Geophysical Research Letters

Glacier tongue calving reduced dense water formation and enhanced carbon uptake

Authors

  • E. H. Shadwick,

    Corresponding author
    • Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tas, Australia
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  • S. R. Rintoul,

    1. Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tas, Australia
    2. CSIRO Marine and Atmospheric Research, Hobart, Tas, Australia
    3. Centre for Australian Weather and Climate Research, Hobart, Tas, Australia
    4. Wealth from Oceans National Research Flagship, Hobart, Tas, Australia
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  • B. Tilbrook,

    1. Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tas, Australia
    2. CSIRO Marine and Atmospheric Research, Hobart, Tas, Australia
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  • G. D. Williams,

    1. Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tas, Australia
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  • N. Young,

    1. Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tas, Australia
    2. Australian Antarctic Division, Hobart, Tas, Australia
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  • A. D. Fraser,

    1. Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tas, Australia
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  • H. Marchant,

    1. Australian National University, Canberra, ACT, Australia
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  • J. Smith,

    1. Geoscience Australia, Canberra, ACT, Australia
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  • T. Tamura

    1. Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tas, Australia
    2. National Institute of Polar Research, Tokyo, Japan
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Corresponding author: E. H. Shadwick, Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tas, Australia. (Elizabeth.Shadwick@utas.edu.au)

Abstract

[1] Dense shelf water formed in the Mertz Polynya supplies the lower limb of the global overturning circulation, ventilating the abyssal Indian and Pacific Oceans. Calving of the Mertz Glacier Tongue (MGT) in February 2010 altered the regional distribution of ice and reduced the size and activity of the polynya. The salinity and density of dense shelf water declined abruptly after calving, consistent with a reduction of sea ice formation in the polynya. Breakout and melt of thick multiyear sea ice released by the movement of iceberg B9B and the MGT freshened near-surface waters. The input of meltwater likely enhanced the availability of light and iron, supporting a diatom bloom that doubled carbon uptake relative to precalving conditions. The enhanced biological carbon drawdown increased the carbonate saturation state, outweighing dilution by meltwater input. These observations highlight the sensitivity of dense water formation, biological productivity, and carbon export to changes in the Antarctic icescape.

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