The rapid ice loss from the Amundsen Sea sector of West Antarctica is a major contributor to global sea-level rise, and is driven by changes in ocean melting. In this study we use high-resolution ocean simulations to understand the mechanisms controlling ice-shelf melting in the eastern Amundsen Sea. Melting is focussed on four ‘hot spots’ of melting of the deep ice where the main glacier trunks cross the grounding line. Secondary areas of elevated melting occur beneath the associated buoyant meltwater plumes, which are guided by ice topography and Coriolis force. The simulations are then used to test simple local parameterisations of melting. The best parameterisation expresses melt rate as a simple function of ocean temperature to the power 3/2, ice slope to the power 1/2, and tapered to zero near the grounding line. This matches the simulated melting with a spatial correlation of r²=0.65, capturing deep melting near the grounding line but omitting melting by the buoyant plumes. This parameterisation also broadly captures the strong melting feedbacks that appear when the model is applied to possible future ice geometries. This leads us to speculate that simple local melting parameterisations may be sufficient in ice sheet forecasts wherever ice shelf buttressing is focussed near the grounding line (such as Thwaites Glacier), but may be inadequate in regions where melting beneath shear margins controls buttressing (such as Pine Island Glacier).

How to cite: Holland, P., Jenkins, A., Bett, D., Bevan, S., and Luckman, A.: Modelling and Parameterisation of Ice-Shelf Melting in the Amundsen Sea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2856, https://doi.org/10.5194/egusphere-egu26-2856, 2026.

How to cite: Reed, B., De Rydt, J., Naughten, K., and Goldberg, D.: Calibration of a coupled ice-ocean model using observations of ice dynamics and basal melt in West Antarctica, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3797, https://doi.org/10.5194/egusphere-egu26-3797, 2026.

The ocean-driven melting of ice shelves is a key impact on ice shelf mass loss and on the stability of the Antarctic ice sheet. However, knowledge is incomplete on the impact of ocean processes on the basal melting of ice shelves, in particular the effects of submesoscale processes. Inspired by recent observations of an eddy beneath an ice tongue (Hancock et al., 2025), we investigate a series of simulations to better understand the effect of eddies on the localised melting of ice shelves. Here, we examine submesoscale eddies beneath an ice shelf using large-eddy simulations that resolve all but the smallest scales of turbulence. In order to resolve the thin mm-scale layers immediately below the ice, the domain size is limited and the eddies are scaled down to be metres in size. The dynamical regime in which these simulations operate is relevant for the ocean application, hence we can relate our simulations to observations and results from large-scale ocean models. We initialise our simulations with a salinity front beneath an ice shelf, with different chosen temperature profiles to match cold and warm ice shelf cavities. Once the simulations are initiated, the front breaks into submesoscale eddies. Our results show that anticyclonic eddies enhance the ice melting by upwelling warm underlying waters. In contrast, cyclonic eddies moderate the melting by downwelling cool meltwater. Our simulated results compare favourably with the existing observations and the application to other ocean regions is also discussed. 

How to cite: Vreugdenhil, C., Gui, W., Gayen, B., and Bhadouriya, A.: The impact of submesoscale ocean eddies on the basal melting of ice shelves using high-resolution simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16663, https://doi.org/10.5194/egusphere-egu26-16663, 2026.

How to cite: Neufeld, J., Conley, R., and Holland, P.: Quantifying melt rates in Antarctic grounding zones using flexural inversion, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21154, https://doi.org/10.5194/egusphere-egu26-21154, 2026.

Wave–ice interactions are widely recognised as one of several mechanisms contributing to ice-shelf front retreat. However, their role at small spatial and temporal scales remains difficult to quantify, particularly under breaking-wave conditions. Here, we investigate wave-induced erosion at the ice–ocean interface by combining satellite observations, laboratory experiments, and simplified, scale-aware modelling.

Ice-front retreat during the austral summer of 2024 is analysed using Sentinel-1 SAR imagery. Multiple coastline-tracking methods are applied to quantify the spatial and temporal variability of the ice front. The observations reveal periodic collapse events that tend to be temporally synchronised with elevated wave activity. This points to a strong link between wave forcing and short-term ice-front instability.

To interpret these observations, we extend classical wave-induced melting formulations by introducing a first-order, breaking-aware modelling procedure. Wave shoaling and depth-limited breaking are accounted for by tracking the evolution of wave height with water depth and by using the near-breaking horizontal particle velocity as the effective velocity scale driving heat transfer at the ice–water interface. This simple approach captures the enhancement of wave-induced erosion associated with irregular and incipiently breaking waves, while remaining computationally efficient.

The formulation is first evaluated using small-scale laboratory experiments conducted at the University of Caen, where harmonic, non-breaking waves interact with an ice cube. In this controlled experiment, measured erosion rates agree well with theoretical predictions, confirming the validity of classical approaches when wave breaking is absent. When applied to field conditions at Fimbulisen, however, the breaking-aware formulation substantially increases predicted erosion rates relative to classical theory but still systematically underestimates observed retreat. The remaining discrepancy points to unresolved turbulence processes associated with fully developed breaking and motivates the need for more advanced theoretical and experimental treatment of wave-breaking-induced mixing at the ice–ocean interface.

How to cite: Lu, W., Mouaze, D., Ghadimi, B., Font, M., Lambert, R., Jubair, S., Wendt, L., Goodwin, H., Moholdt, G., Lubbad, R., and Løset, S.: Wave-induced erosion at ice-shelf fronts under irregular and breaking-wave conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12063, https://doi.org/10.5194/egusphere-egu26-12063, 2026.

Grounding lines are flux gates through which ice discharges into the ocean. Their position reflects ice sheet stability, retreating landward or advancing seaward in response to changes in melting and accumulation, while also exhibiting short-term motion driven by tidal flexure of floating ice. Grounding lines derived from Differential Interferometric SAR (DInSAR) phase are generally regarded as the most accurate [1]. However, most existing datasets lack formal uncertainty estimates, even though grounding line errors directly propagate into ice discharge calculations and can substantially bias estimates of ice mass loss and sea level rise [1]. A further limitation is that DInSAR grounding lines are derived from interferograms combining three or four SAR acquisitions, such that each estimated position represents a superposition of multiple tidal states, complicating the attribution of observed displacements to specific tidal forcing.

We have developed a framework to obtain grounding line positions together with Bayesian estimates of positional uncertainty. Based on this, we generated a dense time series of grounding lines for the Larsen C Ice Shelf spanning 2019–2021, derived from Sentinel-1 line-of-sight (LOS) offsets at a temporal sampling of 6 days. The LOS offsets are part of the operational processing pipeline used by ENVEO IT to produce monthly and annual Sentinel-1 ice-velocity maps, and were computed by tracking features between consecutive SAR backscatter images [2], [3]. Grounding line positions were estimated by fitting the LOS offsets to a one-dimensional elastic beam model [4] and performing Bayesian inversion using the cross entropy based importance sampling for Bayesian updating (CEBU) algorithm [5], which allows the incorporation of external datasets as priors on model parameters. Additionally, the estimated error of the range offsets were explicitly accounted for in the inversion. The resulting dataset provides a dense time series of grounding lines which have a mean distance of 348.07 m from Sentinel-1 DInSAR grounding lines. Because the dataset is derived from SAR backscatter rather than interferometric phase, it is robust to coherence loss and can be used to fill gaps in DInSAR grounding line products over fast-flowing outlet glaciers and ice streams.

References

[1] E. Rignot, J. Mouginot, and B. Scheuchl, “Antarctic grounding line mapping from differential satellite radar interferometry: GROUNDING LINE OF ANTARCTICA,” Geophysical Research Letters, vol. 38, no. 10, 2011

[2] T. Nagler, H. Rott, M. Hetzenecker, J. Wuite, and P. Potin, “The sentinel-1 mission: New opportunities for ice sheet observations,” Remote Sensing, vol. 7, no. 7, pp. 9371–9389, 2015.

[3] J. Wuite, T. Nagler, M. Hetzenecker, and H. Rott, “Ten years of polar ice velocity mapping using Copernicus Sentinel-1,” Remote Sensing of Environment, vol. 332, p. 115 092, Jan. 2026

[4] G. Holdsworth, “Flexure of a Floating Ice Tongue,” Journal of Glaciology, vol. 8, no. 54, pp. 385–397, 1969, 1727-5652

[5] M. Engel, O. Kanjilal, I. Papaioannou, and D. Straub, “Bayesian updating and marginal likelihood estimation by cross entropy based importance sampling,” Journal of Computational Physics, vol. 473, p. 111 746, Jan. 2023

How to cite: Ramanath Tarekere, S., Engel, M., Krieger, L., Wuite, J., Floricioiu, D., and Körner, M.: Spatially and Temporally Dense Grounding Lines from Bayesian Inversion of Sentinel-1 Data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20585, https://doi.org/10.5194/egusphere-egu26-20585, 2026.

Marine-terminating glaciers in central and southeast Greenland are major contributors to Greenland’s dynamic mass loss and include several of its fastest-flowing outlet glaciers. Ice-ocean interactions have a strong control on the dynamics of marine-terminating glaciers, yet observations of region-wide glacier responses to ocean forcing remains limited. Recent dynamic changes across this sector have largely been studied at smaller spatial scales, limiting our understanding of coherent and more widespread regional scale behaviour and responses to environmental forcing.

Here, we use more than a decade of Sentinel-1 satellite observations to measure ice velocity change on 66 marine-terminating glaciers, between 2014 and 2025 and access the impact of ocean and sea-ice anomalies on glacier dynamics. We observe a widespread and pronounced speedup on ice streams in this region with synchronous acceleration beginning in 2016 and peaking around 2020. Speedup is observed on 43 of the 66 glaciers with the majority of speedup exceeding that observed in the mid 2000’s. Six glaciers more than double in speed and several ice streams reach their fastest speeds in at least two decades. This period of acceleration is followed by a widespread deceleration after 2020, although most glaciers remain faster than their pre-2016 velocities.

We investigate the impact of ocean and atmospheric forcing on the ice velocity change to better understand the drivers. Our results indicate that the timing of this region wide acceleration coincides with anomalously warm surface and subsurface ocean temperatures and a prolonged reduction in regional sea-ice concentration, suggesting that ocean driven forcing may have synchronised glacier responses.

These results show that recent ocean driven dynamic change in central and southeast Greenland has been larger and more spatially extensive than previously recognised, highlighting the susceptibility of these glaciers to rapid, synchronous change and the importance of ice-ocean interactions. The sensitivity of the region to ocean forcing shows that this marine terminating part of the Greenland ice sheet is delicately coupled with its environment and should be closely monitored in the future.

How to cite: Evans, M., Hogg, A., Surawy-Stepney, T., Wallis, B., Slater, R., and Rigby, R.: Synchronous velocity change in response to ocean forcing on marine-terminating glaciers in central- and south-eastern Greenland (2014–2025), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9851, https://doi.org/10.5194/egusphere-egu26-9851, 2026.

In recent decades, Greenland’s marine-terminating glaciers have retreated and accelerated, contributing significantly to global sea level rise. The presence of an ice mélange, and its associated buttressing force on a glacier terminus, has a significant impact on glacier advance and retreat. The buttressing force is modulated by the thickness of the ice mélange, which in turn is influenced by mélange melt rate, but our understanding of ice mélange melting remains limited. In particular, a quantitative understanding of how the thickness of an ice mélange impacts melt rates is lacking.

Here, we model the melting of ice mélange by the ocean using the ocean model MITgcm to simulate the water flow in the first 15km down-fjord from the calving front, focusing specifically on the relationship between the melt rate and the mélange thickness. Ice mélange is represented in the model by cuboid icebergs that are thermodynamically active, divert the fluid flow and represent a range of sizes to reflect realistic observed iceberg distributions. We find that melt rate generally increases with mélange thickness and is particularly sensitive to mélange thickness at thicknesses below approximately 100 metres. Based on these simulations, we develop a parameterisation for mélange melt rate as a function of subglacial discharge, oceanic thermal forcing and mélange thickness. We then apply this parameterisation around Greenland to the ice mélange at 27 glaciers. We estimate melt rates in the range 0.05 – 0.92 m/d, which is comparable with observational estimates, and extract the dominant factors that control glacier-to-glacier variability in mélange melt. The development of this parameterisation is a key step in advancing our understanding of the dynamics of ice mélange and enabling a representation of ice mélange in larger climate and ice sheet models.

How to cite: Jain, L., Slater, D., and Nienow, P.: Impact of ice mélange thickness on mélange melt rate in Greenland’s glacial fjords, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14670, https://doi.org/10.5194/egusphere-egu26-14670, 2026.

The Greenland Ice Sheet loses roughly half of its mass by ice discharge at marine terminating 
glaciers. Some of the largest and fastest flowing glaciers around Greenland calve kilometre-scale 
icebergs into long, narrow and deep fjords. These enormous icebergs typically capsize, or “flip” into 
more gravitationally stable orientations, and in doing so are thought to vigorously mix the stratified 
ocean within a small region in front of the glacier front. 
We investigate the effect of sudden ocean mixing events on flow within an idealised, linearly
stratified model fjord using the Oceananigans.jl nonhydrostatic model. A large fraction of the 
available potential energy is rapidly converted to kinetic energy and radiates away as internal waves. 
These internal waves produce pulses of elevated melt rate across the entire glacier front, with 
magnitudes comparable to melt rates due to subglacial discharge plumes. On longer timescales, the 
qualitative character of the response depends on the ratio of fjord width, W, to first baroclinic 
Rossby deformation radius, R. Typical Greenland fjords have W/R between 0.5 and 2.0. Within this 
range of W/R, our model predicts the appearance of a long-lived nearly geostrophic anticyclonic 
eddy spanning the entire width of the fjord, constrained to mid-depths, in front of the glacier 
terminus. This eddy drives a sustained melt anomaly at mid-depths for many days, which may 
promote undercutting. We also investigate sensitivity to the horizontal extent of the region over 
which the fluid is mixed, and find that increasing the mixed volume beyond some critical value 
destabilises the abovementioned eddy, leading to its break up and consequently reducing the 
predicted glacier melt rate. 

How to cite: Tovey Garcia, O. and Wells, A.: Impacts of iceberg capsize-induced sudden ocean mixing on fjord circulation and glacier melt, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22362, https://doi.org/10.5194/egusphere-egu26-22362, 2026.

Interactions between tidewater glaciers and fjord waters play a key role in Greenland Ice Sheet mass loss. However, many of the underlying processes remain hidden beneath the fjord surface. In particular, the coupling between subglacial meltwater discharge, plume formation, fjord circulation, ice mélange conditions, and glacier dynamics is poorly constrained due to the difficulty of obtaining temporally and spatially highly resolved observations in these environments. This lack of observations limits our ability to resolve glacier-fjord interactions, resulting in considerable uncertainties in mass loss projections.

We address this challenge using an extensive time series of terrestrial radar interferometry (TRI) observations collected at the tidewater glacier Eqalorutsit Kangilliit Sermiat in South Greenland. Using this dataset, we analyse meltwater plume activity, ice mélange conditions in the fjord, glacier motion, calving activity, and 3-dimensional fjord circulation at minute-scale temporal resolution over several weeks, presenting an integrated observational view of the glacier–fjord system, including processes occurring below the waterline.

Fjord circulation is inferred using an autonomous iceberg-tracking framework that derives 3-dimensional flow patterns from the motion of icebergs spanning a wide range of sizes. Combining trajectory data with iceberg drafts, estimated from TRI-derived elevation models, allows circulation to be resolved across different water-depth layers within the ~300 m deep fjord. These observations are evaluated alongside fjord stratification measured by CTD profiles. The results reveal a highly complex circulation that varies strongly with water depth, time, and location in the fjord. Icebergs can even move in opposite directions depending on their draft and the dominant current acting on them. These observations are consistent with modelled fjord circulation, placing the measurements within a process-based framework.

Subglacial meltwater discharge and plume dynamics are investigated using a newly developed autonomous plume-detection algorithm applied to terrestrial radar data. Temporal changes in plume surface area are combined with melt modelling and subglacial hydrological routing to estimate meltwater fluxes entering the fjord. In parallel, ice mélange conditions are quantified using time-lapse imagery and radar backscatter, providing insight into mélange rigidity, its temporal evolution, and its influence on calving and terminus dynamics. On short (subdaily) timescales, plume area does not directly reflect discharge magnitude, as ice mélange conditions strongly control whether meltwater reaches the surface. Over longer (daily) timescales, however, plume size evolution generally agrees with estimated discharge variability.

Overall, these results advance our understanding of how subglacial discharge–driven circulation influences ocean-driven melting and glacier terminus stability, with important implications for projecting Greenland Ice Sheet mass loss and assessing fjord ecosystem responses under ongoing climate change.

How to cite: Kneib-Walter, A., Slater, D., Dachauer, A., and Vieli, A.: Resolving glacier–fjord interactions using observations of 3-dimensional fjord circulation, plume activity, and glacier dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6776, https://doi.org/10.5194/egusphere-egu26-6776, 2026.