Response to Filchner–Ronne Ice Shelf cavity warming in a coupled ocean–ice sheet model – Part 1: The ocean perspective

Timmermann, Ralph; Goeller, Sebastian

doi:10.5194/os-13-765-2017

Cited by 53 publications

(56 citation statements)

References 33 publications

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“…There are also more local feedbacks that are not represented in our framework. For example, increased ice-shelf melting can lead to more advection of offshore circumpolar deep water towards the grounding lines and thereby create a positive feedback to melt rates (Hellmer et al, 2017;Timmermann and Goeller, 2017;Donat-Magnin et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

A protocol for calculating basal melt rates in the ISMIP6 Antarctic ice sheet projections

Jourdain¹,

Asay‐Davis²,

Hattermann³

et al. 2019

Preprint

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Abstract. Climate model projections have previously been used to compute ice-shelf basal melt rates in ice-sheet models, but the strategies employed – e.g. ocean input, parameterization, calibration technique, and corrections – have varied widely and are often ad-hoc. Here, a methodology is proposed for the calculation of circum-Antarctic basal melt rates for floating ice, based on climate models, that is suitable for ISMIP6, the Ice Sheet Model Intercomparison Project for CMIP6 (6th Coupled Model Intercomparison Project). The past and future evolution of ocean temperature and salinity is derived from a climate model by estimating anomalies with respect to the modern day, which are added to an present-day climatology constructed from existing observational datasets. Temperature and salinity are extrapolated to any position potentially occupied by a simulated ice shelf. A simple formulation is proposed for a basal-melt parameterization in ISMIP6, constrained by the observed temperature climatology, with a quadratic dependency on either the non-local or local thermal forcing. Two calibration methods are proposed: 1) based on the mean Antarctic melt rate (MeanAnt) and 2) based on melt rates near Pine Island's deep grounding line (PIGL). Future Antarctic mean melt rates are an order of magnitude greater in PIGL than in MeanAnt. The PIGL calibration, and the local parameterization, result in more realistic melt rates near grounding lines. PIGL is also more consistent with observations of interannual melt rate variability underneath Pine Island and Dotson ice shelves. This work stresses the need for more physics and less calibration in the parameterizations, and for more observations of hydrographic properties and melt rates at interannual and decadal time scales.

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Section: Discussionmentioning

confidence: 99%

A protocol for calculating basal melt rates in the ISMIP6 Antarctic ice sheet projections

Jourdain¹,

Asay‐Davis²,

Hattermann³

et al. 2019

Preprint

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“…These results confirm an earlier study (Makinson et al, 2011) demonstrating that adding tide forcing to numerical models substantially increases basal melting along the deep grounding lines of FRIS and increases marine ice formation rates under RIS. Melting in these grounding-line regions has been shown to introduce a positive feedback to w b in response to increased basal slope and wct (Timmermann and Goeller, 2017). In this study, we address the combined influences from change in cavity shape, ocean warming, and tides.…”

Section: Discussionmentioning

confidence: 99%

Tidal influences on a future evolution of the Filchner–Ronne Ice Shelf cavity in the Weddell Sea, Antarctica

et al. 2018

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Abstract. Recent modeling studies of ocean circulation in the southern Weddell Sea, Antarctica, project an increase over this century of ocean heat into the cavity beneath Filchner-Ronne Ice Shelf (FRIS). This increase in ocean heat would lead to more basal melting and a modification of the FRIS ice draft. The corresponding change in cavity shape will affect advective pathways and the spatial distribution of tidal currents, which play important roles in basal melting under FRIS. These feedbacks between heat flux, basal melting, and tides will affect the evolution of FRIS under the influence of a changing climate. We explore these feedbacks with a three-dimensional ocean model of the southern Weddell Sea that is forced by thermodynamic exchange beneath the ice shelf and tides along the open boundaries. Our results show regionally dependent feedbacks that, in some areas, substantially modify the melt rates near the grounding lines of buttressed ice streams that flow into FRIS. These feedbacks are introduced by variations in meltwater production as well as the circulation of this meltwater within the FRIS cavity; they are influenced locally by sensitivity of tidal currents to water column thickness (wct) and non-locally by changes in circulation pathways that transport an integrated history of mixing and meltwater entrainment along flow paths. Our results highlight the importance of including explicit tidal forcing in models of future mass loss from FRIS and from the adjacent grounded ice sheet as individual ice-stream grounding zones experience different responses to warming of the ocean inflow.

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“…The deep bathymetry to the south (Fretwell et al, 2013) and ocean melting likely prevented further migration upstream. Using estimated melt rates of between 1 m/year (Joughin, 2003;Timmermann & Goeller, 2017) and 3.5 m/year (using the minimum ∇.u on the ocean side of the GL; −4 × 10 −3 year −1 , Wearing, 2016, in the steady-state continuity equation) suggests that the GL has Journal of Geophysical Research: Earth Surface 10.1029/2018JF004988 been here for at least 260-900 years given the current ice thickness (900 m), but we cannot rule out it being here for much longer.…”

Section: Timing Of Ice-rise Evolutionmentioning

confidence: 99%

Holocene Formation of Henry Ice Rise, West Antarctica, Inferred From Ice‐Penetrating Radar

Wearing

Kingslake

2019

JGR Earth Surface

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Ice rises are regions of grounded ice embedded within floating ice shelves. The deformation of ice past them increases the back stress generated by the ice shelf, slowing the flow of the ice sheet. We present ground‐based ice‐penetrating radar data from Henry Ice Rise in the Ronne Ice Shelf, West Antarctica, that indicates regrounding during the Holocene. Relic crevasses and melt synclines are observed upstream of the present‐day grounding line. We conclude that these features formed during a previous flow configuration, from which the grounding line has since advanced to its current position. In agreement with previous work, our observations can be explained if initial grounding of the ice shelf occurred on a bathymetric high, forming an ice rumple that migrated upstream and temporarily ungrounded over the topographic high. The grounding line then advanced, preserving relic basal crevasses in the newly grounded ice. Using a simple ice‐flow model, we simulate the burial of these crevasses. While accounting for uncertainty in accumulation, firn density, radar‐derived depth, ice‐thickening history, initial crevasse height, and glacial isostatic adjustment, we estimate a burial time of 6 ± 2 kyr before present for the oldest relic crevasses, indicating that the ice rise formed at approximately this time. This potentially increased the buttressing generated by the Ronne Ice Shelf, causing thickening and advance of the ice sheet. By dating the formation and providing details of ice‐rise formation, these new results can provide useful constraints on both large‐scale ice‐sheet models and models of ice‐rumple and ice‐rise formation.

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Response to Filchner–Ronne Ice Shelf cavity warming in a coupled ocean–ice sheet model – Part 1: The ocean perspective

Cited by 53 publications

References 33 publications

A protocol for calculating basal melt rates in the ISMIP6 Antarctic ice sheet projections

A protocol for calculating basal melt rates in the ISMIP6 Antarctic ice sheet projections

Tidal influences on a future evolution of the Filchner–Ronne Ice Shelf cavity in the Weddell Sea, Antarctica

Holocene Formation of Henry Ice Rise, West Antarctica, Inferred From Ice‐Penetrating Radar

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