Australia: The Land Where Time Began

A biography of the Australian continent 

Totten Glacier – Inland Bed Erosion Indicates Repeated Retreat on a Large Scale

Sea levels rise or lower by metres to decimetres as ice sheets advance or retreat as a result of climate changes. The timing, magnitude and sources of changes of sea level have remained unclear, though the basic relationship is unambiguous; particularly as the contribution of the East Antarctic Ice Sheet (EAIS) is ill defined, restricting appreciation of potential change in the future. Possible collapse of the Totten Glacier into interior basins during warm periods in the past, most notably in the Pliocene (Williams et al., 2010; Patterson et al., 2014; Cook et al., 2013; Pollard, DeConto & Alley, 2015), which has caused lea level to rise by several metres, is suggested by several lines of evidence. However, there has been too little understanding of the structure and long-term evolution of the ice sheet in this region to constraint the extent of past ice sheets. In this paper Aitken et al. have shown that there has been enough erosion of the ice sheet to expose the basement rocks in 2 regions: the head of the Totten Glacier, which was within 150 km of the present grounding line; and deep within the Sabrina Subglacial Basin, 350-550 km from the grounding line. Based on ICECAP aerogeophysical data the results obtained by Aitken et al. they demarcated the marginal zones of 2 distinct EAIS configurations, that are quasi-stable, which correspond to the scale of the ice sheet at the present, with a marginal zone that is near the ice sheet margin of the present, and the retreated ice sheet, with the marginal zone located a great distance inland.  It is suggested by the transitional region of 200-250 km in width that is less eroded, that there was  shorter period exposure to eroding conditions during retreat-advance events, which Aitken et al. suggest are probably driven by instabilities which are ocean-forced. It is indicated by representative ice sheet models that the global sea level that resulted from retreat in this sector can be up to 0.9 m in the modern scale configuration, and exceeds 2 m in the retreated configuration.

Sources & Further reading

Aitken, A. R. A., J. L. Roberts, T. D. v. Ommen, D. A. Young, N. R. Golledge, J. S. Greenbaum, D. D. Blankenship and M. J. Siegert (2016). "Repeated large-scale retreat and advance of Totten Glacier indicated by inland bed erosion." Nature 533(7603): 385-389.