University Of Tasmania
154438 - Southern Ocean biogenic blooms freezing-in Oligocene.pdf (5.02 MB)

Southern Ocean biogenic blooms freezing-in Oligocene colder climates

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journal contribution
posted on 2023-05-21, 15:11 authored by Katharina HochmuthKatharina Hochmuth, Joanne WhittakerJoanne Whittaker, Sauermilch, I, Klocker, A, Gohl, K, LaCasce, JH

Crossing a key atmospheric CO2 threshold triggered a fundamental global climate reorganisation ~34 million years ago (Ma) establishing permanent Antarctic ice sheets. Curiously, a more dramatic CO2 decline (~800-400 ppm by the Early Oligocene(~27 Ma)), postdates initial ice sheet expansion but the mechanisms driving this later, rapid drop in atmospheric carbon during the early Oligocene remains elusive and controversial. Here we use marine seismic reflection and borehole data to reveal an unprecedented accumulation of early Oligocene strata (up to 2.2 km thick over 1500x500 km) with a major biogenic component in the Australian Southern Ocean. High-resolution ocean simulations demonstrate that a tectonically-driven, one-off reorganisation of ocean currents, caused a unique period where current instability coincided with high nutrient input from the Antarctic continent. This unrepeated and short-lived environment favoured extreme bioproductivity and enhanced sediment burial. The size and rapid accumulation of this sediment package potentially holds ~1.067x1015 kg of the 'missing carbon' sequestered during the decline from an Eocene high CO2-world to a mid-Oligocene medium CO2-world, highlighting the exceptional role of the Southern Ocean in modulating long-term climate.


Publication title

Nature Communications



Article number









Institute for Marine and Antarctic Studies


Nature Publishing Group

Place of publication

United Kingdom

Rights statement

© 2022 The Author(s). Open Access This article is licensed under a Creative Commons Attribution 4.0 International License,(CC BY 4.0)

Repository Status

  • Open

Socio-economic Objectives

Climate change models