Geophysical Surveys: The Gamburtsev Mountains

This page was written by Kathryn C. Rose. In this post, Kathryn explains how we can use Geophysical Surveys to investigate the landscape underneath the vast East Antarctic Ice Sheet.

The Gamburtsev Subglacial Mountains

The BEDMAP 2 dataset (Fretwell et al. 2013) shows how ice thickness across the Antarctic continent is variable, with thin ice over the mountains and thick ice over East Antarctica. The cross section shows how the West Antarctic Ice Sheet is grounded below sea level.

This map of ice thickess uses the BEDMAP 2 dataset (Fretwell et al. 2013). Ice thickness across the Antarctic continent is variable, with thin ice over the mountains and thick ice over East Antarctica. You can see the location of the Gamburtsev Mountains underneath Dome A in East Antarctica.

The Gamburtsev Subglacial Mountains are thought to represent the birthplace of the East Antarctic Ice Sheet – the largest ice sheet on Earth.  The mountains lie beneath Dome A, the highest point on the ice sheet in the centre of East Antarctica.  Imagine a mountain range, such as the European Alps, completely buried by ice, in the middle of a continent.  The fact that such a large and high elevation mountain range has been preserved beneath the ice sheet is very unusual.  After millions of years of erosion by water and ice, you would expect only small hills or an undulating landscape to remain.  However, because the Gamburtsevs have remained entombed beneath the ice, they have the potential to hold the longest record of surface processes and landscape evolution in Antarctica.  This means that the topography of the mountains can tell us something about the history of environmental change and ice sheet growth in the interior of East Antarctica over millions of years.

Discovery and exploration

The Gamburtsevs were first discovered by a Russian expedition, collecting seismic data across the interior of East Antarctica in 1958.  It was completely unexpected to find mountains still preserved beneath the ice in the centre of a very old and stable tectonic block.  However, due to the inaccessibility of this region, the high altitudes across Dome A, and the harsh climate of the continental interior, nothing further was done to investigate this enigma.  It took 50 years and an international collaborative team of seven nations to be able to return to this region and survey the mountain range.  The AGAP (Antarctica’s Gamburtsev Province) project carried out an airborne geophysical survey over an area of 182,000 km2, using two twin otter aircraft that collected information on the ice sheet and the underlying topography and geology.

Location of the AGAP survey in East Antarctica (left) and the sub-ice topography of the Gamburtsevs (right) within the central AGAP survey grid (182,000 km2). The topography has been corrected to account for the removal of the ice sheet, so that elevations reflect those under ice free conditions, prior to glaciation.  Note: LV – Lake Vostok.

Location of the AGAP survey in East Antarctica (left) and the sub-ice topography of the Gamburtsevs (right) within the central AGAP survey grid (182,000 km2). The topography has been corrected to account for the removal of the ice sheet, so that elevations reflect those under ice free conditions, prior to glaciation. Note: LV – Lake Vostok.

Geophysical Survey

A twin otter (note two propellors) lands on the runway

A twin otter lands on the runway at Rothera

The Gamburtsev Mountains have been mapped using geophysical survey equipment, mounted on Twin Otter aeroplanes. These aircraft are equipped with ice penetrating radar that allows scientists to look through the ice. See a diagram here to how ice penetrating radar works.

Mapping out the Gamburtsevs

The Gamburtsevs are at least 750 km long and 250 km wide, with peaks along the central mountain ridge averaging between 1.5 and 2.5 km in height, or 2.5 to 3.5 km with the removal of the ice sheet load.  Ice thicknesses vary between 1 to 3 km across the high peaks and deep valleys.  At its thinnest, ice is less than 400 m thick above some peaks, but reaches over 4.5 km in depth on the northern flank of the mountains, where the Gamburtsevs meet the Lambert Rift, at the head of the Lambert Glacier.  The mountains are dissected by a series of valleys that resemble a fluvial drainage system.  Valley widths are typically 20-25 km wide and 100-200 km long.  However, the two largest valleys in the centre of the mountain range are over 350 km in length.

A preserved pre-glacial topography

I published a paper recently in the journal Earth and Planetary Science Letters, where I use the data from the AGAP project to assess long-term landscape and ice sheet evolution across the Gamburtsevs.  I found that the network of mountain valleys strongly resembles a pattern of river drainage.  The geomorphology of this landscape indicates that it has only been slightly modified by local- to regional-scale glacial processes.  The mountains, therefore, retain an ‘alpine’ style landscape, similar to the European Alps, so they appear to be very young, despite their formation over 100 million years ago (Ferraccioli et al., 2011).  This suggests that the continental-scale ice sheet we see today formed rapidly across the mountains.  This slow flowing, cold ice, in the interior of the continent, causes very little erosion and has allowed the landscape to be preserved for millions of years.  Therefore, the landforms preserved beneath the ice reflect potentially the earliest evidence for ice growth in East Antarctica.  This suggests that the Gamburtsevs mark the birth place of the East Antarctic Ice Sheet, over 34 million years ago.

About the Author

Dr Kathryn Rose

Dr Kathryn Rose

Kathryn C. Rose, from the University of Bristol, is a glaciologist with research interests in the Antarctic Ice Sheet, particularly in landscape evolution in glacial environments. She uses ice penetrating radar to peel back the ice to examine the land beneath.

References


Rose et al., 2013, Early East Antarctic Ice Sheet growth recorded in the landscape of the Gamburtsev Subglacial Mountains. Earth and Planetary Science Letters, 375, 1-12.

Further information on the Gamburtsev Subglacial Mountains has been published in the journals Nature and Science.

Bo et al., 2009, Nature 459, 690-694.

Bell et al., 2011, Science 311, 1592-1595.

Ferraccioli et al., 2011, Nature 479, 388-392.

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