Ice Thickness and Bedrock Elevation in Western Neuschwabenland and Berkner Island, Antarctica

ABSTRACT. Time-dependent ice-sheet modelling of a 176 000 km 2 area in western Dronning Maud Land, East Antarctica, provided information on the ice sheet's response to six climate-change scenarios. Another experiment was done to study changes in ice thickness, flow and basal temperature conditions between the present ice configuration and a simulated maximum palaeo-ice sheet.The input to the model included new datasets of bed and surface topography compiled for this study. The results of the six climatechange experiments, including a 0.5³C per century global-warming scenario, show that the ice sheet has a robust behaviour with respect to the different climate changes. The maximum change in ice volume was <5% of the initial volume in all climate runs. This is for only relatively short-term climate changes without major changes in global sea level, and also a simulated ice sheet without an ice shelf. The modelled long-term response time of the ice sheet, 20 kyr or more, indicates that the ice sheet may still be adjusting to the climate change that ended the Last Glacial Maximum. In the maximum palaeo-ice-sheet simulation, with a 5³C climate cooling and the grounding line located at the continentalshelf margin, ice thickness increased drastically downstream from the Heimefrontfjella mountain range but remained basically unaffected on the upstream polar plateau. Compared to present conditions, complex changes in basal temperatures were observed. The extent of areas with basal melting increased, for example in the deep trough of the Veststraumen ice stream. Areas at intermediate elevations in the landscape also experienced increased basal temperatures, with significant areas reaching the melting point. In contrast, high-altitude areas that today are clearly cold-based, such as around Heimefrontfjella and Vestfjella and the Ho« gisen dome, experienced a 5^10³C decrease in basal temperatures in the palaeo-ice-sheet reconstruction. The results suggest that the alpine landscape within these mountain regions was formed by wet-based local glaciers and ice sheets prior to the late Cenozoic.

Section: Study Area and Topographical Datamentioning

confidence: 99%

Numerical modelling of the ice sheet in western Dronning Maud Land, East Antarctica: impacts of present, past and future climates

Näslund¹,

Fastook

Holmlund³

2000

“…2) contains HIR and part of Berkner Island (BI) which is the largest ice rise in Antarctica (Swithinbank and others, 1988). BI rests on a bed that is 200-300 m below sea level (Hoppe and Thyssen, 1988), and reaches 700 m elevation along the eastern edge of the SAR scene. HIR is an oblong feature less than 100 km 2 in size, consisting of stagnant, grounded and crevasse-free ice.…”

Section: Introductionmentioning

confidence: 99%

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

Rignot

MacAyeal

1998

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.

“…The overall aim of the glaciological project is to determine whether this small ice-drainage area of the East Antarctic ice sheet is in balance with the present climate. A large part of this ice-drainage system is marinebased (Hoppe and Thyssen, 1988;Holmlund, unpublished data), which may accentuate the sensitivity of this area to changes in climatic conditions. The part of the project presented in this paper concentrates on the surface-accumulation rate in this area.…”

Section: Introductionmentioning

confidence: 99%

Spatial and temporal patterns in snow accumulation, western Dronning Maud Land, Antarctica

Isaksson

Karlén

1994

ABSTRACT. During the Swedish Antarctic Expedition to Dronning MaudLand, Antarctica, 1988-89 the net accumulation was estimated for an area from the coast to about 400 km inland. Stake measurements were used to obtain the spatial variability and firn cores were used for the temporal variability. The mean annual accumulation for the period 1976-88 is about 0.4 m w.e. for Riiser-Larsenisen and about 0.3 m w.e. for the area above the grounding line. The accumulation rate at higher altitudes, > 2500 m a.s.!., is about 0.1 m w.e. for 1955-88. One record from the ice shelf covers the period 1957-88, and suggests an increase in accumulation of about 12%. Between 1976 and, the accumulation has decreased by about 50%, most likely due to lower temperatures as suggested by the temperature record from Halley.