scholarly journals A mass conserving formalism for ice sheet, solid Earth and sea level interaction

2020 ◽  
Author(s):  
Surendra Adhikari ◽  
Erik R. Ivins ◽  
Eric Larour ◽  
Lambert Caron ◽  
Helene Seroussi
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Ice Sheet ◽  
Geoid Height ◽  
Earth System ◽  
Ice Shelves ◽  
Ocean Mass ◽  
Polar Ice Sheets ◽  
Ice Sheet Dynamics ◽  
And Sea Level

Abstract. Polar ice sheets are important components of any Earth System model. As the domains of land, ocean, and ice sheet change, they must be consistently defined within the lexicon of geodesy. Understanding the interplay between the processes such as ice sheet dynamics, solid Earth deformation, and sea level adjustment requires both consistent and mass conserving descriptions of evolving land and ocean domains, grounded and floating ice masks, coastlines and grounding lines, and bedrock and geoid height as viewed from space. Here we present a geometric description of an evolving ice sheet margin and its relations to sea level change, the position and loading of the solid Earth and include the ice shelves and adjacent ocean mass. We generalize the formulation so that it is applied to arbitrarily distributed ice, bedrock and adjacent ocean, and their interactive evolution. The formalism simplifies computational strategies that seek to conserve mass in Earth System models.

scholarly journals A kinematic formalism for tracking ice–ocean mass exchange on the Earth's surface and estimating sea-level change

2020 ◽  
Vol 14 (9) ◽  
pp. 2819-2833
Author(s):  
Surendra Adhikari ◽  
Erik R. Ivins ◽  
Eric Larour ◽  
Lambert Caron ◽  
Helene Seroussi
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Mass Exchange ◽  
Ice Sheets ◽  
Earth System ◽  
Generic Level ◽  
Ocean Mass ◽  
Geophysical Processes ◽  
Ice Sheet Dynamics ◽  
And Sea Level

Abstract. Polar ice sheets are important components of the Earth system. As the geometries of land, ocean and ice sheets evolve, they must be consistently captured within the lexicon of geodesy. Understanding the interplay between the processes such as ice-sheet dynamics, solid-Earth deformation, and sea-level adjustment requires both geodetically consistent and mass-conserving descriptions of evolving land and ocean domains, grounded ice sheets and floating ice shelves, and their respective interfaces. Here we present mathematical descriptions of a generic level set that can be used to track both the grounding lines and coastlines, in light of ice–ocean mass exchange and complex feedbacks from the solid Earth and sea level. We next present a unified method to accurately compute the sea-level contribution of evolving ice sheets based on the change in ice thickness, bedrock elevation and mean sea level caused by any geophysical processes. Our formalism can be applied to arbitrary geometries and at all timescales. While it can be used for applications with modeling, observations and the combination of two, it is best suited for Earth system models, comprising ice sheets, solid Earth and sea level, that seek to conserve mass.

A kinematic formalism for tracking ice-ocean mass exchange on the Earth's surface and estimating sea-level change 

2021 ◽  
Author(s):  
Surendra Adhikari ◽  
Erik Ivins ◽  
Eric Larour ◽  
Lambert Caron ◽  
Helene Seroussi
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Mass Exchange ◽  
Ice Sheets ◽  
Earth System ◽  
Generic Level ◽  
California Institute Of Technology ◽  
Ocean Mass ◽  
Institute Of Technology ◽  
And Sea Level

<p>Polar ice sheets are important components of the Earth System.  As the geometries of land, ocean, and ice sheets evolve, they must be consistently captured within the lexicon of geodesy.  Understanding the interplay between the processes such as ice-sheet dynamics, solid-Earth deformation, and sea-level adjustment requires both geodetically consistent and mass conserving descriptions of evolving land and ocean domains, grounded ice sheets and floating ice shelves, and their respective interfaces. Here we present mathematical descriptions of a generic level set that can be used to track both the grounding lines and coastlines, in light of ice-ocean mass exchange and complex feedbacks from the solid Earth and sea level. We next present a unified method to accurately compute the sea-level contribution of evolving ice sheets based on the change in ice thickness, bedrock elevation and mean sea level caused by any geophysical processes. Our formalism can be applied to arbitrary geometries and at all time scales. While it can be used for applications with modeling, observations and the combination of two, it is best suited for Earth System models, comprising ice sheets, solid Earth and sea level, that seek to conserve mass.</p><p>© 2020 California Institute of Technology. Government sponsorship is acknowledged.</p>

scholarly journals The Dynamics of Marine Ice Sheets

1979 ◽  
Vol 24 (90) ◽  
pp. 167-177 ◽  
Author(s):  
Robert H. Thomas
Keyword(s):  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Ice Streams ◽  
Ice Shelves ◽  
The North ◽  
West Antarctic ◽  
Grounding Line ◽  
Ice Sheet Dynamics

AbstractMarine ice sheets rest on land that, for the most part, is below sea-level. Ice that flows across the grounding line, where the ice sheet becomes afloat, either calves into icebergs or forms a floating ice shelf joined to the ice sheet. At the grounding line there is a transition from ice-sheet dynamics to ice-shelf dynamics, and the creep-thinning rate in this region is very sensitive to sea depth; rising sea-level causes increased thinning-rates and grounding-line retreat, falling sea-level has the reverse effect. If the bedrock slopes down towards the centre of the ice sheet there may be only two stable modes: a freely-floating ice shelf or a marine ice sheet that extends to the edge of the continental shelf. Once started, collapse of such an ice sheet to form an ice shelf may take place extremely rapidly. Ice shelves which form in embayments of a marine ice sheet, or which are partially grounded, have a stabilizing influence since ice flowing across the grounding line has to push the ice shelf past its sides. Retreat of the grounding line tends to enlarge the ice shelf, which ultimately may become large enough to prevent excessive outflow from the ice sheet so that a new equilibrium grounding line is established; removal of the ice shelf would allow retreat to continue. During the late-Wisconsin glacial maximum there may have been marine ice sheets in the northern hemisphere but the only current example is the West Antarctic ice sheet. This is buttressed by the Ross and Ronne Ice Shelves, and if climatic warming were to prohibit the existence of these ice shelves then the ice sheet would collapse. Field observations suggest that, at present, the ice sheet may be advancing into parts of the Ross Ice Shelf. Such advance, however, would not ensure the security of the ice sheet since ice streams that drain to the north appear to flow directly into the sea with little or no ice shelf to buttress them. If these ice streams do not flow over a sufficiently high bedrock sill then they provide the most likely avenues for ice-sheet retreat.

scholarly journals The Dynamics of Marine Ice Sheets

1979 ◽  
Vol 24 (90) ◽  
pp. 167-177 ◽  
Author(s):  
Robert H. Thomas
Keyword(s):  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Ice Streams ◽  
Ice Shelves ◽  
The North ◽  
West Antarctic ◽  
Grounding Line ◽  
Ice Sheet Dynamics

AbstractMarine ice sheets rest on land that, for the most part, is below sea-level. Ice that flows across the grounding line, where the ice sheet becomes afloat, either calves into icebergs or forms a floating ice shelf joined to the ice sheet. At the grounding line there is a transition from ice-sheet dynamics to ice-shelf dynamics, and the creep-thinning rate in this region is very sensitive to sea depth; rising sea-level causes increased thinning-rates and grounding-line retreat, falling sea-level has the reverse effect. If the bedrock slopes down towards the centre of the ice sheet there may be only two stable modes: a freely-floating ice shelf or a marine ice sheet that extends to the edge of the continental shelf. Once started, collapse of such an ice sheet to form an ice shelf may take place extremely rapidly. Ice shelves which form in embayments of a marine ice sheet, or which are partially grounded, have a stabilizing influence since ice flowing across the grounding line has to push the ice shelf past its sides. Retreat of the grounding line tends to enlarge the ice shelf, which ultimately may become large enough to prevent excessive outflow from the ice sheet so that a new equilibrium grounding line is established; removal of the ice shelf would allow retreat to continue. During the late-Wisconsin glacial maximum there may have been marine ice sheets in the northern hemisphere but the only current example is the West Antarctic ice sheet. This is buttressed by the Ross and Ronne Ice Shelves, and if climatic warming were to prohibit the existence of these ice shelves then the ice sheet would collapse. Field observations suggest that, at present, the ice sheet may be advancing into parts of the Ross Ice Shelf. Such advance, however, would not ensure the security of the ice sheet since ice streams that drain to the north appear to flow directly into the sea with little or no ice shelf to buttress them. If these ice streams do not flow over a sufficiently high bedrock sill then they provide the most likely avenues for ice-sheet retreat.

Slowdown in Antarctic mass loss from solid Earth and sea-level feedbacks

Science ◽  
2019 ◽  
Vol 364 (6444) ◽  
pp. eaav7908 ◽  
Author(s):  
E. Larour ◽  
H. Seroussi ◽  
S. Adhikari ◽  
E. Ivins ◽  
L. Caron ◽  
...  
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
West Antarctica ◽  
Spatiotemporal Resolution ◽  
Amundsen Sea ◽  
Polar Ice Sheets ◽  
Short Time ◽  
The Impact

Geodetic investigations of crustal motions in the Amundsen Sea sector of West Antarctica and models of ice-sheet evolution in the past 10,000 years have recently highlighted the stabilizing role of solid-Earth uplift on polar ice sheets. One critical aspect, however, that has not been assessed is the impact of short-wavelength uplift generated by the solid-Earth response to unloading over short time scales close to ice-sheet grounding lines (areas where the ice becomes afloat). Here, we present a new global simulation of Antarctic evolution at high spatiotemporal resolution that captures all solid Earth processes that affect ice sheets and show a projected negative feedback in grounding line migration of 38% for Thwaites Glacier 350 years in the future, or 26.8% reduction in corresponding sea-level contribution.

scholarly journals Capturing the Interactions Between Ice Sheets, Sea Level and the Solid Earth on a Range of Timescales: A new "time window" algorithm

2021 ◽  
Author(s):  
Holly Kyeore Han ◽  
Natalya Gomez ◽  
Jeannette Xiu Wen Wan
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Temporal Resolution ◽  
Time Window ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Sea Level Changes ◽  
Cpu Time ◽  
West Antarctic ◽  
Ice Sheet Dynamics

Abstract. Retreat and advance of ice sheets perturb the gravitational field, solid surface and rotation of the Earth, leading to spatially variable sea-level changes over a range of timescales (~O100-6 years), which in turn feed back onto ice sheet dynamics. Coupled ice-sheet – sea-level models have been developed to capture the interactive processes between ice sheets, sea level and the solid Earth, but it is computationally challenging to capture short-term interactions (~O100-2 years) precisely within longer (~O103-6 years) simulations. The classic coupling algorithm assigns a uniform temporal resolution in the sea-level model, causing a quadratic increase in total CPU time with the total number of input ice history steps, which increases with either the length or temporal resolution of the simulation. In this study, we introduce a new “time window” algorithm for sea-level models that enables users to define the temporal resolution at which the ice loading history is captured during different time intervals before the current simulation time. Utilizing the time window, we assign a fine temporal resolution (~O100-2 years) for the period of ongoing and recent history of surface ice and ocean loading changes and a coarser temporal resolution (~O103-6 years) for earlier periods in the simulation. This reduces the total CPU time and memory required per model time step while maintaining the precision of the model results. We explore the sensitivity of sea-level model results to the model's temporal resolution and show how this sensitivity feeds back onto ice sheet dynamics in coupled modelling. We apply the new algorithm to simulate the sea-level changes in response to global ice-sheet evolution over two glacial cycles and the rapid collapse of marine sectors of the West Antarctic Ice Sheet in the coming centuries, providing appropriate time window profiles for each of these applications. The time window algorithm improves the total CPU time by ~50–% in each of these examples, and this improvement would increase with longer simulations than considered here. Our algorithm also allows coupling time intervals of annual temporal scale for coupled ice-sheet – sea-level modelling of regions such as the West Antarctic that are characterized by rapid solid Earth response to ice changes due to the thin lithosphere and low mantle viscosities.

scholarly journals Editorial: Past ice sheet dynamics and sea level—placing the future in context

PAGES news ◽  
2009 ◽  
Vol 17 (2) ◽  
pp. 51-52 ◽  
Author(s):  
Mark Siddall ◽  
William G Thompson ◽  
Claire Waelbroeck
Keyword(s):  
Sea Level ◽  
Ice Sheet ◽  
The Future ◽  
Ice Sheet Dynamics ◽  
And Sea Level

Antarctic ice sheet response to upper-bound scenarios

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

<p>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 ‘realism’ 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.</p>

scholarly journals Last Interglacial climate and sea-level evolution from a coupled ice sheet–climate model

2016 ◽  
Vol 12 (12) ◽  
pp. 2195-2213 ◽  
Author(s):  
Heiko Goelzer ◽  
Philippe Huybrechts ◽  
Marie-France Loutre ◽  
Thierry Fichefet
Keyword(s):  
Surface Temperature ◽  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Last Interglacial ◽  
A Minor ◽  
The Antarctic ◽  
The Impact ◽  
And Sea Level

Abstract. As the most recent warm period in Earth's history with a sea-level stand higher than present, the Last Interglacial (LIG,  ∼  130 to 115 kyr BP) is often considered a prime example to study the impact of a warmer climate on the two polar ice sheets remaining today. Here we simulate the Last Interglacial climate, ice sheet, and sea-level evolution with the Earth system model of intermediate complexity LOVECLIM v.1.3, which includes dynamic and fully coupled components representing the atmosphere, the ocean and sea ice, the terrestrial biosphere, and the Greenland and Antarctic ice sheets. In this setup, sea-level evolution and climate–ice sheet interactions are modelled in a consistent framework.Surface mass balance change governed by changes in surface meltwater runoff is the dominant forcing for the Greenland ice sheet, which shows a peak sea-level contribution of 1.4 m at 123 kyr BP in the reference experiment. Our results indicate that ice sheet–climate feedbacks play an important role to amplify climate and sea-level changes in the Northern Hemisphere. The sensitivity of the Greenland ice sheet to surface temperature changes considerably increases when interactive albedo changes are considered. Southern Hemisphere polar and sub-polar ocean warming is limited throughout the Last Interglacial, and surface and sub-shelf melting exerts only a minor control on the Antarctic sea-level contribution with a peak of 4.4 m at 125 kyr BP. Retreat of the Antarctic ice sheet at the onset of the LIG is mainly forced by rising sea level and to a lesser extent by reduced ice shelf viscosity as the surface temperature increases. Global sea level shows a peak of 5.3 m at 124.5 kyr BP, which includes a minor contribution of 0.35 m from oceanic thermal expansion. Neither the individual contributions nor the total modelled sea-level stand show fast multi-millennial timescale variations as indicated by some reconstructions.

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