| Summary: | PP31B-2025 Dinoflagellate cyst and planktic foraminiferal assemblages from a core in the western Iceland Sea were analysed in order to reconstruct the last interglacial (MIS 5e) surface water conditions and compare these with the Holocene climate development. The considerable dissimilarities between the assemblages from the two warm periods suggest that quite different surface water conditions existed during each of the two interglacial stages. Holocene interglacial conditions initiated around 10 ka with a subsurface warming that peaked around 7.5 ka preceding a thermal maximum in the uppermost ocean between 6.5 and 5.5 ka, followed by overall cooling. By contrast, both planktic foraminifers and dinoflagellate cysts show a last interglacial thermal optimum around 120.5 ka, following an increased influence of Atlantic (-type) waters from ~122 ka onward. A major shift of the oceanographic fronts appears to have occurred around 120 ka and marks the onset of slightly cooler conditions that persist until the return to stadial conditions around ~117 ka. This late-MIS 5e cooling in the western Nordic seas is opposite to previous observations of a late MIS 5e thermal optimum in the eastern Nordic seas. Such an opposite trend likely relates to the reorganisation of the oceanic fronts that appears to have occurred in the Nordic seas at ~120 ka. Overall, the MIS 5e assemblages are characterised by higher percentages of typical “Atlantic water” species, compared to the cooler Holocene assemblages. This implies a higher contribution of Atlantic waters in the southwestern Nordic seas, possibly due to a more northward expansion of the Irminger Current under weakened East Greenland/East Icelandic currents, during the last interglacial than during the Holocene. A reduced influence of polar waters in the southwestern Nordic seas is consistent with other evidence of relatively warm conditions during MIS 5e all around southern Greenland.
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