Recent sedimentology at the grounding zone of the Kamb Ice stream, West Antarctica and implications for ice shelf extent

Sediment accumulating beneath floating ice contains a record of ice dynamics in polar regions where in situ observations are rare. In 2019 a hole was melted through a 590m-thick region of the Ross Ice Shelf ∼5 km seawards of the Kamb Ice Stream (KIS) grounding line (82.7841°S, 155.2626°W) to access the seafloor. Imagery from a remotely operated vehicle (ROV, Icefin) shows ocean current-generated ripples likely formed by tidal flow parallel to the grounding line (GL). Observed current speeds <0.15 m s −1 suggest these bedforms may be relict. Larger, dm-scale, ‘furrows’ parallel to the former direction of KIS flow may relate to past grounding line processes. A 0.49 m-long gravity core collected from the seafloor contains weakly stratified diamicton . The sediment matrix comprises variable mixtures of reworked Tertiary biogenic silica, predominantly diatoms, and arkose material. Sediment ε Nd values of ∼7 are consistent with derivation from the WAIS, as is the U-Pb age distribution and modelled late Holocene ice flows. Ramped pyrolysis 14 C analysis shows all fractions are either >30 ka or 14 C dead. By contrast, 210 Pb-210 activity of >30 Bq Kg −1 indicates deposition within the last 120 years. The combination of features suggests rapid rainout deposition from melting of a sediment-laden basal debris layer as the GL retreated, followed by some reworking by ocean currents and little modern accumulation. Although Tertiary diatoms are abundant, unambiguously Late Quaternary forms are absent and we speculate on the implications for Ross Ice Shelf stability. [239 wds] • First imagery, cores and analysis of the seafloor at the Kamb Ice Stream grounding line. • Core comprises diamicton interpreted as grounding line retreat sequence since the 19th Century. • Diatom and provenance data are interpreted in terms of WAIS stability.

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Publication Details

Journal
Quaternary Science Reviews
Published
2024-10-22
DOI
https://doi.org/10.1016/j.quascirev.2024.108988
Primary Topic
Cryospheric studies and observations
Type
article
Field-Weighted Citation Impact
0.00

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article

Recent sedimentology at the grounding zone of the Kamb Ice stream, West Antarctica and implications for ice shelf extent

Sarah U. Neuhaus, Pieter Vermeesch, Jocelyn Christine Turnbull, Andrew Mullen et al.
Quaternary Science Reviews
Cryospheric studies and observations
article

Recent sedimentology at the grounding zone of the Kamb Ice stream, West Antarctica and implications for ice shelf extent

Sarah U. Neuhaus, Pieter Vermeesch, Jocelyn Christine Turnbull, Andrew Mullen, James Marschalek, Shaun Eaves, Cliff Atkins, Andrew Carter, Richard Levy, David M. Harwood, Benjamin Hurwitz, Craig L. Stevens, Enrica Quartini, Peter Washam, Adam P. Martin, Justin Lawrence, Theo Calkin, Jason J. Coenen, Christina Hulbe, Huw Horgan, Nicholas R. Golledge, Gavin Dunbar, B. E. Schmidt, Catherine Ginnane
article en

Abstract

Sediment accumulating beneath floating ice contains a record of ice dynamics in polar regions where in situ observations are rare. In 2019 a hole was melted through a 590m-thick region of the Ross Ice Shelf ∼5 km seawards of the Kamb Ice Stream (KIS) grounding line (82.7841°S, 155.2626°W) to access the seafloor. Imagery from a remotely operated vehicle (ROV, Icefin) shows ocean current-generated ripples likely formed by tidal flow parallel to the grounding line (GL). Observed current speeds <0.15 m s −1 suggest these bedforms may be relict. Larger, dm-scale, ‘furrows’ parallel to the former direction of KIS flow may relate to past grounding line processes. A 0.49 m-long gravity core collected from the seafloor contains weakly stratified diamicton . The sediment matrix comprises variable mixtures of reworked Tertiary biogenic silica, predominantly diatoms, and arkose material. Sediment ε Nd values of ∼7 are consistent with derivation from the WAIS, as is the U-Pb age distribution and modelled late Holocene ice flows. Ramped pyrolysis 14 C analysis shows all fractions are either >30 ka or 14 C dead. By contrast, 210 Pb-210 activity of >30 Bq Kg −1 indicates deposition within the last 120 years. The combination of features suggests rapid rainout deposition from melting of a sediment-laden basal debris layer as the GL retreated, followed by some reworking by ocean currents and little modern accumulation. Although Tertiary diatoms are abundant, unambiguously Late Quaternary forms are absent and we speculate on the implications for Ross Ice Shelf stability. [239 wds] • First imagery, cores and analysis of the seafloor at the Kamb Ice Stream grounding line. • Core comprises diamicton interpreted as grounding line retreat sequence since the 19th Century. • Diatom and provenance data are interpreted in terms of WAIS stability.

Quaternary Science ReviewsVol. 344
University of Nebraska–Lincoln (US), GNS Science (NZ), Planetary Science Institute (US), Georgia Institute of Technology (US), Honeybee Robotics (United States) (US), University of California, Santa Cruz (US), Cornell University (US), ETH Zurich (CH), Victoria University of Wellington (NZ), Instituto Tecnológico del Salmón (CL), Imperial College London (GB), University of Otago (NZ), Birkbeck, University of London (GB)
Sight Research UK, Natural Environment Research Council
Life below water
Openalex Percentile: Top 78%
Cryospheric studies and observations
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