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  • 1. Adinugroho, Sigit
    et al.
    Vallot, Dorothée
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Westrin, Pontus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Strand, Robin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Calving events detection and quantification from time-lapse images in Tunabreen glacier2015Ingår i: Proc. 9th International Conference on Information & Communication Technology and Systems, Piscataway, NJ: IEEE , 2015, s. 61-65Konferensbidrag (Refereegranskat)
  • 2.
    How, Penelope
    et al.
    Univ Edinburgh, Sch GeoSci, Inst Geog, Edinburgh, Midlothian, Scotland;Univ Ctr Svalbard, Dept Arctic Geol, Longyearbyen, Norway;Univ York, Dept Environm & Geog, York, N Yorkshire, England.
    Schild, Kristin M.
    Univ Oregon, Dept Earth Sci, Eugene, OR 97403 USA;Univ Maine, Climate Change Inst, Orono, ME USA.
    Benn, Douglas I.
    Univ St Andrews, Dept Geog & Sustainable Dev, St Andrews, Fife, Scotland.
    Noormets, Riko
    Univ Ctr Svalbard, Dept Arctic Geol, Longyearbyen, Norway.
    Kirchner, Nina
    Stockholm Univ, Dept Phys Geog, Stockholm, Sweden.
    Luckman, Adrian
    Swansea Univ, Dept Geog, Coll Sci, Swansea, W Glam, Wales;Univ Ctr Svalbard, Dept Arctic Geophys, Longyearbyen, Norway.
    Vallot, Dorothée
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Hulton, Nicholas R. J.
    Univ Edinburgh, Sch GeoSci, Inst Geog, Edinburgh, Midlothian, Scotland;Univ Ctr Svalbard, Dept Arctic Geol, Longyearbyen, Norway.
    Borstad, Chris
    Univ Ctr Svalbard, Dept Arctic Geophys, Longyearbyen, Norway.
    Calving controlled by melt-under-cutting: detailed calving styles revealed through time-lapse observations2019Ingår i: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 60, nr 78, s. 20-31Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a highly detailed study of calving dynamics at Tunabreen, a tidewater glacier in Svalbard. A time-lapse camera was trained on the terminus and programmed to capture images every 3 seconds over a 28-hour period in August 2015, producing a highly detailed record of 34 117 images from which 358 individual calving events were distinguished. Calving activity is characterised by frequent events (12.8 events h(-1)) that are small relative to the spectrum of calving events observed, demonstrating the prevalence of small-scale calving mechanisms. Five calving styles were observed, with a high proportion of calving events (82%) originating at, or above, the waterline. The tidal cycle plays a key role in the timing of calving events, with 68% occurring on the falling limb of the tide. Calving activity is concentrated where meltwater plumes surface at the glacier front, and a similar to 5 m undercut at the base of the glacier suggests that meltwater plumes encourage melt-under-cutting. We conclude that frontal ablation at Tunabreen may be paced by submarine melt rates, as suggested from similar observations at glaciers in Svalbard and Alaska. Using submarine melt rate to calculate frontal ablation would greatly simplify estimations of tidewater glacier losses in prognostic models.

  • 3.
    Lindbäck, Katrin
    et al.
    Norwegian Polar Res Inst, Framsentret, Postboks 6606, N-9296 Tromso, Norway.
    Kohler, Jack
    Norwegian Polar Res Inst, Framsentret, Postboks 6606, N-9296 Tromso, Norway.
    Pettersson, Rickard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Nuth, Christopher
    Univ Oslo, Postboks 1047 Blindern, N-0316 Oslo, Norway.
    Langley, Kirsty
    Asiaq Greenland Survey, Postboks 1003, Nuuk 3900, Greenland.
    Messerli, Alexandra
    Norwegian Polar Res Inst, Framsentret, Postboks 6606, N-9296 Tromso, Norway.
    Vallot, Dorothée
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Matsuoka, Kenichi
    Norwegian Polar Res Inst, Framsentret, Postboks 6606, N-9296 Tromso, Norway.
    Brandt, Ola
    Norwegian Coastal Adm, Kystveien 30, N-4841 Arendal, Norway.
    Subglacial topography, ice thickness, and bathymetry of Kongsfjorden, northwestern Svalbard2018Ingår i: Earth System Science Data, ISSN 1866-3508, E-ISSN 1866-3516, Vol. 10, nr 4, s. 1769-1781Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Svalbard tidewater glaciers are retreating, which will affect fjord circulation and ecosystems when glacier fronts become land-terminating. Knowledge of the subglacial topography and bathymetry under retreating glaciers is important to modelling future scenarios of fjord circulation and glacier dynamics. We present high-resolution (150m gridded) digital elevation models of subglacial topography, ice thickness, and ice surface elevation of five tidewater glaciers in Kongsfjorden (1100 km(2)), northwestern Spitsbergen, based on similar to 1700 km airborne and ground-based ice-penetrating radar profiles. The digital elevation models (DEMs) cover the tidewater glaciers Blomstrandbreen, Conwaybreen, Kongsbreen, Kronebreen, and Kongsvegen and are merged with bathymetric and land DEMs for the non-glaciated areas. The large-scale subglacial topography of the study area is characterized by a series of troughs and highs. The minimum subglacial elevation is 180m above sea level (a.s.l.), the maximum subglacial elevation is 1400m a.s.l., and the maximum ice thickness is 740m. Three of the glaciers, Kongsbreen, Kronebreen, and Kongsvegen, have the potential to retreat by similar to 10 km before they become land-terminating. The compiled data set covers one of the most studied regions in Svalbard and is valuable for future studies of glacier dynamics, geology, hydrology, and fjord circulation.

  • 4.
    Memon, Shahbaz
    et al.
    Forschungszentrum Julich, Julich Supercomp Ctr, Leo Brandt Str, D-52428 Julich, Germany;Univ Iceland, Fac Ind Engn Mech Engn & Comp Sci, Reykjavik, Iceland.
    Vallot, Dorothée
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Zwinger, Thomas
    CSC IT Ctr Sci Ltd, Espoo, Finland.
    Åstrom, Jan
    CSC IT Ctr Sci Ltd, Espoo, Finland.
    Neukirchen, Helmut
    Univ Iceland, Fac Ind Engn Mech Engn & Comp Sci, Reykjavik, Iceland.
    Riedel, Morris
    Forschungszentrum Julich, Julich Supercomp Ctr, Leo Brandt Str, D-52428 Julich, Germany;Univ Iceland, Fac Ind Engn Mech Engn & Comp Sci, Reykjavik, Iceland.
    Book, Matthias
    Univ Iceland, Fac Ind Engn Mech Engn & Comp Sci, Reykjavik, Iceland.
    Scientific workflows applied to the coupling of a continuum (Elmer v8.3) and a discrete element (HiDEM v1.0) ice dynamic model2019Ingår i: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 12, nr 7, s. 3001-3015Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Scientific computing applications involving complex simulations and data-intensive processing are often composed of multiple tasks forming a workflow of computing jobs. Scientific communities running such applications on computing resources often find it cumbersome to manage and monitor the execution of these tasks and their associated data. These workflow implementations usually add overhead by introducing unnecessary input/output (I/O) for coupling the models and can lead to sub-optimal CPU utilization. Furthermore, running these workflow implementations in different environments requires significant adaptation efforts, which can hinder the reproducibility of the underlying science. High-level scientific workflow management systems (WMS) can be used to automate and simplify complex task structures by providing tooling for the composition and execution of workflows - even across distributed and heterogeneous computing environments. The WMS approach allows users to focus on the underlying high-level workflow and avoid low-level pitfalls that would lead to non-optimal resource usage while still allowing the workflow to remain portable between different computing environments. As a case study, we apply the UNICORE workflow management system to enable the coupling of a glacier flow model and calving model which contain many tasks and dependencies, ranging from pre-processing and data management to repetitive executions in heterogeneous high-performance computing (HPC) resource environments. Using the UNICORE workflow management system, the composition, management, and execution of the glacier modelling workflow becomes easier with respect to usage, monitoring, maintenance, reusability, portability, and reproducibility in different environments and by different user groups. Last but not least, the workflow helps to speed the runs up by reducing model coupling I/O overhead and it optimizes CPU utilization by avoiding idle CPU cores and running the models in a distributed way on the HPC cluster that best fits the characteristics of each model.

  • 5.
    Vallot, Dorothée
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    First-principles Simulations and the Criticality of Calving Glaciers: Termini of calving glaciers as self-organized critical systems2014Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The algorithm of a first principles calving-simulation computer-code is outlined and demonstrated. The code is particle-based and uses Newtonian dynamics to simulate ice-fracture, motion and calving. The code can simulate real-size glacier but is only able to simualte individual calving events within a few tens of minutes in duration. The code couples to the Elmer/Ice ice flow-simulation code: Elmer is employed to produce various glacier geomteries, which are then tested for stability using the particle code. In this way it is possible to pin-point the location of calving fronts. The particle simulation code and field observations are engaged to investigate the criticality of calving glaciers. The calving mass and inter-event waiting times both have power-law distributions with the same critical exponents as found for Abelian sand-pile models. This indicate that calving glaciers share characteristics with Self-Organized Critical systems (SOC). This would explain why many glacier found in nature may become unstable as a result of even minor changes in their environment. An SOC calving glacier at the critical point will display so large fluctuations in calving rate that it will render the concept 'average calving rate' more or less useless. I.e. 'average calving rate' will depend on measurement time and always have fluctuaions in the range of 100% more or less independent of the averaging time.

  • 6.
    Vallot, Dorothée
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Modelling calving and sliding of Svalbard outlet glaciers: Spatio-temporal changes and interactions2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Future sea level rise associated to global warming is one of the greatest societal and environmental challenges of tomorrow. A large part of the contribution comes from glaciers and ice sheets discharging ice and meltwater into the ocean and the recent worldwide increase is worrying. Future predictions of sea level rise try to encompass the complex processes of ice dynamics through glacier modelling but there are still large uncertainties due to the lack of observations or too coarse parameterisation, particularly for processes occurring at the glacier interfaces with the bed (sliding) and with the ocean (calving). This thesis focuses on modelling these processes from two marine-terminating glaciers in Svalbard, Kronebreen and Tunabreen. By inverting three years of high temporal resolution time-series of surface velocities on Kronebreen, basal properties are retrieved with the ice flow model Elmer/Ice in Paper I. Results suggest that surface melt during the summer greatly influences the dynamics of the following season and that sliding laws for such glaciers should be adapted to local and global processes changing in space and time. The subglacial drainage system, fed by the surface melt, is modelled in Paper II during two melting seasons. Results show different configurations of efficient and inefficient drainage systems between years and the importance of using a sliding law dependent on spatio-temporal changes in effective pressure. The interaction with the ocean is incorporated in Paper III by combining a series of models, including an ice flow model, a plume model and a particle model for discrete calving and compares the output with observations. Results show the importance of glacier geometry, sliding and undercutting on calving rate and location. However, more observations and analytic methods are needed. Time-lapse imagery placed in front of Tunabreen have been deployed and a method of automatic detection for iceberg calving is presented in Paper IV. Results show the influence of the rising plume in calving and the front destabilisation of the local neighbourhood.

    Delarbeten
    1. Basal dynamics of Kronebreen, a fast-flowing tidewater glacier in Svalbard: non-local spatio-temporal response to water input
    Öppna denna publikation i ny flik eller fönster >>Basal dynamics of Kronebreen, a fast-flowing tidewater glacier in Svalbard: non-local spatio-temporal response to water input
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    2017 (Engelska)Ingår i: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652, Vol. 63, nr 242, s. 1012-1024Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    We evaluate the variability in basal friction for Kronebreen, Svalbard, a fast-flowing tidewater glacier. We invert 3 years (2013–15) of surface velocities at high temporal resolution (generally 11 days), to estimate the changing basal properties of the glacier. Our results suggest that sliding behaviour of Kronebreen within a year is primarily influenced by changes in water input patterns during the meltwater season and basal friction is highly variable from a year to another. At present, models usually employ parameterisations to encompass the complex physics of glacier sliding by mathematically simulate their net effect. For such ice masses with strong seasonal variations of surface melt, the spatio-temporal patterns of basal friction imply that it is neither possible nor appropriate to use a parameterisation for bed friction that is fixed in space and/or time, at least in a timescale of a few years. Basal sliding may not only be governed by local processes such as basal topography or summer melt, but also be mediated by factors that vary over a larger distance and over a longer time period such as subglacial hydrology organisation, ice-thickness changes or calving front geometry.

    Nyckelord
    Arctic glaciology, glacier modelling, ice dynamics, ice velocity, subglacial processes
    Nationell ämneskategori
    Naturgeografi
    Forskningsämne
    Geovetenskap med inriktning mot naturgeografi
    Identifikatorer
    urn:nbn:se:uu:diva-334293 (URN)10.1017/jog.2017.69 (DOI)000418852500007 ()
    Tillgänglig från: 2017-11-22 Skapad: 2017-11-22 Senast uppdaterad: 2018-02-05Bibliografiskt granskad
    2. Modelled subglacial hydrology and basal sliding at Kronebreen, a tidewater glacier in Svalbard
    Öppna denna publikation i ny flik eller fönster >>Modelled subglacial hydrology and basal sliding at Kronebreen, a tidewater glacier in Svalbard
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    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Nationell ämneskategori
    Multidisciplinär geovetenskap
    Forskningsämne
    Geovetenskap med inriktning mot naturgeografi
    Identifikatorer
    urn:nbn:se:uu:diva-334778 (URN)
    Tillgänglig från: 2017-11-27 Skapad: 2017-11-27 Senast uppdaterad: 2017-11-27
    3. Effects of undercutting and sliding on calving: a global approach applied to Kronebreen, Svalbard
    Öppna denna publikation i ny flik eller fönster >>Effects of undercutting and sliding on calving: a global approach applied to Kronebreen, Svalbard
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    2018 (Engelska)Ingår i: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 12, s. 609-625Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In this paper, we study the effects of basal friction, sub-aqueous undercutting and glacier geometry on the calving process by combining six different models in an offline-coupled workflow: a continuum-mechanical ice flow model (Elmer/Ice), a climatic mass balance model, a simple sub-glacial hydrology model, a plume model, an undercutting model and a discrete particle model to investigate fracture dynamics (Helsinki Discrete Element Model, HiDEM). We demonstrate the feasibility of reproducing the observed calving retreat at the front of Kronebreen, a tidewater glacier in Svalbard, during a melt season by using the output from the first five models as input to HiDEM. Basal sliding and glacier motion are addressed using Elmer/Ice, while calving is modelled by HiDEM. A hydrology model calculates subglacial drainage paths and indicates two main outlets with different discharges. Depending on the discharge, the plume model computes frontal melt rates, which are iteratively projected to the actual front of the glacier at subglacial discharge locations. This produces undercutting of different sizes, as melt is concentrated close to the surface for high discharge and is more diffuse for low discharge. By testing different configurations, we show that undercutting plays a key role in glacier retreat and is necessary to reproduce observed retreat in the vicinity of the discharge locations during the melting season. Calving rates are also influenced by basal friction, through its effects on near-terminus strain rates and ice velocity.

    Nationell ämneskategori
    Naturvetenskap Multidisciplinär geovetenskap
    Forskningsämne
    Geovetenskap med inriktning mot naturgeografi
    Identifikatorer
    urn:nbn:se:uu:diva-334771 (URN)10.5194/tc-12-609-2018 (DOI)000425729800002 ()
    Tillgänglig från: 2017-11-27 Skapad: 2017-11-27 Senast uppdaterad: 2018-05-02Bibliografiskt granskad
    4. Automatic detection of calving events from time-lapse imagery at Tunabreen, Svalbard
    Öppna denna publikation i ny flik eller fönster >>Automatic detection of calving events from time-lapse imagery at Tunabreen, Svalbard
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    2019 (Engelska)Ingår i: Geoscientific Instrumentation, Methods and Data Systems, ISSN 2193-0856, E-ISSN 2193-0864, Vol. 8, s. 113-127Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Calving is an important process in glacier systems terminating in the ocean, and more observations are needed to improve our understanding of the undergoing processes and parameterize calving in larger-scale models. Time-lapse cameras are good tools for monitoring calving fronts of glaciers and they have been used widely where conditions are favourable. However, automatic image analysis to detect and calculate the size of calving events has not been developed so far. Here, we present a method that fills this gap using image analysis tools. First, the calving front is segmented. Second, changes between two images are detected and a mask is produced to delimit the calving event. Third, we calculate the area given the front and camera positions as well as camera characteristics. To illustrate our method, we analyse two image time series from two cameras placed at different locations in 2014 and 2015 and compare the automatic detection results to a manual detection. We find a good match when the weather is favourable, but the method fails with dense fog or high illumination conditions. Furthermore, results show that calving events are more likely to occur (i) close to where subglacial meltwater plumes have been observed to rise at the front and (ii) close to one another.

    Nationell ämneskategori
    Multidisciplinär geovetenskap
    Forskningsämne
    Geovetenskap med inriktning mot naturgeografi
    Identifikatorer
    urn:nbn:se:uu:diva-334776 (URN)10.5194/gi-8-113-2019 (DOI)000462819000001 ()
    Forskningsfinansiär
    Wallenbergstiftelserna
    Tillgänglig från: 2017-11-27 Skapad: 2017-11-27 Senast uppdaterad: 2019-04-12Bibliografiskt granskad
  • 7.
    Vallot, Dorothée
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Pettersson, Rickard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Luckman, Adrien
    Benn, Douglas I.
    Zwinger, Thomas
    van Pelt, Ward J. J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Kohler, Jack
    Schäfer, Martina
    Claremar, Björn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Hulton, Nick R. J.
    Basal dynamics of Kronebreen, a fast-flowing tidewater glacier in Svalbard: non-local spatio-temporal response to water input2017Ingår i: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652, Vol. 63, nr 242, s. 1012-1024Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We evaluate the variability in basal friction for Kronebreen, Svalbard, a fast-flowing tidewater glacier. We invert 3 years (2013–15) of surface velocities at high temporal resolution (generally 11 days), to estimate the changing basal properties of the glacier. Our results suggest that sliding behaviour of Kronebreen within a year is primarily influenced by changes in water input patterns during the meltwater season and basal friction is highly variable from a year to another. At present, models usually employ parameterisations to encompass the complex physics of glacier sliding by mathematically simulate their net effect. For such ice masses with strong seasonal variations of surface melt, the spatio-temporal patterns of basal friction imply that it is neither possible nor appropriate to use a parameterisation for bed friction that is fixed in space and/or time, at least in a timescale of a few years. Basal sliding may not only be governed by local processes such as basal topography or summer melt, but also be mediated by factors that vary over a larger distance and over a longer time period such as subglacial hydrology organisation, ice-thickness changes or calving front geometry.

  • 8.
    Åström, Jan A.
    et al.
    CSC–IT Centre for Science.
    Vallot, Dorothée
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Schäfer, Martina
    Finnish Meteorological Institute.
    Welty, Ethan Z.
    Institute of Arctic and Alpine Research, University of Colorado.
    O'Neel, Shad
    Institute of Arctic and Alpine Research, University of Colorado.
    Bartholomaus, Timothy
    University of Texas Institute for Geophysics.
    Liu, Yan
    State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Global Change and Earth System Science, Beijing Normal University.
    Riikilä, Timothy
    Department of Physics and Nanoscience Center, University of Jyväskylä.
    Zwinger, Thomas
    CSC–IT Centre for Science.
    Timonen, Jussi
    Department of Physics and Nanoscience Center, University of Jyväskylä.
    Moore, John
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära. State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Global Change and Earth System Science, Beijing Normal University.
    Termini of calving glaciers as self-organized critical systems2014Ingår i: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 7, nr 12, s. 874-878Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Over the next century, one of the largest contributions to sea level rise will come from ice sheets and glaciers calving ice into the ocean1. Factors controlling the rapid and nonlinear variations in calving fluxes are poorly understood, and therefore difficult to include in prognostic climate-forced land-ice models. Here we analyse globally distributed calving data sets from Svalbard, Alaska (USA), Greenland and Antarctica in combination with simulations from a first-principles, particle-based numerical calving model to investigate the size and inter-event time of calving events. We find that calving events triggered by the brittle fracture of glacier ice are governed by the same power-law distributions as avalanches in the canonical Abelian sandpile model2. This similarity suggests that calving termini behave as self-organized critical systems that readily flip between states of sub-critical advance and super-critical retreat in response to changes in climate and geometric conditions. Observations of sudden ice-shelf collapse and tidewater glacier retreat in response to gradual warming of their environment3 are consistent with a system fluctuating around its critical point in response to changing external forcing. We propose that self-organized criticality provides a yet unexplored framework for investigations into calving and projections of sea level rise.

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