Preprints
https://doi.org/10.5194/cp-2023-101
https://doi.org/10.5194/cp-2023-101
04 Jan 2024
 | 04 Jan 2024
Status: a revised version of this preprint is currently under review for the journal CP.

Nordic Seas Deep-Water susceptible to enhanced freshwater export to the subpolar North Atlantic during peak MIS 11

Michelle J. Curran, Christophe Colin, Megan Murphy O’Connor, Ulysses S. Ninnemann, and Audrey Morley

Abstract. Recent investigations into Marine Isotope Stage (MIS) 11 (424–403 ka), an unusually long and warm interglacial of the Quaternary Period, have found that the Atlantic Meridional Overturning Circulation remained strong while background melting of the Greenland Ice-Sheet (GIS) was high, and resulted in a fresh and cold surface ocean in the Nordic Seas. These investigations support the hypothesis that deep-water formation may not be as susceptible to future GIS melting as previously thought. Here we test this hypothesis and present a palaeoceanographic investigation of a freshwater-related abrupt climate event recorded in the eastern North Atlantic during peak interglacial conditions (~412 ka), when the GIS was as small or smaller than today. Using sediment core DSDP-610B recovered from the western Rockall Trough we reconstruct the evolution of Nordic Seas Deep-Water (NSDW) using benthic carbon isotope, Neodymium isotopes, and grain-size analysis paired with end-member modelling. Further, a combination of planktonic foraminiferal assemblage census and Ice-Rafted Debris counts allow us to reconstruct surface water properties including temperature and the movement of oceanic fronts throughout this event. Our results demonstrate that a reduction of NSDW only occurs once GIS melt and polar freshwater reaches subpolar latitudes. We hypothesise that the reorganisation of fresh and cold surface waters from the Nordic Seas into the subpolar North Atlantic was responsible for an AMOC-related cold event centred at 412 ka. Placing our results in the palaeogeographical context of the North Atlantic Region we tentatively propose that the ocean-atmosphere climate dynamics linking the Nordic Seas with the subpolar North Atlantic played and will play a crucial role for the stability of NSDW formation in the future, considering the enhanced melting and overall hydrological cycle at high Northern latitudes predicted for future climate scenarios.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Michelle J. Curran, Christophe Colin, Megan Murphy O’Connor, Ulysses S. Ninnemann, and Audrey Morley

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2023-101', Anonymous Referee #1, 30 Jan 2024
  • RC2: 'Comment on cp-2023-101', Anonymous Referee #2, 31 Jan 2024
  • RC3: 'Comment on cp-2023-101', Anonymous Referee #3, 27 Feb 2024
Michelle J. Curran, Christophe Colin, Megan Murphy O’Connor, Ulysses S. Ninnemann, and Audrey Morley
Michelle J. Curran, Christophe Colin, Megan Murphy O’Connor, Ulysses S. Ninnemann, and Audrey Morley

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Short summary
Our multi-proxy examination of an abrupt climate event during peak MIS11 reveals new evidence that the reorganisation of Polar and Atlantic Waters at subpolar latitudes is central mechanistically for the stability of North Atlantic Deep Water formation. We conclude that high-magnitude AMOC variability is possible without the addition of freshwater or Icebergs to deep water formation regions challenging established knowledge of AMOC sensitivity and stability during warm climates.