The Response of Ice Sheets to Climate Variability

Snow, Kate; Goldberg, Daniel; Holland, Paul R.; Jordan, James; Arthern, Robert; Jenkins, Adrian

doi:10.1002/2017gl075745

Cited by 28 publications

(41 citation statements)

References 22 publications

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“…The low melt rates near the grounding line in the velocity-dependent models are due to low velocities just beneath the shelf. This is in line with idealized models using velocity-dependent melt rates (Little et al, 2009;Snow et al, 2017), which also suggest low melting at the grounding line. The RTOPO model (see Figure S3) does indicate elevated melt rates along Dotson's west margin, but the poor agreement in every other respect is likely due to the incorrect bathymetry.…”

Section: Modeled Melt Ratessupporting

confidence: 87%

How Accurately Should We Model Ice Shelf Melt Rates?

Goldberg

Gourmelen

Kimura

et al. 2019

Geophysical Research Letters

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127

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Assessment of ocean‐forced ice sheet loss requires that ocean models be able to represent sub‐ice shelf melt rates. However, spatial accuracy of modeled melt is not well investigated, and neither is the level of accuracy required to assess ice sheet loss. Focusing on a fast‐thinning region of West Antarctica, we calculate spatially resolved ice‐shelf melt from satellite altimetry and compare against results from an ocean model with varying representations of cavity geometry and ocean physics. Then, we use an ice‐flow model to assess the impact of the results on grounded ice. We find that a number of factors influence model‐data agreement of melt rates, with bathymetry being the leading factor; but this agreement is only important in isolated regions under the ice shelves, such as shear margins and grounding lines. To improve ice sheet forecasts, both modeling and observations of ice‐ocean interactions must be improved in these critical regions.

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Section: Modeled Melt Ratessupporting

confidence: 87%

How Accurately Should We Model Ice Shelf Melt Rates?

Goldberg

Gourmelen

Kimura

et al. 2019

Geophysical Research Letters

Self Cite

127

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show abstract

“…A caveat of this approach is that we may overestimate warming in regions that are already relatively warm but that switch from cold to warm conditions in the CMIP models. As ice shelves act as low-pass filters (Snow et al, 2017), we do not attempt to represent seasonal variability in the ocean forcing, e.g., we do not represent melting by seasonally warming Antarctic Surface Water. Because of the quadratic formulation, accounting for the seasonal variability might change the average melt rates, but we are unsure whether the observational datasets can accurately represent the seasonal cycle (mostly due to the lack of observations in winter), and we leave this for future developments.…”

Section: Approachmentioning

confidence: 99%

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

et al. 2020

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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 a 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 nonlocal 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 timescales.

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“…A caveat of this approach is that we may overestimate warming in regions that are already relatively warm, but that switch from cold to warm conditions in the CMIP models. As ice shelves act as low pass filters (Snow et al, 2017), we do not attempt to represent seasonal variability in the ocean forcing, e.g. we do not represent melting by seasonally warming Antarctic Surface Water.…”

Section: Approachmentioning

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.

show abstract

The Response of Ice Sheets to Climate Variability

Cited by 28 publications

References 22 publications

How Accurately Should We Model Ice Shelf Melt Rates?

How Accurately Should We Model Ice Shelf Melt Rates?

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

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