Abstract
Accurate models of past Antarctic ice sheet behaviour require realistic reconstructions of the evolution of bedrock topography. However, other than a preliminary attempt to reconstruct Antarctic topography at the Eocene–Oligocene boundary, the long-term evolution of Antarctica's subglacial topography throughout its glacial history has not previously been quantified. Here, we derive new reconstructions of Antarctic topography for four key time slices in Antarctica's climate and glacial history: the Eocene–Oligocene boundary (ca. 34 Ma), the Oligocene–Miocene boundary (ca. 23 Ma), the mid-Miocene climate transition (ca. 14 Ma), and the mid-Pliocene warm period (ca. 3.5 Ma). To reconstruct past topography, we consider a series of processes including ice sheet loading, volcanism, thermal subsidence, horizontal plate motion, erosion, sedimentation and flexural isostatic adjustment, and validate our models where possible using onshore and offshore geological constraints. Our reconstructions show that the land area of Antarctica situated above sea level was ~25% larger at the Eocene–Oligocene boundary than at the present-day. Offshore sediment records and terrestrial constraints indicate that the incision of deep subglacial topographic troughs around the margin of East Antarctica occurred predominantly in the Oligocene and early Miocene, whereas in West Antarctica erosion and sedimentation rates accelerated after the mid-Miocene. Changes to the topography after the mid-Pliocene were comparatively minor. Our new palaeotopography reconstructions provide a critical boundary condition for models seeking to understand past behaviour of the Antarctic Ice Sheet, and have implications for estimating changes in global ice volume, temperature, and sea level across major Cenozoic climate transitions.
Highlights
Numerical ice sheet model simulations are widely used as a means of predicting the response of Earth's continental ice sheets to future climatic change, and in turn their contribution to global sea level rise (DeConto and Pollard, 2016; Golledge et al, 2015)
We aim to produce topographic reconstructions at the following time slices, which correspond to climatic transitions that are commonly the focus of ice sheet modelling studies: The Eocene–Oligocene boundary
We produce a separate reconstruction of minimum and maximum topography, which provide end-member scenarios that encapsulate the cumulative uncertainties associated with each stage of the reconstruction process, and a median topography representing a ‘middle-ground’ between the two end-members (Section 3)
Summary
Numerical ice sheet model simulations are widely used as a means of predicting the response of Earth's continental ice sheets to future climatic change, and in turn their contribution to global sea level rise (DeConto and Pollard, 2016; Golledge et al, 2015). These models are typically evaluated with recourse to their ability to reproduce past ice sheet behaviour during periods of warmer climate and ice sheet volume loss, which is constrained by geological and oceanographic data. We refrain from addressing the evolution of the oceanic realm (i.e. beyond the modern continental shelf edge), since this is the main focus of on-going work on the reconstruction of the palaeobathymetry of the Southern Ocean (Hochmuth et al, in prep.)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
