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Abstract Parameterization of submarine melting represents a large source of uncertainty in modeling ice sheet response to climate change. Here we present in situ observations of melt at near‐vertical ice faces using a novel instrument platform mounted rigidly to icebergs. We investigate boundary layer dynamics controlling melt across 31 measurement periods that span a range of momentum and thermal forcing (1–12 cm/s flows and 3–10 K). While melt generally scales with velocity and temperature, we find substantially enhanced melt linked with unsteady forcing. Several implementations of the three‐equation melt parameterization show melt can be predicted within a factor of 2 if the model is evaluated with peak near‐boundary velocities and flows are quasi‐steady. However, if flows are unsteady or the model is evaluated with low‐resolution velocities, melt is underpredicted by 2– We conclude that understanding the detailed character of near‐boundary flows is critical for submarine melt predictions. 

Parameterization of submarine melt at near-vertical ice faces is a significant source of uncertainty in predicting ice mass loss and freshwater input into the ocean. Direct observations in this environment have historically been hindered by the dangers posed by actively calving glacier termini and potentially unstable icebergs. Aimed at filling this gap, this dataset contains observations from robotically-deployed Meltstakes at the near-vertical sides of icebergs in Xeitl Geeyí (LeConte Bay, Alaska). Measured quantities are ocean temperature, ocean salinity, ocean velocity, and backscatter data used to track the retreat (melt) of the ice-ocean interface. The observations are separated into 31 discrete segments (lasting 13-71 minutes) under which ocean forcing is relatively stationary and a reliable melt rate can be determined from the backscatter data. These sets of observations enable a direct comparison between small-scale oceanic forcing (~1 meter) and localized submarine melt rate across a wide parameter space (3-10°Celsius and 1-12 centimeters per second (cm/s) flows). Additionally, the observations allow testing of ice-ocean melt rate parameterizations. For more information about the Meltstake platform, see: Nash, J.D., Weiss, K., Wengrove, M.E., Osman, N., Pettit, E.C., Zhao, K., Jackson, R.H., Nahorniak, J., Jensen, K., Tindal, E., Skyllingstad, E., Cohen, N., and Sutherland, D (2024) Turbulent Dynamics of Buoyant Melt Plumes Adjacent Near-Vertical Glacier Ice. Geophysical Research Letters, 51, e2024GL108790. https://doi.org/10.1029/ 2024GL108790 

{"Abstract":["These data include processed multibeam sonar and drone-derived three-dimensional point clouds of icebergs surveyed between 2022 and 2023 in Xeitl Geeyí’ (LeConte Bay), Southeast Alaska. Thirteen grounded icebergs were mapped using Norbit iWBMS and Winghead i77h/i80s sonars, and one recently capsized floating iceberg was mapped using a DJI Air 2S drone. The datasets were collected to quantify submarine iceberg morphology and surface roughness as part of a broader effort to improve understanding of ice–ocean interactions at near-vertical ice-ocean boundaries. The methods and analyses are described in Cohen et al. (submitted in 2025), "Characterizing submarine ice roughness at icebergs from a temperate tidewater glacier", under review in the Journal of Glaciology. All data are georeferenced to World Geodetic System 1984 (WGS 84) and Universal Transverse Mercator Zone 8 N (meters in easting/northing)."]} 

Abstract At tidewater glaciers, the ocean supplies heat for submarine ice melt and the glacier supplies freshwater that impacts ocean circulation. Models that employ buoyant plume theory are widely used to represent the effects of subglacial discharge on both glacier melt and freshwater export, but a scarcity of observations means that these models are largely unvalidated. The challenges and inherent risks of working near actively calving glaciers make it difficult to collect in situ observations. This study, conducted at Xeitl Sít’ (LeConte Glacier) in southeast Alaska, reports the first observations of velocity and geometry of the upwelling core of a subglacial discharge plume. This subglacial discharge plume rises along an overcut ice face, with vertical velocities in excess of 1 m s⁻¹, and a plume shape consistent with subglacial discharge emerging from a narrow outlet. Buoyant plume theory, as commonly applied, fails to replicate the observed entrainment, underestimating the plume's volume flux by more than 50%. Large eddy simulations reveal that over half of this mismatch can be attributed to the overcut slope of the ice, which enhances entrainment. Enhanced mixing near the grounding line may account for the additional entrainment. Accurate representation of plume geometry and entrainment is critical for understanding plume‐driven melt of the terminus and the initial mixing of glacial meltwater as it is exported into the ocean. 

Abstract Inspiring Girls* Expeditions is a global organization that empowers 16- to 18-year-old youth through 12-day backcountry science and art expeditions, including in the US Arctic and Subarctic. Because science and outdoor fields are historically white- and male-dominated, Inspiring Girls* follows an intersectional approach to welcome youth with marginalized genders, people of color, Indigenous people, and other marginalized groups into these arenas. Inspiring Girls* also provides professional development for early career scientist, artist, and outdoor guide instructors. We discuss how Inspiring Girls* leverages our own research as well as best practices from the literature to prioritize such strategies as intentionally building diverse teams, offering a tuition-free format, and participating in community learning to reimagine the inclusivity of science and outdoor fields in the Arctic and beyond. 

Basal channels, which are troughs carved into the undersides of ice shelves by buoyant plumes of water, are modulators of ice-shelf basal melt and structural stability. In this study, we track the evolution of 12 large basal channels beneath ice shelves of the Amundsen and Bellingshausen seas region in West Antarctica using the Landsat record since its start in the 1970s through 2020. We observe examples of channel growth, interactions with ice-shelf features, and systematic changes in sinuosity that give insight into the life cycles of basal channels. We use the last two decades of the record, combined with contemporary ice-flow velocity datasets, to separate channel-path evolution into components related to advection by ice flow and those controlled by other forcings, such as ocean melt or surface accumulation. Our results show that ice-flow-independent lateral channel migration is overwhelmingly to the left when viewed down-flow, suggesting that it is dominated by Coriolis-influenced ocean melt. By applying a model of channel-path evolution dominantly controlled by ice flow and ocean melt, we show that the majority of channels surveyed exhibit non-steady behavior that serves as a novel proxy for increased ocean forcing in West Antarctica starting at least in the early 1970s. 

Abstract. In late March 2011, landfast sea ice (hereafter, “fast ice”) formed in the northern Larsen B embayment and persisted continuously as multi-year fast ice until January 2022. In the 11 years of fast-ice presence, the northern Larsen B glaciers slowed significantly, thickened in their lower reaches, and developed extensive mélange areas, leading to the formation of ice tongues that extended up to 16 km from the 2011 ice fronts. In situ measurements of ice speed on adjacent ice shelf areas spanning 2011 to 2017 show that the fast ice provided significant resistive stress to ice flow. Fast-ice breakout began in late January 2022 and was closely followed by retreat and breakup of both the fast-ice mélange and the glacier ice tongues. We investigate the probable triggers for the loss of fast ice and document the initial upstream glacier responses. The fast-ice breakup is linked to the arrival of a strong ocean swell event (>1.5 m amplitude; wave period waves >5 s) originating from the northeast. Wave propagation to the ice front was facilitated by a 12-year low in sea ice concentration in the northwestern Weddell Sea, creating a near-ice-free corridor to the open ocean. Remote sensing data in the months following the fast-ice breakout reveals an initial ice flow speed increase (>2-fold), elevation loss (9 to 11 m), and rapid calving of floating and grounded ice for the three main embayment glaciers Crane (11 km), Hektoria (25 km), and Green (18 km). 

Abstract Feedbacks between ice melt, glacier flow and ocean circulation can rapidly accelerate ice loss at tidewater glaciers and alter projections of sea-level rise. At the core of these projections is a model for ice melt that neglects the fact that glacier ice contains pressurized bubbles of air due to its formation from compressed snow. Current model estimates can underpredict glacier melt at termini outside the region influenced by the subglacial discharge plume by a factor of 10–100 compared with observations. Here we use laboratory-scale experiments and theoretical arguments to show that the bursting of pressurized bubbles from glacier ice could be a source of this discrepancy. These bubbles eject air into the seawater, delivering additional buoyancy and impulses of turbulent kinetic energy to the boundary layer, accelerating ice melt. We show that real glacier ice melts 2.25 times faster than clear bubble-free ice when driven by natural convection in a laboratory setting. We extend these results to the geophysical scale to show how bubble dynamics contribute to ice melt from tidewater glaciers. Consequently, these results could increase the accuracy of modelled predictions of ice loss to better constrain sea-level rise projections globally. 

Knowledge gaps about how the ocean melts Antarctica’s ice shelves, borne from a lack of observations, lead to large uncertainties in sea level predictions. Using high-resolution maps of the underside of Dotson Ice Shelf, West Antarctica, we reveal the imprint that ice shelf basal melting leaves on the ice. Convection and intermittent warm water intrusions form widespread terraced features through slow melting in quiescent areas, while shear-driven turbulence rapidly melts smooth, eroded topographies in outflow areas, as well as enigmatic teardrop-shaped indentations that result from boundary-layer flow rotation. Full-thickness ice fractures, with bases modified by basal melting and convective processes, are observed throughout the area. This new wealth of processes, all active under a single ice shelf, must be considered to accurately predict future Antarctic ice shelf melt. 

Abstract Rift propagation, rather than basal melt, drives the destabilization and disintegration of the Thwaites Eastern Ice Shelf. Since 2016, rifts have episodically advanced throughout the central ice-shelf area, with rapid propagation events occurring during austral spring. The ice shelf's speed has increased by ~70% during this period, transitioning from a rate of 1.65 m d⁻¹in 2019 to 2.85 m d⁻¹by early 2023 in the central area. The increase in longitudinal strain rates near the grounding zone has led to full-thickness rifts and melange-filled gaps since 2020. A recent sea-ice break out has accelerated retreat at the western calving front, effectively separating the ice shelf from what remained of its northwestern pinning point. Meanwhile, a distributed set of phase-sensitive radar measurements indicates that the basal melting rate is generally small, likely due to a widespread robust ocean stratification beneath the ice–ocean interface that suppresses basal melt despite the presence of substantial oceanic heat at depth. These observations in combination with damage modeling show that, while ocean forcing is responsible for triggering the current West Antarctic ice retreat, the Thwaites Eastern Ice Shelf is experiencing dynamic feedbacks over decadal timescales that are driving ice-shelf disintegration, now independent of basal melt.