Sensitivity of Greenland ice sheet projections to spatial resolution in higher-order simulations: the AWI contribution to ISMIP6-Greenland using ISSM

Rückamp, Martin; Goelzer, Heiko; Humbert, Angelika

doi:10.5194/tc-2019-329

Cited by 4 publications

(6 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Of particular importance for sea-level predictions are observations of ice streams that transport ice from the interior of the ice sheet to the margin, where it either melts or calves into icebergs. Dynamic processes of ice sheets in Greenland and Antarctica have been progressively included in numerical models to project sea-level changes (Robinson and others, 2012; Church and others, 2013; Goelzer and others, 2020; Rückamp and others, 2020). To simulate present ice stream flow and determine its contribution to the mass balance of ice sheets, we have to understand the natural variability of ice stream dynamics on time scales of tens to thousands of years (Robel and others, 2013).…”

Section: Introductionmentioning

confidence: 99%

Bed topography and subglacial landforms in the onset region of the Northeast Greenland Ice Stream

et al. 2020

View full text Add to dashboard Cite

The Northeast Greenland Ice Stream (NEGIS) is an important dynamic component for the total mass balance of the Greenland ice sheet, as it reaches up to the central divide and drains 12% of the ice sheet. The geometric boundary conditions and in particular the nature of the subglacial bed of the NEGIS are essential to understand its ice flow dynamics. We present a record of more than 8000 km of radar survey lines of multi-channel, ultra-wideband radio echo sounding data covering an area of 24 000 km2, centered on the drill site for the East Greenland Ice-core Project (EGRIP), in the upper part of the NEGIS catchment. Our data yield a new detailed model of ice-thickness distribution and basal topography in the region. The enhanced resolution of our bed topography model shows features which we interpret to be caused by erosional activity, potentially over several glacial–interglacial cycles. Off-nadir reflections from the ice–bed interface in the center of the ice stream indicate a streamlined bed with elongated subglacial landforms. Our new bed topography model will help to improve the basal boundary conditions of NEGIS prescribed for ice flow models and thus foster an improved understanding of the ice-dynamic setting.

show abstract

Section: Introductionmentioning

confidence: 99%

Bed topography and subglacial landforms in the onset region of the Northeast Greenland Ice Stream

et al. 2020

View full text Add to dashboard Cite

show abstract

“…During the last 9000 years, the computed topography is continuously nudged towards the (slightly smoothed) observed present-day topography. Prior to 1000 years ago, this is done by the method described by Rückamp et al (2019). For the last 1000 years, the "implied Table A1.…”

Section: A4 Iltspik-sicopolismentioning

confidence: 99%

“…In the vertical, we use terrain-following coordinates with 81 layers in the ice domain and 41 layers in the thermal lithosphere layer below. The present-day surface temperature is parameterized (Fausto et al, 2009;Rückamp et al, 2019). The bed topography is BedMachine v3 (Morlighem et al, 2017), the geothermal heat flux is by Greve (2019), and glacial isostatic adjustment (GIA) is modelled by the local-lithosphere-relaxing-asthenosphere (LLRA) approach with a time lag of 3000 years (Le Meur and Huybrechts, 1996).…”

Section: A4 Iltspik-sicopolismentioning

confidence: 99%

The future sea-level contribution of the Greenland ice sheet: a multi-model ensemble study of ISMIP6

et al. 2020

Self Cite

View full text Add to dashboard Cite

Abstract. The Greenland ice sheet is one of the largest contributors to global mean sea-level rise today and is expected to continue to lose mass as the Arctic continues to warm. The two predominant mass loss mechanisms are increased surface meltwater run-off and mass loss associated with the retreat of marine-terminating outlet glaciers. In this paper we use a large ensemble of Greenland ice sheet models forced by output from a representative subset of the Coupled Model Intercomparison Project (CMIP5) global climate models to project ice sheet changes and sea-level rise contributions over the 21st century. The simulations are part of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6). We estimate the sea-level contribution together with uncertainties due to future climate forcing, ice sheet model formulations and ocean forcing for the two greenhouse gas concentration scenarios RCP8.5 and RCP2.6. The results indicate that the Greenland ice sheet will continue to lose mass in both scenarios until 2100, with contributions of 90±50 and 32±17 mm to sea-level rise for RCP8.5 and RCP2.6, respectively. The largest mass loss is expected from the south-west of Greenland, which is governed by surface mass balance changes, continuing what is already observed today. Because the contributions are calculated against an unforced control experiment, these numbers do not include any committed mass loss, i.e. mass loss that would occur over the coming century if the climate forcing remained constant. Under RCP8.5 forcing, ice sheet model uncertainty explains an ensemble spread of 40 mm, while climate model uncertainty and ocean forcing uncertainty account for a spread of 36 and 19 mm, respectively. Apart from those formally derived uncertainty ranges, the largest gap in our knowledge is about the physical understanding and implementation of the calving process, i.e. the interaction of the ice sheet with the ocean.

show abstract

“…Societal ability to accurately predict global sea levels in future climates depends, in part, on the fidelity of ice flow patterns predicted by these models. This, in turn, depends on sliding speeds (Rückamp et al, 2020) via basal hydrologic conditions, which evolve according to the spatial distribution and timing of melt water delivery to the subglacial system (e.g., Banwell et al, 2016). State-of-the-art ice-sheet projections, such as those from ISMIP6, currently do not explicitly include meltwater inputs to the bed (Nowicki et al, 2020), and most current development work in this area is focused on climate model -ice-sheet model coupling for improving surface mass balance (e.g., Goelzer et al, 2020).…”

Section: Parameterizing Moulins In Ice-sheet Modelsmentioning

confidence: 99%

Challenges in predicting Greenland supraglacial lake drainages at the regional scale

Poinar¹,

Andrews²

2020

Preprint

View full text Add to dashboard Cite

Abstract. A leading hypothesis for the mechanism of fast supraglacial lake drainages is that transient extensional stresses briefly allow crevassing in otherwise-compressive ice flow regimes. Lake water can then hydrofracture the crevasse to the base of the ice sheet, and river inputs can maintain this connection as a moulin. If future ice-sheet models are to accurately represent moulins, we must understand their formation processes, timescales, and locations. Here, we use remote-sensing velocity products to constrain the relationship between strain rates and lake drainages across ~ 1600 km2 in Pâkitsoq, western Greenland, between 2002–2019. We find significantly more-extensional background strain rates at moulins associated with fast-draining lakes than at slow-draining or non-draining lake moulins. We test whether moulins in more-extensional background settings drain their lakes earlier, but find insignificant correlation. To investigate the frequency that strain-rate transients are associated with fast lake drainage, we examined Landsat-derived strain rates over 16- and 32-day periods at moulins associated with 240 fast lake drainage events over 18 years. A low signal-to-noise ratio, the presence of water, and the multi-week repeat cycle obscured any resolution of the hypothesized transient strain rates. Our results support the hypothesis that transient strain rates drive fast lake drainages. However, the current generation of ice-sheet velocity products, even when stacked across hundreds of fast lake drainages, cannot resolve these transients. Thus, observational progress in understanding lake drainage initiation will rely on field-based tools such as GPS networks and photogrammetry.

show abstract

Sensitivity of Greenland ice sheet projections to spatial resolution in higher-order simulations: the AWI contribution to ISMIP6-Greenland using ISSM

Cited by 4 publications

References 36 publications

Bed topography and subglacial landforms in the onset region of the Northeast Greenland Ice Stream

Bed topography and subglacial landforms in the onset region of the Northeast Greenland Ice Stream

The future sea-level contribution of the Greenland ice sheet: a multi-model ensemble study of ISMIP6

Challenges in predicting Greenland supraglacial lake drainages at the regional scale

Contact Info

Product

Resources

About