Henning Åkesson

• Holmes, Felicity A; Dongen, Eef Van; Nilsson, Johan; O'Regan, Matt; Barnett, Jamie & Åkesson, Henning [Show all 10 contributors for this article] (2026). Examining drivers of the early 20th century retreat of Ryder Glacier's ice tongue in Northern Greenland. Annals of Glaciology. ISSN 0260-3055. p. 30–30. doi: 10.1017/aog.2026.10058. Full text in Research Archive Show summary

  The northern sector of the Greenland Ice Sheet contains some of the ice sheet’s last remaining glaciers with floating ice tongues. One of these glaciers is Ryder Glacier, which has been relatively stable in recent decades, in contrast to the neighbouring Petermann and C.H. Ostenfeld glaciers. Understanding Ryder Glacier’s future behaviour is important as ice-tongue loss could lead to acceleration and increased ice discharge. Meanwhile, it is unclear whether Greenlandwide modelling attempts are able to accurately resolve the influence of fjord and bedrock topography and small-scale variations in ice dynamics for a glacier like Ryder. To fill these gaps, here we conduct targeted high-resolution modelling of Ryder Glacier until the year 2300. We find that mass loss is dominated by discharge under a low-emissions scenario all the way to 2300, leading to a sea level contribution of between 0.8 and 2 mm depending on the amount of ocean warming. Discharge also plays a key role under a high-emissions scenario up until 2100, after which a strongly negative surface mass balance becomes the dominant driver of mass loss. This negative surface mass balance leads to a much higher sea level rise contribution by 2300 of between 44 and 52 mm, with little sensitivity to the range of ocean warming scenarios used in this study.

• Haualand, Kristine Flacké; Pontoppidan, Marie; Åkesson, Henning & Sauter, Tobias (2026). Glacier thinning causes warmer and drier regional climate at the Jostedalsbreen ice cap in western Norway. Weather and Climate Dynamics (WCD). 7(2), p. 1050–1050. doi: 10.5194/wcd-7-1033-2026. Full text in Research Archive Show summary

  Abstract. Glacier recession gives rise to changes in land surface type and topography that are poorly represented in atmospheric models but may have important local impacts on climate. Implementing these changes in the Weather Research and Forecasting (WRF) model for the Jostedalsbreen ice cap in western Norway results in warmer and drier regional climate with less snow that can amplify glacier recession through a positive feedback effect. Most of the climatic response to glacier recession is related to the surface lowering associated with ice melt, resulting in reduced orographic lifting of moist air masses and higher surface pressure. The climatic response to glacier recession is largest where the ice melts but is also evident in adjacent valleys several kilometers away from the ice cap. While the warming by glacier recession amplifies effects of global warming, reduced precipitation counteracts the projected regional increase in precipitation. These findings should be included in estimates of glacier mass balance and have implications for agriculture, hydropower, tourism, and biodiversity around glacierised landscapes.

• Nanni, Ugo; Bouchayer, Coline Lili Mathy; Åkesson, Henning; Lefeuvre, Pierre-Marie; Mannerfelt, Erik Schytt & Köhler, Andreas [Show all 12 contributors for this article] (2025). Observed positive feedback between surface ablation and crevasse formation drives glacier acceleration and potential surge. Nature Communications. 16(1). doi: 10.1038/s41467-025-66349-9. Full text in Research Archive Show summary

  Sudden glacier acceleration and instability, e.g. surges, strongly influence glacier ice loss. However, lack of in-situ observations of the involved processes hampers our ability to understand, quantify and model such a role. We present an analysis of the initiation of a surge (Kongsvegen glacier, Svalbard), focusing on the interplay between climatic and glacier-specific drivers. We integrate two decades of in-situ observations (GNSS, borehole and surface seismometers) with runoff simulations, and remotely sensed surface-elevation changes. We show that initial glacier thinning led to localized acceleration and crevassing. Then, we show that stronger surface melt enabled meltwater to reach the glacier bed. This input promotes high basal water pressure and glacier sliding, and in turn further surface crevassing. Our observations suggest that this positive feedback leads to the expansion of the initially localized instability. Our findings highlight mechanisms that could trigger glacier instabilities under a warming atmosphere beyond the High Arctic.

• Holmes, Felicity A.; Barnett, Jamie; Åkesson, Henning; Morlighem, Mathieu; Nilsson, Johan & Kirchner, Nina [Show all 7 contributors for this article] (2025). Sea level rise contribution from Ryder Glacier in northern Greenland varies by an order of magnitude by 2300 depending on future emissions. The Cryosphere. ISSN 1994-0416. 19(7), p. 2695–2714. doi: 10.5194/tc-19-2695-2025. Full text in Research Archive Show summary

  The northern sector of the Greenland Ice Sheet contains some of the ice sheet's last remaining glaciers with floating ice tongues. One of these glaciers is Ryder Glacier, which has been relatively stable in recent decades, in contrast to the neighbouring Petermann and C.H. Ostenfeld glaciers. Understanding Ryder Glacier's future behaviour is important as ice-tongue loss could lead to acceleration and increased ice discharge. Meanwhile, it is unclear whether Greenland-wide modelling attempts are able to accurately resolve the influence of fjord and bedrock topography and small-scale variations in ice dynamics for a glacier like Ryder. To fill these gaps, here we conduct targeted high-resolution modelling of Ryder Glacier until the year 2300. We find that mass loss is dominated by discharge under a low-emissions scenario all the way to 2300, leading to a sea level contribution of between 0.8 and 2 mm depending on the amount of ocean warming. Discharge also plays a key role under a high-emissions scenario up until 2100, after which a strongly negative surface mass balance becomes the dominant driver of mass loss. This negative surface mass balance leads to a much higher sea level rise contribution by 2300 of between 44 and 52 mm, with little sensitivity to the range of ocean warming scenarios used in this study.

• Barnett, Jamie; Holmes, Felicity A.; Cuzzone, Joshua; Åkesson, Henning; Morlighem, Mathieu & O'Regan, Matt [Show all 9 contributors for this article] (2025). Simulating the Holocene evolution of Ryder Glacier, North Greenland. The Cryosphere. ISSN 1994-0416. 19(9), p. 3631–3653. doi: 10.5194/tc-19-3631-2025. Full text in Research Archive Show summary

  The Greenland Ice Sheet's negative mass balance is driven by a sensitivity to a warming atmosphere and ocean. The fidelity of ice-sheet models in accounting for ice–ocean interaction is inherently uncertain and often constrained against recent fluctuations in the ice-sheet margin from the previous decades. The geological record can be used to contextualise ice-sheet mass loss and understand the drivers of changes at the marine margin across climatic shifts and previous extended warm periods, aiding our understanding of future ice-sheet behaviour. Here, we use the Ice-sheet and Sea-level System Model (ISSM) to explore the Holocene evolution of Ryder Glacier draining into Sherard Osborn Fjord, North Greenland. Our modelling results are constrained with terrestrial reconstructions of the paleo-ice-sheet margin and an extensive marine sediment record from Sherard Osborn Fjord that details ice dynamics over the past 12.5 ka years. By employing a consistent mesh resolution of <1 km at the ice–ocean boundary, we assess the importance of atmospheric and oceanic changes to Ryder Glacier's Holocene behaviour. Our simulations show that the initial retreat of the ice margin after the Younger Dryas cold period was driven by a warming climate and the resulting fluctuations in surface mass balance. Changing atmospheric conditions remain the first-order control in the timing of ice retreat during the Holocene. We find ice–ocean interactions become increasingly fundamental to Ryder's retreat in the mid-Holocene, with higher-than-contemporary melt rates required to force grounding line retreat and capture the collapse of the ice tongue during the Holocene Thermal Maximum. Regrowth of the tongue during the neoglacial cooling of the late Holocene is necessary to advance the terrestrial and marine margins of the glacier. Our results stress the importance of accurately resolving the ice–ocean interface in modelling efforts over centennial and millennial timescales, in particular the role of floating ice tongues and submarine melt, and provide vital analogies for the future evolution of Ryder in a warming climate.

• Åkesson, Henning; Sjursen, Kamilla Hauknes; Schuler, Thomas; Dunse, Thorben; Andreassen, Liss Marie & Gillespie, Mette Kusk [Show all 9 contributors for this article] (2025). Recent history and future demise of Jostedalsbreen, the largest ice cap in mainland Europe. The Cryosphere. ISSN 1994-0416. 19(11), p. 5871–5902. doi: 10.5194/tc-19-5871-2025. Full text in Research Archive Show summary

  Glaciers and ice caps worldwide are in strong decline, and models project this trend to continue with future warming, with strong environmental and socio-economic implications. The Jostedalsbreen ice cap is the largest ice cap on the European mainland (458 km2 in 2019) and occupies 20 % of the total glacier area of mainland Norway. Here we simulate the evolution of Jostedalsbreen since 1960, and its fate in a changing climate in the 21st-century and beyond (2300). This ice cap consists of glacier units with a great diversity in shape, steepness, hypsometry, and flow speed. We employ a coupled model system with higher-order three-dimensional ice dynamics forced by simulated surface mass balance that fully accounts for the mass-balance elevation feedback. We find that Jostedalsbreen may lose 12 %–74 % of its present-day volume until 2100, depending on future greenhouse gas emissions. With mid-range results obtained using the climate model ECEARTH/CCLM, Jostedalsbreen is projected to lose 49 % (RCP4.5) and 63 % (RCP8.5) of its contemporary ice volume by 2100. Regardless of emission scenario, the ice cap is likely to split into three parts during the second half of the 21st century. Our results suggest that Jostedalsbreen will likely be more resilient than many smaller glaciers and ice caps in Scandinavia. However, we show that by the year 2100, the ice cap may be committed to a complete disappearance during the 22nd century, under high emissions (RCP8.5). Under medium 21st-century emissions (RCP4.5), the ice cap is bound to shrink by 90 % until 2300. Further simulations indicate that substantial mass losses undergone until 2100 are irreversible; the ice cap would not recover to its contemporary volume if the future surface mass balance was reversed to that of the present-day. Our study demonstrates a model approach for complex ice masses with numerous outlet glaciers such as ice caps, and how tightly linked future mass loss is to future greenhouse-gas emissions. Finally, uncertainties in future climate conditions, particularly precipitation, appear to be the largest source of uncertainty in future projections of maritime ice masses like Jostedalsbreen.

• Sjursen, Kamilla Hauknes; Dunse, Thorben; Schuler, Thomas; Andreassen, Liss Marie & Åkesson, Henning (2024). Spatiotemporal mass-balance variability of Jostedalsbreen Ice Cap, Norway, revealed by a temperature-index model using Bayesian inference. Annals of Glaciology. ISSN 0260-3055. 66(e1), p. 1–18. doi: 10.1017/aog.2024.41. Full text in Research Archive
• Troch, Matthias; Åkesson, Henning; Cuzzone, Joshua & Bertrand, Sebastien (2024). Precipitation drives western Patagonian glacier variability and may curb future ice mass loss. Scientific Reports. 14. doi: 10.1038/s41598-024-77486-4. Full text in Research Archive Show summary

  Two-thirds of all glaciers worldwide are projected to disappear by 2100 CE. Large uncertainties however remain in maritime settings, where some glaciers have recently gained mass in response to increased snowfall. One of these regions is southern Patagonia, where increased precipitation since the 1980s seems to have attenuated glacier retreat. Whether this exceptional behavior will continue in a warmer future is unclear. Here, we use a numerical ice-flow model constrained by paleoglaciological data to simulate how climate variability influenced the evolution of three maritime outlet glaciers of the Southern Patagonian Icefield during the last 6000 years. Our experiments suggest that precipitation drove 67% of the centennial-scale fluctuations in the volume of the modeled glaciers. When applied to the temperature projected by 2100 CE, our simulations show that precipitation needs to increase by 10–50% to maintain present-day glacier volumes, depending on the climate scenario (SSP1-2.6 to SSP5-8.5). This implies that if greenhouse-gas emission cuts fail, these glaciers will enter a warmer regime unseen over the last 6000 years, where precipitation cannot offset glacier mass loss. Conversely, if emissions are curtailed, increased precipitation could halt mass loss of some of Patagonia’s largest glaciers, and potentially of other maritime glaciers worldwide.

• Frank, Thomas; Åkesson, Henning; Fleurian, Basile de; Morlighem, M. & Nisancioglu, Kerim Hestnes (2022). Geometric controls of tidewater glacier dynamics. The Cryosphere. ISSN 1994-0416. 16(2), p. 581–601. doi: 10.5194/tc-16-581-2022. Full text in Research Archive Show summary

  Retreat of marine outlet glaciers often initiates depletion of inland ice through dynamic adjustments of the upstream glacier. The local topography of a fjord may promote or inhibit such retreat, and therefore fjord geometry constitutes a critical control on ice sheet mass balance. To quantify the processes of ice–topography interactions and enhance the understanding of the dynamics involved, we analyze a multitude of topographic fjord settings and scenarios using the Ice-sheet and Sea-level System Model (ISSM). We systematically study glacier retreat through a variety of artificial fjord geometries and quantify the modeled dynamics directly in relation to topographic features. We find that retreat in an upstream-widening or upstream-deepening fjord does not necessarily promote retreat, as suggested by previous studies. Conversely, it may stabilize a glacier because converging ice flow towards a constriction enhances lateral and basal shear stress gradients. An upstream-narrowing or upstream-shoaling fjord, in turn, may promote retreat since fjord walls or bed provide little stability to the glacier where ice flow diverges. Furthermore, we identify distinct quantitative relationships directly linking grounding line discharge and retreat rate to fjord topography and transfer these results to a long-term study of the retreat of Jakobshavn Isbræ. These findings offer new perspectives on ice–topography interactions and give guidance to an ad hoc assessment of future topographically induced ice loss based on knowledge of the upstream fjord geometry.

• Åkesson, Henning Martin; Morlighem, Mathieu; Nilsson, Johan; Stranne, Christian & Jakobsson, Martin (2022). Petermann ice shelf may not recover after a future breakup. Nature Communications. 13. doi: 10.1038/s41467-022-29529-5. Full text in Research Archive Show summary

  Floating ice shelves buttress inland ice and curtail grounded-ice discharge. Climate warming causes melting and ultimately breakup of ice shelves, which could escalate ocean-bound ice discharge and thereby sea-level rise. Should ice shelves collapse, it is unclear whether they could recover, even if we meet the goals of the Paris Agreement. Here, we use a numerical ice-sheet model to determine if Petermann Ice Shelf in northwest Greenland can recover from a future breakup. Our experiments suggest that post-breakup recovery of confined ice shelves like Petermann’s is unlikely, unless iceberg calving is greatly reduced. Ice discharge from Petermann Glacier also remains up to 40% higher than today, even if the ocean cools below present-day temperatures. If this behaviour is not unique for Petermann, continued near-future ocean warming may push the ice shelves protecting Earth’s polar ice sheets into a new retreated high-discharge state which may be exceedingly difficult to recover from.

• Åkesson, Henning; Morlighem, Mathieu; O'Regan, Matt & Jakobsson, Martin (2021). Future Projections of Petermann Glacier Under Ocean Warming Depend Strongly on Friction Law. Journal of Geophysical Research (JGR): Earth Surface. ISSN 2169-9003. 126. doi: 10.1029/2020JF005921. Full text in Research Archive Show summary

  Basal friction heavily controls the dynamics of fast-flowing glaciers. However, the best approach to modeling friction is unclear, increasing uncertainties in projections of future mass loss and sea-level rise. Here, we compare six friction laws and evaluate them for Petermann Glacier in northern Greenland, using a higher order three-dimensional ice-sheet model. We model glacier retreat and mass loss under an ocean-only warming until year 2300, while not considering the effects of a future warmer atmosphere. Regardless of the friction law, we find that breakup of Petermann's ice shelf is likely to occur within the next decades. However, future grounding-line retreat differs by 10s of km and estimates of sea-level rise may quadruple, depending on the friction law employed. A bedrock ridge halts the retreat for four of the laws, and Petermann retreats furthest when applying a Budd or a Coulomb-type “till law.” Depending on the friction law, sea-level contributions differ by 133% and 282% by 2300 for 2°C and 5°C ocean warming scenarios, respectively.

• Jakobsson, Martin; Mayer, Larry; Nilsson, Johan; Stranne, Christian; Calder, Bryan & O'Regan, Matt [Show all 31 contributors for this article] (2020). Ryder Glacier in northwest Greenland is shielded from warm Atlantic water by a bathymetric sill. Communications Earth & Environment. 1. doi: 10.1038/s43247-020-00043-0. Full text in Research Archive Show summary

  The processes controlling advance and retreat of outlet glaciers in fjords draining the Greenland Ice Sheet remain poorly known, undermining assessments of their dynamics and associated sea-level rise in a warming climate. Mass loss of the Greenland Ice Sheet has increased six-fold over the last four decades, with discharge and melt from outlet glaciers comprising key components of this loss. Here we acquired oceanographic data and multibeam bathymetry in the previously uncharted Sherard Osborn Fjord in northwest Greenland where Ryder Glacier drains into the Arctic Ocean. Our data show that warmer subsurface water of Atlantic origin enters the fjord, but Ryder Glacier’s floating tongue at its present location is partly protected from the inflow by a bathymetric sill located in the innermost fjord. This reduces under-ice melting of the glacier, providing insight into Ryder Glacier’s dynamics and its vulnerability to inflow of Atlantic warmer water.

• Åkesson, Henning; Gyllencreutz, Richard; Mangerud, Jan; Svendsen, John-Inge; Nick, Faezeh M. & Nisancioglu, Kerim Hestnes (2020). Rapid retreat of a Scandinavian marine outlet glacier in response to warming at the last glacial termination. Quaternary Science Reviews. ISSN 0277-3791. 250. doi: 10.1016/j.quascirev.2020.106645. Full text in Research Archive Show summary

  Marine outlet glaciers on Greenland are retreating, yet it is unclear if the recent fast retreat will persist, and how atmosphere and ocean warming will impact future retreat. We show how a marine outlet glacier in Hardangerfjorden retreated rapidly in response to the abrupt warming following the Younger Dryas cold period (approximately 11,600 years before present). This almost 1000 m deep fjord, with several sills at 300–500 m depth, hosted a 175 km long outlet glacier at the western rim of the Scandinavian Ice Sheet. We use a dynamic ice-flow model constrained by well-dated terminal and lateral moraines to simulate the reconstructed 500-year retreat of Hardangerfjorden glacier. The model includes an idealized oceanic and atmospheric forcing based on reconstructions, but excludes the surface mass balance-elevation feedback. Our simulations show a highly episodic retreat driven by surface melt and warming fjord waters, paced by the fjord bathymetry. Warming air and ocean temperatures by 4–5 °C during the period of retreat result in a 125-km retreat of Hardangerfjorden glacier in 500 years. Retreat rates throughout the deglaciation vary by an order of magnitude from 50 to 2500 m a−1, generally close to 200 m a−1, punctuated by brief events of swift retreat exceeding 500 m a−1, each event lasting a few decades. We show that the fastest retreat rates occur in regions of the bed with the largest retrograde slopes; ice shelf length and fjord water depth is less important. Our results have implications for modern glacial fjord settings similar to Hardangerfjorden, where high retreat rates have been observed. Our findings imply that increasing air temperatures and warming subsurface waters in Greenland fjords will continue to drive extensive retreat of marine outlet glaciers. However, the recent high retreat rates are not expected to be sustained for longer than a few decades due to constraints by the fjord bathymetry.

• Reinardy, Benedict T.I.; Booth, Adam; Hughes, Anna; Boston, Clare M.; Åkesson, Henning & Bakke, Jostein [Show all 9 contributors for this article] (2019). Spatial distribution of cold-ice within a temperate glacier - implications for glacier dynamics, sediment transport and foreland geomorphology. The Cryosphere. ISSN 1994-0416. 13, p. 827–843. doi: 10.5194/tc-13-827-2019. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes & Nick, Faezeh M. (2018). Impact of fjord geometry on grounding line stability. Frontiers in Earth Science. 6. doi: 10.3389/feart.2018.00071. Full text in Research Archive Show summary

  Recent and past retreat of marine-terminating glaciers are broadly consistent with observed ocean warming, yet responses vary significantly within regions experiencing similar ocean conditions. We assess how fjord geometry modulates glacier response to a regional ocean warming on decadal to millennial time scales, by using an idealized, numerical model of fast-flowing glaciers including a crevasse-depth calving criterion. Our simulations show that, given identical climate forcing, grounding line responses can differ by tens of kilometers due to variations in channel width. We identify fjord mouths and embayments as vulnerable geometries, showing that glaciers in these fjords are prone to rapid, irreversible retreat, independent of the presence of a fjord sill. This irreversible retreat has relevance for the potential future recovery of marine ice sheets, if the current anthropogenic warming is reduced, or reversed, as well as for the response of marine ice sheets to past climate states; including the warm Bølling-Allerød interstadial, the Younger Dryas cold reversal and the Little Ice Age.

• Steiger, Nadine; Nisancioglu, Kerim Hestnes; Åkesson, Henning; Fleurian, Basile de & Nick, Faezeh M. (2018). Simulated retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry. The Cryosphere. ISSN 1994-0416. 12(7), p. 2249–2266. doi: 10.5194/tc-12-2249-2018. Full text in Research Archive Show summary

  Rapid retreat of Greenland's marine-terminating glaciers coincides with regional warming trends, which have broadly been used to explain these rapid changes. However, outlet glaciers within similar climate regimes experience widely contrasting retreat patterns, suggesting that the local fjord geometry could be an important additional factor. To assess the relative role of climate and fjord geometry, we use the retreat history of Jakobshavn Isbræ, West Greenland, since the Little Ice Age (LIA) maximum in 1850 as a baseline for the parameterization of a depth- and width-integrated ice flow model. The impact of fjord geometry is isolated by using a linearly increasing climate forcing since the LIA and testing a range of simplified geometries. We find that the total length of retreat is determined by external factors – such as hydrofracturing, submarine melt and buttressing by sea ice – whereas the retreat pattern is governed by the fjord geometry. Narrow and shallow areas provide pinning points and cause delayed but rapid retreat without additional climate warming, after decades of grounding line stability. We suggest that these geometric pinning points may be used to locate potential sites for moraine formation and to predict the long-term response of the glacier. As a consequence, to assess the impact of climate on the retreat history of a glacier, each system has to be analyzed with knowledge of its historic retreat and the local fjord geometry.

• Åkesson, Henning; Morlighem, Mathieu; Nisancioglu, Kerim Hestnes; Svendsen, John-Inge & Mangerud, Jan (2018). Atmosphere-driven ice sheet mass loss paced by topography: Insights from modelling the south-western Scandinavian Ice Sheet. Quaternary Science Reviews. ISSN 0277-3791. 195, p. 32–47. doi: 10.1016/j.quascirev.2018.07.004. Full text in Research Archive Show summary

  Marine-terminating glaciers and ice streams are important controls of ice sheet mass balance. However, understanding of their long-term response to external forcing is limited by relatively short observational records of present-day glaciers and sparse geologic evidence for paleo-glaciers. Here we use a high-resolution ice sheet model with an accurate representation of grounding line dynamics to study the deglaciation of the marine-based south-western Norwegian sector of the Scandinavian Ice Sheet and its sensitivity to ocean and atmosphere forcing. We find that the regional response to a uniform climate change is highly dependent on the local bedrock topography, consistent with ice sheet reconstructions. Our simulations suggest that ocean warming is able to trigger initial retreat in several fjords, but is not sufficient to explain retreat everywhere. Widespread retreat requires additional ice thinning driven by surface melt. Once retreat is triggered, the underlying bedrock topography and fjord width control the rate and extent of retreat, while multi-millennial changes over the course of deglaciation are modulated by surface melt. We suggest that fjord geometry, ice-ocean interactions and grounding line dynamics are vital controls of decadal-to centennial scale ice sheet mass loss. However, we postulate that atmospheric changes are the most important drivers of widespread ice sheet demise, and will likely trump oceanic influence on future ice sheet mass loss and resulting sea level rise over centennial and longer time scales.

• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Giesen, Rianne H. & Morlighem, Mathieu (2017). Simulating the evolution of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene and its sensitivity to climate change. The Cryosphere. ISSN 1994-0416. 11, p. 281–302. doi: 10.5194/tc-11-281-2017. Full text in Research Archive Show summary

  Understanding of long-term dynamics of glaciers and ice caps is vital to assess their recent and future changes, yet few long-term reconstructions using ice flow models exist. Here we present simulations of the maritime Hardangerjøkulen ice cap in Norway from the mid-Holocene through the Little Ice Age (LIA) to the present day, using a numerical ice flow model combined with glacier and climate reconstructions. In our simulation, under a linear climate forcing, we find that Hardangerjøkulen grows from ice-free conditions in the mid-Holocene to its maximum extent during the LIA in a nonlinear, spatially asynchronous fashion. During its fastest stage of growth (2300–1300 BP), the ice cap triples its volume in less than 1000 years. The modeled ice cap extent and outlet glacier length changes from the LIA until today agree well with available observations. Volume and area for Hardangerjøkulen and several of its outlet glaciers vary out-of-phase for several centuries during the Holocene. This volume–area disequilibrium varies in time and from one outlet glacier to the next, illustrating that linear relations between ice extent, volume and glacier proxy records, as generally used in paleoclimatic reconstructions, have only limited validity. We also show that the present-day ice cap is highly sensitive to surface mass balance changes and that the effect of the ice cap hypsometry on the mass balance–altitude feedback is essential to this sensitivity. A mass balance shift by +0.5 m w.e. relative to the mass balance from the last decades almost doubles ice volume, while a decrease of 0.2 m w.e. or more induces a strong mass balance–altitude feedback and makes Hardangerjøkulen disappear entirely. Furthermore, once disappeared, an additional +0.1 m w.e. relative to the present mass balance is needed to regrow the ice cap to its present-day extent. We expect that other ice caps with comparable geometry in, for example, Norway, Iceland, Patagonia and peripheral Greenland may behave similarly, making them particularly vulnerable to climate change.

• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Giesen, Rianne H. & Morlighem, Mathieu (2016). Simulating asymmetric growth and retreat of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene. The Cryosphere Discussions. doi: 10.5194/tc-2016-62. Full text in Research Archive Show summary

  Changes to the volume of glaciers and ice caps currently amount to half of the total cryospheric contribution to sea-level rise and are projected to remain substantial throughout the 21st century. To simulate glacier behavior on centennial and longer time scales, models rely on simplified dynamics and tunable parameters for processes not well understood. Model calibration is often done using present-day observations, even though the relationship between parameters and parametrized processes may be altered for significantly different glacier states. In this study, we simulate the evolution of the Hardangerjøkulen ice cap in southern Norway from the mid-Holocene through the Little Ice Age (LIA) to the present-day. For both the calibration and transient experiments, we run an ensemble using a two-dimensional ice flow model with local mesh refinement. For the Holocene, we apply a simple surface mass balance forcing based on climate reconstructions. For the LIA until 1962, we use geomorphological evidence and measured outlet glacier positions to find a mass balance history, while from 1963 until today we use direct mass balance measurements. Given a linear climate forcing, we find that Hardangerjøkulen grew from ice-free conditions in the mid-Holocene, to its maximum LIA extent in a highly non-linear fashion. During the fastest stage of growth (2200-1200 BP), the ice cap tripled its ice volume over only 1000 years. We also reveal an intriguing spatial asymmetry during advance and retreat; the western ice cap and the northern outlet glacier Midtdalsbreen grow first and disappear first. In contrast, the eastern part, including the northeastern outlet glacier Blåisen, grows last and disappears last. Furthermore, volume and area of several outlet glaciers, as well as of the entire ice cap, vary out-of-phase for multiple centuries during the late Holocene, before varying in-phase approaching the LIA. We relate this to bed topography and the mass balance-altitude feedback, and challenge canonical linear assumptions between ice cap extent and glacier proxy records. Thus, we provide new insight into long-term dynamical response of ice caps to climate change, relevant for paleoglaciological studies and future predictions. Our model simulates ice cap extent and outlet glacier length changes from the LIA until today that are close to observations. We show that present-day Hardangerjøkulen is extremely sensitive to surface mass balance changes, mainly due to a strong mass balance-altitude feedback for the gently sloping surface topography of the ice cap.

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• Åkesson, Henning; Straume, Eivind Olavson & Nisancioglu, Kerim Hestnes (2026). Ice music festival Oslo - science workshop. doi: https:/icemusicfestival.com/ice-music-oslo-2026. Full text in Research Archive
• Yılmaz, Yeliz A.; Aalstad, Kristoffer; Guillet, Gregoire; Rounce, David; Tober, Brandon & Yang, Ruitang [Show all 8 contributors for this article] (2026). Probabilistic calibration of glacier projections using data assimilation. doi: 10.5194/egusphere-egu26-14845. Full text in Research Archive Show summary

  Global glacier mass loss is accelerating, yet considerable spread in projected glacier changes remains due to model structure, forcing, and parameter uncertainty. Most global glacier projections rely on relatively simple models where calibration approaches are essential to constrain uncertainty by using scarce observations. Probabilistic calibration strategies that help with quantifying uncertainities have recently incorporated into a limited number of global glacier models. As a next step, we suggest employing Bayesian data assimilation methods with untapped potential to integrate multi source observations (in-situ, satellite, reanalysis) when calibrating global glacier model projections.Here, we present a probabilistic calibration framework for the Python Glacier Evolution Model (PyGEM) based on ensemble-based data assimilation. Two data assimilation techniques (PBS and AdaPBS) are used to calibrate mass balance parameters to constrain future projections of glacio-hydrological variables (surface mass balance and runoff) between 2015 and 2100 under four SSP climate scenarios across the Scandinavian region. In this work, we compare our calibration results with commonly used deterministic and probabilistic glacier model calibration algorithms which are already in use in PyGEM. Our probabilistic calibration framework based on data assimilation has the potential to quantify and disentangle uncertainties from climate forcing, model structure, and parameters. Better constrained and uncertainty-aware glacier models increases confidence in projections of future glacier change and their relevant impacts. This work paves the way for producing policy relevant global glacier projections and scenarios with their uncertainty estimates within the ERC-AdG GLACMASS project.

• Dunse, Thorben; Sjursen, Kamilla Hauknes; Åkesson, Henning; Andreassen, Liss Marie; Schuler, Thomas & Gillespie, Mette Kusk [Show all 7 contributors for this article] (2026). Current state and future evolution of the largest ice cap in mainland Europe: Jostedalsbreen, Western Norway. Full text in Research Archive Show summary

  The Jostedalsbreen ice cap in western Norway covers an area of 458 km2 and comprises an ice volume of ~70 km3, making it the largest glacier in mainland Europe. It features a high elevation plateau that feeds 81 individual glacier units, including several steep outlet glaciers. This presentation highlights key findings from glacier simulations performed as part of the JOSTICE project (2020-2025), which aimed at assessing ongoing and future changes in the mass balance and ice volume of Jostedalsbreen, along with their ecological and societal impacts on hydropower production, tourism and agriculture. To investigate the historical climatic mass balance of Jostedalsbreen, we employed a temperature-index approach forced by gridded temperature and precipitation data from seNorge. Our model was calibrated through Bayesian inference using in-situ observations of seasonal and annual mass balances, supplemented by decadal geodetic mass balances for each glacier. Between 1960 and 2020, the overall mass balance of Jostedalsbreen was near zero; however, we observe significant spatiotemporal variability driven by trends in winter precipitation and snow accumulation before 2000, followed by increased summer temperatures and ablation in subsequent years. For future projections, we conducted coupled simulations of glacier mass balance and ice-dynamics to fully account for changes in glacier geometry and the mass-balance elevation feedback. The mass balance model is forced by multi-model climate ensembles and distinct greenhouse-gas emission scenarios. Three-dimensional ice-dynamic simulations capitalize on new maps of ice thickness and bedrock topography, derived from extensive ice-radar surveys as part of the JOSTICE project. Our findings indicate moderate mass losses until the mid-21st century, with increased accumulation over the glacier plateau partially offsetting progressively more negative mass balances at the glacier termini. However, we anticipate accelerated mass losses in the second half of the century as the ablation area expands to include substantial portions of the glacier plateau. We predict that Jostedalsbreen could lose between one half to two thirds of its current ice volume by 2100, depending on climate model and greenhouse-gas emission scenarios RCP4.5 and RCP8.5, respectively. Furthermore, Jostedalsbreen is expected to fragment into three separate glaciers, regardless of the emission scenario.

• Åkesson, Henning (2026). Hva er en isbre? Hva gjør en forsker? Besøk på Levre skole. Full text in Research Archive
• Tjoflot, Gunn Kristin; Åkesson, Henning & Andreassen, Liss Marie (2026). Mainland Europe’s largest glacier may be halved by 2100. [Internet]. Titan.uio.no. Full text in Research Archive Show summary

  A new study presents projections for Jostedalsbreen in a future warmer climate. Scientists used an advanced computer model to simulate the glacier's melting and dynamics across various scenarios.

• Tjoflot, Gunn Kristin; Åkesson, Henning & Andreassen, Liss Marie (2025). Norges største isbre står i fare for å halveres innen århundreskiftet - Titan.uio.no. [Internet]. Titan.uio.no. Full text in Research Archive Show summary

  En ny studie viser hva som vil skje med Jostedalsbreen i varmere klima. Forskere bruker en avansert datamodell til å beregne hvordan isbreen smelter og beveger seg under ulike scenarioer.

• Ourkiya, Asmae & Åkesson, Henning (2025). EGU Blogs - GeoRoundup: the highlights of EGU Journals published during November! doi: https:/blogs.egu.eu/geolog/2025/11/28/georoundup-the-highlights-of-egu-journals-published-during-november-2025-2-2-2-2-2/. Full text in Research Archive
• Åkesson, Henning; Andreassen, Liss Marie & Schuler, Thomas (2025). Norges største isbre kan være halvert om 75 år. doi: https:/www.forskersonen.no/isbre-klima-meninger/norges-storste-isbre-kan-vaere-halvert-om-75-ar/2581055. Full text in Research Archive Show summary

  POPULÆRVITENSKAP: Jostedalsbreen vil miste mye is og dele seg opp i en rekke mindre deler fram mot 2100

• Aasen, Kristine Ramberg; Rognaldsen, Eirik; Larsen, Hanne; Skifjeld, Anne; Knežević, Milana & Elster, Kristian [Show all 8 contributors for this article] (2025). Norge kan miste 32 vinterdager i løpet av de neste 75 årene. [Internet]. NRK. doi: https:/www.nrk.no/klima/norge-kan-miste-32-vinterdager-i-lopet-av-de-neste-75-arene-1.17621876. Full text in Research Archive Show summary

  Norge står overfor dramatiske endringer, viser den største rapporten om klima i Norge på ti år. – Jeg er overrasket, sier en av forskerne bak studien.

• Åkesson, Henning & Sjursen, Kamilla Hauknes (2025). Model code and metadata supporting the publication of the Åkesson et al. paper about Jostedalsbreen ice cap. doi: 10.5281/ZENODO.17304935. Full text in Research Archive Show summary

  Assets supporting the publication of the Åkesson et al. paper about Jostedalsbreen ice cap

• Åkesson, Henning & Sjursen, Kamilla Hauknes (2025). Modelled future evolution of Jostedalsbreen ice cap, Norway. doi: 10.5281/ZENODO.17472491. Full text in Research Archive Show summary

  This dataset contains the modelled evolution of key glacier variables for Jostedalsbreen ice cap in Norway, as detailed in Åkesson et al. (2025).

• Schellenberger, Thomas & Åkesson, Henning (2025). Ice-surface velocity in 1996 of Jostedalsbreen ice cap, Norway from European Remote Sensing satellite (ERS-1/-2) data. doi: 10.5281/zenodo.17541329. Full text in Research Archive Show summary

  This dataset contains x- and y- components of the ice-surface velocity of Jostedalsbreen ice cap in winter 1996. The data covers the southern, northern and some of the central parts of the ice cap.

• Sjursen, Kamilla Hauknes; Dunse, Thorben; Schuler, Thomas; Andreassen, Liss Marie & Åkesson, Henning (2025). Surface mass balance of Jostedalsbreen ice cap, 1960-2100. Full text in Research Archive
• Yde, Jacob C.; Åkesson, Henning; Gillespie, Mette Kusk; Kielland, Pål Gran; Hove, Marit Haugan & Nesje, Wenche [Show all 9 contributors for this article] (2025). Interactive exhibition display of Jostedalsbreen. Full text in Research Archive
• Åkesson, Henning (2025). Ice sheets and glaciers - past to future. Full text in Research Archive
• Åkesson, Henning; Sjursen, Kamilla Hauknes; Schuler, Thomas; Dunse, Thorben; Andreassen, Liss Marie & Gillespie, Mette Kusk [Show all 9 contributors for this article] (2025). Recent history and future demise of Jostedalsbreen, the largest ice cap in mainland Europe. doi: 10.5194/egusphere-egu25-10323. Full text in Research Archive Show summary

  Glaciers and ice caps worldwide are in strong decline, and models project this trend to continue with future warming, with strong natural and socioeconomic implications. The Jostedalsbreen ice cap is the largest ice cap on the European continent (500 km2 in 1966, 458 km2 in 2019) and occupies 20% of the total glacier area of mainland Norway. Here we simulate the evolution of Jostedalsbreen since 1960, and its fate in a changing climate in the 21st-century and beyond (2300). This ice cap contains glacier units with a great diversity in shape, steepness, hypsometry, and flow speed. We employ a coupled model system annually accounting for the mass-balance elevation feedback, with 3-d ice dynamics and simulated surface mass balance constrained by Bayesian inference. We find that Jostedalsbreen may lose 12-74% of its present-day volume, depending on future emissions. Regardless of scenario, the ice cap is likely to split into three parts during the second half of the 21st century. Our results suggest that Jostedalsbreen will likely be more resilient than many smaller glaciers and ice caps in Scandinavia. However, we show in simulations to the year 2300 that by the year 2100, the ice cap may be committed to a complete disappearance during the 22nd century, under high emissions. Under medium 21st-century emissions, the ice cap is bound to shrink by 90% until 2300. Further simulations indicate that substantial mass losses undergone until 2100 are irreversible. Our study illustrates a model approach for complex ice masses with numerous outlet glaciers such as ice caps, and how tightly linked future mass loss is to future greenhouse-gas emissions. Finally, uncertainties in future climate conditions appear to be the largest source of uncertainty in future evolution of ice caps like Jostedalsbreen.

• Robson, Benjamin Aubrey; Andreassen, Liss Marie & Åkesson, Henning (2025). Jostedalsbreen ice-surface topography 1966. doi: 10.5281/zenodo.17425322. Full text in Research Archive Show summary

  This dataset contains a digital terrain model (DTM) representing the surface topography of Jostedalsbreen, Norway, for the year 1966.

• Nisancioglu, Kerim Hestnes & Åkesson, Henning (2025). Hardangerjøkulen - fortidshistorien og fremtidsutsiktene. doi: https:/www.hotelfinse1222.no/finsefest. Full text in Research Archive
• Åkesson, Henning; Sjursen, Kamilla Hauknes; Schuler, Thomas Vikhamar; Dunse, Thorben; Andreassen, Liss Marie & Gillespie, Mette Kusk [Show all 9 contributors for this article] (2025). The future fate of the largest ice cap in mainland Europe. Full text in Research Archive
• Tjoflot, Gunn Kristin & Åkesson, Henning (2025). Økt snøfall kan redde truede isbreer i Sør-Amerika. Teknisk Ukeblad. ISSN 0040-2354. Full text in Research Archive Show summary

  På samme måte som de norske breene, sliter isbreene i Sør-Amerika i varmen. Men en ny forskningsstudie avslører en overraskelse om isbreene i Patagonia.

• Schuler, Thomas; Nanni, Ugo; Bouchayer, Coline Lili Mathy; Åkesson, Henning; Lefeuvre, Pierre-Marie & Mannerfelt, Erik Schytt [Show all 9 contributors for this article] (2024). Observed weakening of glacier ice-bed interface caused by climatic and hydro-mechanical feedbacks: towards glacier-wide acceleration? Full text in Research Archive Show summary

  Stronger and more widespread surface melt may alter the flow of glaciers and ice sheets and trigger instability. However, observational deficiencies hamper our ability to better understand and thus predict such responses. We deployed surface and borehole seismometers along the centerline of a High Arctic glacier in Svalbard. The records span over six years and are analyzed in relation to the measured increase of surface velocity. We complement our seismic analysis (icequakes and seismic noise) with long-term measurements of glacier-surface velocity, surface-elevation changes, and runoff modeling. Since 2000, we observe glacier thinning and steepening, coinciding with acceleration of up to 1000%. In response, new crevasses have opened and provide access pathways for surface melt water to the base of the glacier, affecting the ice-bed coupling. This mechanism represents a positive hydro-mechanical feedback that fuels further acceleration and crevassing. This feedback may have wider implications for triggering of glacier-wide instabilities, increasing short-term sea-level rise and local hazards. Beyond the Arctic, we suggest that, under a warming atmosphere, glaciers may transition from stable to unstable flow through such a mechanism.

• Tjoflot, Gunn Kristin; Åkesson, Henning & Kjellin, Simen (2024). Studietur i Jotunheimen ble til unik utstilling om oppdagelsen av istiden. [Internet]. Titan.uio.no. Full text in Research Archive
• Sjursen, Kamilla Hauknes; Dunse, Thorben; Schuler, Thomas Vikhamar; Andreassen, Liss Marie & Åkesson, Henning (2024). Spatiotemporal variability in mass balance of Jostedalsbreen ice cap 1960-2020, using a temperature-index model with data assimilation. Full text in Research Archive
• Åkesson, Henning; Sjursen, Kamilla Hauknes; Andreassen, Liss Marie; Schuler, Thomas Vikhamar; Dunse, Thorben & Gillespie, Mette Kusk [Show all 8 contributors for this article] (2024). History and future demise of Jostedalsbreen, the largest ice cap in mainland Europe. Full text in Research Archive
• Barnett, Jamie; Holmes, Felicity A.; Åkesson, Henning; Nilsson, Johan; Kirchner, Nina & Jakobsson, Martin (2024). Modelling the evolution of Ryder Glacier, Greenland, through the Holocene to investigate its responses to marine and atmospheric forcings. EGU General Assembly Conference Abstracts. doi: 10.5194/egusphere-egu24-15939. Full text in Research Archive
• Holmes, Felicity A.; Barnett, Jamie; Åkesson, Henning; Nilsson, Johan; Kirchner, Nina & Jakobsson, Martin (2024). Modelling Ryder Glacier in Northern Greenland until 2100 under various emissions scenarios; Under which circumstances is the ice tongue lost? EGU General Assembly Conference Abstracts. doi: 10.5194/egusphere-egu24-15935. Full text in Research Archive
• Sjursen, Kamilla Hauknes; Dunse, Thorben; Schuler, Thomas Vikhamar; Andreassen, Liss Marie & Åkesson, Henning (2024). Modelling mass balance of glaciers in Norway. Full text in Research Archive
• Troch, Matthias & Åkesson, Henning (2024). LA NIEVE PODRÍA SALVAR LOS GLACIARES DE LA PATAGONIA. [Internet]. Radio Polar. Full text in Research Archive
• Troch, Matthias & Åkesson, Henning (2024). La nieve podría salvar los glaciares de la Patagonia. [Internet]. Cooperativa Sciencia. Full text in Research Archive
• Åkesson, Henning (2023). Istiden i bilder - skolebesøk fra Nadderud VGS. Full text in Research Archive
• Tjoflot, Gunn Kristin & Åkesson, Henning (2023). GeoOnsdag Spesial "Arven etter Esmark" - Sjå opptak frå foredraget. [Internet]. UiO.no. Full text in Research Archive
• Åkesson, Henning; Kjellin, Simen; Hirsti, Linn Katrine; Etzelmüller, Bernd & Lilleøren, Karianne Staalesen (2023). Utstilling: Arven etter Esmark – Fra oppdagelsen av istiden til dens betydning for dagens forskning. Full text in Research Archive
• Etzelmüller, Bernd; Lilleøren, Karianne Staalesen; Conrad, Clinton Phillips; Åkesson, Henning & Lund, Martin (2023). GeoOnsdag Spesial "Arven etter Esmark" - Sjå opptak frå foredraget. [Internet]. https://www.mn.uio.no/geo/om/organisasjon/geohyd/aktuelt/geo. Full text in Research Archive
• Åkesson, Henning; Sjursen, Kamilla Hauknes; Andreassen, Liss Marie; Gillespie, Mette Kusk; Huss, Matthias & Schuler, Thomas [Show all 7 contributors for this article] (2023). Glaciers and people around mainland Europe’s largest ice cap – the JOSTICE project. Full text in Research Archive Show summary

  Here we present highlights from an ongoing multifaceted research project about mainland Europe's largest ice cap. The JOSTICE project (jostice.no) is funded by the Research Council of Norway and assesses present and future changes of glacier evolution and mass balance, runoff, and the local climate of the Jostedalsbreen ice cap in western Norway. The project works tightly with the local people and stakeholders to provide the scientific basis for sustainable adaptation strategies for future hydropower production, agriculture and tourism. Through this, we show how JOSTICE serves as inspiration for similar future interdisciplinary Arctic initiatives in Svalbard and beyond. Here we specifically highlight how we use coupled numerical simulations of glacier dynamics, surface mass balance and glacier evolution. Thereby we determine which glacier areas that are bound to disappear under projected future climate change. Finally, several hundred thousand guests visit Jostedalsbreen every year. In this light, we show how we work with the local tourism industry to plan and adapt to an ice cap in decline.

• Åkesson, Henning & Bogen, Annika Celin (2023). Hvordan kan Norge ha en av verdens lengste kystlinjer? [Internet]. Ung.forskning.no. Full text in Research Archive
• Åkesson, Henning; Etzelmüller, Bernd; Lund, Erik Martin; Conrad, Clinton Phillips & Lilleøren, Karianne Staalesen (2023). Arven etter Esmark - GeoOnsdag Spesial. Full text in Research Archive Show summary

  Arven etter Esmark, Bernd Etzelmüller/Karianne Lilleøren Imagining Esmark’s Lost Scandinavian Ice, Clint Conrad Gårsdagens is - fremtidens fasit, Henning Åkesson Wind of change, Martin Lund

• Åkesson, Henning (2022). More difficult than expected for glaciers to recover from climate warming. [Internet]. Science Daily. Full text in Research Archive
• Åkesson, Henning (2022). More difficult than expected for glaciers to recover from climate warming. [Internet]. Stockholm University website. Full text in Research Archive
• Åkesson, Henning; Morlighem, Mathieu; Nilsson, Johan; Stranne, Christian & Jakobsson, Martin (2022). Petermann Ice Shelf may not recover from a future breakup. Full text in Research Archive
• Åkesson, Henning (2022). Ice shelves will struggle to recover from global warming. [Internet]. Earth.com. Full text in Research Archive
• Åkesson, Henning (2022). Vanskelig for isbreer å bygge seg opp igjen etter global oppvarming. [Internet]. Titan.uio.no. Full text in Research Archive
• Åkesson, Henning (2022). Study illustrates irreversibility of ice shelf collapse. [Internet]. SAT PRWire. Full text in Research Archive
• Åkesson, Henning (2022). Los glaciares lo tienen cada vez más difícil para recuperarse del cambio climático  . [Internet]. Eltiempo.es. Full text in Research Archive
• Åkesson, Henning (2022). More difficult than expected for glaciers to recover from climate warming. [Internet]. Thinking Port. Full text in Research Archive
• Åkesson, Henning (2022). More Damaging Than Previously Thought: Glaciers Might Not Be Able To Recover From Climate Change. [Internet]. SciTechDaily. Full text in Research Archive
• Åkesson, Henning (2022). Gletscher erholen sich langsamer als erwartet von der Klimaerwärmung. [Internet]. Climate-academy.org. Full text in Research Archive
• Åkesson, Henning (2022). Kaum noch Hoffnung für Gletscher, etwas Hoffnung für Eisbären. [Internet]. Der Spiegel. Full text in Research Archive
• Åkesson, Henning (2022). Nyheter från Vetenskapsradion. [Radio]. Sveriges Radio. Full text in Research Archive
• Åkesson, Henning (2022). Recovery of Confined Ice Shelves Like Petermann's is Unlikely Post-Breakup. [Internet]. Azo Cleantech. Full text in Research Archive
• Åkesson, Henning (2022). Recovery of Broken ice Shelves More Difficult Than Expected. [Internet]. Newclick.in. Full text in Research Archive
• Åkesson, Henning (2022). More Damaging Than Previously Thought: Glaciers Might Not Be Able To Recover From Climate Change. [Internet]. Today UK News. Full text in Research Archive
• Åkesson, Henning (2022). Une étude illustre l’irréversibilité d’un effondrement des plateformes de glace. [Internet]. Sciencepost.fr. Full text in Research Archive
• Åkesson, Henning (2022). More difficult than expected for glaciers to recover from climate warming. [Internet]. YubaNet. Full text in Research Archive
• Åkesson, Henning (2022). More Difficult Than Expected For Glaciers To Recover From Climate Warming. [Internet]. Newswise. Full text in Research Archive
• Åkesson, Henning (2022). More difficult than expected for glaciers to recover from climate warming. [Internet]. Scienmag. Full text in Research Archive
• Åkesson, Henning (2022). Más difícil de lo esperado para que los glaciares se recuperen del calentamiento climático. [Internet]. F1 Mundial. Full text in Research Archive
• Åkesson, Henning (2022). More difficult than expected for glaciers to recover from climate warming. [Internet]. VerveTimes. Full text in Research Archive
• Åkesson, Henning (2022). Glacier recovery from global warming is more difficult than previous estimates. [Internet]. News9. Full text in Research Archive
• Åkesson, Henning (2022). Svårare än väntat for glaciärer att återhämta sig från klimatuppvärmningen. [Internet]. Aftonbladet. Full text in Research Archive
• Åkesson, Henning (2022). Istungor livsviktiga för glaciärers återhämtning. [Internet]. Forskning.se. Full text in Research Archive
• Åkesson, Henning (2022). Isbreer kan miste beskyttelsen for alltid hvis istungene forsvinner. [Internet]. Forsking.no. Full text in Research Archive
• Nisancioglu, Kerim Hestnes & Åkesson, Henning (2022). Hardangerjøkulen - fortidshistorien og fremtidsutsiktene. Full text in Research Archive
• Åkesson, Henning (2022). More difficult than expected for glaciers to recover from climate warming. [Internet]. Phys.org. Full text in Research Archive
• Åkesson, Henning (2022). More Difficult Than Expected For Glaciers To Recover From Climate Warming. [Internet]. Sciencenewsnet.in. Full text in Research Archive
• Åkesson, Henning (2021). The rocky road to accurate sea-level projections - dirt and water under Greenland control future sea-level rise. [Internet]. Bolin Centre for Climate Research website. Full text in Research Archive
• Åkesson, Henning (2021). Demise of a glacier, uncovering a fjord. [Internet]. Stockholm University website. Full text in Research Archive
• Åkesson, Henning; Morlighem, Mathieu; Jakobsson, Martin; Nilsson, Johan & Stranne, Christian (2021). Can Petermann recover from future collapse of its ice shelf? Full text in Research Archive
• Åkesson, Henning (2021). The rocky road to accurate sea-level predictions. [Internet]. ScienMag - Science Magazine. Full text in Research Archive
• Åkesson, Henning (2021). We urgently need to reconsider the under-ice landscapes of glaciers. [Internet]. Labroots. Full text in Research Archive
• Åkesson, Henning (2021). Greenland's largest glacier through the year 2300. [Internet]. American Geophysical Union (AGU) YouTube Channel. Full text in Research Archive
• Åkesson, Henning (2020). This is how Hardanger melted at record speed from the last ice age. [Internet]. Alkhaleej Today. Full text in Research Archive
• Åkesson, Henning (2020). Norsk isbre smeltet i rekordfart - gir en pekepinn om framtiden på Grønland. [Internet]. NRK.no. Full text in Research Archive
• Frank, Thomas; Åkesson, Henning; Fleurian, Basile de & Nisancioglu, Kerim Hestnes (2020). Geometric Controls of Fjord Glacier Dynamics. Full text in Research Archive Show summary

  Retreat of marine outlet glaciers and ice shelves may initiate depletion of inland ice and lead to ice loss that by far exceeds what would be expected from ocean and atmospheric warming alone. Many marine outlet glaciers draining large parts of past and present ice masses have shown non-linear and variable retreat rates, with adjacent glaciers sometimes showing a highly different response to the same large-scale climate forcing. This suggests that individual glacier characteristics play a dominant role in governing retreat. There is widespread evidence that the dynamic glacier adjustment to an external forcing is highly influenced by fjord topography. However, whether this stabilizes the glacier, or promotes enhanced retreat, depends on the shape of the fjord. So far, no rigorous, systematic assessment of the exact influence of certain geometric features such as overdeepenings or embayments has been undertaken in a model framework that incorporates all relevant processes in a 3D layout. Here, we analyze a multitude of topographic settings and scenarios using the Ice Sheet System Model (ISSM), which accounts for all relevant physics in a 3D framework. Using artificial fjord geometries, we investigate glacier-topography interaction and quantify the modeled glacier response directly in relation to topographic features. In light of our modeled topographic influence on glacier retreat, we consider whether we reliably can extrapolate observations from a few well-monitored glaciers to those less studied. Furthermore, we discuss implications for past and future ice sheet mass loss and associated sea-level rise. Finally, a deeper understanding of processes at the glacier front improves confidence in the climate signal derived from the deglacial landscape, as glacier-proximal landforms can more confidently be linked to climate.

• Åkesson, Henning (2020). Demise of a glacier, uncovering of a fjord. [Internet]. Phys.org. Full text in Research Archive
• Åkesson, Henning (2020). Demise of a glacier, uncovering of the Hardangerfjord. [Internet]. Forskning.no/ScienceNorway. Full text in Research Archive
• Åkesson, Henning (2020). Snowhow - Vinteren kommer. [TV]. NRK TV. Full text in Research Archive
• Paasche, Øyvind & Åkesson, Henning (2019). Let’s Start Teaching Scientists How to Withstand Attacks on Fact. EOS. ISSN 0096-3941. Full text in Research Archive
• Åkesson, Henning (2018). Isbreene forsvinner. [TV]. NRK Vestlandsrevyen. Full text in Research Archive
• Åkesson, Henning (2018). Hardangerjøkulen kan bli helt borte. [Journal]. Bergens Tidende. Full text in Research Archive
• Åkesson, Henning (2018). Full retrett for norske isbrear? [Internet]. Framtida.no. Full text in Research Archive
• Åkesson, Henning (2018). – Vi er i ferd med å miste breene som i dag er en del av landskapet vårt. [Internet]. Bergens Tidende. Full text in Research Archive
• Åkesson, Henning (2018). Flere norske isbreer i ferd med å forsvinne. [TV]. TV2 Nyhetskanalen. Full text in Research Archive
• Åkesson, Henning (2018). Brer over breen - Slik skal sveitserne bremse bresmeltingen. [Journal]. Dagens næringsliv. Full text in Research Archive
• Paasche, Øyvind & Åkesson, Henning (2018). Scientific Integrity in a Politically Challenged World (Session TM 6, Conveners). Full text in Research Archive
• Nisancioglu, Kerim Hestnes; Åkesson, Henning & Steiger, Nadine (2018). Rapid deglaciation of Norwegian and Greenland fjords. Full text in Research Archive
• Åkesson, Henning; Gyllencreutz, Richard; Mangerud, Jan; Nick, Faezeh M. & Nisancioglu, Kerim Hestnes (2018). Fast retreat of a marine outlet glacier in western Norway at the last glacial termination. Full text in Research Archive Show summary

  Observations of marine outlet glaciers covering the last few decades show speedup and accelerated retreat, and the geologic record testaments that catastrophic changes occurred also in the past. However, the time scales of rapid outlet glacier retreat and the underlying drivers are still unclear. Here, we study the collapse of Hardangerfjorden glacier, an outlet glacier of the Scandinavian Ice Sheet, during the transition from the Younger Dryas cold period to the warming in early Holocene. We use dated terminal and lateral moraines as constraints for a simple ice flow model including calving. Our experiments suggest a fast and highly variable retreat history driven by surface melt and warming fjord waters, paced by fjord bathymetry as well as ice shelf dynamics. Grounding line retreat in response to the rapid, large early Holocene warming is simulated at rates below 200 m/a, punctuated by brief spells of swift retreat exceeding 500 m/a. Our findings imply that warming subsurface waters will continue to drive retreat of marine outlet glaciers in Greenland and elsewhere, but that recent elevated retreat rates observed are not likely to be sustained longer than a few decades. On centennial scales, retreat will likely be increasingly driven by a warming atmosphere.

• Åkesson, Henning (2018). I spotted this beautiful Norwegian ice cap from the air recently — and as it turns out, it’s doomed. [Internet]. Discover Magazine. Full text in Research Archive
• Åkesson, Henning (2017). DELINGPOLE: 'Global Warming' Is a Myth, Say 58 Scientific Papers in 2017. [Internet]. Breitbart. Full text in Research Archive
• Åkesson, Henning (2017). Breitbart misrepresents research from 58 scientific papers to falsely claim that they disprove human-caused global warming. [Internet]. Climate Feedback. Full text in Research Archive
• Åkesson, Henning (2017). 80 Graphs From 58 New (2017) Papers Invalidate Claims Of Unprecedented Global-Scale Modern Warming. [Internet]. Notrickzone.com. Full text in Research Archive
• Åkesson, Henning (2017). En historisk økonomisk gamble. Finansavisen. ISSN 0803-9518. p. 42–42. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Morlighem, Mathieu; Nick, Faezeh M.; Mangerud, Jan & Svendsen, John-Inge (2017). What controls changes of marine outlet glaciers? Full text in Research Archive
• Åkesson, Henning (2017). Hardangerjøkulen: The Real-Life Hoth is Disappearing. [Internet]. GlacierHub.org. Full text in Research Archive
• Åkesson, Henning (2017). Møt en forsker - hva skjer med isbreer og klima? Full text in Research Archive
• Åkesson, Henning (2017). Hardangerjøkulen i endring: - hva kan fortiden lære oss, og hva vil framtiden bringe? Full text in Research Archive
• Åkesson, Henning; Morlighem, Mathieu & Nisancioglu, Kerim Hestnes (2017). Modelling grounding line retreat during deglaciation of Western Norway using ISSM. Full text in Research Archive
• Åkesson, Henning (2017). Klima i endring - hva skjer, hva kan vi gjøre, og hvilke muligheter åpner seg opp? Full text in Research Archive
• Åkesson, Henning (2017). Low snow cover threatens Swiss ski resorts. [Internet]. Breaking Property News. Full text in Research Archive
• Åkesson, Henning (2017). Low snow cover threatens Swiss ski resorts. [Internet]. Climate News Network. Full text in Research Archive
• Åkesson, Henning; Nick, Faezeh M.; Nisancioglu, Kerim Hestnes & Steiger, Nadine (2017). How fjord geometry controls marine-terminating glacier stability. Full text in Research Archive
• Åkesson, Henning (2017). Kan smelte bort. [Journal]. Vi menn. Full text in Research Archive
• Åkesson, Henning; Morlighem, Mathieu; Nisancioglu, Kerim Hestnes; Svendsen, John-Inge & Mangerud, Jan (2017). Modelling grounding line retreat during deglaciation of the Western Fennoscandian Ice Sheet using ISSM. Full text in Research Archive
• Åkesson, Henning (2017). - Ekspressversjonen er at det blir varmare og Hardangerjøkulen smeltar. [Internet]. Hardanger Folkeblad nett. Full text in Research Archive
• Åkesson, Henning (2017). Isbre kan vera borte om 50 år. [Journal]. Hardanger Folkeblad. Full text in Research Archive
• Paasche, Øyvind & Åkesson, Henning (2017). Nordic support for American climate science. [Journal]. UArctic website. Full text in Research Archive
• Åkesson, Henning (2017). Norwegian ice cap 'exceptionally sensitive' to climate change. [Internet]. Phys.org. Full text in Research Archive
• Åkesson, Henning & Engeset, Rune Verpe (2017). Nesten alle de norske isbreene kan smelte helt bort innen 100 år. [Internet]. NRK P3 Nyheter. Full text in Research Archive
• Åkesson, Henning & Engeset, Rune Verpe (2017). Isbreer kan forsvinne dette århundret. [Radio]. NRK P2 Nyhetsmorgen. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Giesen, Rianne H. & Morlighem, Mathieu (2017). Simulating the history of Hardangerjøkulen ice cap and its sensitivity to climate change. Full text in Research Archive
• Åkesson, Henning; Paasche, Øyvind & Lysbakken, Audun (2017). Lysbakken: - Trump angriper sannheten og vitenskapen. [Journal]. Bergens Tidende. Full text in Research Archive
• Åkesson, Henning & Karlsen, Ola (2017). Om 100 år kan de norske isbreene ha smeltet. [Internet]. ABC Nyheter. Full text in Research Archive
• Åkesson, Henning & Engeset, Rune Verpe (2017). Isbreer kan forsvinne dette århundret. [Radio]. NRK Hordaland. Full text in Research Archive
• Åkesson, Henning & Engeset, Rune Verpe (2017). Hardangerjøkulen kan forsvinne. [TV]. NRK Vestlandsrevyen. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes & Sylte, Gudrun (2017). Hardangerjøkulen kan smelte vekk i løpet av dette århundret. [Internet]. energiogklima.no. Full text in Research Archive
• Åkesson, Henning (2017). Norwegian ice cap 'exceptionally sensitive' to climate change. [Internet]. ScienceDaily.com. Full text in Research Archive
• Åkesson, Henning; Paasche, Øyvind & Njåstad, Marthe (2017). Har startet støttekampanje for amerikansk forskning. [Internet]. På Høyden. Full text in Research Archive
• Åkesson, Henning; Engeset, Rune Verpe; Olsen, Adrian Nyhammer; Angell, Elise & Johansen, Even Norheim (2017). 300 meter tykk isbre kan være borte om 50 år. [Internet]. NRK.no. Full text in Research Archive
• Åkesson, Henning & Engeset, Rune Verpe (2017). 300 meter tykk isbre kan være borte om 50 år. [Internet]. Kraftnytt.no. Full text in Research Archive
• Åkesson, Henning (2017). Denne isbreen kan være borte om 50 år. [TV]. NRK Dagsrevyen. Full text in Research Archive
• Åkesson, Henning; Steiger, Nadine; Nisancioglu, Kerim Hestnes & Nick, Faezeh M. (2017). How fjord geometry controls marine-terminating glacier stability. Full text in Research Archive
• Åkesson, Henning; Paasche, Øyvind & Sylte, Gudrun (2017). Sanker støtte for amerikansk forskning. [Internet]. energiogklima.no. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Giesen, Rianne H. & Morlighem, Mathieu (2017). Simulating the history of Hardangerjøkulen ice cap and its sensitivity to climate change. Full text in Research Archive
• Steiger, Nadine; Nisancioglu, Kerim Hestnes; Åkesson, Henning & Nick, Faezeh M. (2017). Modeling the retreat of the Jakobshavn Glacier from the LIA and into the future. Full text in Research Archive
• Åkesson, Henning; Nick, Faezeh M. & Nisancioglu, Kerim Hestnes (2016). Effect of fjord geometry on ice sheet stability. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes & Steiger, Nadine (2016). Marine ice sheet stability and climate interactions. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Giesen, Rianne H. & Morlighem, Mathieu (2016). Simulating asymmetric growth and retreat of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene. Full text in Research Archive
• Steiger, Nadine; Nisancioglu, Kerim Hestnes; Nick, Faezeh M. & Åkesson, Henning (2016). Modelling marine-terminating glaciers in a warming climate. Full text in Research Archive
• Åkesson, Henning; Nick, Faezeh M.; Nisancioglu, Kerim Hestnes & Steiger, Nadine (2016). On the impact of fjord geometry on grounding line stability. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Giesen, Rianne H. & Morlighem, Mathieu (2016). Modelled non-linear response to climate of Hardangerjøkulen ice cap, southern Norway, since the mid-Holocene. Full text in Research Archive
• Åkesson, Henning & Steiger, Nadine (2016). Breer, klima og klimagassutslipp - hva er det som skjer? Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Steiger, Nadine & Nick, Faezeh M. (2016). Effect of fjord geometry on tidewater glacier stability. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Nick, Faezeh M. & Steiger, Nadine (2016). Effect of fjord geometry on marine-terminating glacier stability. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Svendsen, John-Inge; Mangerud, Jan; Hughes, Anna L.C. & Vasskog, Kristian [Show all 7 contributors for this article] (2015). Marine outlet glacier stability on centennial time scales. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Giesen, Rianne H. & Morlighem, Mathieu (2015). Modelling mass balance and dynamics of Hardangerjøkulen Ice Cap, Southern Norway. Full text in Research Archive
• Jensen, Mari Fjalstad & Åkesson, Henning (2015). Hva gjør en klimaforsker? Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes & Nick, Faezeh M. (2015). Fjord geometry and marine outlet glacier stability on centennial time scales. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes & Nick, Faezeh M. (2015). Fjord geometry and marine outlet glacier stability on deglaciation time scales. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Svendsen, John-Inge; Mangerud, Jan; Hughes, Anna L.C. & Vasskog, Kristian [Show all 7 contributors for this article] (2015). Deglaciation of the Norwegian fjords. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Giesen, Rianne H. & Morlighem, Mathieu (2015). Simulating Hardangerjøkulen ice cap, southern Norway, since the Little Ice Age. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Svendsen, John-Inge; Mangerud, Jan; Hughes, Anna L.C. & Vasskog, Kristian [Show all 7 contributors for this article] (2015). Deglaciation of the Norwegian fjords. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Giesen, Rianne H. & Morlighem, Mathieu (2015). Simulating the climatic response of Hardangerjøkulen ice cap since the Little Ice Age. Full text in Research Archive
• Åkesson, Henning (2015). Breer og klima: hva er det som skjer? - og hvordan vi vet det. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes & Nick, Faezeh M. (2015). Fjord geometry and marine outlet glacier stability on centennial time scales. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Giesen, Rianne H. & Morlighem, Mathieu (2014). Simulating the climatic response of Hardangerjøkulen ice cap with ISSM. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Giesen, Rianne H. & Morlighem, Mathieu (2014). Simulating Hardangerjøkulen ice cap, southern Norway, since the Little Ice Age. Full text in Research Archive
• Åkesson, Henning; Nisancioglu, Kerim Hestnes; Giesen, Rianne H. & Morlighem, Mathieu (2014). Simulating the climatic response of Hardangerjøkulen ice cap since the Little Ice Age. Full text in Research Archive
• Åkesson, Henning (2018). Deglaciation of the Norwegian fjords. Universitetet i Bergen. Full text in Research Archive Show summary

  Melting glaciers and ice sheets are perhaps the most visible signs of a warming cli- mate. Glaciers are retreating on every continent, ice sheets are shedding icebergs into a warming ocean at an accelerating rate, and the atmosphere melts more ice as tempera- tures rise. Despite these lines of evidence, and a growing scientific and public attention to melting ice; we are still not able to present robust numbers of future sea level rise. While the overall picture is one of retreat and meltdown, complex patterns arise when we zoom in within a certain region. The geologic record testaments both collapse and periods of growth, and provides important clues to future mass loss. However, these records show that variable responses were present within regions exposed to the same climate forcing. This is also found in Greenland and Antarctica today, where observations reveal that neighbouring glaciers respond differently to the same climate warming. Caution is therefore needed when explaining the responses of these glaciers. The instrumental record helps us to improve process understanding, yet is unable to assess changes over time scales longer than a few decades. The geologic record provides a longer perspective, but is not able to resolve short-lived variations. This time scale issue is critical because we need to understand both the short-term and long- term response to improve understanding of glacier and ice sheet dynamics and their sensitivity to climate change. In this thesis, we use a suite of numerical model tools combined with geological data to assess how external forcing triggers and drives short- and long-term change. Equally important, we study how site-specific factors such as topography can prevent, delay, dampen, amplify, and override the ambient forcing. We assess theoretical cases as well as past and present glaciers in Norway and Greenland, with the goal to answer the overarching question: how do glaciers and ice sheets respond to climate change? We move from the sensitivity of a Norwegian ice cap to Holocene climate change in Paper I, via the impact of fjord geometry on grounding line stability in Paper II, to the abrupt retreat of the nearby Hardangerfjorden glacier during the Younger Dryas cold period in Paper III. We continue with the most active glacier in Greenland in Paper IV, and finish with a comprehensive study of the triggers and drivers of the deglaciation of the Norwegian fjords in Paper V. For marine-terminating glaciers, we find that grounding line dynamics and ice- ocean interactions are fundamental over time scales up to a century or two. Beyond this time frame, changes to the surface mass balance are likely to drive widespread, multi-centennial to millennial scale deglaciation. Based on the results presented in this thesis, we also suggest that topography is a factor that cannot be ignored. Once triggered, the response to climate change is to a large degree controlled by the under- lying bed topography of ice caps (Paper I), and by the fjord bathymetry and width of marine-terminating glaciers (Papers II–V). The implications are that continued intense studies of warming seas around Green- land and Antarctica are justified, but also that assessments of atmospheric-induced melt will be important to estimate long-term sea level change. The striking impact of topo- graphic factors found in this thesis also shows a potential to use geometry to predict future evolution and estimate past retreat and advance.

• Åkesson, Henning; Nisancioglu, Kerim Hestnes & Svendsen, John-Inge (2018). Deglaciation of the Norwegian fjords. Universitetet i Bergen. ISSN 9788230838549. Full text in Research Archive

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