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

Abstract

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.

Influence of anisotropy on velocity and age distribution at Scharffenbergbotnen blue ice area

“…The surface of the major part of the East Antarctic Plateau ice sheet may have been about 100 m lower in the last glacial than at present (Jouzel et al, 1989;Pattyn, 1999;Ritz et al, 2001). In contrast, the surface elevation at the margins of the plateau may have been hundreds of meters higher (Näslund et al, 2000;Hättestrand and Johansen, 2005).…”

“…As only limited geomorphological information on LGM geometry is available (Näslund et al, 2000;Hättestrand and Johansen, 2005), at least the first two of these items are largely undetermined. Additionally the computational effort required to run a full-Stokes model for such a long period, with relatively unconstrained geometrical evolution, renders a prognostic simulation from LGM a highly unrealistic approach.…”

Dating Antarctic blue ice areas using a novel ice flow model

“…Equilibration times for the ice sheet to respond to changes in climate are only in the order of a few thousands of years [Näslund et al, 2000], and a reduction in temperature of the ice sheet by 10°C increases its stiffness by about 3.5 times [Paterson, 1994]. Slight changes in ice thickness could result in different surface slopes and thus velocities.…”

“…Ice from the first 500 m of the flow line (>50 thousand years old) originates from more than 10 km away. The northern small BIA (Figure 4) contains relatively young ice as it is an open-type BIA, and accumulation rates and velocities outside the valley [Näslund et al, 2000] are much higher than within it ( Figure 5). The small accumulation area inside the valley supplies ice that is up to 20 thousand years old to the main BIA.…”

The surficial and subglacial geomorphology of western Dronning Maud Land, Antarctica

“…Upland areas of the territory are highly likely to have been a nucleation site for early development of Antarctic ice (DeConto & Pollard, 2003;Jamieson & Sugden, 2008), and they are likely to act as a key pinning point of the present-day EAIS. Modelling suggested that the majority of ice within DML is cold-based at present (Näslund, Fastook, & Holmlund, 2000). Given the potential for landscape preservation under such non-erosive ice, it is possible that the subglacial DML uplands may contain evidence for earlier, smaller ice conditions, with the possibility that landforms could have been preserved since the 14 Ma expansion of Antarctic ice or even EAIS inception at 34 Ma.…”