EGU2020-21713
https://doi.org/10.5194/egusphere-egu2020-21713
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

AMOC step-wise inception during the present interglacial recorded by Nd-isotopes.

Lucie Menabreaz1, Claude Hillaire-Marcel1, Maccali Jenny2, André Poirier1, Bassam Ghaleb1, and Evan Edinger3
Lucie Menabreaz et al.
  • 1GEOTOP-UQAM, CP 8888, Montreal (Qc), H3C 3P8, Canada (lucie.menabreaz@gmail.com)
  • 2University of Bergen, PB 7803, N-5020 Bergen, Norway
  • 3Memorial University of Newfoundland, St. John’s, NL A1B 3X9, Canada

The Atlantic Meridional Overturning Circulation (AMOC) and the production rate of the North Atlantic Deep Water (NADW) are major components of the North Atlantic climate-system, with important hemispheric climatic influences. The post-glacial history of the AMOC, as reconstructed from Nd-isotopes (εNd) in biogenic minerals and sediments, demonstrates its sensitivity to freshwater fluxes, leading to concerns about its near-future response to the ongoing accelerated Greenland/Arctic ice melting. Whereas the early Holocene inception of the deep NADW components originating from the Nordic Seas has been well documented from such εNd-data, information on the status of its western, shallower and most sensitive component, the Labrador Sea Water (LSW), is still missing. New εNd-measurements in corals from the Labrador Slope provide the means to fill this gap. These data demonstrate that convection in the Labrador Sea was fully implemented by ca. 4 ka BP only, i.e., well after the final demise of the Laurentide ice-sheet. The time- and space-transgressive pattern of the full AMOC inception implies more complex driving mechanisms than meltwater fluxes only. Whereas the late Holocene neo-glacial cooling trend could have played here a minor role, the penetration and strengthening of the Irminger Current into the Labrador Sea has likely been the driving force.

How to cite: Menabreaz, L., Hillaire-Marcel, C., Jenny, M., Poirier, A., Ghaleb, B., and Edinger, E.: AMOC step-wise inception during the present interglacial recorded by Nd-isotopes. , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21713, https://doi.org/10.5194/egusphere-egu2020-21713, 2020

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Presentation version 1 – uploaded on 04 May 2020
  • CC1: Comment on EGU2020-21713, Antoon Kuijpers, 04 May 2020

    Labrador Sea  convection fully implemented first later in the Holocene ( i.e. after ca 4.0 ka) : possible role of widespread melting of the western sector of the Greenland Ice Sheet , with maximum 4.4 - 4.0 ka ( see Kuijpers et al., this session) ?

    • AC1: Reply to CC1, Lucie Menabreaz, 14 May 2020

      very interesting timing. Although Nd-record of intermediate to deep waters of the LS does not allow identifying this erosional product input, it may have an impact indeed. Notwithstanding time resolution of our Nd record, do you think it is possible that fresher labrador current would have been counterbalanced by more saline inputs south of Iceland within the SPG ? 

      • CC2: Reply to AC1, Antoon Kuijpers, 14 May 2020

        Indeed, as you wrote in your reply , where you suggested the possibility of increasing salt influx via the eastern sector of the Subpolar gyre (SPG) at these times of strong melting / LC freshening, enhanced SPG (surface) circulation could have contributed improving deep convection conditions. Strong SPG cyclonic circulation leads to eddy salt fluxes promoting formation of dense waters and deep mixing in the SPG centre (Born and Stocker 2014).