Articles | Volume 16, issue 7
https://doi.org/10.5194/tc-16-2725-2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/tc-16-2725-2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| Highlight paper
| 
13 Jul 2022
Research article | Highlight paper |
| 13 Jul 2022
| 13 Jul 2022
A probabilistic framework for quantifying the role of anthropogenic climate change in marine-terminating glacier retreats
John Erich Christian
CORRESPONDING AUTHOR
Institute for Geophysics, University of Texas at Austin, Austin, Texas 78758, USA
School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia 30318, USA
Alexander A. Robel
School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia 30318, USA
Ginny Catania
Institute for Geophysics, University of Texas at Austin, Austin, Texas 78758, USA
Related authors
Samuel T. Kodama, Tamara Pico, Alexander A. Robel, John Erich Christian, Natalya Gomez, Casey Vigilia, Evelyn Powell, Jessica Gagliardi, Slawek Tulaczyk, and Terrence Blackburn
EGUsphere, https://doi.org/10.5194/egusphere-2024-3465, https://doi.org/10.5194/egusphere-2024-3465, 2024
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Glacial isostatic adjustment (gravitational, rotational, and solid Earth responses to changes in ice load) slows the retreat of marine-terminating ice sheets. However, the models that reveal this interaction use coarse resolution bathymetry, missing potential impacts of small length scale topographic highs. We pair a high-resolution bathymetry model with a simple model of grounding line stability to predict zones of potential grounding line stability in the Ross Sea over the past deglaciation.
Daniel R. Otto, Gerard H. Roe, and John Erich Christian
EGUsphere, https://doi.org/10.5194/egusphere-2024-3309, https://doi.org/10.5194/egusphere-2024-3309, 2024
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Glaciers respond slowly to changes in climate, meaning that they are not yet adjusted to the present-day level of warming. Using a simple model, we find that the median Alaskan glacier has undergone only 27 % of the retreat necessary to equilibrate to the current climate. Our findings hold even when accounting for large uncertainties, suggesting that substantial retreat is inevitable even if future warming slows or stabilizes.
Gerard H. Roe, John Erich Christian, and Ben Marzeion
The Cryosphere, 15, 1889–1905, https://doi.org/10.5194/tc-15-1889-2021, https://doi.org/10.5194/tc-15-1889-2021, 2021
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The worldwide retreat of mountain glaciers and consequent loss of ice mass is one of the most obvious signs of a changing climate and has significant implications for the hydrology and natural hazards in mountain landscapes. Consistent with our understanding of the human role in temperature change, we demonstrate that the central estimate of the size of the human-caused mass loss is essentially 100 % of the observed loss. This assessment resolves some important inconsistencies in the literature.
John Erich Christian, Alexander A. Robel, Cristian Proistosescu, Gerard Roe, Michelle Koutnik, and Knut Christianson
The Cryosphere, 14, 2515–2535, https://doi.org/10.5194/tc-14-2515-2020, https://doi.org/10.5194/tc-14-2515-2020, 2020
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Short summary
We use simple, physics-based models to compare how marine-terminating glaciers respond to changes at their marine margin vs. inland surface melt. Initial glacier retreat is more rapid for ocean changes than for inland changes, but in both cases, glaciers will continue responding for millennia. We analyze several implications of these differing pathways of change. In particular, natural ocean variability must be better understood to correctly identify the anthropogenic role in glacier retreat.
Samuel T. Kodama, Tamara Pico, Alexander A. Robel, John Erich Christian, Natalya Gomez, Casey Vigilia, Evelyn Powell, Jessica Gagliardi, Slawek Tulaczyk, and Terrence Blackburn
EGUsphere, https://doi.org/10.5194/egusphere-2024-3465, https://doi.org/10.5194/egusphere-2024-3465, 2024
Short summary
Short summary
Glacial isostatic adjustment (gravitational, rotational, and solid Earth responses to changes in ice load) slows the retreat of marine-terminating ice sheets. However, the models that reveal this interaction use coarse resolution bathymetry, missing potential impacts of small length scale topographic highs. We pair a high-resolution bathymetry model with a simple model of grounding line stability to predict zones of potential grounding line stability in the Ross Sea over the past deglaciation.
Daniel R. Otto, Gerard H. Roe, and John Erich Christian
EGUsphere, https://doi.org/10.5194/egusphere-2024-3309, https://doi.org/10.5194/egusphere-2024-3309, 2024
Short summary
Short summary
Glaciers respond slowly to changes in climate, meaning that they are not yet adjusted to the present-day level of warming. Using a simple model, we find that the median Alaskan glacier has undergone only 27 % of the retreat necessary to equilibrate to the current climate. Our findings hold even when accounting for large uncertainties, suggesting that substantial retreat is inevitable even if future warming slows or stabilizes.
Nicole Abib, David A. Sutherland, Rachel Peterson, Ginny Catania, Jonathan D. Nash, Emily L. Shroyer, Leigh A. Stearns, and Timothy C. Bartholomaus
The Cryosphere, 18, 4817–4829, https://doi.org/10.5194/tc-18-4817-2024, https://doi.org/10.5194/tc-18-4817-2024, 2024
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The melting of ice mélange, or dense packs of icebergs and sea ice in glacial fjords, can influence the water column by releasing cold fresh water deep under the ocean surface. However, direct observations of this process have remained elusive. We use measurements of ocean temperature, salinity, and velocity bookending an episodic ice mélange event to show that this meltwater input changes the density profile of a glacial fjord and has implications for understanding tidewater glacier change.
Meghana Ranganathan, Alexander A. Robel, Alexander Huth, and Ravindra Duddu
EGUsphere, https://doi.org/10.5194/egusphere-2024-1850, https://doi.org/10.5194/egusphere-2024-1850, 2024
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The rate of ice loss from ice sheets is controlled by the flow of ice from the center of the ice sheet and internal fracturing of the ice. These are coupled – fractures can reduce the viscosity of ice and enable more rapid flow, and rapid flow can cause fracturing of ice. We present a simplified way of representing damage that is applicable to long-timescale flow estimates. Using this model, we find that including fracturing into an ice sheet simulation can increase the loss of ice by 13–29 %.
Madeline S. Mamer, Alexander A. Robel, Chris C. K. Lai, Earle Wilson, and Peter Washam
EGUsphere, https://doi.org/10.5194/egusphere-2024-1970, https://doi.org/10.5194/egusphere-2024-1970, 2024
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In this work, we simulate estuary-like seawater intrusions into the subglacial hydrologic system for marine outlet glaciers. We find the largest controls on seawater intrusion are the subglacial space geometry and meltwater discharge velocity. Further, we highlight the importance of extending ocean-forced ice loss to grounded portions of the ice sheet, which is currently not represented in models coupling ice sheets to ocean dynamics.
Ziad Rashed, Alexander Robel, and Helene Seroussi
EGUsphere, https://doi.org/10.5194/egusphere-2024-1435, https://doi.org/10.5194/egusphere-2024-1435, 2024
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Sermeq Kujalleq, Greenland's largest glacier, has significantly retreated since the late 1990s in response to warming ocean temperatures. Using a large ensemble approach, our simulations show that the retreat is mainly initiated by the arrival of warm water but sustained and accelerated by the glacier's position over deeper bed troughs and vigorous calving. We highlight the need for models of ice mélange to project glacier behavior under rapid calving regimes.
Alexander A. Robel, Vincent Verjans, and Aminat A. Ambelorun
The Cryosphere, 18, 2613–2623, https://doi.org/10.5194/tc-18-2613-2024, https://doi.org/10.5194/tc-18-2613-2024, 2024
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The average size of many glaciers and ice sheets changes when noise is added to the system. The reasons for this drift in glacier state is intrinsic to the dynamics of how ice flows and the bumpiness of the Earth's surface. We argue that not including noise in projections of ice sheet evolution over coming decades and centuries is a pervasive source of bias in these computer models, and so realistic variability in glacier and climate processes must be included in models.
Jason M. Amundson, Alexander A. Robel, Justin C. Burton, and Kavinda Nissanka
EGUsphere, https://doi.org/10.5194/egusphere-2024-297, https://doi.org/10.5194/egusphere-2024-297, 2024
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Some fjords contain dense packs of icebergs referred to as ice mélange. Ice mélange can affect the stability of marine-terminating glaciers by resisting the calving of new icebergs and by modifying fjord currents and water properties. We have developed the first numerical model of ice mélange that captures its granular nature and that is suitable for long time-scale simulations. The model is capable of explaining why some glaciers are more strongly influenced by ice mélange than others.
Lizz Ultee, Alexander A. Robel, and Stefano Castruccio
Geosci. Model Dev., 17, 1041–1057, https://doi.org/10.5194/gmd-17-1041-2024, https://doi.org/10.5194/gmd-17-1041-2024, 2024
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The surface mass balance (SMB) of an ice sheet describes the net gain or loss of mass from ice sheets (such as those in Greenland and Antarctica) through interaction with the atmosphere. We developed a statistical method to generate a wide range of SMB fields that reflect the best understanding of SMB processes. Efficiently sampling the variability of SMB will help us understand sources of uncertainty in ice sheet model projections.
Enze Zhang, Ginny Catania, and Daniel T. Trugman
The Cryosphere, 17, 3485–3503, https://doi.org/10.5194/tc-17-3485-2023, https://doi.org/10.5194/tc-17-3485-2023, 2023
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Glacier termini are essential for studying why glaciers retreat, but they need to be mapped automatically due to the volume of satellite images. Existing automated mapping methods have been limited due to limited automation, lack of quality control, and inadequacy in highly diverse terminus environments. We design a fully automated, deep-learning-based method to produce termini with quality control. We produced 278 239 termini in Greenland and provided a way to deliver new termini regularly.
Vincent Verjans, Alexander A. Robel, Helene Seroussi, Lizz Ultee, and Andrew F. Thompson
Geosci. Model Dev., 15, 8269–8293, https://doi.org/10.5194/gmd-15-8269-2022, https://doi.org/10.5194/gmd-15-8269-2022, 2022
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We describe the development of the first large-scale ice sheet model that accounts for stochasticity in a range of processes. Stochasticity allows the impacts of inherently uncertain processes on ice sheets to be represented. This includes climatic uncertainty, as the climate is inherently chaotic. Furthermore, stochastic capabilities also encompass poorly constrained glaciological processes that display strong variability at fine spatiotemporal scales. We present the model and test experiments.
Evan Carnahan, Ginny Catania, and Timothy C. Bartholomaus
The Cryosphere, 16, 4305–4317, https://doi.org/10.5194/tc-16-4305-2022, https://doi.org/10.5194/tc-16-4305-2022, 2022
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The Greenland Ice Sheet primarily loses mass through increased ice discharge. We find changes in discharge from outlet glaciers are initiated by ocean warming, which causes a change in the balance of forces resisting gravity and leads to acceleration. Vulnerable conditions for sustained retreat and acceleration are predetermined by the glacier-fjord geometry and exist around Greenland, suggesting increases in ice discharge may be sustained into the future despite a pause in ocean warming.
Sophie Goliber, Taryn Black, Ginny Catania, James M. Lea, Helene Olsen, Daniel Cheng, Suzanne Bevan, Anders Bjørk, Charlie Bunce, Stephen Brough, J. Rachel Carr, Tom Cowton, Alex Gardner, Dominik Fahrner, Emily Hill, Ian Joughin, Niels J. Korsgaard, Adrian Luckman, Twila Moon, Tavi Murray, Andrew Sole, Michael Wood, and Enze Zhang
The Cryosphere, 16, 3215–3233, https://doi.org/10.5194/tc-16-3215-2022, https://doi.org/10.5194/tc-16-3215-2022, 2022
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Terminus traces have been used to understand how Greenland's glaciers have changed over time; however, manual digitization is time-intensive, and a lack of coordination leads to duplication of efforts. We have compiled a dataset of over 39 000 terminus traces for 278 glaciers for scientific and machine learning applications. We also provide an overview of an updated version of the Google Earth Engine Digitization Tool (GEEDiT), which has been developed specifically for the Greenland Ice Sheet.
Alexander A. Robel, Earle Wilson, and Helene Seroussi
The Cryosphere, 16, 451–469, https://doi.org/10.5194/tc-16-451-2022, https://doi.org/10.5194/tc-16-451-2022, 2022
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Warm seawater may intrude as a thin layer below glaciers in contact with the ocean. Mathematical theory predicts that this intrusion may extend over distances of kilometers under realistic conditions. Computer models demonstrate that if this warm seawater causes melting of a glacier bottom, it can cause rates of glacier ice loss and sea level rise to be up to 2 times faster in response to potential future ocean warming.
Gerard H. Roe, John Erich Christian, and Ben Marzeion
The Cryosphere, 15, 1889–1905, https://doi.org/10.5194/tc-15-1889-2021, https://doi.org/10.5194/tc-15-1889-2021, 2021
Short summary
Short summary
The worldwide retreat of mountain glaciers and consequent loss of ice mass is one of the most obvious signs of a changing climate and has significant implications for the hydrology and natural hazards in mountain landscapes. Consistent with our understanding of the human role in temperature change, we demonstrate that the central estimate of the size of the human-caused mass loss is essentially 100 % of the observed loss. This assessment resolves some important inconsistencies in the literature.
John Erich Christian, Alexander A. Robel, Cristian Proistosescu, Gerard Roe, Michelle Koutnik, and Knut Christianson
The Cryosphere, 14, 2515–2535, https://doi.org/10.5194/tc-14-2515-2020, https://doi.org/10.5194/tc-14-2515-2020, 2020
Short summary
Short summary
We use simple, physics-based models to compare how marine-terminating glaciers respond to changes at their marine margin vs. inland surface melt. Initial glacier retreat is more rapid for ocean changes than for inland changes, but in both cases, glaciers will continue responding for millennia. We analyze several implications of these differing pathways of change. In particular, natural ocean variability must be better understood to correctly identify the anthropogenic role in glacier retreat.
Alexander A. Robel, Christian Schoof, and Eli Tziperman
The Cryosphere, 10, 1883–1896, https://doi.org/10.5194/tc-10-1883-2016, https://doi.org/10.5194/tc-10-1883-2016, 2016
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Portions of the Antarctic Ice Sheet edge that rest on upward-sloping beds have the potential to collapse irreversibly and raise global sea level. Using a numerical model, we show that changes in the slipperiness of sediments beneath fast-flowing ice streams can cause them to persist on upward-sloping beds for hundreds to thousands of years before reversing direction. This type of behavior is important to consider as a possibility when interpreting observations of ongoing ice sheet change.
Related subject area
Discipline: Ice sheets | Subject: Climate Interactions
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Tobias Zolles and Andreas Born
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The Greenland ice sheet largely depends on the climate state. The uncertainties associated with the year-to-year variability have only a marginal impact on our simulated surface mass budget; this increases our confidence in projections and reconstructions. Basing the simulations on proxies, e.g., temperature, results in overestimates of the surface mass balance, as climatologies lead to small amounts of snowfall every day. This can be reduced by including sub-monthly precipitation variability.
Julien Beaumet, Michel Déqué, Gerhard Krinner, Cécile Agosta, Antoinette Alias, and Vincent Favier
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We use empirical run-time bias correction (also called flux correction) to correct the systematic errors of the ARPEGE atmospheric climate model. When applying the method to future climate projections, we found a lesser poleward shift and an intensification of the maximum of westerly winds present in the southern high latitudes. This yields a significant additional warming of +0.6 to +0.9 K of the Antarctic Ice Sheet with respect to non-corrected control projections using the RCP8.5 scenario.
Alice Barthel, Cécile Agosta, Christopher M. Little, Tore Hattermann, Nicolas C. Jourdain, Heiko Goelzer, Sophie Nowicki, Helene Seroussi, Fiammetta Straneo, and Thomas J. Bracegirdle
The Cryosphere, 14, 855–879, https://doi.org/10.5194/tc-14-855-2020, https://doi.org/10.5194/tc-14-855-2020, 2020
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We compare existing coupled climate models to select a total of six models to provide forcing to the Greenland and Antarctic ice sheet simulations of the Ice Sheet Model Intercomparison Project (ISMIP6). We select models based on (i) their representation of current climate near Antarctica and Greenland relative to observations and (ii) their ability to sample a diversity of projected atmosphere and ocean changes over the 21st century.
Peter J. Irvine, David W. Keith, and John Moore
The Cryosphere, 12, 2501–2513, https://doi.org/10.5194/tc-12-2501-2018, https://doi.org/10.5194/tc-12-2501-2018, 2018
Short summary
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Stratospheric aerosol geoengineering, a form of solar geoengineering, is a proposal to add a reflective layer of aerosol to the upper atmosphere. This would reduce sea level rise by slowing the melting of ice on land and the thermal expansion of the oceans. However, there is considerable uncertainty about its potential efficacy. This article highlights key uncertainties in the sea level response to solar geoengineering and recommends approaches to address these in future work.
Marcus Lofverstrom and Johan Liakka
The Cryosphere, 12, 1499–1510, https://doi.org/10.5194/tc-12-1499-2018, https://doi.org/10.5194/tc-12-1499-2018, 2018
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Co-editor-in-chief
This paper provides a complete and novel perspective on how to attribute changes in glaciers to anthropogenic warming. It is accessible, well written with clear figures, and will certainly be of interest to the wider community.
This paper provides a complete and novel perspective on how to attribute changes in glaciers to...
Short summary
Marine-terminating glaciers have recently retreated dramatically, but the role of anthropogenic forcing remains uncertain. We use idealized model simulations to develop a framework for assessing the probability of rapid retreat in the context of natural climate variability. Our analyses show that century-scale anthropogenic trends can substantially increase the probability of retreats. This provides a roadmap for future work to formally assess the role of human activity in recent glacier change.
Marine-terminating glaciers have recently retreated dramatically, but the role of anthropogenic...
