The Gamburtsev mountains and the origin and early evolution of the Antarctic Ice Sheet

Abstract

Ice-sheet development in Antarctica was a result of significant and rapid global climate change about 34 million years ago. Ice-sheet and climate modelling suggest reductions in atmospheric carbon dioxide (less than three times the pre-industrial level of 280 parts per million by volume) that, in conjunction with the development of the Antarctic Circumpolar Current, led to cooling and glaciation paced by changes in Earth's orbit. Based on the present subglacial topography, numerical models point to ice-sheet genesis on mountain massifs of Antarctica, including the Gamburtsev mountains at Dome A, the centre of the present ice sheet. Our lack of knowledge of the present-day topography of the Gamburtsev mountains means, however, that the nature of early glaciation and subsequent development of a continental-sized ice sheet are uncertain. Here we present radar information about the base of the ice at Dome A, revealing classic Alpine topography with pre-existing river valleys overdeepened by valley glaciers formed when the mean summer surface temperature was around 3 degrees C. This landscape is likely to have developed during the initial phases of Antarctic glaciation. According to Antarctic climate history (estimated from offshore sediment records) the Gamburtsev mountains are probably older than 34 million years and were the main centre for ice-sheet growth. Moreover, the landscape has most probably been preserved beneath the present ice sheet for around 14 million years.

The evolution of the subglacial landscape of Antarctica

“…Our results are supported by a recent remote sensing study of the Gamburtsev Mountains showing features typical of local mountain glaciation 23 under warm-based glacial conditions, creating U-shaped valleys, overdeepenings and corries (Bo et al, 2009). The Gamburtsevs have since experienced little or no erosion due to the presence of cold-based ice for at least 34 Myrs.…”

“…This landscape is typical of passive continental margin evolution where most uplift and incision occurs within tens of millions of years of plate separation which, in this case, occurred around 55 Myrs ago (Jamieson and Sugden, 2008). Moreover, the Gamburtsev subglacial mountains in central east Antarctica display local valley features preserved since the earliest stages of glaciation (Bo et al, 2009). On a wider scale, topographic analysis shows the structure of the drainage underneath the Antarctic Ice Sheet essentially retains a pre-glacial fluvial structure.…”

“…Mountains (Bo et al, 2009). Fluvial denudation along the uplifted rim of the Transantarctic Mountains is of the order of 4-6 km since early rifting in the Cretaceous (Fitzgerald and Stump, 1997).…”

How old is the ice beneath Dome A, Antarctica?

“…We can ignore the increase in horizontal flow and argue that the increase in vertical velocity is small in areas with low horizontal velocity and basal shear, and also small compared with the uncertainty in geothermal flux, which we explore. A network of extensive ice penetrating radar (Cui et al, 2010;Sun et al, 2009;Bell et al, 2011;Tang et al, 2011), topographic (Zhang et al, 2007), and shallow ice core surveys (Jiang et al, 2012;Xiao et al, 2008) in the region surrounding the Kunlun field station provides input data for the model and helps to constrain the model results to meet observations. A 30 × 30 km 2 domain with an unstructured mesh of about 300 m horizontal resolution was embedded within a coarse (3 km) 70 × 70 km 2 unstructured mesh domain centred at Kunlun station (Fig.…”

“…Severinghaus, 2010;Van Liefferinge and Pattyn, 2013). The Gamburtsev subglacial mountains beneath Dome A were a major centre of ice-sheet nucleation during the Cenozoic (DeConto and Pollard, 2003;Sun et al, 2009), and hence potentially can provide ancient ice for paleoclimatic research. Kunlun station (80 • 25 01 S, 77 • 06 58 E, 4092 m a.s.l.)…”