Bathymetric mapping of the Arctic seafloor remains challenging due to persistent sea ice, which limits systematic surveys and degrades multibeam echosounder (MBES) data through reduced swath width, ice interference, and vessel-induced noise. As a result, Digital Terrain Models (DTMs) derived from MBES data in ice-covered regions are often fragmented, coarse, and incomplete, obscuring bottom morphological features. These includes submarine glacial landforms that are informative of past glacier extents and ice-sheet dynamics. Standard interpolation is commonly used for upsampling and gap-filling but systematically oversmooths seafloor morphology, removing the small-scale variability central to glacial geomorphological interpretation.Here, we investigate whether domain-informed generative super-resolution can recover geomorphologically meaningful structure in degraded Arctic bathymetry. We target upscaling from 100–200 m grid cell resolution to 25 m (4×–8×), with explicit emphasis on preserving glacial landforms rather than optimizing pixel-wise fidelity. We compile (i) 25 m MBES-derived bathymetry from surveys near northern Greenland and around Svalbard, which is downsampled to 100 m and 200 m to create controlled low-resolution inputs, and (ii) a larger set of terrestrial post-glacial Digital Elevation Models (DEMs) from Norway, Iceland, and the Hudson Bay region derived from airborne LiDAR and satellite products. The terrestrial DEMs provide a geomorphological prior without hydroacoustic artifacts and are used for training, while MBES data are reserved exclusively for evaluation in the Arctic bathymetry use case, acknowledging the domain shift between terrestrial and submarine environments.We train a conditional diffusion model with a U-Net backbone to generate 25 m terrain conditioned on low-resolution inputs. In controlled downsampling experiments, conventional super-resolution metrics show limited separation from deterministic baselines; however, distributional similarity, quantified using the Wasserstein distance of elevation-value distributions, consistently improves. Qualitative assessments in regions such as Svalbard, Nares Strait, and Victoria Fjord show that the diffusion model produces sharper glacial lineations, more distinct retreat moraines, and clearer iceberg scour patterns than interpolation-based methods. To better quantify these geomorphological improvements, we introduce a Fourier-domain evaluation based on radial power spectral density and cross-correlation. Frequency-domain analysis shows that diffusion outputs more closely match the spectral characteristics of the 25 m reference data and tend to restore mid-wavelength power associated with glacial bedforms. Overall, the results suggest that domain-informed generative super-resolution can produce more interpretable bathymetric grids, while underscoring the need for evaluation metrics aligned with geomorphological realism.

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.

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.

Submarine glacial landforms in fjords are imprints of the dynamic behaviour of marine-terminating glaciers and are informative about their most recent retreat phase. Here we use detailed multibeam bathymetry to map glacial landforms in Petermann Fjord and Nares Strait, northwestern Greenland. A large grounding-zone wedge (GZW) demonstrates that Petermann Glacier stabilised at the fjord mouth for a considerable time, likely buttressed by an ice shelf. This stability was followed by successive backstepping of the ice margin down the GZW’s retrograde backslope forming small retreat ridges to 680 m current depth (∼730–800 m palaeodepth). Iceberg ploughmarks occurring somewhat deeper show that thick, grounded ice persisted to these water depths before final breakup occurred. The palaeodepth limit of the recessional moraines is consistent with final collapse driven by marine ice cliff instability (MICI) with retreat to the next stable position located underneath the present Petermann ice tongue, where the seafloor is unmapped.

The hypothesis of a km-thick ice shelf covering the entire Arctic Ocean during peak glacial conditions was proposed nearly half a century ago. Floating ice shelves preserve few direct traces after their disappearance, making reconstructions difficult. Seafloor imprints of ice shelves should, however, exist where ice grounded along their flow paths. Here we present new evidence of ice-shelf groundings on bathymetric highs in the central Arctic Ocean, resurrecting the concept of an ice shelf extending over the entire central Arctic Ocean during at least one previous ice age. New and previously mapped glacial landforms together reveal flow of a spatially coherent, in some regions >1-km thick, central Arctic Ocean ice shelf dated to marine isotope stage 6 (∼140 ka). Bathymetric highs were likely critical in the ice-shelf development by acting as pinning points where stabilizing ice rises formed, thereby providing sufficient back stress to allow ice shelf thickening.

The Swedish-Russian-US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions (SWERUS-C3) is a multi-investigator, multi-disciplinary program aimed at increasing our understanding of ...

Pine Island Glacier drains portions of the West Antarctic Ice Sheet into the Amundsen Sea. During the Last Glacial Maximum the glacier extended nearly 500 km from its present location onto the outer continental shelf. Unusually restricted sea-ice cover during the austral summer of 2010 allowed for a systematic multibeam swath-bathymetric and chirp sonar survey of the mid-shelf section of Pine Island Trough. The mapped glacial landforms reveal new information about the paleo-Pine Island Ice Stream's dynamic retreat from the mid-shelf area and confirm previous suggestion of a retreat in distinct steps. The periods of grounding line stability during the overall retreat phase are marked by sediment accumulations, i.e. grounding zone wedges. These wedges are here mapped in sufficient detail to characterize spatial dimensions and estimate the volume of deposited sediment. Considering a range of sediment flux rates from the paleo-Pine Island Ice Stream we estimate that the largest and most clearly defined grounding zone wedge, located at about 73 degrees S in the surveyed area, took between 600 and 2000 years to form. The ice stream retreated landward of this wedge before 12.3 cal ka BP. The swath-bathymetric imagery of landforms in Pine Island Trough includes glacial features that suggest that retreat between periods of grounding line stability may be associated with episodes of ice shelf break-up. The depths of grounding line wedges decrease in a landward direction, from 740 to 670 m, and record elevation of the grounding line as it stepped landward. In all, the grounding line elevation varied by only similar to 80 m over a distance of just over 100 km, implying a low ice sheet profile during retreat. Finally, we revisited seismic reflection profile NB9902, acquired along Pine Island Trough in 1999, in combination with the newly acquired swath-bathymetric imagery from 2010. Together these data show that the ice stream paused during its retreat to form grounding zone wedges at an area in central Pine Island Trough where a high in dipping bedrock strata exists and the glacial trough is narrow, forming a bathymetric "bottle neck". (C) 2011 Elsevier Ltd. All rights reserved.

The International Bathymetric Chart of the Arctic Ocean (IBCAO) released its first gridded bathymetric compilation in 1999. The IBCAO bathymetric portrayals have since supported a wide range of Arctic science activities, for example, by providing constraint for ocean circulation models and the means to define and formulate hypotheses about the geologic origin of Arctic undersea features. IBCAO Version 3.0 represents the largest improvement since 1999 taking advantage of new data sets collected by the circum‐Arctic nations, opportunistic data collected from fishing vessels, data acquired from US Navy submarines and from research ships of various nations. Built using an improved gridding algorithm, this new grid is on a 500 meter spacing, revealing much greater details of the Arctic seafloor than IBCAO Version 1.0 (2.5 km) and Version 2.0 (2.0 km). The area covered by multibeam surveys has increased from ∼6% in Version 2.0 to ∼11% in Version 3.0.

The catastrophic break-ups of the floating Larsen A and B ice shelves (Antarctica) in 1995 and 2002 and associated acceleration of glaciers that flowed into these ice shelves were among the most dramatic glaciological events observed in historical time. This raises a question about the larger West Antarctic ice shelves. Do these shelves, with their much greater glacial discharge, have a history of collapse? Here we describe features from the seafloor in Pine Island Bay, West Antarctica, which we interpret as having been formed during a massive ice shelf break-up and associated grounding line retreat. This evidence exists in the form of seafloor landforms that we argue were produced daily as a consequence of tidally influenced motion of mega-icebergs maintained upright in an iceberg armada produced from the disintegrating ice shelf and retreating grounding line. The break-up occurred prior to ca. 12 ka and was likely a response to rapid sea-level rise or ocean warming at that time.

Mapped Submarine Landforms in Pine Island Bay, West Antarctica, Indicate Past Ice Shelf Disintegration and Grounding line Retreat

The Moberg et al. (Nature 433(7026):613–617, 2005 . doi: 10.1038/nature03265 ; M05) reconstruction of northern hemisphere temperature variations from proxy data has been criticised; the M05 method may artificially inflate low-frequency variance relative to reality. We test this assertion by undertaking several pseudoproxy experiments in three climate model simulations—one control run and two forced simulations that include several time-varying radiative forcings. The pseudoproxy series are designed to have the same variance spectra as the real M05 proxies, primarily to mimic the low-resolution character of several series. A simple composite-plus-scale (CPS) method is also analysed. In the CPS case all input data behave like annually resolved proxies. The spectral domain performance of both M05 and CPS is found to be dependent on the noise type and noise level in pseudoproxies, on the variance spectrum of the climate model simulation, and on the degree of data smoothing. CPS performs better than M05 in most investigated cases with the control run, but leads to deflated low-frequency variance in some cases. With M05, low-frequency variance tend to be inflated for the control run but not for one of the forced runs and only very slightly with the other forced simulation. Hence, the M05 approach does not routinely inflate low-frequency variance. In our experiment, the M05 approach performs better in the spectral domain than CPS when applied to forced climate model simulations. The results underscore the importance of evaluating the variance spectrum of climate reconstructions.

On the basis of a zonally averaged two-hemisphere ocean model, this study investigates howthe asymmetric thermohaline circulation depends on the equator-to-pole as well as the pole-to-pole density difference. Numerical experiments are conducted with prescribed surface density distributions as well as with mixed boundary conditions. Further, two different representations of the small-scale vertical mixing are considered, viz. constant and stability-dependent vertical diffusivity. The two mixing representations yield the opposite overturning responses when the equator-to-pole density difference is changed, keeping the shape of the surface density field invariant. However, the overturning responses of the two representations are qualitatively similar when the degree of asymmetry of the surface density field is changed, keeping the density difference invariant. This applies essentially when the freshwater forcing is increased for fixed thermal boundary conditions. For a fixed freshwater forcing, on the other hand, an increase of the equator-to-pole temperature difference yields a weaker asymmetric circulation when the stability-dependent diffusivity is employed, whereas the reverse holds true for the constant diffusivity representation. Further, the numerical experiments show that the hysteresis characteristics of the asymmetric thermohaline circulation may be sensitive the nature of the small-scale vertical mixing.