Erosion and deposition beneath the Subantarctic Front since the Early Oligocene

Research output: Contribution to journalArticle

Abstract

The Antarctic Circumpolar Current (ACC) spills across the Falkland Plateau into the South Atlantic as a series of high-velocity jets. These currents are a driving force for global overturning circulation, and affect climate by modulating CO2 exchange between the atmosphere and ocean, but their timing of onset remains controversial. We present new evidence of strong currents associated with the Subantarctic Front (SAF) jet since the earliest Oligocene (~34 Ma) based on a widespread erosional surface on the Falkland Plateau, preserved below a 30,000 km2 contourite sand deposit. This is the largest such feature ever to be recognized, and provides the most robust constraint of the initiation of the SAF to date. By contrast, the South Falkland Slope Drift is dominated by contourite mud of Pleistocene-Recent age, substantially younger than previous estimates, indicating a significant decrease in long-term current strength at that time. As ACC strength is primarily a function of the position of the South-Westerly Winds, our data indicates that associated currents are likely to increase substantially in a warming world. Likely implications include increased upwelling and associated carbon flux from the deep ocean to the atmosphere, a positive feedback loop not included in most future projections of atmospheric CO2.

Original languageEnglish
Article number9296
JournalScientific Reports
Volume9
DOIs
Publication statusPublished - 26 Jun 2019

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contourite
Oligocene
circumpolar current
erosion
plateau
atmosphere
ocean
carbon flux
westerly
upwelling
mud
warming
Pleistocene
sand
climate
young
world

ASJC Scopus subject areas

  • General

Cite this

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title = "Erosion and deposition beneath the Subantarctic Front since the Early Oligocene",
abstract = "The Antarctic Circumpolar Current (ACC) spills across the Falkland Plateau into the South Atlantic as a series of high-velocity jets. These currents are a driving force for global overturning circulation, and affect climate by modulating CO2 exchange between the atmosphere and ocean, but their timing of onset remains controversial. We present new evidence of strong currents associated with the Subantarctic Front (SAF) jet since the earliest Oligocene (~34 Ma) based on a widespread erosional surface on the Falkland Plateau, preserved below a 30,000 km2 contourite sand deposit. This is the largest such feature ever to be recognized, and provides the most robust constraint of the initiation of the SAF to date. By contrast, the South Falkland Slope Drift is dominated by contourite mud of Pleistocene-Recent age, substantially younger than previous estimates, indicating a significant decrease in long-term current strength at that time. As ACC strength is primarily a function of the position of the South-Westerly Winds, our data indicates that associated currents are likely to increase substantially in a warming world. Likely implications include increased upwelling and associated carbon flux from the deep ocean to the atmosphere, a positive feedback loop not included in most future projections of atmospheric CO2.",
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Erosion and deposition beneath the Subantarctic Front since the Early Oligocene. / Nicholson, Uisdean; Stow, Dorrik.

In: Scientific Reports, Vol. 9, 9296, 26.06.2019.

Research output: Contribution to journalArticle

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