Description: Bathymetry (seafloor depth), is a critical parameter providing the geospatial context for a multitude of marine scientific studies. Since 1997, the International Bathymetric Chart of the Arctic Ocean (IBCAO) has been the authoritative source of bathymetry for the Arctic Ocean. IBCAO has merged its efforts with the Nippon Foundation-GEBCO-Seabed 2030 Project, with the goal of mapping all of the oceans by 2030. Here we present the latest version (IBCAO Ver. 4.0), with more than twice the resolution (200 × 200 m versus 500 × 500 m) and with individual depth soundings constraining three times more area of the Arctic Ocean (∼19.8% versus 6.7%), than the previous IBCAO Ver. 3.0 released in 2012. Modern multibeam bathymetry comprises ∼14.3% in Ver. 4.0 compared to ∼5.4% in Ver. 3.0. Thus, the new IBCAO Ver. 4.0 has substantially more seafloor morphological information that offers new insights into a range of submarine features and processes; for example, the improved portrayal of Greenland fjords better serves predictive modelling of the fate of the Greenland Ice Sheet.

Description: 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.

Description: About 16% of the Greenland Ice Sheet drains in the area of the Northeast Greenland shelf between 76°N and 80.5°N via marine terminating glaciers. Most of it is via the Northeast Greenland Ice Stream, the largest ice stream of Greenland. During ice ages, the ice sheet extended onto the continental shelf and modern-day cross-shelf troughs were filled by ice streams. In this study, high-resolution hydro-acoustic data acquired during three decades of research were jointly investigated to reveal the past glacial conditions. Our data shows that Westwind Trough and Norske Trough were filled by fast flowing ice streams that extended to the shelf edge during the last glacial maximum. In between the cross-shelf troughs, ice domes resided on shallow banks that may have contributed about a decimetre to global sea level. Most probably these ice domes initiated fast ice flow through sinks in the inter-trough area. In Westwind Trough, ice sheet retreat to the inner shelf after the last glacial maximum was intermittent. In contrast, in Norske Trough the ice sheet retreat appears relatively rapid with no evidences for phases of grounding line stabilization. Probably during the Younger Dryas, the ice sheet readvanced to a mid-shelf position in both troughs documented by grounding zone wedges. During this time, a thick ice shelf was present in Norske Trough releasing tabular icebergs. Ice sheet retreat from the mid-shelf to the coastline during Holocene deglaciation was rapid.

Description: Through the interplay of a stabilising cold-water coral framework and a dynamic sedimentary environment, cold-water coral carbonate mounds create distinctive centres of bio-geological accumulation in often complex (continental margin) settings. The IODP Expedition 307 drilling of the Challenger Mound (eastern Porcupine Seabight; NE Atlantic) not only retrieved the first complete developmental history of a coral carbonate mound, it also exposed a unique, Early-Pleistocene sedimentary sequence of exceptional resolution along the mid-latitudinal NE Atlantic margin. In this study, a comprehensive assessment of the Challenger Mound as an archive of Quaternary palaeo-environmental change and long-term coral carbonate mound development is presented. New and existing environmental proxy records, including clay mineralogy, planktonic foraminifer and calcareous nannofossil biostratigraphy and assemblage counts, planktonic foraminifer oxygen isotopes and siliciclastic particle-size, are thereby discussed within a refined chronostratigraphic and climatic context. Overall, the development of the ChallengerMound shows a strong affinity to the Plio-Pleistocene evolution of the Northern Hemisphere climate system, albeit not being completely in phase with it. The two major oceanographic and climatic transitions of the Plio-Pleistocene e the Late Pliocene/Early Pleistocene intensification of continental ice-sheet development and the mid-Pleistocene transition to the more extremely variable and more extensively glaciated late Quaternary e mark twomajor thresholds in Challenger Mound development: its Late Pliocene (〉2.74 Ma) origin and itsMiddleeLate Pleistocene to recent decline. Distinct surface-water perturbations (i.e. water-mass/polar front migrations, productivity changes, melt-water pulses) are identified throughout the sequence, which can be linked to the intensity and extent of ice development on the nearby BritisheIrish Isles since the earliest Pleistocene. Glaciation-induced shifts in surfacewater primary productivity are thereby proposed to fundamentally control cold-water coral growth, which in turn influences on-mound sediment accumulation and, hence, coral carbonate mound development throughout the Pleistocene. As local factors, such as proximal ice-sheet dynamics and on-mound changes in cold-water coral density, significantly affected the development of the Challenger Mound, they can potentially explain the nature of its palaeo-record and its offsets with the periodicities of global climate variability. On the other hand, owing to this unique setting, a regionally exceptional, high-resolution palaeo-record of Early Pleistocene (ca 2.6 to 2.1 Ma) environmental change (including early BritisheIrish ice-sheet development), broadly in phase with the 41 ka-paced global climate system, is preserved in the lower Challenger Mound. All in all, the Challenger Mound record highlights the wider relevance of coral carbonate mound archives and their potential to capture unique records from dynamic (continental margin) environments.

Description: New swath-bathymetric data acquired in 2010 and 2015 indicate a variety of glacial landforms in cross-shelf troughs of the Melville Bay (northeast Baffin Bay). These landforms reveal that, at their maximum extent, ice streams in the troughs crossed the shelf all the way to the shelf edge. Moraines, grounding-zone wedges (GZWs) and subglacial till lobes on the continental shelf define a pattern of variable ice stream retreat in the individual troughs. On the outer shelf, in the northern cross-shelf trough, ice-stream retreat was slow compared to more episodic retreat in the central (at least one stabilization on the outer shelf) and southern cross-shelf trough (re-advances at the shelf edge and fast retreat thereafter). Large GZWs on the mid-to inner shelf of the troughs indicate periods of grounding-zone stabilization. According to glacial landforms, the final retreat across the inner shelf (before 8.41 ka BP) was episodic to slow. Furthermore, evidence has been found for localized ice domes with minor ice-streams on inter-trough banks. The glacial landforms in Melville Bay, thus, indicate the varying and discontinuous ice sheet retreat history across the Northwest Greenland continental shelf.