Ice pumps and their rates

Lewis, E. L.; Perkin, R. G.

doi:10.1029/jc091ic10p11756

Cited by 249 publications

(202 citation statements)

References 25 publications

(13 reference statements)

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“…In the Holland et al (2009) study the presence of marine ice was inferred from the absence of basal reflections in radar data where a surface return was obtained. Freeze-on results in a mushy transitional interface (Lewis and Perkin, 1986;Craven et al, 2009), rather than a sharp reflector, and would therefore result in reduced seismic reflection amplitude. There are however a number of other factors that can contribute to reflector amplitude: source coupling, receiver coupling, attenuation within the ice column, reflector geometry, the presence of water-filled crevasses near the ice-base and acoustic impedance contrast across the reflector.…”

Section: Marine Ice Beneath Larsen Cmentioning

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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Section: Marine Ice Beneath Larsen Cmentioning

confidence: 99%

Seabed topography beneath Larsen C Ice Shelf from seismic soundings

et al. 2014

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“…The ice pump may also act on ridged sea ice (Lewis & Perkin 1986;Jeffries et al 1995), but the smaller vertical extent of this ice means that the mechanism is unlikely to dominate basal phase changes. Lewis & Perkin's original consideration of the ice pump concentrated solely on direct melting and freezing at the ice-water interface, concluding that the rate of an ice pump is limited by the maximum melt rate (which is moderated by the stabilizing effect of meltwater on the water column) and the rate at which the meltwater is transported to the freezing zone (Lewis & Perkin 1986). However, the possible formation of frazil ice crystals in the rising meltwater plume complicates the analysis of ice pumps considerably.…”

Section: Introductionmentioning

confidence: 99%

“…Any sufficiently thick body of ice that is in contact with seawater could therefore initiate an ice pump. If infinitesimal melting occurs at depth, the resulting meltwater rises owing to its buoyancy, supercooling causes ice formation to occur, and brine rejection from this freezing may induce a compensating downwards flow at some distance from the ice, leading to more melting at depth and a self-sustaining overturning circulation (Lewis & Perkin 1986).…”

Section: Introductionmentioning

confidence: 99%

“…The 'ice pump' is a heat engine which melts ice at depth and deposits it at a shallower location (Lewis & Perkin 1983, 1986. If water at the surface freezing temperature sinks, it has the potential to melt ice at depth owing to the decrease in the freezing temperature of seawater with increasing pressure (≈ −7.53 × 10 −3 • C bar −1 ).…”

Section: Introductionmentioning

confidence: 99%

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Frazil dynamics and precipitation in a water column with depth-dependent supercooling

Holland

Feltham

2005

J. Fluid Mech.

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When seawater becomes supercooled, collections of small ice crystals, known as frazil ice, form and grow. A model of frazil ice dynamics is presented that deals explicitly with the buoyant settling of frazil crystals onto an overlying surface. This yields further insight into transport associated with the ice pump mechanism, whereby ice is melted at depth and transferred to a shallower location as a result of the pressure variation of seawater's freezing temperature. The model is applied to a vertical cross-section through an Ice Shelf Water plume beneath Filchner-Ronne Ice Shelf, Antarctica, and helps to elucidate the depth-variation in its properties for the first time, as well as predicting the precipitation rate of frazil crystals. The model predicts that frazil ice should be preferentially located in a narrow layer near the ice shelf base as a result of the maximum supercooling there and an influx of crystals rising under their own buoyancy. The deposition of these crystals onto the ice shelf is governed by the balance between crystal rising and turbulent transfer of frazil away from the shelf, which is investigated in some detail.

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“…The freezing point of seawater decreases with increasing pressure. Therefore, at the back of deep ice-shelf cavities, the decreased freezing point of seawater provides a large potential for thermal driving of melting, leading to melting at depth and a buoyant melt water plume (Lewis and Perkin, 1986). Increased melting leads to the localised thinning of an ice shelf, and potentially to the acceleration of the glacier behind it, as the buttressing effect of the shelf is decreased (Dupont and Alley, 2005).…”

Section: Introductionmentioning

confidence: 99%

Simulated melt rates for the Totten and Dalton ice shelves

et al. 2014

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Abstract. The Totten Glacier is rapidly losing mass. It has been suggested that this mass loss is driven by changes in oceanic forcing; however, the details of the ice-ocean interaction are unknown. Here we present results from an ice shelf-ocean model of the region that includes the Totten, Dalton and Moscow University ice shelves, based on the Regional Oceanic Modeling System for the period 1992-2007. Simulated area-averaged basal melt rates (net basal mass loss) for the Totten and Dalton ice shelves are 9.1 m ice yr −1 (44.5 Gt ice yr −1 ) and 10.1 m ice yr −1 (46.6 Gt ice yr −1 ), respectively. The melting of the ice shelves varies strongly on seasonal and interannual timescales. Basal melting (mass loss) from the Totten ice shelf spans a range of 5.7 m ice yr −1 (28 Gt ice yr −1 ) on interannual timescales and 3.4 m ice yr −1 (17 Gt ice yr −1 ) on seasonal timescales.This study links basal melt of the Totten and Dalton ice shelves to warm water intrusions across the continental shelf break and atmosphere-ocean heat exchange. Totten ice shelf melting is high when the nearby Dalton polynya interannual strength is below average, and vice versa. Melting of the Dalton ice shelf is primarily controlled by the strength of warm water intrusions across the Dalton rise and into the ice shelf cavity. During periods of strong westward coastal current flow, Dalton melt water flows directly under the Totten ice shelf further reducing melting. This is the first such modelling study of this region to provide a valuable framework for directing future observational and modelling efforts.

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Ice pumps and their rates

Cited by 249 publications

References 25 publications

Seabed topography beneath Larsen C Ice Shelf from seismic soundings

Seabed topography beneath Larsen C Ice Shelf from seismic soundings

Frazil dynamics and precipitation in a water column with depth-dependent supercooling

Simulated melt rates for the Totten and Dalton ice shelves

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