Ice shelf basal melt rates from a high-resolution digital elevation model (DEM) record for Pine Island Glacier, Antarctica

Abstract. Ocean-induced basal melting is responsible for much of the Amundsen Sea Embayment ice loss in recent decades, but the total magnitude and spatiotemporal evolution of this melt is poorly constrained. To address this problem, we generated a record of high-resolution digital elevation models (DEMs) for Pine Island Glacier (PIG) using commercial sub-meter satellite stereo imagery and integrated additional 2002–2015 DEM and altimetry data. We implemented a Lagrangian elevation change (Dh∕Dt) framework to estimate ice shelf basal melt rates at 32–256 m resolution. We describe this methodology and consider basal melt rates and elevation change over the PIG ice shelf and lower catchment from 2008 to 2015. We document the evolution of Eulerian elevation change (dh∕dt) and upstream propagation of thinning signals following the end of rapid grounding line retreat around 2010. Mean full-shelf basal melt rates for the 2008–2015 period were ∼82–93 Gt yr−1, with ∼200–250 m yr−1 basal melt rates within large channels near the grounding line, ∼10–30 m yr−1 over the main shelf, and ∼0–10 m yr−1 over the North shelf and South shelf, with the notable exception of a small area with rates of ∼50–100 m yr−1 near the grounding line of a fast-flowing tributary on the South shelf. The observed basal melt rates show excellent agreement with, and provide context for, in situ basal melt-rate observations. We also document the relative melt rates for kilometer-scale basal channels and keels at different locations on the ice shelf and consider implications for ocean circulation and heat content. These methods and results offer new indirect observations of ice–ocean interaction and constraints on the processes driving sub-shelf melting beneath vulnerable ice shelves in West Antarctica.

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Ice shelf basal melt rates from a high-resolution DEM record for Pine Island Glacier, Antarctica

10.5194/tc-2018-209 ◽

2018 ◽

Cited By ~ 3

Author(s):

David E. Shean ◽

Ian R. Joughin ◽

Pierre Dutrieux ◽

Benjamin E. Smith ◽

Etienne Berthier

Keyword(s):

High Resolution ◽

Ocean Circulation ◽

Heat Content ◽

Elevation Change ◽

Ice Shelf ◽

Amundsen Sea ◽

The North ◽

Grounding Line ◽

Total Magnitude ◽

Basal Melting

Abstract. Ocean-induced basal melting is directly and indirectly responsible for much of the Amundsen Sea Embayment ice loss in recent decades, but the total magnitude and spatiotemporal evolution of this melt is poorly constrained. To address this problem, we generated a record of high-resolution Digital Elevation Models (DEMs) for Pine Island Glacier (PIG) using commercial sub-meter satellite stereo imagery and integrated additional 2002–2015 DEM/altimetry data. We implemented a Lagrangian elevation change (Dh/Dt) framework to estimate ice shelf basal melt rates at 32–256-m resolution. We describe this methodology and consider basal melt rates and elevation change over the PIG shelf and lower catchment from 2008–2015. We document the evolution of Eulerian elevation change (dh/dt) and upstream propagation of thinning signals following the end of rapid grounding line retreat around 2010. Mean full-shelf basal melt rates for the 2008–2015 period were ~82–93 Gt/yr, with ~ 200–250 m/yr basal melt rates within large channels near the grounding line, ~ 10–30 m/yr over the main shelf, and ~ 0–10 m/yr over the North and South shelves, with the notable exception of a small area with rates of ~ 50–100 m/yr near the grounding line of a fast-flowing tributary on the South shelf. The observed basal melt rates show excellent agreement with, and provide context for, in situ basal melt rate observations. We also document the relative melt rates for km-scale basal channels and keels at different locations on the shelf and consider implications for ocean circulation and heat content. These methods and results offer new indirect observations of ice-ocean interaction and constraints on the processes driving sub-shelf melting beneath vulnerable ice shelves in West Antarctica.

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Brief communication: PICOP, a new ocean melt parameterization under ice shelves combining PICO and a plume model

The Cryosphere ◽

10.5194/tc-13-1043-2019 ◽

2019 ◽

Vol 13 (3) ◽

pp. 1043-1049 ◽

Cited By ~ 7

Author(s):

Tyler Pelle ◽

Mathieu Morlighem ◽

Johannes H. Bondzio

Keyword(s):

Ocean Circulation ◽

Numerical Models ◽

Three Dimensional ◽

Ice Sheet ◽

Ice Shelf ◽

Ice Streams ◽

Amundsen Sea ◽

Ice Shelves ◽

Grounding Line ◽

Basal Melting

Abstract. Basal melting at the bottom of Antarctic ice shelves is a major control on glacier dynamics, as it modulates the amount of buttressing that floating ice shelves exert onto the ice streams feeding them. Three-dimensional ocean circulation numerical models provide reliable estimates of basal melt rates but remain too computationally expensive for century-scale projections. Ice sheet modelers therefore routinely rely on simplified parameterizations based on either ice shelf depth or more sophisticated box models. However, existing parameterizations do not accurately resolve the complex spatial patterns of sub-shelf melt rates that have been observed over Antarctica's ice shelves, especially in the vicinity of the grounding line, where basal melting is one of the primary drivers of grounding line migration. In this study, we couple the Potsdam Ice-shelf Cavity mOdel (PICO, Reese et al., 2018) to a buoyant plume melt rate parameterization (Lazeroms et al., 2018) to create PICOP, a novel basal melt rate parameterization that is easy to implement in transient ice sheet numerical models and produces a melt rate field that is in excellent agreement with the spatial distribution and magnitude of observations for several ocean basins. We test PICOP on the Amundsen Sea sector of West Antarctica, Totten, and Moscow University ice shelves in East Antarctica and the Filchner-Ronne Ice Shelf and compare the results to PICO. We find that PICOP is able to reproduce inferred high melt rates beneath Pine Island, Thwaites, and Totten glaciers (on the order of 100 m yr−1) and removes the “banding” pattern observed in melt rates produced by PICO over the Filchner-Ronne Ice Shelf. PICOP resolves many of the issues contemporary basal melt rate parameterizations face and is therefore a valuable tool for those looking to make future projections of Antarctic glaciers.

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Ice-shelf basal channels in a coupled ice/ocean model

Journal of Glaciology ◽

10.3189/2012jog12j003 ◽

2012 ◽

Vol 58 (212) ◽

pp. 1227-1244 ◽

Cited By ~ 56

Author(s):

Carl V. Gladish ◽

David M. Holland ◽

Paul R. Holland ◽

Stephen F. Price

Keyword(s):

Ocean Circulation ◽

Coupled System ◽

Ocean Model ◽

Subsurface Water ◽

Ice Thickness ◽

Ice Shelf ◽

First Approximation ◽

Grounding Line ◽

History Of ◽

Basal Melting

AbstractA numerical model for an interacting ice shelf and ocean is presented in which the ice- shelf base exhibits a channelized morphology similar to that observed beneath Petermann Gletscher’s (Greenland) floating ice shelf. Channels are initiated by irregularities in the ice along the grounding line and then enlarged by ocean melting. To a first approximation, spatially variable basal melting seaward of the grounding line acts as a steel-rule die or a stencil, imparting a channelized form to the ice base as it passes by. Ocean circulation in the region of high melt is inertial in the along-channel direction and geostrophically balanced in the transverse direction. Melt rates depend on the wavelength of imposed variations in ice thickness where it enters the shelf, with shorter wavelengths reducing overall melting. Petermann Gletscher’s narrow basal channels may therefore act to preserve the ice shelf against excessive melting. Overall melting in the model increases for a warming of the subsurface water. The same sensitivity holds for very slight cooling, but for cooling of a few tenths of a degree a reorganization of the spatial pattern of melting leads, surprisingly, to catastrophic thinning of the ice shelf 12 km from the grounding line. Subglacial discharge of fresh water along the grounding line increases overall melting. The eventual steady state depends on when discharge is initiated in the transient history of the ice, showing that multiple steady states of the coupled system exist in general.

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Representation of basal melting in idealised coupled ice sheet ocean models

10.5194/egusphere-egu21-10448 ◽

2021 ◽

Author(s):

Chen Zhao ◽

Rupert Gladstone ◽

Ben Galton-Fenzi ◽

David Gwyther

Keyword(s):

Ocean Circulation ◽

Critical Role ◽

Ice Sheet ◽

Ocean Model ◽

Periodic Pattern ◽

Regional Ocean Modeling System ◽

Ice Shelf ◽

Grounding Line ◽

Ocean Models ◽

Basal Melting

<p>The ocean-driven basal melting has important implications for the stability of ice shelves in Antarctic, which largely affects the ice sheet mass balance, ocean circulation, and subsequently global sea level rise. Due to the limited observations in the ice shelf cavities, the couple ice sheet ocean models have been playing a critical role in examining the processes governing basal melting. In this study we use the Framework for Ice Sheet-Ocean Coupling (FISOC) to couple the Elmer/Ice full-stokes ice sheet model and the Regional Ocean Modeling System (ROMS) ocean model to model ice shelf/ocean interactions for an idealised three-dimensional domain. Experiments followed the coupled ice sheet&#8211;ocean experiments under the first phase of the Marine Ice Sheet&#8211;Ocean Model Intercomparison Project (MISOMIP1). A periodic pattern in the simulated mean basal melting rates is found to be highly consistent with the maximum barotropic stream function and also the grounding line retreat row by row, &#160;which is likely to be related with the gyre break down near the grounding line caused by some non-physical instability events from the ocean bottom. Sensitivity tests are carried out, showing that this periodic pattern is not sensitive to the choice of couple time intervals and horizontal eddy viscosities but sensitive to vertical resolution in the ocean model, the chosen critical water column thickness in the wet-dry scheme, and the tracer properties for the nudging dry cells at the ice-ocean interface boundary. Further simulations are necessary to better explain the mechanism involved in the couple ice-ocean system, which is very significant for its application on the realistic ice-ocean systems in polar regions.</p>

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On the coupled response to ice-shelf basal melting

Journal of Glaciology ◽

10.3189/2012jog11j037 ◽

2012 ◽

Vol 58 (208) ◽

pp. 203-215 ◽

Cited By ~ 14

Author(s):

Christopher M. Little ◽

Daniel Goldberg ◽

Anand Gnanadesikan ◽

Michael Oppenheimer

Keyword(s):

Temporal Evolution ◽

Closed Form Solution ◽

Form Solution ◽

Ice Shelf ◽

Ice Streams ◽

Amundsen Sea ◽

Ice Shelves ◽

Grounding Line ◽

Tightly Coupled ◽

Basal Melting

AbstractIce-shelf basal melting is tightly coupled to ice-shelf morphology. Ice shelves, in turn, are coupled to grounded ice via their influence on compressive stress at the grounding line (‘ice-shelf buttressing’). Here, we examine this interaction using a local parameterization that relates the basal melt rate to the ice-shelf thickness gradient. This formulation permits a closed-form solution for a steady-state ice tongue. Time-dependent numerical simulations reveal the spatial and temporal evolution of ice-shelf/ice-stream systems in response to changes in ocean temperature, and the influence of morphology-dependent melting on grounding-line retreat. We find that a rapid (<1 year) re-equilibration in upstream regions of ice shelves establishes a spatial pattern of basal melt rates (relative to the grounding line) that persists over centuries. Coupling melting to ice-shelf shape generally, but not always, increases grounding-line retreat rates relative to a uniform distribution with the same area- average melt rate. Because upstream ice-shelf thickness gradients and retreat rates increase nonlinearly with thermal forcing, morphology-dependent melting is more important to the response of weakly buttressed, strongly forced ice streams grounded on beds that slope upwards towards the ocean (e.g. those in the Amundsen Sea).

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A High-Resolution Antarctic Grounding Zone Product from ICESat-2 Laser Altimetry

10.5194/essd-2021-255 ◽

2021 ◽

Author(s):

Tian Li ◽

Geoffrey Dawson ◽

Stephen Chuter ◽

Jonathan Bamber

Keyword(s):

High Resolution ◽

Critical Role ◽

Ice Sheet ◽

Ice Shelf ◽

Laser Altimetry ◽

Amundsen Sea ◽

Ross Ice Shelf ◽

Synthetic Aperture Radar Interferometry ◽

Grounding Line ◽

And Migration

Abstract. The Antarctic grounding zone, which is the transition between the fully grounded ice sheet to freely floating ice shelf, plays a critical role in ice sheet instability, mass budget calculations and ice sheet model projections. It is therefore important to continuously monitor its location and migration over time. Here we present the first ICESat-2-derived high-resolution grounding zone product of the Antarctica Ice Sheet, including three important boundaries: the inland limit of tidal flexure (Point F), inshore limit of hydrostatic equilibrium (Point H) and the break-in-slope (Point Ib). This dataset was derived from automated techniques developed in this study, using ICESat-2 laser altimetry repeat tracks between 30 March 2019 and 30 September 2020. The new grounding zone product has a near complete coverage of the Antarctica Ice Sheet with a total of 21346 Point F, 18149 Point H and 36765 Point Ib identified, including the difficult to survey grounding zones, such as the fast-flowing glaciers draining into the Amundsen Sea Embayment. The locations of newly derived ICESat-2 landward limit of tidal flexure agree well with the most recent differential synthetic aperture radar interferometry (DInSAR) observations in 2018, with the mean absolute separation and standard deviation of 0.02 and 0.02 km, respectively. By comparing the ICESat-2-derived grounding zone with the previous grounding zone products, we find up-to 15 km grounding line retreat on the Crary Ice Rise of Ross Ice Shelf and the pervasive landward grounding line migration along the Amundsen Sea Embayment during the past two decades. We also identify the presence of ice plain on the Filchner-Ronne Ice Shelf and the influence of oscillating ocean tides on the grounding zone migration. The product derived from this study is available at https://doi.org/10.5523/bris.bnqqyngt89eo26qk8keckglww (Li et al., 2021) and is archived and maintained at the National Snow and Ice Data Center.

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Pine Island glacier ice shelf melt distributed at kilometre scales

The Cryosphere ◽

10.5194/tc-7-1543-2013 ◽

2013 ◽

Vol 7 (5) ◽

pp. 1543-1555 ◽

Cited By ~ 77

Author(s):

P. Dutrieux ◽

D. G. Vaughan ◽

H. F. J. Corr ◽

A. Jenkins ◽

P. R. Holland ◽

...

Keyword(s):

High Resolution ◽

Sea Level ◽

Surface Velocity ◽

Ice Shelf ◽

Ice Streams ◽

West Antarctic ◽

Grounding Line ◽

Glacier Ice ◽

Basal Melting ◽

Broad Scale

Abstract. By thinning and accelerating, West Antarctic ice streams are contributing about 10% of the observed global sea level rise. Much of this ice loss is from Pine Island Glacier, which has thinned since at least 1992, driven by changes in ocean heat transport beneath its ice shelf and retreat of the grounding line. Details of the processes driving this change, however, remain largely elusive, hampering our ability to predict the future behaviour of this and similar systems. Here, a Lagrangian methodology is developed to measure oceanic melting of such rapidly advecting ice. High-resolution satellite and airborne observations of ice surface velocity and elevation are used to quantify patterns of basal melt under the Pine Island Glacier ice shelf and the associated adjustments to ice flow. At the broad scale, melt rates of up to 100 m yr−1 occur near the grounding line, reducing to 30 m yr−1 just 20 km downstream. Between 2008 and 2011, basal melting was largely compensated by ice advection, allowing us to estimate an average loss of ice to the ocean of 87 km3 yr−1, in close agreement with 2009 oceanographically constrained estimates. At smaller scales, a network of basal channels typically 500 m to 3 km wide is sculpted by concentrated melt, with kilometre-scale anomalies reaching 50% of the broad-scale basal melt. Basal melting enlarges the channels close to the grounding line, but farther downstream melting tends to diminish them. Kilometre-scale variations in melt are a key component of the complex ice–ocean interaction beneath the ice shelf, implying that greater understanding of their effect, or very high resolution models, are required to predict the sea-level contribution of the region.

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Brief communication: PICOP, a new ocean melt parameterization under ice shelves combining PICO and a plume model

10.5194/tc-2018-216 ◽

2018 ◽

Author(s):

Tyler Pelle ◽

Mathieu Morlighem ◽

Johannes H. Bondzio

Keyword(s):

Ocean Circulation ◽

Numerical Models ◽

Three Dimensional ◽

Ice Sheet ◽

Ice Shelf ◽

Ice Streams ◽

Amundsen Sea ◽

Ice Shelves ◽

Box Models ◽

Grounding Line

Abstract. Basal melt at the bottom of Antarctic ice shelves is a major control on glacier dynamics, as it modulates the amount of buttressing that floating ice shelves exert onto the ice streams feeding them. Three-dimensional ocean circulation numerical models provide reliable estimates of basal melt rates but remain too computationally expensive for century scale projections. Ice sheet modelers therefore routinely rely on simplified parameterizations either based on ice shelf depth or on more sophisticated box models. However, existing parameterizations do not accurately resolve the complex spatial patterns of sub-shelf melt rates that have been observed over Antarctica's ice shelves, especially in the vicinity of the grounding line, where basal melt is one of the primary drivers of grounding line migration. In this study, we couple the Potsdam Ice-shelf Cavity mOdel (PICO) to a buoyant Plume melt rate parameterization to create PICOP, a novel basal melt rate parameterization that is easy to implement in transient ice sheet numerical models and produces a melt rate field that is in excellent agreement with the spatial distribution and magnitude of observations for a wide variety of ocean basins. We test PICOP on the Amundsen Sea sector of West Antarctica, Totten and Moscow University ice shelves in Eastern Antarctica, and the Ronne-Filchner ice shelf and compare the results to PICO. We find that PICOP is able to reproduce the high melt rates near the grounding lines of Pine Island, Thwaites, and Totten glaciers (on the order of 100 m/yr) and removes the “banding” pattern observed in melt rates produced by PICO over the Ronne-Filchner ice shelf. PICOP resolves many of the issues contemporary basal melt rate parameterizations face and is therefore a valuable tool for those looking to make future projections of Antarctic glaciers.

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Pine Island Glacier ice shelf melt distributed at kilometre scales

The Cryosphere Discussions ◽

10.5194/tcd-7-1591-2013 ◽

2013 ◽

Vol 7 (2) ◽

pp. 1591-1620 ◽

Cited By ~ 4

Author(s):

P. Dutrieux ◽

D. G. Vaughan ◽

H. F. J. Corr ◽

A. Jenkins ◽

P. R. Holland ◽

...

Keyword(s):

High Resolution ◽

Sea Level ◽

Surface Velocity ◽

Ice Shelf ◽

Ice Streams ◽

West Antarctic ◽

Grounding Line ◽

Glacier Ice ◽

Basal Melting ◽

Broad Scale

Abstract. By thinning and accelerating, West Antarctic ice streams are contributing about 10% of the observed global sea level rise. Much of this ice loss is from Pine Island Glacier, which has thinned since at least 1992, driven by changes in ocean heat transport beneath its ice shelf and retreat of the grounding line. Details of the processes driving this change, however, remain largely elusive, hampering our ability to predict the future behaviour of this and similar systems. Here, a Lagrangian methodology is developed to measure oceanic melting of such rapidly advecting ice. High-resolution satellite and airborne observations of ice surface velocity and elevation are used to quantify patterns of basal melt under the Pine Island Glacier ice shelf and the associated adjustments to ice flow. At the broad scale, melt rates of up to 100 m yr−1 occur near the grounding line, reducing to 30 m yr−1 just 20 km downstream. Between 2008 and 2011, basal melting was largely compensated by ice advection, allowing us to estimate an average loss of ice to the ocean of 87 km3 yr−1, in close agreement with 2009 oceanographically-constrained estimates. At smaller scales, a network of basal channels typically 500 m to 3 km wide is sculpted by concentrated melt, with kilometre-scale anomalies reaching 50% of the broad-scale basal melt. Basal melting enlarges the channels close to the grounding line, but farther downstream melting tends to diminish them. Kilometre-scale variations in melt are a key component of the complex ice-ocean interaction beneath the ice shelf, implying that greater understanding of their effect, or very high resolution models, are required to predict the sea-level contribution of the region.

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