Observations beneath Pine Island Glacier in West Antarctica and implications for its retreat

Jenkins, Adrian; Dutrieux, Pierre; Jacobs, Stanley S.; McPhail, S.D.; Perrett, James; Webb, A.; White, David

doi:10.1038/ngeo890

Cited by 515 publications

(618 citation statements)

References 26 publications

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“…These oceanographic data reveal strengthening circulation in an enlarged sub-ice shelf cavity, leading to faster ice melting. The emergence of an enlarged ocean cavity has resulted in part from retreat of the glacier across a submarine bank upon which it was formerly grounded [Jenkins et al, 2010], allowing relatively warm (~4 C above freezing) seawater to access the glacier grounding line.…”

Section: Discussionmentioning

confidence: 99%

Sustained retreat of the Pine Island Glacier

Park

Gourmelen

Shepherd

et al. 2013

Geophysical Research Letters

118

133

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[1] We use satellite observations to show that, between 1992 and 2011, the Pine Island Glacier hinge line retreated at a rate of 0.95 AE 0.09 km yr À1 despite a progressive steepening and shoaling of the glacier surface and bedrock slopes, respectively, which ought to impede retreat. The retreat has remained constant because the glacier terminus has thinned at an accelerating rate of 0.53 AE 0.15 m yr À2 , with comparable changes upstream. This acceleration is consistent with an intensification of ocean-driven melting in the cavity beneath the floating section of the glacier. The pattern of hinge-line retreat meanders and is concentrated in isolated regions until ice becomes locally buoyant. Because the glacier-ocean system does not appear to have reached a position of relative stability, the lower limit of sea level projections may be too conservative.

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Section: Discussionmentioning

confidence: 99%

Sustained retreat of the Pine Island Glacier

Park

Gourmelen

Shepherd

et al. 2013

Geophysical Research Letters

118

133

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“…PIG in particular has shown a nearly continuous acceleration (Joughin et al 2003) and thinning (Wingham et al 2009) during recent years. Recent evidence shows that this thinning is due to an inland grounding line migration from the 1970s to present by 30 km (Jenkins et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Representing Grounding Line Dynamics in Numerical Ice Sheet Models: Recent Advances and Outlook

Docquier¹,

Perichon²,

Pattyn³

2011

The Earth's Cryosphere and Sea Level Change

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Recent satellite observations of the Antarctic and Greenland ice sheets show accelerated ice flow and associated ice sheet thinning along coastal outlet glaciers in contact with the ocean. Both processes are the result of grounding line retreat due to melting at the grounding line (the grounding line is the contact of the ice sheet with the ocean, where it starts to float and forms an ice shelf or ice tongue). Such rapid ice loss is not yet included in large-scale ice sheet models used for IPCC projections, as most of the complex processes are poorly understood. Here we report on the state-of-the art of grounding line migration in marine ice sheets and address different ways in which grounding line migration can be attributed and represented in ice sheet models. Using onedimensional ice flow models of the ice sheet/ice shelf system we carried out a number of sensitivity experiments with different spatial resolutions and stress approximations. These are verified with semi-analytical steady state solutions. Results show that, in large-scale finite-difference models, grounding line migration is dependent on the numerical treatment (e.g. staggered/non-staggered grid) and the level of physics involved (e.g. shallow-ice/ shallow-shelf approximation).

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“…Accurate knowledge of the bathymetry beneath ice shelves is critical to modelling and understanding the contribution of basal melting to ice shelf thinning and subsequent instability (Jenkins et al, 2010;Grosfeld et al, 1997). Due to the difficulty of mapping the cavity directly, sub-ice shelf bathymetry remains relatively poorly known: radar energy is highly attenuated by sea water and therefore precludes airborne radio echo sounding; direct measurements with autonomous underwater vehicles are expensive and complex.…”

Section: Introductionmentioning

confidence: 99%

Seabed topography beneath Larsen C Ice Shelf from seismic soundings

et al. 2014

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Abstract. Seismic reflection soundings of ice thickness and seabed depth were acquired on the Larsen C Ice Shelf in order to test a sub-ice shelf bathymetry model derived from the inversion of IceBridge gravity data. A series of lines was collected, from the Churchill Peninsula in the north to the Joerg Peninsula in the south, and also towards the ice front. Sites were selected using the bathymetry model derived from the inversion of free-air gravity data to indicate key regions where sub-ice shelf oceanic circulation may be affected by ice draft and seabed depth. The seismic velocity profile in the upper 100 m of firn and ice was derived from shallow refraction surveys at a number of locations. Measured temperatures within the ice column and at the ice base were used to define the velocity profile through the remainder of the ice column. Seismic velocities in the water column were derived from previous in situ measurements. Uncertainties in ice and water cavity thickness are in general <10 m. Compared with the seismic measurements, the rootmean-square error in the gravimetrically derived bathymetry at the seismic sites is 162 m. The seismic profiles prove the non-existence of several bathymetric features that are indicated in the gravity inversion model, significantly modifying the expected oceanic circulation beneath the ice shelf. Similar features have previously been shown to be highly significant in affecting basal melt rates predicted by ocean models. The discrepancies between the gravity inversion results and the seismic bathymetry are attributed to the assumption of uniform geology inherent in the gravity inversion process and also the sparsity of IceBridge flight lines. Results indicate that care must be taken when using bathymetry models derived by the inversion of free-air gravity anomalies. The bathymetry results presented here will be used to improve existing sub-ice shelf ocean circulation models.

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Observations beneath Pine Island Glacier in West Antarctica and implications for its retreat

Abstract: Thinning ice in West Antarctica

Cited by 515 publications

References 26 publications

Sustained retreat of the Pine Island Glacier

Sustained retreat of the Pine Island Glacier

Representing Grounding Line Dynamics in Numerical Ice Sheet Models: Recent Advances and Outlook

Seabed topography beneath Larsen C Ice Shelf from seismic soundings

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