Relict sea-floor ploughmarks record deep-keeled Antarctic icebergs to 45°S on the Argentine margin

López-Martı́nez, Jerónimo; Muñoz, Araceli; Dowdeswell, Julian A.; Linés, Clara; Acosta, Juan

doi:10.1016/j.margeo.2011.08.002

Cited by 25 publications

(11 citation statements)

References 39 publications

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“…In Pine Island Bay, no iceberg-keel plough marks present wide, flat-based morphologies and, whilst we do observe 86 multi-keeled plough marks, these are limited in number (<1% of the total observed), comprise no more than two parallel incisions per feature, and are no more than 444 m wide. By contrast, multi-keeled iceberg plough marks with 'toothcomb-like' morphologies, observed previously on the Argentine margin north of the Falkland Islands 12 and in M'Clure Strait, Canadian Arctic 11 , imply the grounding of icebergs with basal widths of ~2 km and ~2.7 km, respectively. Thus, a tabular iceberg genesis for Pine Island Bay plough marks is not supported.…”

mentioning

confidence: 58%

Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks

Wise

Dowdeswell

Larter

2017

Nature

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Marine ice-cliff instability (MICI) processes could accelerate future retreat of the Antarctic Ice Sheet if ice shelves that buttress grounding lines more than 800 metres below sea level are lost. The present-day grounding zones of the Pine Island and Thwaites glaciers in West Antarctica need to retreat only short distances before they reach extensive retrograde slopes. When grounding zones of glaciers retreat onto such slopes, theoretical considerations and modelling results indicate that the retreat becomes unstable (marine ice-sheet instability) and thus accelerates. It is thought that MICI is triggered when this retreat produces ice cliffs above the water line with heights approaching about 90 metres. However, observational evidence confirming the action of MICI has not previously been reported. Here we present observational evidence that rapid deglacial ice-sheet retreat into Pine Island Bay proceeded in a similar manner to that simulated in a recent modelling study, driven by MICI. Iceberg-keel plough marks on the sea-floor provide geological evidence of past and present iceberg morphology, keel depth and drift direction. From the planform shape and cross-sectional morphologies of iceberg-keel plough marks, we find that iceberg calving during the most recent deglaciation was not characterized by small numbers of large, tabular icebergs as is observed today, which would produce wide, flat-based plough marks or toothcomb-like multi-keeled plough marks. Instead, it was characterized by large numbers of smaller icebergs with V-shaped keels. Geological evidence of the form and water-depth distribution of the plough marks indicates calving-margin thicknesses equivalent to the threshold that is predicted to trigger ice-cliff structural collapse as a result of MICI. We infer rapid and sustained ice-sheet retreat driven by MICI, commencing around 12,300 years ago and terminating before about 11,200 years ago, which produced large numbers of icebergs smaller than the typical tabular icebergs produced today. Our findings demonstrate the effective operation of MICI in the past, and highlight its potential contribution to accelerated future retreat of the Antarctic Ice Sheet.

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mentioning

confidence: 58%

Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks

Wise

Dowdeswell

Larter

2017

Nature

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“…South of 45˚S, the multi-beam bathymetry show 0.3-32 km long, 73 to 685 m wide and 10-25 m deep grooves cut the upper slope, they trend northeast. From their similarity to known iceberg plow marks López-Martínez et al (2011) inferred that icebergs from Antarctica cut them in the Late Pleistocene.…”

Section: Continental Slopementioning

confidence: 99%

Geomorphology and shallow structure of a segment of the Atlantic Patagonian margin

Muñoz¹,

Acosta²,

Cristobo³

et al. 2013

Earth-Science Reviews

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“…3). The furrows are 10-15 m deep with respect [49], the Canadian margin [66], in Pine Island Bay, Antarctica [40], and on the Argentine continental margin [55]. They are produced by the seafloor scouring of mega-scale iceberg keels (megabergs, [27,87]).…”

Section: Outer Shelf Iceberg Scoursmentioning

confidence: 99%

Marine sedimentary record of Meltwater Pulse 1a along the NW Barents Sea continental margin

Lucchi

Sagnotti

Camerlenghi

et al. 2015

Arktos

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The upper continental slope of the Storfjorden-Kveithola Trough Mouth Fans (NW Barents Sea) contains a several m-thick late Pleistocene sequence of plumites composed of laminated mud interbedded with sand/silt layers. Radiocarbon ages revealed that deposition occurred during about 130 years at a very high sedimentation rate of 3.4 cm a-1 , at about 7 km from the present shelf break. Palaeomagnetic and rock magnetic analyses confirm the existence of a prominent, short-living sedimentary event. The plumites appear laterally continuous and were correlated with the sedimentary sequences described west of Svalbard and neighboring glacial depositional systems representing a major event at regional scale appointed to correspond to the deep-sea sedimentary record of Meltwater Pulse-1a. We also present new sedimentological and geochemical insights, and multi-beam data adding information on the palaeoenvironmental characteristics during MWP-1a and ice sheet decay in the NW Barents Sea.

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Relict sea-floor ploughmarks record deep-keeled Antarctic icebergs to 45°S on the Argentine margin

Cited by 25 publications

References 39 publications

Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks

Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks

Geomorphology and shallow structure of a segment of the Atlantic Patagonian margin

Marine sedimentary record of Meltwater Pulse 1a along the NW Barents Sea continental margin

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