Special Aspects of the Central Part of Filchner-Ronne Ice Shelf, Antarctica

Thyssen, F.

doi:10.1017/s0260305500006509

Cited by 57 publications

(77 citation statements)

References 5 publications

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“…For ice column thicknesses, H over z 100 m, the simple relationq over = q c À 13463 kg m À 2 /H over holds, leading to the hydrostatic relation h = 0.11337H + 13.046 m, if water density is taken as q w = 1032 kg m À 3 . This again is similar to the situation assumed for the FRIS (Thyssen, 1988;Jenkins and Doake, 1991). For H over < 100 m,q over is calculated by a modified equation, which ensures steadiness at H over = 100 m and includes a snow cover density of 370 kg m À 3 (Fig.…”

Section: Model Initializationmentioning

confidence: 76%

The evolution of a coupled ice shelf–ocean system under different climate states

Grosfeld

Sandhäger

2004

Global and Planetary Change

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Based on a new approach for coupled applications of an ice shelf model and an ocean general circulation model, we investigate the evolution of an ice shelf -ocean system and its sensitivity to changed climatic boundary conditions. Combining established 3D models into a coupled model system enabled us to study the reaction and feedbacks of each component to changes at their interface, the ice shelf base. After calculating the dynamics for prescribed initial ice shelf and bathymetric geometries, the basal mass balance determines the system evolution. In order to explore possible developments for given boundary conditions, an idealized geometry has been chosen, reflecting basic features of the Filchner -Ronne Ice Shelf, Antarctica. The model system is found to be especially sensitive in regions where high ablation or accretion rates occur. Ice Shelf Water formation as well as the build up of a marine ice body, resulting from accretion of marine ice, is simulated, indicating strong interaction processes.To improve consistency between modeled and observed ice shelf behavior, we incorporate the typical cycle of steady ice front advance and sudden retreat due to tabular iceberg calving in our time-dependent simulations. Our basic hypothesis is that iceberg break off is associated with abrupt crack propagation along elongated anomalies of the inherent stress field of the ice body. This new concept yields glaciologically plausible results and represents an auspicious basis for the development of a thorough calving criterion.Experiments under different climatic conditions (ocean warming of 0.2 and 0.5 jC and doubled surface accumulation rates) show the coupled model system to be sensitive especially to ocean warming. Increased basal melt rates of 100% for the 0.5 jC ocean warming scenario and an asymmetric development of ice shelf thicknesses suggest a high vulnerability of ice shelf regions, which represent pivotal areas between the Antarctic Ice Sheet and the Southern Ocean. D

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Section: Model Initializationmentioning

confidence: 76%

The evolution of a coupled ice shelf–ocean system under different climate states

Grosfeld

Sandhäger

2004

Global and Planetary Change

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“…Where marine ice is present, icepenetrating radar generally does not propagate into the saline marine ice layer; hence the radar only records the thickness of the meteoric ice. As result, significant differences between the radar (meteoric-only) and hydrostatic-equilibrium (full column) derived thicknesses indicate the presence of marine ice (Crabtree and Doake, 1986;Robin et al, 1983;Thyssen, 1988). No such differences are found for Dotson, indicating little or no marine ice (further details can be found in the Supplement).…”

Section: History Of Meltmentioning

confidence: 98%

Changes in flow of Crosson and Dotson ice shelves, West Antarctica, in response to elevated melt

et al. 2018

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Abstract. Crosson and Dotson ice shelves are two of the most rapidly changing outlets in West Antarctica, displaying both significant thinning and grounding-line retreat in recent decades. We used remotely sensed measurements of velocity and ice geometry to investigate the processes controlling their changes in speed and grounding-line position over the past 20 years. We combined these observations with inverse modeling of the viscosity of the ice shelves to understand how weakening of the shelves affected this speedup. These ice shelves have lost mass continuously since the 1990s, and we find that this loss results from increasing melt beneath both shelves and the increasing speed of Crosson. High melt rates persisted over the period covered by our observations (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014), with the highest rates beneath areas that ungrounded during this time. Grounding-line flux exceeded basin-wide accumulation by about a factor of 2 throughout the study period, consistent with earlier studies, resulting in significant loss of grounded as well as floating ice. The near doubling of Crosson's speed in some areas during this time is likely the result of weakening of its margins and retreat of its grounding line. This speedup contrasts with Dotson, which has maintained its speed despite increasingly high melt rates near its grounding line, likely a result of the sustained competency of the shelf. Our results indicate that changes to melt rates began before 1996 and suggest that observed increases in melt in the 2000s compounded an ongoing retreat of this system. Advection of a channel along Dotson, as well as the grounding-line position of Kohler Glacier, suggests that Dotson experienced a change in flow around the 1970s, which may be the initial cause of its continuing retreat.

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“…To account fo r the eventual calving of ice-shelf frag ments, we suggest that ice melange which fills rifts may eventually weaken as the rifts propagate toward the ice front where basal melting becomes a significant source of mass loss (Thyssen, 1988). Basal melting of a fe w m a I should ex ceed the nat ural growth rate of sea ice due to heat losses into the atmosphere, reduce its thickness and weaken its me chanical competence.…”

Section: Fringe Fjat! Erns Within Riftsmentioning

confidence: 99%

Ice-shelf dynamics near the front of the Filchner—Ronne Ice Shelf, Antarctica, revealed by SAR interferometry

Rignot

MacAyeal

1998

J. Glaciol.

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Fifteen synthetic aperture radar (SAR) images of the Ronne Ice Shelf (also referred to as the Filchner-Ronne Ice Shelf), Antarctica, obtained by the European remote-sensing satellites ERS-1 and -2, are used to study ice-shelf dynamics near two ends of the iceberg-calving front. Interferograms constructed from these SAR images are used to resolve the ice-shelf displacement along several directions in response to both ocean tide and long-term creep flow. Tidal motion is separated from creep flow using differential interferometry, i.e. two or more interferograms in which fringe patterns common to all are predominantly associated with creep flow. Creep-flow velocities thus determined compare well with prior ice-shelf velocity surveys. Using these data, we studied the influence of large-scale rifts, ice rises and coastal separation on the ice-shelf flow. Many of the large rifts that appear to form the boundaries where tabular icebergs may eventually detach from the ice shelf are filled with a melange of sea ice, ice-shelf debris and wind-blown snow. The interferograms show that this melange tends to deform coherently in response to the ice-shelf flow and has sufficient strength to trap large tabular ice-shelf fragments for several decades before the fragments eventually become icebergs. In many instances, the motion of the tabular fragments is a rigid-body rotation about a vertical axis that is driven by velocity shear within the melange. Tfhe mechanical role of the rift-filling melange may be to bind tabular ice-shelf fragments to the main ice shelf before they calve. This suggests two possible mechanisms by which climate could influence tabular iceberg calving. First, spatial gradients in oceanic and atmospheric temperature may determine where the melange melts and, thus, the location of the iceberg-caking margin. Second, melting or weakening of ice melange as a consequence of climate change could trigger a sudden or widespread release of tabular icebergs and lead to rapid ice-shelf disintegration.

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Special Aspects of the Central Part of Filchner-Ronne Ice Shelf, Antarctica

Cited by 57 publications

References 5 publications

The evolution of a coupled ice shelf–ocean system under different climate states

The evolution of a coupled ice shelf–ocean system under different climate states

Changes in flow of Crosson and Dotson ice shelves, West Antarctica, in response to elevated melt

Ice-shelf dynamics near the front of the Filchner—Ronne Ice Shelf, Antarctica, revealed by SAR interferometry

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