Decoding major Climate Mysteries over the last 1.5 million years: Sea Surface Temperature Reconstruction at IODP Site U1385, Iberian Margin.

The Iberian Margin provides a remarkably accurate record of millennial-scale climate variability, making it an invaluable site for deciphering historical changes in climate and oceanography. This region’s exceptional sensitivity to high latitude processes, such as meltwater discharges into the Northeast Atlantic, significantly influence ocean dynamics, nutrient supply, and climate change impacts. These processes play a pivotal role in understanding the complex interplay between the ocean, ice, and climate systems. IODP 339 Site U1385, also known as the “Shackleton site”, drilled at a water depth of 2582 mbsl, reaching a total depth of 155.9 m below the seafloor. The oxygen isotope and carbon isotope records confirm that Site U1385 contains a continuous hemipelagic sedimentation from the Holocene to 1.45 million years (MIS 47), providing a reference record of millennial-scale climate variability. Here, we present a high-resolution Sea Surface Temperature (SST) record that unveils the climate variability over the last 1.45 million years.  This record provides a comprehensive interpretation of the millennial climate variability of major climatic disruptions, namely the Mid Brunhes Event and Mid Pleistocene Transition (MPT). SST data reveals a clear change on the orbital-driven forcing on the MPT time interval 1200 to 800 ka, thereby contributing to our understanding the underlying mechanisms on glacial/interglacial and centennial to millennial scales. Furthermore the SST record shows extreme cold events occurred not only after the MPT but also during and after this enigmatic period. The highest temperatures were recorded during Interglacial periods, overall the record and coincident with maximum insolation (precession minimum), suggesting an orbital dependence of the Sea Surface Temperature (SST) over the past 1.45 million years. This SST record significantly contribute to documenting the major climate shifts and their relation to global climate change. This becomes particularly crucial as the IODP Expedition 397 enables the extension of this exceptional sediment record into the Pliocene.