habitats. The methodology is based on the underwater photogrammetry workflow and two different point cloud classification methods adopted for sponge detection in 3D point clouds, to facilitate habitat mapping with a focus on the central of Karasik seamount where an extensive and dense assemblage of the Geodia sponges is dominating the seafloor.

Research vessels equipped with fibre optic and copper-cored coaxial cables support the live onboard inspection of high-bandwidth marine data in real time. This allows for towed still-image and video sleds to be equipped with latest-generation higher-resolution digital camera systems and additional sensors. During RV Polarstern expedition PS118 in February–April 2019, the recently developed Ocean Floor Observation and Bathymetry System (OFOBS) of the Alfred Wegener Institute was used to collect still-image and video data from the seafloor at a total of 11 predominantly ice-covered locations in the northern Weddell Sea and Powell Basin. Still images of 26-megapixel resolution and HD (high-definition) quality video data were recorded throughout each deployment. In addition to downward-facing video and still-image cameras, the OFOBS also mounted side-scanning and forward-facing acoustic systems, which facilitated safe deployment in areas of high topographic complexity, such as above the steep flanks of the Powell Basin and the rapidly shallowing, iceberg-scoured Nachtigaller Shoal. To localise collected data, the OFOBS system was equipped with a Posidonia transponder for ultra-short baseline triangulation of OFOBS positions. All images are available from: https://doi.org/10.1594/PANGAEA.911904 (Purser et al., 2020).