Recent sedimentology at the grounding zone of the Kamb Ice stream, West Antarctica and implications for ice shelf extent
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Date
2024-11-15
Publication Type
Journal Article
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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 εNd 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 ¹⁴C analysis shows all fractions are either >30 ka or ¹⁴C dead. By contrast, ²¹⁰Pb-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]
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published
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Journal / series
Volume
344
Pages / Article No.
108988
Publisher
Elsevier
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Subject
Ice streams; WAIS; diatom; Ross Ice shelf; Sub-ice shelf access
Organisational unit
09599 - Farinotti, Daniel / Farinotti, Daniel