EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2026-809 Atlantic water intrusions onto the Scotian Shelf during the past 8.6 ka BP Kolling Henriette M. https://orcid.org/0000-0003-4198-941X 1 Kienast Markus 5 Matzerath Peter https://orcid.org/0009-0003-1455-3351 1 Gottschalk Julia https://orcid.org/0000-0002-0403-3059 1 Kienast Stephanie https://orcid.org/0000-0003-3867-4919 2 Frick Daniel A. https://orcid.org/0000-0002-8530-3064 1 Gross Felix https://orcid.org/0000-0002-0749-829X 1 3 Wharton Jack 4 Thornalley David https://orcid.org/0000-0001-5885-5499 4 Schneider Ralph R. 1 Institute of Geosciences, Kiel University, Ludewig-Meyn-Straße 10, 24118 Kiel, Germany Department of Oceanography, Dalhousie University, 1355 Oxford Street, Halifax B3H 4R2 NS, Canada Center for Ocean and Society, University of Kiel, Kiel, Germany Department of Geography, University College London, London, UK deceased 17 02 2026 2026 1 35 Copyright: © 2026 Henriette M. Kolling et al. 2026 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-809/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-809/egusphere-2026-809.pdf

The Scotian Shelf lies at the confluence of warm Gulf Stream (GS) waters and the cold Labrador Current (LC), making it highly sensitive to large- and small-scale climate variability. Modern observations show rapid regional warming accelerated by episodic GS-derived intrusions, yet Holocene paleoceanographic reconstructions from this margin are sparse and often conflicting with respect to the frequency and extent of intrusion events. Here, we present high-resolution Mg/Ca-derived sea-surface temperature (SST) and planktonic δ¹⁸O records from St. Anns Basin on the north-eastern Scotian Shelf that provide new insights into the hydrographic surface-ocean variability of the past 8.5 ka calibrated Before Present (cal BP). While the SST record does not capture the 8.2 ka event, this event is evident in the δ¹⁸O and Ca/Sr records, indicating that its freshwater signal reached the Scotian Shelf. Reconstructed SSTs are generally cold from ~8.5 to ~6.2 cal ka BP, followed by a gradual increase in mean SSTs punctuated by multiple short-lived warm and saline events beginning around 6 cal ka BP, at 6.0–5.8, 5.5–5.4, 5.1–4.9, 3.2–3.1, 2.5–2.2 and 1.05–0.8 cal ka BP, which we interpret as intrusions of GS-sourced slope waters. We attribute these events to basin-scale reorganizations of the GS-LC system, consistent with the minimum/maximum modal state framework of Pickart et al. (1999). Minimum modal state circulation, characterized by a strong onshore LC and an intensified Deep Western Boundary Current (DWBC), which is dominated by Denmark Strait Overflow water, creates a sharp front which restricts intrusions of warm water onto the Scotian Shelf. Maximum modal state conditions feature a weakened LC and increased Labrador Sea Water (LSW) contribution to the DWBC, and reduce cross-slope temperature and salinity gradients that permit GS-derived waters to penetrate the shelf. Overall, our results indicate that warm-water intrusions occurred regularly throughout the past 6.5 ka BP with magnitudes of 6.7 °C and 1.5 psu comparable to those observed today.

 Deutsche Forschungsgemeinschaft DFG GPF20-1-039