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https://doi.org/10.5194/egusphere-2026-3764
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/egusphere-2026-3764
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
07 Jul 2026
| 07 Jul 2026
Status: this preprint is open for discussion and under review for Climate of the Past (CP).
Evolution of deep-water circulation in the North-East Atlantic during the latest Miocene warming
Abstract. Understanding the possible responses of Atlantic Meridional Overturning Circulation (AMOC) to climate warming is one of the major challenges of modern oceanography. Today, the lower (deeper) southward flowing limb of AMOC consists of the North Atlantic deep water (NADW), which is predominantly formed by deep water convection in the ocean basins to the north and south of Iceland. The southward transit of deep water formed in the northerly basins (Greenland-Iceland-Norwegian Seas) is constrained by gateway geometry to two major flow pathways to the east and west of Iceland. To the south of Iceland extensive deep-sea sediment archives, in the form of contourite drifts, are deposited by these currents and have provided critical information about AMOC and NADW dynamics through the Pleistocene. Here we make use of recently recovered cores from one of these sediment drifts (Gardar Drift, IODP Expedition 395, Site U1564,), that records the deep Iceland-Scotland Overflow water (ISOW) dynamics back to the warm climates states of the late Miocene to Pliocene. By combining sedimentological and X-Ray fluorescence derived elemental proxy evidence, we reconstructed deep ocean current activity and carbonate preservation between 5.0–6.2 million years ago (Ma). The record supports the periodic presence of deep currents since the latest Miocene, as well as a distinct ISOW weakening that coincided with the global warming trend, and the severe restriction on Mediterranean Outflow Water, just before the Miocene-Pliocene boundary. Low carbonate preservation hints to the presence of corrosive water masses in the North Atlantic following the termination of the Messinian salinity crisis.
How to cite. Karatsolis, B.-T., Sinnesael, M., Dunkley Jones, T., Drury, A. J., LeVay, L., Briais, A., Parnell-Turner, R., Hanson, E., Pearson, P. N., Morris, M., Svadlenak, H., Hemming, S. R., Jasper, C. E., Di Chiara, A., Satolli, S., Friedman, S., Dwyer, D., and Claeys, P.: Evolution of deep-water circulation in the North-East Atlantic during the latest Miocene warming, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2026-3764, 2026.
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Boris-Theofanis Karatsolis
CORRESPONDING AUTHOR
Archaeology, Environmental changes & Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
Department of Geosciences, University of Fribourg, Chemin du Musée 6, 1700 Fribourg, Switzerland
Matthias Sinnesael
Geology, School of Natural Sciences, Trinity College Dublin, The University of Dublin, College Green, Dublin 02, Ireland
Tom Dunkley Jones
School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
Anna Joy Drury
School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK
Leah LeVay
Scientific Ocean Drilling, Texas A&M University, 1000 Discovery Drive, College Station TX 77845, USA
Anne Briais
Geo-Ocean, Centre National de la Recherche Scientifique (CNRS), Institut Universitaire Européen de la Mer, Rue Dumont d’Urville, 29280 Plouzané, France
Ross Parnell-Turner
Institute of Geophysics & Planetary Physics, Scripps Institution of Oceanography, University of California, San Diego, La Jolla CA 92093, USA
Emma Hanson
School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
Paul N. Pearson
Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, United Kingdom
Margaret Morris
Institute of Geophysics & Planetary Physics, Scripps Institution of Oceanography, University of California, San Diego, La Jolla CA 92093, USA
Haley Svadlenak
Institute of Geophysics & Planetary Physics, Scripps Institution of Oceanography, University of California, San Diego, La Jolla CA 92093, USA
Sidney R. Hemming
Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA
Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA
Claire E. Jasper
Ocean Sciences Department, University of California, Santa Cruz, Santa Cruz, CA, USA
Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA
Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA
Anita Di Chiara
Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143 Roma, Italy
Sara Satolli
Department of Engineering and Geology, University of Chieti-Pescara, Viale Pindaro 42, 65127 Pescara, Italy
Sarah Friedman
School of Earth, Environment & Sustainability, Georgia Southern University, Statesboro, GA 30458, USA
Department of Geological Sciences, New Mexico State University, Las Cruces, NM 88003, USA
Deepa Dwyer
College of Earth Ocean and Atmospheric Sciences, Oregon State University, 1500 SW, Jefferson Way, Corvallis OR 97331, USA
Philippe Claeys
Archaeology, Environmental changes & Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
Pacific Centre for Isotope and Geochemical Research, Dept Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada
Short summary
The lower branch of the Atlantic Meridional overturning consists of deep-water currents which flow within North Atlantic basins and deposit sediments known as contourite drifts. Fluctuations in the accumulation and the lithology of these drifts can help us understand deep-ocean circulation during past warm intervals. In this study we investigated the sedimentary archive of the Gardar Drift and identified a weakening in bottom current activity across the latest Miocene climatic warming.
The lower branch of the Atlantic Meridional overturning consists of deep-water currents which...
Manuscript titled " Evolution of deep-water circulation in the North-East Atlantic during the latest Miocene warming" by Karatsolis et al., et al. [egusphere-2026-3764] present an original unpublished major element data (XRF-scan) and astronomical tunning for site U1564 (Gardar drift) between 5.0 to 6.2 Ma. A large number of studies have already shown that Gardar drift is a great site for paleaoceanographic studies aimed at reconstructing the AMOC and the study period, which includes the Miocene/Pliocene transition, is a key moment when major climatic, tectonic and global thermohaline circulation changes of maximum interest took place.
The data obtained is high resolution and looks fantastic. Astronomical tunning is base in magnetostratigraphy (only two tie points) and Carbonate content obtained from major element data (Ca/Ti ratio) and shipboard-measured CaCO3.
The greatest weakness of the presented study is that authors base all their work on element composition obtained by XRF-Scan (mainly Ca/Ti, and slightly Zr/Rb and Ti/K ratios). With these data, the authors have done a magnificent job but at the same it is a major limitation for the discussion and the conclusions that can be drawn. The study also is based on a previous paper at the same site by Sinnesael et al., 2025 that covers a different period, which gives greater robustness to the work presented
Despite all the issues presented, I believe that the conclusions obtained by the authors are in line with the nature of the data and the range of error of the age model. Three intervals are distinguished that affect the evolution of the AMOC and that are similar to those observed in other regions on a global scale, only for this reason I think it is worth publishing this study although we must wait a little longer to have more data (SST, oxygen isotopes in forams, a detailed study of carbonate, increase age model tie point etc…) to reach more robust conclusions, as the authors point out in their conclusions.
However, at this moment I can only recommend publication after minor/major revision because the whole interpretation about the presence of waters originating in the southern hemisphere that promote corrosion in carbonates seems to me too poorly supported. To add something more in this regard, having only XRF-Scan data available, the authors could explore the correlation between Sr and Ca along the control or the Ca/Sr ratio. In both cases it can give us an idea of what may be happening with carbonates. Plotting this elemental ratio could be a nice support for carbonate discussion.
It is also not clear whether the Ti/K ratio is associated with changes in Iceland-sourced terrigenous input (as proposed in previous studies) or with changes in the ratio of fine to coarse material associated with the activity of the currents that give rise to the contourite. The two ratios (Zr/Rb and Ti/K) have a very high similarity (Fig. 7) during the Interval I and II, and only show some differences during interval III. The authors could include a simple figure to indicate how an intense/weak current contributes more or less material from Iceland or if, on the contrary, both ratios depend on the current intensity and therefore on the concentration between fine (Rb and K) or coarse material (Ti and Zr).
In addition, in table 1 the authors assume that warm moments result in a higher carbonate content in the record. However, the Ca/Ti ratio in the Atlantic represents in most cases the dilution of carbonate by the detrital material (in stead of paleoproductivity, even more in a contourite drift setting) and taking into account the dramatic changes that occur during the period studied, I dare to predict that when the authors have paleo-SST or stable isotope data available, it is quite possible that the Ca/Ti peaks will change their relationship with orbital parameters along studied interval. This should not be a problem for the observations and conclusions reached and the authors themselves recognize a gap (error range) between 10 and 25 kyr. So, again, the problem is that Ca/Ti ratio is sensitive to everything (carbonate corrosion, detrital input, carbonate production, winnowing...) and it is impossible to know what is happening in the environment having this ratio alone, without further support from other proxies or observations.
It would also be helpful, but not mandatory, to perform Principal Component Analyses (PCA) in obtained elemental database at each interval, to see if Ca and Sr lose their correlation showing that something is changing in carbonates, or if we are moving from a more contouritic sedimentation to one dominated by more pelagic component (May be Bahr, A. et al., 2014 G3 approach could help to see how the different components of PC1 or PC2 could be associate with more or less pelagic/contourite influence).
Finally, in the discussion chapter dedicated to tectonics/thermohaline circulation, authors could also briefly talk about the changes in the thermohaline circulation forced by tectonics that is seen in other regions, like these affecting the AMOC associate with the closure of the Central American Seaway (Karas et al., 2017 Sci Rep.) or the Indian ocean (Antartic ice sheet expansion, Indonesian Troughflow (Tagliaro et al., 2022 Paleoceanography and Paleoclimatology)… with these planetary changes authors may explain why the relationship observed in the study area (AMOC) with CO2 is not so obvious. In fact, the discussion on CO2 is not very clear in the current version either.
Minor comments:
I hope these comments are helpful to the authors.