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Australia: The Land Where Time Began |
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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.
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.
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Author: M.H.Monroe Email: admin@austhrutime.com Sources & Further reading |