Facing the Gamburtsev Subglacial Mountains: What other ranges do they look like?
Abstract
Mountain ranges serve as nucleation sites for continental ice sheets over multiple glacial cycles. During warmer interglacial periods, such ranges provide a toe-hold for snow accumulation and small glaciers that expand as temperatures drop in response to declining carbon dioxide levels. Once an ice sheet grows beyond a critical size, its basal thermal regime favors melting and development of water networks. Studies of deglaciated ice sheet beds indicate a complex thermal regime where cold-based areas are interspersed with warm, temperate areas. The Gamburtsev Subglacial Mountains are a massive range in central East Antarctica. They are Earth's only completely ice-covered mountain range. Results from ice penetrating radar reveal steep headwalls with semicircular planform lying along high ridges and with peaks above 2500 m in the central mountain core. These likely represent cirque headwalls and provide evidence for widespread mountain glaciers within the Gamburtsevs. Headwalls are often accompanied by discrete overdeepenings that indicate occupation by cirque glaciers, and the cirque elevations are relatively uniform from north to south, spanning a distance of roughly 750 km. Such mountain glacier features have been preserved since the start of continental-scale glaciation (>33.9 Myr ago). Preservation results from freezing conditions beneath the ice sheet that have reduced erosion despite active water networks. Reconstructions of temperature indicate 17.1--19.3 +/- 4 at sea level, consistent with sedimentary proxies from the early Eocene (48--58 Myr ago). Here, we compare the Gamburtsevs to other mountain ranges using statistical tests. We focus on comparisons among mountain hypsometries, or the distributions of area with elevation. We introduce two tests, a decay-length test that relates the form of the peaks of the individual ranges and a χ2 goodness-of-fit test for the overall distribution. Results show that there is a striking similarity to mountains that are significantly younger. Similarly glaciated mountain ranges, in general, bear little resemblance to the Gamburtsevs. Mountain ranges with smaller, more active glaciers are similar in overall form. From our analysis, we conclude that the climate shift from pre-glacial to full glacial conditions in Antarctica was rapid.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMEP41A0791C
- Keywords:
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- 0726 CRYOSPHERE Ice sheets;
- 0768 CRYOSPHERE Thermal regime;
- 1824 HYDROLOGY Geomorphology: general;
- 8103 TECTONOPHYSICS Continental cratons