A large-scale numerical model for computing isochrone geometry

Hindmarsh, Richard C. A.; Vieli, Gwendolyn J.-M. C. Leysinger; Parrenin, Frédéric

doi:10.3189/172756409789097450

Cited by 31 publications

(37 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The vertical velocity field is derived from mass conservation combined with the incompressibility condition for ice. Given an ice sheet in steady state, a simple analytical expression can be obtained, based on the horizontal balance velocities (Hindmarsh, 1999;Hindmarsh et al, 2009). Expressed in local coordinates, and in the absence of subglacial melting, this leads to…”

Section: Velocity Fieldmentioning

confidence: 99%

Using ice-flow models to evaluate potential sites of million year-old ice in Antarctica

2013

View full text Add to dashboard Cite

Abstract. Finding suitable potential sites for an undisturbed record of million-year old ice in Antarctica requires slowmoving ice (preferably an ice divide) and basal conditions that are not disturbed by large topographic variations. Furthermore, ice should be thick and cold basal conditions should prevail, since basal melting would destroy the bottom layers. However, thick ice (needed to resolve the signal at sufficient high resolution) increases basal temperatures, which is a conflicting condition for finding a suitable drill site. In addition, slow moving areas in the center of ice sheets are also low-accumulation areas, and low accumulation reduces potential cooling of the ice through vertical advection. While boundary conditions such as ice thickness and accumulation rates are relatively well constrained, the major uncertainty in determining basal thermal conditions resides in the geothermal heat flow (GHF) underneath the ice sheet. We explore uncertainties in existing GHF data sets and their effect on basal temperatures of the Antarctic Ice Sheet, and propose an updated method based on Pattyn (2010) to improve existing GHF data sets in agreement with known basal temperatures and their gradients to reduce this uncertainty. Both complementary methods lead to a better comprehension of basal temperature sensitivity and a characterization of potential ice coring sites within these uncertainties. The combination of both modeling approaches show that the most likely oldest ice sites are situated near the divide areas (close to existing deep drilling sites, but in areas of smaller ice thickness) and across the Gamburtsev Subglacial Mountains.

show abstract

Section: Velocity Fieldmentioning

confidence: 99%

Using ice-flow models to evaluate potential sites of million year-old ice in Antarctica

2013

View full text Add to dashboard Cite

show abstract

“…Other feedbacks relate ice sheet dynamics to basal sliding through thermoviscous instabilities, which may lead to limitcycle behaviour in ice sheets (Payne, 1995;Pattyn, 1996) as well as ice stream development in the absence of strong basal topographic control (Payne and Dongelmans, 1997;Payne et al, 2000;Hindmarsh et al, 2009). More elaborate subglacial water flow models have since been developed, exhibiting similar feedback mechanisms in ice discharge (Schoof, 2010).…”

Section: Introductionmentioning

confidence: 99%

Sea-level response to melting of Antarctic ice shelves on multi-centennial timescales with the fast Elementary Thermomechanical Ice Sheet model (f.ETISh v1.0)

2017

View full text Add to dashboard Cite

Abstract. The magnitude of the Antarctic ice sheet's contribution to global sea-level rise is dominated by the potential of its marine sectors to become unstable and collapse as a response to ocean (and atmospheric) forcing. This paper presents Antarctic sea-level response to sudden atmospheric and oceanic forcings on multi-centennial timescales with the newly developed fast Elementary Thermomechanical Ice Sheet (f.ETISh) model. The f.ETISh model is a vertically integrated hybrid ice sheet-ice shelf model with vertically integrated thermomechanical coupling, making the model twodimensional. Its marine boundary is represented by two different flux conditions, coherent with power-law basal sliding and Coulomb basal friction. The model has been compared to existing benchmarks.Modelled Antarctic ice sheet response to forcing is dominated by sub-ice shelf melt and the sensitivity is highly dependent on basal conditions at the grounding line. Coulomb friction in the grounding-line transition zone leads to significantly higher mass loss in both West and East Antarctica on centennial timescales, leading to 1.5 m sea-level rise after 500 years for a limited melt scenario of 10 m a −1 under freely floating ice shelves, up to 6 m for a 50 m a −1 scenario. The higher sensitivity is attributed to higher ice fluxes at the grounding line due to vanishing effective pressure.Removing the ice shelves altogether results in a disintegration of the West Antarctic ice sheet and (partially) marine basins in East Antarctica. After 500 years, this leads to a 5 m and a 16 m sea-level rise for the power-law basal sliding and Coulomb friction conditions at the grounding line, respectively. The latter value agrees with simulations by DeConto and Pollard (2016) over a similar period (but with different forcing and including processes of hydrofracturing and cliff failure).The chosen parametrizations make model results largely independent of spatial resolution so that f.ETISh can potentially be integrated in large-scale Earth system models.

show abstract

“…The age of isochrones in a flowing ice cap can be regarded as a transport equation and solved accordingly. Following, e.g., Hindmarsh et al [2009], age is denoted X and the ageing equation is

\frac{\partial X}{\partial t} + v \cdot \nabla X = 1,

where v is the velocity field. The solution of this equation has been discussed in several studies [e.g., Greve et al , 2002; Parrenin et al , 2006].…”

Section: Methodsmentioning

confidence: 99%

“…Thus the horizontal velocity u can be calculated from the expression u =

bold \bar{u}

v ( ζ , r ) where

bold \bar{u}

is the vertically averaged velocity. We investigate both scenarios with the assumption that the horizontal surface velocities are equal to the balance velocities calculated from the surface slope and the mass balance (for information on calculating balance velocities see Hindmarsh et al [2009]). The vertical velocity field is found using the continuity equation.…”

Section: Methodsmentioning

confidence: 99%

Testing for flow in the north polar layered deposits of Mars using radar stratigraphy and a simple 3D ice-flow model

Karlsson¹,

Holt²,

Hindmarsh³

2011

Geophys. Res. Lett.

View full text Add to dashboard Cite

The water‐ice‐rich north polar layered deposits (NPLD) of Mars play a key role in the Martian climate through an active exchange of water vapor with the atmosphere. Conditions are not currently amenable for flow of the NPLD; however, gross morphological evidence for past flow suggests the possibility of a warmer climate in the past. Here we present the first comparison of internal stratigraphy predicted by a flow model with that observed by an orbital radar sounder. We have analyzed radar data from Gemina Lingula, the southernmost tongue of the NPLD, acquired by the Shallow Radar on board NASA’s Mars Reconnaissance Orbiter. The data shows extensive internal reflections and several radar reflectors were mapped to create gridded surfaces of this part of the NPLD. All the mapped radar reflectors were smooth with no sudden dips towards the surface or the bedrock. The internal radar reflectors were then compared with modeled isochrones in two different areas of Gemina Lingula under the assumption of flow occurring. Results indicate that flow of ice is unlikely to have occurred between the main dome and Gemina Lingula. Furthermore, we found no evidence for the existence of a prior ablation zone in Gemina Lingula as predicted in another study.

show abstract

A large-scale numerical model for computing isochrone geometry

Cited by 31 publications

References 32 publications

Using ice-flow models to evaluate potential sites of million year-old ice in Antarctica

Using ice-flow models to evaluate potential sites of million year-old ice in Antarctica

Sea-level response to melting of Antarctic ice shelves on multi-centennial timescales with the fast Elementary Thermomechanical Ice Sheet model (f.ETISh v1.0)

Testing for flow in the north polar layered deposits of Mars using radar stratigraphy and a simple 3D ice-flow model

Contact Info

Product

Resources

About