Competing influences of the ocean, atmosphere and solid earth on transient Miocene Antarctic ice sheet variability

Abstract. Benthic δ18O levels vary strongly during the warmer-than-modern early- and mid-Miocene (23 to 14 Myr ago), suggesting a dynamic Antarctic ice sheet (AIS). So far, however, realistic simulations of the Miocene AIS have been limited to equilibrium states under different CO2 levels and orbital settings. Earlier transient simulations lacked ice-sheet-atmosphere interactions, and used a present-day rather than Miocene Antarctic bedrock topography. Here, we quantify the effect of ice-sheet-atmosphere interactions, running IMAU-ICE using climate forcing from Miocene simulations by the general circulation model GENESIS. Utilising a recently developed matrix interpolation method enables us to interpolate the climate forcing based on CO2 levels (between 280 and 840 ppm) as well as ice sheet configurations (between no ice and a large ice sheet). We furthermore implement recent reconstructions of Miocene Antarctic bedrock topography. We find that the positive albedo-temperature feedback, partly compensated by the negative ice-volume-precipitation feedback, increases hysteresis in the relation between CO2 and ice volume (V). Together, these ice-sheet-atmosphere interactions decrease the amplitude of AIS variability caused by 40-kyr forcing CO2 cycles by 21 % in transient simulations. Thereby, they also diminish the contribution of AIS variability to benthic δ18O fluctuations. Furthermore, we show that under equal atmospheric and oceanic forcing, the amplitude of 40-kyr transient AIS variability becomes 10 % smaller during the early- and mid-Miocene, due to the evolving bedrock topography. Lastly, we quantify the influence of ice shelf formation around the Antarctic margins, by comparing simulations with Last Glacial Maximum (LGM) basal melt conditions, to ones in which ice shelf growth is prevented. Ice shelf formation increases hysteresis in the CO2-V relation, and amplifies 40-kyr AIS variability by 19 % using LGM basal melt rates, and by 5 % in our reference setting.

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First results from coupling the Parallel Ice Sheet Model with the Modular Ocean Model via an Antarctic ice-shelf cavity module

10.5194/egusphere-egu21-6063 ◽

2021 ◽

Author(s):

Moritz Kreuzer ◽

Ronja Reese ◽

Willem Huiskamp ◽

Stefan Petri ◽

Torsten Albrecht ◽

...

Keyword(s):

Time Scales ◽

General Circulation ◽

Ice Sheet ◽

Circulation Model ◽

Ocean Model ◽

Global Ocean ◽

Ice Shelf ◽

Antarctic Ice Sheet ◽

First Results ◽

The Antarctic

The past and future evolution of the Antarctic Ice Sheet is largely controlled by interactions between the ocean and floating ice shelves. To investigate these interactions, coupled ocean and ice sheet model configurations are required. Previous modelling studies have mostly relied on high resolution configurations, limiting these studies to individual glaciers or regions over short time scales of decades to a few centuries. To study global and long term interactions, we developed a framework to couple the dynamic ice sheet model PISM with the global ocean general circulation model MOM5 via the ice-shelf cavity module PICO. Since ice-shelf cavities are not resolved by MOM5, but parameterized with the box model PICO, the framework allows the ice sheet and ocean model to be run at resolution of 16&#8201;km and 3 degrees, respectively. We present first results from our coupled setup and discuss stability, feedbacks, and interactions of the Antarctic Ice Sheet and the global ocean system on millennial time scales.

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Coupling framework (1.0) for the ice sheet model PISM (1.1.1) and the ocean model MOM5 (5.1.0) via the ice-shelf cavity module PICO

10.5194/gmd-2020-230 ◽

2020 ◽

Author(s):

Moritz Kreuzer ◽

Ronja Reese ◽

Willem Nicholas Huiskamp ◽

Stefan Petri ◽

Torsten Albrecht ◽

...

Keyword(s):

Time Scales ◽

General Circulation ◽

Ice Sheet ◽

Circulation Model ◽

Ocean Model ◽

Global Ocean ◽

Energy Fluxes ◽

Ice Shelf ◽

Antarctic Ice Sheet ◽

Wide Range

Abstract. The past and future evolution of the Antarctic Ice Sheet is largely controlled by interactions between the ocean and floating ice shelves. To investigate these interactions, coupled ocean and ice sheet model configurations are required. Previous modelling studies have mostly relied on high resolution configurations, limiting these studies to individual glaciers or regions over short time scales of decades to a few centuries. We present a framework to couple the dynamic ice sheet model PISM with the global ocean general circulation model MOM5 via the ice-shelf cavity module PICO. Since ice-shelf cavities are not resolved by MOM5, but parameterized with the box model PICO, the framework allows the ice sheet and ocean model to be run at resolution of 16 km and 3 degree, respectively. This approach makes the coupled configuration a useful tool for the analysis of interactions between the entire Antarctic Ice Sheet and the Earth system over time spans on the order of centuries to millennia. In this study we describe the technical implementation of this coupling framework: sub-shelf melting in the ice sheet model is calculated by PICO from modeled ocean temperatures and salinities at the depth of the continental shelf and, vice versa, the resulting mass and energy fluxes from the melting at the ice-ocean interface are transferred to the ocean model. Mass and energy fluxes are shown to be conserved to machine precision across the considered model domains. The implementation is computationally efficient as it introduces only minimal overhead. The framework deals with heterogeneous spatial grid geometries, varying grid resolutions and time scales between the ice and ocean model in a generic way, and can thus be adopted to a wide range of model setups.

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Antarctic ice sheet response to upper-bound scenarios

10.5194/egusphere-egu21-11823 ◽

2021 ◽

Author(s):

Sainan Sun ◽

Frank Pattyn

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Upper Bound ◽

Ice Sheet ◽

Climate Forcing ◽

Ice Shelf ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

Basal Sliding ◽

The Antarctic

Mass loss of the Antarctic ice sheet contributes the largest uncertainty of future sea-level rise projections. Ice-sheet model predictions are limited by uncertainties in climate forcing and poor understanding of processes such as ice viscosity. The Antarctic BUttressing Model Intercomparison Project (ABUMIP) has investigated the 'end-member' scenario, i.e., a total and sustained removal of buttressing from all Antarctic ice shelves, which can be regarded as the upper-bound physical possible, but implausible contribution of sea-level rise due to ice-shelf loss. In this study, we add successive layers of &#8216;realism&#8217; to the ABUMIP scenario by considering sustained regional ice-shelf collapse and by introducing ice-shelf regrowth after collapse with the inclusion of ice-sheet and ice-shelf damage (Sun et al., 2017). Ice shelf regrowth has the ability to stabilize grounding lines, while ice shelf damage may reinforce ice loss. In combination with uncertainties from basal sliding and ice rheology, a more realistic physical upperbound to ice loss is sought. Results are compared in the light of other proposed mechanisms, such as MICI due to ice cliff collapse.

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Modelled response of the volume and thickness of the Antarctic ice sheet to the advance of the grounded area

Annals of Glaciology ◽

10.3189/172756410791392808 ◽

2010 ◽

Vol 51 (55) ◽

pp. 41-48 ◽

Cited By ~ 13

Author(s):

Fuyuki Saito ◽

Ayako Abe-Ouchi

Keyword(s):

Climate Change ◽

Sea Level ◽

Volume Change ◽

Numerical Experiments ◽

Ice Sheet ◽

Ice Shelf ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

Ice Volume ◽

The Antarctic

AbstractNumerical experiments are performed for the Antarctic ice sheet to study the sensitivity of the ice volume to variations in the area of grounded ice and to changes in the climate during the most recent deglaciation. The effect of the variations in the grounded area is found to be the major source of changes in the ice volume, while the effect of climate change was minor. The maximum possible contribution of the ice-volume change to sea-level rise during the deglaciation is estimated to be 36 m, which covers most values estimated in previous studies. The effect of the advance of the ice-sheet margin over those regions not connected to the major ice shelves contributes one-third of the total ice-volume change, which is comparable to the effect of the grounding of the Filchner–Ronne Ice Shelf and the contribution of the Ross and Amery Ice Shelves together.

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Numerical reconstructions of the Northern Hemisphere ice sheets through the last glacial-interglacial cycle

Climate of the Past ◽

10.5194/cp-3-15-2007 ◽

2007 ◽

Vol 3 (1) ◽

pp. 15-37 ◽

Cited By ~ 80

Author(s):

S. Charbit ◽

C. Ritz ◽

G. Philippon ◽

V. Peyaud ◽

M. Kageyama

Keyword(s):

Northern Hemisphere ◽

General Circulation ◽

Ice Sheets ◽

Ice Sheet ◽

Maximum Amplitude ◽

The Other ◽

Climate Forcing ◽

Last Glacial ◽

Ice Volume ◽

The Last Glacial

Abstract. A 3-dimensional thermo-mechanical ice-sheet model is used to simulate the evolution of the Northern Hemisphere ice sheets through the last glacial-interglacial cycle. The ice-sheet model is forced by the results from six different atmospheric general circulation models (AGCMs). The climate evolution over the period under study is reconstructed using two climate equilibrium simulations performed for the Last Glacial Maximum (LGM) and for the present-day periods and an interpolation through time between these snapshots using a glacial index calibrated against the GRIP δ18O record. Since it is driven by the timing of the GRIP signal, the temporal evolution of the ice volume and the ice-covered area is approximately the same from one simulation to the other. However, both ice volume curves and spatial distributions of the ice sheets present some major differences from one AGCM forcing to the other. The origin of these differences, which are most visible in the maximum amplitude of the ice volume, is analyzed in terms of differences in climate forcing. This analysis allows for a partial evaluation of the ability of GCMs to simulate climates consistent with the reconstructions of past ice sheets. Although some models properly reproduce the advance or retreat of ice sheets in some specific areas, none of them is able to reproduce both North American or Eurasian ice complexes in full agreement with observed sea-level variations and geological data. These deviations can be attributed to shortcomings in the climate forcing and in the LGM ice-sheet reconstruction used as a boundary condition for GCM runs, but also to missing processes in the ice-sheet model itself.

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Inferring the Last Interglacial West Antarctic Ice Sheet from the coupling of an ice core water stable isotope record and an atmospheric general circulation model

10.5194/egusphere-egu2020-16787 ◽

2020 ◽

Author(s):

Sentia Goursaud ◽

Louise Sime ◽

Eric Wolff

Keyword(s):

General Circulation ◽

Ice Core ◽

Ice Sheet ◽

Circulation Model ◽

Last Interglacial ◽

Antarctic Ice Sheet ◽

West Antarctic Ice Sheet ◽

West Antarctic ◽

Isotope Record ◽

Water Stable Isotope

The Last Interglacial period (130-115 ka BP, hereafter LIG) is often considered as a prime example to study the effect of warmer-than-present temperatures on polar ice sheets evolution. As the debate mainly focuses on the causes and tipping point of a potential collapse of the West Antarctic Ice Sheet (hereafter WAIS), few investigations examine the consequences of a wais collapse in terms of atmospheric circulation. However, a knowledge of the state of the atmosphere is necessary to use proxy data recorded in ice cores. By analysing a new ice core drilled in Skytrain ice rise and using climate modeling, the WACSWAIN (WArm Climate Stability of West Antarctic ice sheet in the last Interglacial) aims to reconstruct WAIS extent during the LIG. Here, we use simulations from the atmospheric general circulation model HadCM3 with different WAIS configurations. We show that changes in temperature are directly linked to changes in orography through thermodynamic effects, as well as a linear sea ice extent rise over the Pacific Ocean with the WAIS reduction explained by a reversal of meridional winds turning southwards as the WAIS disappears. At the Skytrain ice rise, we show that not only the isotopic thermometer can be applied, but we also suggest that the water stable isotope record imprinted in the ice core will allow us to quantify the wais reduction.

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The Response of Ice Shelf Basal Melting to Variations in Ocean Temperature

Journal of Climate ◽

10.1175/2007jcli1909.1 ◽

2008 ◽

Vol 21 (11) ◽

pp. 2558-2572 ◽

Cited By ~ 185

Author(s):

Paul R. Holland ◽

Adrian Jenkins ◽

David M. Holland

Keyword(s):

Ocean Circulation ◽

General Circulation ◽

Ice Sheet ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Flow Speed ◽

Ocean Warming ◽

Ocean Temperature ◽

Ice Shelf ◽

Ice Shelves

Abstract A three-dimensional ocean general circulation model is used to study the response of idealized ice shelves to a series of ocean-warming scenarios. The model predicts that the total ice shelf basal melt increases quadratically as the ocean offshore of the ice front warms. This occurs because the melt rate is proportional to the product of ocean flow speed and temperature in the mixed layer directly beneath the ice shelf, both of which are found to increase linearly with ocean warming. The behavior of this complex primitive equation model can be described surprisingly well with recourse to an idealized reduced system of equations, and it is shown that this system supports a melt rate response to warming that is generally quadratic in nature. This study confirms and unifies several previous examinations of the relation between melt rate and ocean temperature but disagrees with other results, particularly the claim that a single melt rate sensitivity to warming is universally valid. The hypothesized warming does not necessarily require a heat input to the ocean, as warmer waters (or larger volumes of “warm” water) may reach ice shelves purely through a shift in ocean circulation. Since ice shelves link the Antarctic Ice Sheet to the climate of the Southern Ocean, this finding of an above-linear rise in ice shelf mass loss as the ocean steadily warms is of significant importance to understanding ice sheet evolution and sea level rise.

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The GRISLI ice sheet model (version 2.0): calibration and validation for multi-millennial changes of the Antarctic ice sheet

10.5194/gmd-2018-105 ◽

2018 ◽

Cited By ~ 1

Author(s):

Aurélien Quiquet ◽

Christophe Dumas ◽

Catherine Ritz ◽

Vincent Peyaud ◽

Didier M. Roche

Keyword(s):

Ice Sheet ◽

Climate Forcing ◽

Antarctic Ice Sheet ◽

Ice Volume ◽

Grounding Line ◽

Version 2.0 ◽

The Antarctic ◽

Climate Proxies ◽

Ice Model

Abstract. In this paper we present the GRISLI (Grenoble Ice Sheet and Land Ice) model in its newest revision (version 2.0). Whilst GRISLI is applicable to any given geometry, we focus here on the Antarctic ice sheet because it highlights the importance of grounding line dynamics. Important improvements have been implemented since its original version (Ritz et al., 2001) including notably an explicit flux computation at the grounding line based on the analytical formulations of Schoof (2007) and Tsai et al. (2015) and a basal hydrology model. A calibration of the mechanical parameters of the model based on an ensemble of 150 members sampled with a Latin Hypercube method is used. The ensemble members performance is assessed relative to the deviation from present-day observed Antarctic ice thickness. The model being designed for multi-millenial long- term integrations, we also present glacial-interglacial ice sheet changes throughout the last 400 kyr using the best ensemble members. To achieve this goal, we construct a simple climatic perturbation of present-day climate forcing fields based on two climate proxies, both atmospheric and oceanic. The model is able to reproduce expected grounding line advances during glacials and subsequent retreats during terminations with reasonable glacial-interglacial ice volume changes.

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Modelling the Antarctic ice-sheet changes through time

Annals of Glaciology ◽

10.1017/s0260305500016591 ◽

1994 ◽

Vol 20 ◽

pp. 291-297 ◽

Cited By ~ 1

Author(s):

W.F. Budd ◽

D. Jenssen ◽

B. Coutts

Keyword(s):

Sea Level ◽

General Circulation ◽

Ice Sheet ◽

Circulation Model ◽

Glacial Cycle ◽

Climatic Forcing ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

Future Global Warming ◽

The Antarctic

A new assessment is made of the possible range of responses of the Antarctic ice sheet to future global warming by performing a series of sensitivity tests to prescribed climatic forcing with an ice-sheet model. The model includes thermodynamics; it is three-dimensional, with 20 km horizontal grid spacing and 30 points in the vertical, and it treats the ice shelves explicitly. To obtain an appropriate initial present state for the ice sheet, it has been necessary to perform a series of simulations through the last glacial cycle with prescribed forcing including accumulation, sea level are less importantly climatic temperature. For the future climatic forcing, General Circulation Model simulations have been used with particular concern for the changes in the sea-ice cover and ocean warming. Effects of progressive changes have been examined with increases of basal-melt rates up to 10 m a1, surface annual mean temperatures by up to 7°C and surface-accumulation rates to double the present values. Without additional accumulation, the increased basal melt of 10 m a-1would greatly reduce the ice shelves and contribute to sea-level rise of 0.3 m in 100 years and over 0.6 m by 500 years. The additional accumulation counteracts this to dive about zero change by 100 years and -1.2 m by 500 years.

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Coupling framework (1.0) for the PISM (1.1.4) ice sheet model and the MOM5 (5.1.0) ocean model via the PICO ice shelf cavity model in an Antarctic domain

Geoscientific Model Development ◽

10.5194/gmd-14-3697-2021 ◽

2021 ◽

Vol 14 (6) ◽

pp. 3697-3714

Author(s):

Moritz Kreuzer ◽

Ronja Reese ◽

Willem Nicholas Huiskamp ◽

Stefan Petri ◽

Torsten Albrecht ◽

...

Keyword(s):

General Circulation ◽

Ice Sheet ◽

Ocean Model ◽

Global Ocean ◽

Cavity Model ◽

Energy Fluxes ◽

Ice Shelf ◽

Antarctic Ice Sheet ◽

Wide Range ◽

The Antarctic

Abstract. The past and future evolution of the Antarctic Ice Sheet is largely controlled by interactions between the ocean and floating ice shelves. To investigate these interactions, coupled ocean and ice sheet model configurations are required. Previous modelling studies have mostly relied on high-resolution configurations, limiting these studies to individual glaciers or regions over short timescales of decades to a few centuries. We present a framework to couple the dynamic ice sheet model PISM (Parallel Ice Sheet Model) with the global ocean general circulation model MOM5 (Modular Ocean Model) via the ice shelf cavity model PICO (Potsdam Ice-shelf Cavity mOdel). As ice shelf cavities are not resolved by MOM5 but are parameterized with the PICO box model, the framework allows the ice sheet and ocean components to be run at resolutions of 16 km and 3∘ respectively. This approach makes the coupled configuration a useful tool for the analysis of interactions between the Antarctic Ice Sheet and the global ocean over time spans of the order of centuries to millennia. In this study, we describe the technical implementation of this coupling framework: sub-shelf melting in the ice sheet component is calculated by PICO from modelled ocean temperatures and salinities at the depth of the continental shelf, and, vice versa, the resulting mass and energy fluxes from melting at the ice–ocean interface are transferred to the ocean component. Mass and energy fluxes are shown to be conserved to machine precision across the considered component domains. The implementation is computationally efficient as it introduces only minimal overhead. Furthermore, the coupled model is evaluated in a 4000 year simulation under constant present-day climate forcing and is found to be stable with respect to the ocean and ice sheet spin-up states. The framework deals with heterogeneous spatial grid geometries, varying grid resolutions, and timescales between the ice and ocean component in a generic way; thus, it can be adopted to a wide range of model set-ups.

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