Human-induced climate change causes ocean warming, leading to tropicalization in regions like the Gulf of Cadiz on the southern Portuguese margin. To understand past ecosystem conditions and predict future changes, we examine the species composition of planktonic foraminifera to reconstruct past oceanographic conditions, like sea surface temperature (SST). This study uses sediment samples from IODP Site U1387 (36°48'N, 7°43' W) and focuses on using Marine Isotope Stage 31 (MIS 31), deemed a “super-interglacial” at higher latitudes, as a baseline for current climate change. The Gulf of Cadiz allows us to investigate changes in planktonic foraminifera fauna linked to warm tropical or cooler transitional waters.
Evidence for a mixing of the subtropical Azores Current and temperate Portugal Current at Site U1387, with influence of a northward flowing subsurface current along the NW African Margin was found. MIS 31 recorded four phases: an initial interstadial warming, a period dominated by upwelling, a period with a consistent warm SST, and stadial/interstadial oscillations during the transition into MIS 30. MIS 31 was not a “super-interglacial” at this mid-latitude site. However, there was a dominance of subtropical species and some tropical species indicating tropicalization on the species level.
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