Publications by category
Journal articles
Burls NJ, Bradshaw C, De Boer AM, Herold N, Huber M, Pound M, Donnadieu Y, Farnsworth A, Frigola Boix A, Gasson EGW, et al (In Press). Simulating Miocene warmth: insights from an opportunistic Multi-Model ensemble (MioMIP1).
Marschalek JW, Zurli L, Talarico F, van de Flierdt T, Vermeesch P, Carter A, Beny F, Bout-Roumazeilles V, Sangiorgi F, Hemming SR, et al (2021). A large West Antarctic Ice Sheet explains early Neogene sea-level amplitude.
Nature,
600(7889), 450-455.
Abstract:
A large West Antarctic Ice Sheet explains early Neogene sea-level amplitude.
Early to Middle Miocene sea-level oscillations of approximately 40-60 m estimated from far-field records1-3 are interpreted to reflect the loss of virtually all East Antarctic ice during peak warmth2. This contrasts with ice-sheet model experiments suggesting most terrestrial ice in East Antarctica was retained even during the warmest intervals of the Middle Miocene4,5. Data and model outputs can be reconciled if a large West Antarctic Ice Sheet (WAIS) existed and expanded across most of the outer continental shelf during the Early Miocene, accounting for maximum ice-sheet volumes. Here we provide the earliest geological evidence proving large WAIS expansions occurred during the Early Miocene (~17.72-17.40 Ma). Geochemical and petrographic data show glacimarine sediments recovered at International Ocean Discovery Program (IODP) Site U1521 in the central Ross Sea derive from West Antarctica, requiring the presence of a WAIS covering most of the Ross Sea continental shelf. Seismic, lithological and palynological data reveal the intermittent proximity of grounded ice to Site U1521. The erosion rate calculated from this sediment package greatly exceeds the long-term mean, implying rapid erosion of West Antarctica. This interval therefore captures a key step in the genesis of a marine-based WAIS and a tipping point in Antarctic ice-sheet evolution.
Abstract.
Author URL.
Halberstadt ARW, Chorley H, Levy RH, Naish T, DeConto RM, Gasson E, Kowalewski DE (2021). CO2 and tectonic controls on Antarctic climate and ice-sheet evolution in the mid-Miocene. Earth and Planetary Science Letters, 564, 116908-116908.
Ashley KE, McKay R, Etourneau J, Jimenez-Espejo FJ, Condron A, Albot A, Crosta X, Riesselman C, Seki O, Massé G, et al (2021). Mid-Holocene Antarctic sea-ice increase driven by marine ice sheet retreat.
Climate of the Past,
17(1), 1-19.
Abstract:
Mid-Holocene Antarctic sea-ice increase driven by marine ice sheet retreat
Abstract. Over recent decades Antarctic sea-ice extent has increased, alongside
widespread ice shelf thinning and freshening of waters along the Antarctic
margin. In contrast, Earth system models generally simulate a decrease in
sea ice. Circulation of water masses beneath large-cavity ice shelves is not
included in current Earth System models and may be a driver of this
phenomena. We examine a Holocene sediment core off East Antarctica that
records the Neoglacial transition, the last major baseline shift of
Antarctic sea ice, and part of a late-Holocene global cooling trend. We
provide a multi-proxy record of Holocene glacial meltwater input, sediment
transport, and sea-ice variability. Our record, supported by high-resolution
ocean modelling, shows that a rapid Antarctic sea-ice increase during the
mid-Holocene (∼ 4.5 ka) occurred against a backdrop of
increasing glacial meltwater input and gradual climate warming. We suggest
that mid-Holocene ice shelf cavity expansion led to cooling of surface
waters and sea-ice growth that slowed basal ice shelf melting.
Incorporating this feedback mechanism into global climate models will be
important for future projections of Antarctic changes.
.
Abstract.
Burls NJ, Bradshaw CD, De Boer AM, Herold N, Huber M, Pound M, Donnadieu Y, Farnsworth A, Frigola A, Gasson E, et al (2021). Simulating Miocene Warmth: Insights from an Opportunistic Multi-Model Ensemble (MioMIP1).
Paleoceanography and Paleoclimatology,
36(5).
Abstract:
Simulating Miocene Warmth: Insights from an Opportunistic Multi-Model Ensemble (MioMIP1)
The Miocene epoch, spanning 23.03–5.33 Ma, was a dynamic climate of sustained, polar amplified warmth. Miocene atmospheric CO2 concentrations are typically reconstructed between 300 and 600 ppm and were potentially higher during the Miocene Climatic Optimum (16.75–14.5 Ma). With surface temperature reconstructions pointing to substantial midlatitude and polar warmth, it is unclear what processes maintained the much weaker-than-modern equator-to-pole temperature difference. Here, we synthesize several Miocene climate modeling efforts together with available terrestrial and ocean surface temperature reconstructions. We evaluate the range of model-data agreement, highlight robust mechanisms operating across Miocene modeling efforts and regions where differences across experiments result in a large spread in warming responses. Prescribed CO2 is the primary factor controlling global warming across the ensemble. On average, elements other than CO2, such as Miocene paleogeography and ice sheets, raise global mean temperature by ∼2°C, with the spread in warming under a given CO2 concentration (due to a combination of the spread in imposed boundary conditions and climate feedback strengths) equivalent to ∼1.2 times a CO2 doubling. This study uses an ensemble of opportunity: models, boundary conditions, and reference data sets represent the state-of-art for the Miocene, but are inhomogeneous and not ideal for a formal intermodel comparison effort. Acknowledging this caveat, this study is nevertheless the first Miocene multi-model, multi-proxy comparison attempted so far. This study serves to take stock of the current progress toward simulating Miocene warmth while isolating remaining challenges that may be well served by community-led efforts to coordinate modeling and data activities within a common analytical framework.
Abstract.
Full text.
Steinthorsdottir M, Coxall HK, de Boer AM, Huber M, Barbolini N, Bradshaw CD, Burls NJ, Feakins SJ, Gasson E, Henderiks J, et al (2021). The Miocene: the Future of the Past.
Paleoceanography and Paleoclimatology,
36(4).
Full text.
DeConto RM, Pollard D, Alley RB, Velicogna I, Gasson E, Gomez N, Sadai S, Condron A, Gilford DM, Ashe EL, et al (2021). The Paris Climate Agreement and future sea-level rise from Antarctica.
Nature,
593(7857), 83-89.
Full text.
Paxman GJG, Gasson EGW, Jamieson SSR, Bentley MJ, Ferraccioli F (2020). Long‐Term Increase in Antarctic Ice Sheet Vulnerability Driven by Bed Topography Evolution. Geophysical Research Letters, 47(20).
Gasson E, Keisling B (2020). The Antarctic Ice Sheet: a Paleoclimate Modeling Perspective. Oceanography, 33(2).
Levy RH, Meyers SR, Naish TR, Golledge NR, McKay RM, Crampton JS, DeConto RM, De Santis L, Florindo F, Gasson EGW, et al (2019). Antarctic ice-sheet sensitivity to obliquity forcing enhanced through ocean connections. Nature Geoscience, 12(2), 132-137.
Ely JC, Clark CD, Hindmarsh RCA, Hughes ALC, Greenwood SL, Bradley SL, Gasson E, Gregoire L, Gandy N, Stokes CR, et al (2019). Recent progress on combining geomorphological and geochronological data with ice sheet modelling, demonstrated using the last British–Irish Ice Sheet. Journal of Quaternary Science, 36(5), 946-960.
Paxman GJG, Jamieson SSR, Ferraccioli F, Bentley MJ, Ross N, Armadillo E, Gasson EGW, Leitchenkov G, DeConto RM (2018). Bedrock Erosion Surfaces Record Former East Antarctic Ice Sheet Extent. Geophysical Research Letters, 45(9), 4114-4123.
Gasson EGW, DeConto RM, Pollard D, Clark CD (2018). Numerical simulations of a kilometre-thick Arctic ice shelf consistent with ice grounding observations. Nature Communications, 9(1).
Colleoni F, De Santis L, Montoli E, Olivo E, Sorlien CC, Bart PJ, Gasson EGW, Bergamasco A, Sauli C, Wardell N, et al (2018). Past continental shelf evolution increased Antarctic ice sheet sensitivity to climatic conditions. Scientific Reports, 8(1).
Golledge NR, Thomas ZA, Levy RH, Gasson EGW, Naish TR, McKay RM, Kowalewski DE, Fogwill CJ (2017). Antarctic climate and ice-sheet configuration during the early Pliocene interglacial at 4.23 Ma.
Climate of the Past,
13(7), 959-975.
Abstract:
Antarctic climate and ice-sheet configuration during the early Pliocene interglacial at 4.23 Ma
Abstract. The geometry of Antarctic ice sheets during warm periods of the geological past is difficult to determine from geological evidence, but is important to know because such reconstructions enable a more complete understanding of how the ice-sheet system responds to changes in climate. Here we investigate how Antarctica evolved under orbital and greenhouse gas conditions representative of an interglacial in the early Pliocene at 4.23 Ma, when Southern Hemisphere insolation reached a maximum. Using offline-coupled climate and ice-sheet models, together with a new synthesis of high-latitude palaeoenvironmental proxy data to define a likely climate envelope, we simulate a range of ice-sheet geometries and calculate their likely contribution to sea level. In addition, we use these simulations to investigate the processes by which the West and East Antarctic ice sheets respond to environmental forcings and the timescales over which these behaviours manifest. We conclude that the Antarctic ice sheet contributed 8.6 ± 2.8 m to global sea level at this time, under an atmospheric CO2 concentration identical to present (400 ppm). Warmer-than-present ocean temperatures led to the collapse of West Antarctica over centuries, whereas higher air temperatures initiated surface melting in parts of East Antarctica that over one to two millennia led to lowering of the ice-sheet surface, flotation of grounded margins in some areas, and retreat of the ice sheet into the Wilkes Subglacial Basin. The results show that regional variations in climate, ice-sheet geometry, and topography produce long-term sea-level contributions that are non-linear with respect to the applied forcings, and which under certain conditions exhibit threshold behaviour associated with behavioural tipping points.
.
Abstract.
Lunt DJ, Huber M, Anagnostou E, Baatsen MLJ, Caballero R, DeConto R, Dijkstra HA, Donnadieu Y, Evans D, Feng R, et al (2017). The DeepMIP contribution to PMIP4: Experimental design for model simulations of the EECO, PETM, and pre-PETM (version 1.0).
Geoscientific Model Development,
10(2), 889-901.
Abstract:
The DeepMIP contribution to PMIP4: Experimental design for model simulations of the EECO, PETM, and pre-PETM (version 1.0)
Past warm periods provide an opportunity to evaluate climate models under extreme forcing scenarios, in particular high (> 800ppmv) atmospheric CO2 concentrations. Although a post hoc intercomparison of Eocene (∼ 50 Ma) climate model simulations and geological data has been carried out previously, models of past high-CO2 periods have never been evaluated in a consistent framework. Here, we present an experimental design for climate model simulations of three warm periods within the early Eocene and the latest Paleocene (the EECO, PETM, and pre-PETM). Together with the CMIP6 pre-industrial control and abrupt 4 × CO2 simulations, and additional sensitivity studies, these form the first phase of DeepMIP-the Deep-time Model Intercomparison Project, itself a group within the wider Paleoclimate Modelling Intercomparison Project (PMIP). The experimental design specifies and provides guidance on boundary conditions associated with palaeogeography, greenhouse gases, astronomical configuration, solar constant, land surface processes, and aerosols. Initial conditions, simulation length, and output variables are also specified. Finally, we explain how the geological data sets, which will be used to evaluate the simulations, will be developed.
Abstract.
Full text.
Levy R, Harwood D, Florindo F, Sangiorgi F, Tripati R, von Eynatten H, Gasson E, Kuhn G, Tripati A, DeConto R, et al (2016). Antarctic ice sheet sensitivity to atmospheric CO. <sub>2</sub>. variations in the early to mid-Miocene.
Proceedings of the National Academy of Sciences,
113(13), 3453-3458.
Abstract:
Antarctic ice sheet sensitivity to atmospheric CO. 2. variations in the early to mid-Miocene
Significance
.
. New information from the ANDRILL-2A drill core and a complementary ice sheet modeling study show that polar climate and Antarctic ice sheet (AIS) margins were highly dynamic during the early to mid-Miocene. Changes in extent of the AIS inferred by these studies suggest that high southern latitudes were sensitive to relatively small changes in atmospheric CO
. 2
. (between 280 and 500 ppm). Importantly, reconstructions through intervals of peak warmth indicate that the AIS retreated beyond its terrestrial margin under atmospheric CO
. 2
. conditions that were similar to those projected for the coming centuries.
.
Abstract.
Gasson E, DeConto RM, Pollard D, Levy RH (2016). Dynamic Antarctic ice sheet during the early to mid-Miocene.
Proceedings of the National Academy of Sciences,
113(13), 3459-3464.
Abstract:
Dynamic Antarctic ice sheet during the early to mid-Miocene
Significance
.
. Atmospheric concentrations of carbon dioxide are projected to exceed 500 ppm in the coming decades. It is likely that the last time such levels of atmospheric CO
. 2
. were reached was during the Miocene, for which there is geologic data for large-scale advance and retreat of the Antarctic ice sheet. Simulating Antarctic ice sheet retreat is something that ice sheet models have struggled to achieve because of a strong hysteresis effect. Here, a number of developments in our modeling approach mean that we are able to simulate large-scale variability of the Antarctic ice sheet for the first time. Our results are also consistent with a recently recovered sedimentological record from the Ross Sea presented in a companion article.
.
Abstract.
Gasson E, DeConto RM, Pollard D (2016). Modeling the oxygen isotope composition of the Antarctic ice sheet and its significance to Pliocene sea level. Geology, 44(10), 827-830.
Gasson E, DeConto R, Pollard D (2015). Antarctic bedrock topography uncertainty and ice sheet stability. Geophysical Research Letters, 42(13), 5372-5377.
de Boer B, Dolan AM, Bernales J, Gasson E, Goelzer H, Golledge NR, Sutter J, Huybrechts P, Lohmann G, Rogozhina I, et al (2015). Simulating the Antarctic ice sheet in the late-Pliocene warm period: PLISMIP-ANT, an ice-sheet model intercomparison project.
The Cryosphere,
9(3), 881-903.
Abstract:
Simulating the Antarctic ice sheet in the late-Pliocene warm period: PLISMIP-ANT, an ice-sheet model intercomparison project
Abstract. In the context of future climate change, understanding the nature and behaviour of ice sheets during warm intervals in Earth history is of fundamental importance. The late Pliocene warm period (also known as the PRISM interval: 3.264 to 3.025 million years before present) can serve as a potential analogue for projected future climates. Although Pliocene ice locations and extents are still poorly constrained, a significant contribution to sea-level rise should be expected from both the Greenland ice sheet and the West and East Antarctic ice sheets based on palaeo sea-level reconstructions. Here, we present results from simulations of the Antarctic ice sheet by means of an international Pliocene Ice Sheet Modeling Intercomparison Project (PLISMIP-ANT). For the experiments, ice-sheet models including the shallow ice and shelf approximations have been used to simulate the complete Antarctic domain (including grounded and floating ice). We compare the performance of six existing numerical ice-sheet models in simulating modern control and Pliocene ice sheets by a suite of five sensitivity experiments. We include an overview of the different ice-sheet models used and how specific model configurations influence the resulting Pliocene Antarctic ice sheet. The six ice-sheet models simulate a comparable present-day ice sheet, considering the models are set up with their own parameter settings. For the Pliocene, the results demonstrate the difficulty of all six models used here to simulate a significant retreat or re-advance of the East Antarctic ice grounding line, which is thought to have happened during the Pliocene for the Wilkes and Aurora basins. The specific sea-level contribution of the Antarctic ice sheet at this point cannot be conclusively determined, whereas improved grounding line physics could be essential for a correct representation of the migration of the grounding-line of the Antarctic ice sheet during the Pliocene.
.
Abstract.
Golledge NR, Kowalewski DE, Naish TR, Levy RH, Fogwill CJ, Gasson EGW (2015). The multi-millennial Antarctic commitment to future sea-level rise. Nature, 526(7573), 421-425.
Gasson E, Lunt DJ, DeConto R, Goldner A, Heinemann M, Huber M, LeGrande AN, Pollard D, Sagoo N, Siddall M, et al (2014). Uncertainties in the modelled CO2 threshold for Antarctic glaciation.
Climate of the Past,
10(2), 451-466.
Abstract:
Uncertainties in the modelled CO2 threshold for Antarctic glaciation
Abstract. A frequently cited atmospheric CO2 threshold for the onset of Antarctic glaciation of ~780 ppmv is based on the study of DeConto and Pollard (2003) using an ice sheet model and the GENESIS climate model. Proxy records suggest that atmospheric CO2 concentrations passed through this threshold across the Eocene–Oligocene transition ~34 Ma. However, atmospheric CO2 concentrations may have been close to this threshold earlier than this transition, which is used by some to suggest the possibility of Antarctic ice sheets during the Eocene. Here we investigate the climate model dependency of the threshold for Antarctic glaciation by performing offline ice sheet model simulations using the climate from 7 different climate models with Eocene boundary conditions (HadCM3L, CCSM3, CESM1.0, GENESIS, FAMOUS, ECHAM5 and GISS_ER). These climate simulations are sourced from a number of independent studies, and as such the boundary conditions, which are poorly constrained during the Eocene, are not identical between simulations. The results of this study suggest that the atmospheric CO2 threshold for Antarctic glaciation is highly dependent on the climate model used and the climate model configuration. A large discrepancy between the climate model and ice sheet model grids for some simulations leads to a strong sensitivity to the lapse rate parameter.
.
Abstract.
Little SH, Vance D, Siddall M, Gasson E (2013). A modeling assessment of the role of reversible scavenging in controlling oceanic dissolved Cu and Zn distributions. Global Biogeochemical Cycles, 27(3), 780-791.
Gasson E, Siddall M, Lunt DJ, Rackham OJL, Lear CH, Pollard D (2012). Exploring uncertainties in the relationship between temperature, ice volume, and sea level over the past 50 million years. Reviews of Geophysics, 50(1).
Publications by year
In Press
Burls NJ, Bradshaw C, De Boer AM, Herold N, Huber M, Pound M, Donnadieu Y, Farnsworth A, Frigola Boix A, Gasson EGW, et al (In Press). Simulating Miocene warmth: insights from an opportunistic Multi-Model ensemble (MioMIP1).
2021
Marschalek JW, Zurli L, Talarico F, van de Flierdt T, Vermeesch P, Carter A, Beny F, Bout-Roumazeilles V, Sangiorgi F, Hemming SR, et al (2021). A large West Antarctic Ice Sheet explains early Neogene sea-level amplitude.
Nature,
600(7889), 450-455.
Abstract:
A large West Antarctic Ice Sheet explains early Neogene sea-level amplitude.
Early to Middle Miocene sea-level oscillations of approximately 40-60 m estimated from far-field records1-3 are interpreted to reflect the loss of virtually all East Antarctic ice during peak warmth2. This contrasts with ice-sheet model experiments suggesting most terrestrial ice in East Antarctica was retained even during the warmest intervals of the Middle Miocene4,5. Data and model outputs can be reconciled if a large West Antarctic Ice Sheet (WAIS) existed and expanded across most of the outer continental shelf during the Early Miocene, accounting for maximum ice-sheet volumes. Here we provide the earliest geological evidence proving large WAIS expansions occurred during the Early Miocene (~17.72-17.40 Ma). Geochemical and petrographic data show glacimarine sediments recovered at International Ocean Discovery Program (IODP) Site U1521 in the central Ross Sea derive from West Antarctica, requiring the presence of a WAIS covering most of the Ross Sea continental shelf. Seismic, lithological and palynological data reveal the intermittent proximity of grounded ice to Site U1521. The erosion rate calculated from this sediment package greatly exceeds the long-term mean, implying rapid erosion of West Antarctica. This interval therefore captures a key step in the genesis of a marine-based WAIS and a tipping point in Antarctic ice-sheet evolution.
Abstract.
Author URL.
Halberstadt ARW, Chorley H, Levy RH, Naish T, DeConto RM, Gasson E, Kowalewski DE (2021). CO2 and tectonic controls on Antarctic climate and ice-sheet evolution in the mid-Miocene. Earth and Planetary Science Letters, 564, 116908-116908.
Ashley KE, McKay R, Etourneau J, Jimenez-Espejo FJ, Condron A, Albot A, Crosta X, Riesselman C, Seki O, Massé G, et al (2021). Mid-Holocene Antarctic sea-ice increase driven by marine ice sheet retreat.
Climate of the Past,
17(1), 1-19.
Abstract:
Mid-Holocene Antarctic sea-ice increase driven by marine ice sheet retreat
Abstract. Over recent decades Antarctic sea-ice extent has increased, alongside
widespread ice shelf thinning and freshening of waters along the Antarctic
margin. In contrast, Earth system models generally simulate a decrease in
sea ice. Circulation of water masses beneath large-cavity ice shelves is not
included in current Earth System models and may be a driver of this
phenomena. We examine a Holocene sediment core off East Antarctica that
records the Neoglacial transition, the last major baseline shift of
Antarctic sea ice, and part of a late-Holocene global cooling trend. We
provide a multi-proxy record of Holocene glacial meltwater input, sediment
transport, and sea-ice variability. Our record, supported by high-resolution
ocean modelling, shows that a rapid Antarctic sea-ice increase during the
mid-Holocene (∼ 4.5 ka) occurred against a backdrop of
increasing glacial meltwater input and gradual climate warming. We suggest
that mid-Holocene ice shelf cavity expansion led to cooling of surface
waters and sea-ice growth that slowed basal ice shelf melting.
Incorporating this feedback mechanism into global climate models will be
important for future projections of Antarctic changes.
.
Abstract.
Burls NJ, Bradshaw CD, De Boer AM, Herold N, Huber M, Pound M, Donnadieu Y, Farnsworth A, Frigola A, Gasson E, et al (2021). Simulating Miocene Warmth: Insights from an Opportunistic Multi-Model Ensemble (MioMIP1).
Paleoceanography and Paleoclimatology,
36(5).
Abstract:
Simulating Miocene Warmth: Insights from an Opportunistic Multi-Model Ensemble (MioMIP1)
The Miocene epoch, spanning 23.03–5.33 Ma, was a dynamic climate of sustained, polar amplified warmth. Miocene atmospheric CO2 concentrations are typically reconstructed between 300 and 600 ppm and were potentially higher during the Miocene Climatic Optimum (16.75–14.5 Ma). With surface temperature reconstructions pointing to substantial midlatitude and polar warmth, it is unclear what processes maintained the much weaker-than-modern equator-to-pole temperature difference. Here, we synthesize several Miocene climate modeling efforts together with available terrestrial and ocean surface temperature reconstructions. We evaluate the range of model-data agreement, highlight robust mechanisms operating across Miocene modeling efforts and regions where differences across experiments result in a large spread in warming responses. Prescribed CO2 is the primary factor controlling global warming across the ensemble. On average, elements other than CO2, such as Miocene paleogeography and ice sheets, raise global mean temperature by ∼2°C, with the spread in warming under a given CO2 concentration (due to a combination of the spread in imposed boundary conditions and climate feedback strengths) equivalent to ∼1.2 times a CO2 doubling. This study uses an ensemble of opportunity: models, boundary conditions, and reference data sets represent the state-of-art for the Miocene, but are inhomogeneous and not ideal for a formal intermodel comparison effort. Acknowledging this caveat, this study is nevertheless the first Miocene multi-model, multi-proxy comparison attempted so far. This study serves to take stock of the current progress toward simulating Miocene warmth while isolating remaining challenges that may be well served by community-led efforts to coordinate modeling and data activities within a common analytical framework.
Abstract.
Full text.
Steinthorsdottir M, Coxall HK, de Boer AM, Huber M, Barbolini N, Bradshaw CD, Burls NJ, Feakins SJ, Gasson E, Henderiks J, et al (2021). The Miocene: the Future of the Past.
Paleoceanography and Paleoclimatology,
36(4).
Full text.
DeConto RM, Pollard D, Alley RB, Velicogna I, Gasson E, Gomez N, Sadai S, Condron A, Gilford DM, Ashe EL, et al (2021). The Paris Climate Agreement and future sea-level rise from Antarctica.
Nature,
593(7857), 83-89.
Full text.
2020
Paxman GJG, Gasson EGW, Jamieson SSR, Bentley MJ, Ferraccioli F (2020). Long‐Term Increase in Antarctic Ice Sheet Vulnerability Driven by Bed Topography Evolution. Geophysical Research Letters, 47(20).
Gasson E, Keisling B (2020). The Antarctic Ice Sheet: a Paleoclimate Modeling Perspective. Oceanography, 33(2).
2019
Levy RH, Meyers SR, Naish TR, Golledge NR, McKay RM, Crampton JS, DeConto RM, De Santis L, Florindo F, Gasson EGW, et al (2019). Antarctic ice-sheet sensitivity to obliquity forcing enhanced through ocean connections. Nature Geoscience, 12(2), 132-137.
Ely JC, Clark CD, Hindmarsh RCA, Hughes ALC, Greenwood SL, Bradley SL, Gasson E, Gregoire L, Gandy N, Stokes CR, et al (2019). Recent progress on combining geomorphological and geochronological data with ice sheet modelling, demonstrated using the last British–Irish Ice Sheet. Journal of Quaternary Science, 36(5), 946-960.
2018
Paxman GJG, Jamieson SSR, Ferraccioli F, Bentley MJ, Ross N, Armadillo E, Gasson EGW, Leitchenkov G, DeConto RM (2018). Bedrock Erosion Surfaces Record Former East Antarctic Ice Sheet Extent. Geophysical Research Letters, 45(9), 4114-4123.
Gasson EGW, DeConto RM, Pollard D, Clark CD (2018). Numerical simulations of a kilometre-thick Arctic ice shelf consistent with ice grounding observations. Nature Communications, 9(1).
Colleoni F, De Santis L, Montoli E, Olivo E, Sorlien CC, Bart PJ, Gasson EGW, Bergamasco A, Sauli C, Wardell N, et al (2018). Past continental shelf evolution increased Antarctic ice sheet sensitivity to climatic conditions. Scientific Reports, 8(1).
2017
Golledge NR, Thomas ZA, Levy RH, Gasson EGW, Naish TR, McKay RM, Kowalewski DE, Fogwill CJ (2017). Antarctic climate and ice-sheet configuration during the early Pliocene interglacial at 4.23 Ma.
Climate of the Past,
13(7), 959-975.
Abstract:
Antarctic climate and ice-sheet configuration during the early Pliocene interglacial at 4.23 Ma
Abstract. The geometry of Antarctic ice sheets during warm periods of the geological past is difficult to determine from geological evidence, but is important to know because such reconstructions enable a more complete understanding of how the ice-sheet system responds to changes in climate. Here we investigate how Antarctica evolved under orbital and greenhouse gas conditions representative of an interglacial in the early Pliocene at 4.23 Ma, when Southern Hemisphere insolation reached a maximum. Using offline-coupled climate and ice-sheet models, together with a new synthesis of high-latitude palaeoenvironmental proxy data to define a likely climate envelope, we simulate a range of ice-sheet geometries and calculate their likely contribution to sea level. In addition, we use these simulations to investigate the processes by which the West and East Antarctic ice sheets respond to environmental forcings and the timescales over which these behaviours manifest. We conclude that the Antarctic ice sheet contributed 8.6 ± 2.8 m to global sea level at this time, under an atmospheric CO2 concentration identical to present (400 ppm). Warmer-than-present ocean temperatures led to the collapse of West Antarctica over centuries, whereas higher air temperatures initiated surface melting in parts of East Antarctica that over one to two millennia led to lowering of the ice-sheet surface, flotation of grounded margins in some areas, and retreat of the ice sheet into the Wilkes Subglacial Basin. The results show that regional variations in climate, ice-sheet geometry, and topography produce long-term sea-level contributions that are non-linear with respect to the applied forcings, and which under certain conditions exhibit threshold behaviour associated with behavioural tipping points.
.
Abstract.
Lunt DJ, Huber M, Anagnostou E, Baatsen MLJ, Caballero R, DeConto R, Dijkstra HA, Donnadieu Y, Evans D, Feng R, et al (2017). The DeepMIP contribution to PMIP4: Experimental design for model simulations of the EECO, PETM, and pre-PETM (version 1.0).
Geoscientific Model Development,
10(2), 889-901.
Abstract:
The DeepMIP contribution to PMIP4: Experimental design for model simulations of the EECO, PETM, and pre-PETM (version 1.0)
Past warm periods provide an opportunity to evaluate climate models under extreme forcing scenarios, in particular high (> 800ppmv) atmospheric CO2 concentrations. Although a post hoc intercomparison of Eocene (∼ 50 Ma) climate model simulations and geological data has been carried out previously, models of past high-CO2 periods have never been evaluated in a consistent framework. Here, we present an experimental design for climate model simulations of three warm periods within the early Eocene and the latest Paleocene (the EECO, PETM, and pre-PETM). Together with the CMIP6 pre-industrial control and abrupt 4 × CO2 simulations, and additional sensitivity studies, these form the first phase of DeepMIP-the Deep-time Model Intercomparison Project, itself a group within the wider Paleoclimate Modelling Intercomparison Project (PMIP). The experimental design specifies and provides guidance on boundary conditions associated with palaeogeography, greenhouse gases, astronomical configuration, solar constant, land surface processes, and aerosols. Initial conditions, simulation length, and output variables are also specified. Finally, we explain how the geological data sets, which will be used to evaluate the simulations, will be developed.
Abstract.
Full text.
2016
Levy R, Harwood D, Florindo F, Sangiorgi F, Tripati R, von Eynatten H, Gasson E, Kuhn G, Tripati A, DeConto R, et al (2016). Antarctic ice sheet sensitivity to atmospheric CO. <sub>2</sub>. variations in the early to mid-Miocene.
Proceedings of the National Academy of Sciences,
113(13), 3453-3458.
Abstract:
Antarctic ice sheet sensitivity to atmospheric CO. 2. variations in the early to mid-Miocene
Significance
.
. New information from the ANDRILL-2A drill core and a complementary ice sheet modeling study show that polar climate and Antarctic ice sheet (AIS) margins were highly dynamic during the early to mid-Miocene. Changes in extent of the AIS inferred by these studies suggest that high southern latitudes were sensitive to relatively small changes in atmospheric CO
. 2
. (between 280 and 500 ppm). Importantly, reconstructions through intervals of peak warmth indicate that the AIS retreated beyond its terrestrial margin under atmospheric CO
. 2
. conditions that were similar to those projected for the coming centuries.
.
Abstract.
Gasson E, DeConto RM, Pollard D, Levy RH (2016). Dynamic Antarctic ice sheet during the early to mid-Miocene.
Proceedings of the National Academy of Sciences,
113(13), 3459-3464.
Abstract:
Dynamic Antarctic ice sheet during the early to mid-Miocene
Significance
.
. Atmospheric concentrations of carbon dioxide are projected to exceed 500 ppm in the coming decades. It is likely that the last time such levels of atmospheric CO
. 2
. were reached was during the Miocene, for which there is geologic data for large-scale advance and retreat of the Antarctic ice sheet. Simulating Antarctic ice sheet retreat is something that ice sheet models have struggled to achieve because of a strong hysteresis effect. Here, a number of developments in our modeling approach mean that we are able to simulate large-scale variability of the Antarctic ice sheet for the first time. Our results are also consistent with a recently recovered sedimentological record from the Ross Sea presented in a companion article.
.
Abstract.
Gasson E, DeConto RM, Pollard D (2016). Modeling the oxygen isotope composition of the Antarctic ice sheet and its significance to Pliocene sea level. Geology, 44(10), 827-830.
2015
Gasson E, DeConto R, Pollard D (2015). Antarctic bedrock topography uncertainty and ice sheet stability. Geophysical Research Letters, 42(13), 5372-5377.
de Boer B, Dolan AM, Bernales J, Gasson E, Goelzer H, Golledge NR, Sutter J, Huybrechts P, Lohmann G, Rogozhina I, et al (2015). Simulating the Antarctic ice sheet in the late-Pliocene warm period: PLISMIP-ANT, an ice-sheet model intercomparison project.
The Cryosphere,
9(3), 881-903.
Abstract:
Simulating the Antarctic ice sheet in the late-Pliocene warm period: PLISMIP-ANT, an ice-sheet model intercomparison project
Abstract. In the context of future climate change, understanding the nature and behaviour of ice sheets during warm intervals in Earth history is of fundamental importance. The late Pliocene warm period (also known as the PRISM interval: 3.264 to 3.025 million years before present) can serve as a potential analogue for projected future climates. Although Pliocene ice locations and extents are still poorly constrained, a significant contribution to sea-level rise should be expected from both the Greenland ice sheet and the West and East Antarctic ice sheets based on palaeo sea-level reconstructions. Here, we present results from simulations of the Antarctic ice sheet by means of an international Pliocene Ice Sheet Modeling Intercomparison Project (PLISMIP-ANT). For the experiments, ice-sheet models including the shallow ice and shelf approximations have been used to simulate the complete Antarctic domain (including grounded and floating ice). We compare the performance of six existing numerical ice-sheet models in simulating modern control and Pliocene ice sheets by a suite of five sensitivity experiments. We include an overview of the different ice-sheet models used and how specific model configurations influence the resulting Pliocene Antarctic ice sheet. The six ice-sheet models simulate a comparable present-day ice sheet, considering the models are set up with their own parameter settings. For the Pliocene, the results demonstrate the difficulty of all six models used here to simulate a significant retreat or re-advance of the East Antarctic ice grounding line, which is thought to have happened during the Pliocene for the Wilkes and Aurora basins. The specific sea-level contribution of the Antarctic ice sheet at this point cannot be conclusively determined, whereas improved grounding line physics could be essential for a correct representation of the migration of the grounding-line of the Antarctic ice sheet during the Pliocene.
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Abstract.
Golledge NR, Kowalewski DE, Naish TR, Levy RH, Fogwill CJ, Gasson EGW (2015). The multi-millennial Antarctic commitment to future sea-level rise. Nature, 526(7573), 421-425.
2014
Gasson E, Lunt DJ, DeConto R, Goldner A, Heinemann M, Huber M, LeGrande AN, Pollard D, Sagoo N, Siddall M, et al (2014). Uncertainties in the modelled CO2 threshold for Antarctic glaciation.
Climate of the Past,
10(2), 451-466.
Abstract:
Uncertainties in the modelled CO2 threshold for Antarctic glaciation
Abstract. A frequently cited atmospheric CO2 threshold for the onset of Antarctic glaciation of ~780 ppmv is based on the study of DeConto and Pollard (2003) using an ice sheet model and the GENESIS climate model. Proxy records suggest that atmospheric CO2 concentrations passed through this threshold across the Eocene–Oligocene transition ~34 Ma. However, atmospheric CO2 concentrations may have been close to this threshold earlier than this transition, which is used by some to suggest the possibility of Antarctic ice sheets during the Eocene. Here we investigate the climate model dependency of the threshold for Antarctic glaciation by performing offline ice sheet model simulations using the climate from 7 different climate models with Eocene boundary conditions (HadCM3L, CCSM3, CESM1.0, GENESIS, FAMOUS, ECHAM5 and GISS_ER). These climate simulations are sourced from a number of independent studies, and as such the boundary conditions, which are poorly constrained during the Eocene, are not identical between simulations. The results of this study suggest that the atmospheric CO2 threshold for Antarctic glaciation is highly dependent on the climate model used and the climate model configuration. A large discrepancy between the climate model and ice sheet model grids for some simulations leads to a strong sensitivity to the lapse rate parameter.
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Abstract.
2013
Little SH, Vance D, Siddall M, Gasson E (2013). A modeling assessment of the role of reversible scavenging in controlling oceanic dissolved Cu and Zn distributions. Global Biogeochemical Cycles, 27(3), 780-791.
2012
Gasson E, Siddall M, Lunt DJ, Rackham OJL, Lear CH, Pollard D (2012). Exploring uncertainties in the relationship between temperature, ice volume, and sea level over the past 50 million years. Reviews of Geophysics, 50(1).