Distinct seasonal changes and precession forcing of surface and subsurface temperatures in the mid-latitudinal North Atlantic during the onset of the Late Pliocene

• Main Authors: Pang, Xiaolei, Voelker, Antje Helga Luise, Lu, Sihua, Ding, Xuan
• Format: Text
• Language: English
• Published: 2024
• Subjects: Ice Sheet; north atlantic current; North Atlantic
• Online Access: https://doi.org/10.5194/egusphere-2024-603; https://egusphere.copernicus.org/preprints/2024/egusphere-2024-603/

The Late Pliocene marks the intensification of Northern Hemisphere Glaciation, offering a unique opportunity to study climate evolution and ice-sheet related feedback mechanisms. In this study, we present high-resolution Mg/Ca-based sea surface (SST) and subsurface temperatures (SubT) derived from foraminiferal species Globigerinoides ruber and Globorotalia hirsuta , respectively, at the Integrated Ocean Drilling Project (IODP) Expedition 306 Site U1313 in the mid-latitudinal North Atlantic during the early Late Pliocene, 3.65 – 3.37 million years ago (Ma). We find distinct differences between our new G. ruber Mg/Ca-based SST record and previously published alkenone-based SST record from the same location. These discrepancies in both absolute values and variations highlight distinct seasonal influences. The G. ruber Mg/Ca-based SST data, reflecting summer temperatures, were primarily influenced by local summer insolation, showing a dominant precession cycle. Conversely, the variations in alkenone-based SST are found to be more indicative of cold season changes, despite previous interpretations of these records as reflecting annual mean temperatures. A simultaneous decline in Mg/Ca-based SST and SubT records from 3.65 to 3.5 Ma suggests a diminished poleward oceanic heat transport, implying a weakening of the North Atlantic Current. A comparison with early Pleistocene G. ruber Mg/Ca-based SST records shows a shift in the dominant climatic cycle from precession to obliquity, alongside a marked increase in amplitude, indicating an enhanced influence of obliquity cycles correlated with the expansion of Northern Hemisphere ice sheets.