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Deep Ocean storage of heat and CO2 in the Fram Strait, Arctic Ocean during the last glacial period
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  • Mohamed M. Ezat,
  • Tine L. Rasmussen,
  • Mathis P. Hain,
  • Mervyn Greaves,
  • James W B Rae,
  • Katarzyna Zamelczyk,
  • Thomas M Marchitto,
  • Sönke Szidat,
  • Luke C Skinner
Mohamed M. Ezat
UiT

Corresponding Author:[email protected]

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Tine L. Rasmussen
UiT
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Mathis P. Hain
University of California, Santa Cruz
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Mervyn Greaves
Cambridge University
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James W B Rae
University of St. Andrews
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Katarzyna Zamelczyk
UiT
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Thomas M Marchitto
University of Colorado Boulder
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Sönke Szidat
University of Bern
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Luke C Skinner
Cambridge University
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Abstract

The Fram Strait is the only deep gateway between the Arctic Ocean and the Nordic Seas and thus is a key area to study past changes in ocean circulation and the marine carbon cycle. Here, we study deep ocean temperature, δ18O, carbonate chemistry (i.e., carbonate ion concentration, [CO32-]), and nutrient content in the Fram Strait during the late glacial (35,000–19,000 years BP) and the Holocene based on benthic foraminiferal geochemistry and carbon cycle modelling. Our results indicate a thickening of Atlantic water penetrating into the northern Nordic Seas, forming a subsurface Atlantic intermediate water layer reaching to at least ~2600 m water depth during most of the late glacial period. The recirculating Atlantic layer was characterized by relatively high [CO32-] and low δ13C during the late glacial, and provides evidence for a Nordic Seas source to the glacial North Atlantic intermediate water flowing at 2000–3000 m water depth, most likely via the Denmark Strait. In addition, we discuss evidence for enhanced terrestrial carbon input to the Nordic Seas at ~23.5 ka. Comparing our δ13C and qualitative [CO32-] records with results of carbon cycle box modelling suggests that the total terrestrial CO2 release during this carbon input event was low, slow, or directly to the atmosphere.