EGU2020-5875
https://doi.org/10.5194/egusphere-egu2020-5875
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

A significant acceleration of ice volume discharge preceded a major retreat of a West Antarctic paleo-ice stream

Phil Bart1 and Slawek Tulaczyk2
Phil Bart and Slawek Tulaczyk
  • 1Louisiana State University, Geology and Geophysics, Baton Rouge, United States of America (pbart@lsu.edu)
  • 2University of California, Santa Cruz, Earth and Planetary Sciences, United States of America (stulaczyk@ucsc.edu

For the period between 14.7 and 11.5 cal. (calibrated) kyr B.P, the sediment flux of Bindschadler Ice Stream (BIS; West Antarctica) averaged 1.7 × 108 m3 a−1. This implies that BIS velocity averaged 500 ± 120 m a-1. At a finer resolution, the data suggest two stages of ice stream flow. During the first 2400 ± 400 years of a grounding-zone stillstand, ice stream flow averaged 200 ± 90 m a-1. Following ice-shelf breakup at 12.3 ± 0.2 cal. kyr B.P., flow accelerated to 1350 ± 580 m a-1. The estimated ice volume discharge after breakup exceeds the balance velocity by a factor of two and implies ice mass imbalance of ~40 Gt a-1 just before the grounding zone retreated >200 km. We interpret that the paleo-BIS maintained sustainable discharge throughout the grounding-zone stillstand first due to the buttressing effect of its fringing ice shelf and then later (i.e., after ice-shelf breakup) due to the stabilizing effects of grounding-zone wedge aggradation. Major paleo–ice stream retreat, shortly after the ice-shelf breakup that triggered the inferred ice flow acceleration, substantiates the current concerns about rapid, near-future retreat of major glaciers in the Amundsen Sea sector where Pine Island and Thwaites Glaciers are already experiencing ice-shelf instability and grounding-zone retreat that have triggered upstream-propagating thinning and ice acceleration.

How to cite: Bart, P. and Tulaczyk, S.: A significant acceleration of ice volume discharge preceded a major retreat of a West Antarctic paleo-ice stream, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5875, https://doi.org/10.5194/egusphere-egu2020-5875, 2020

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