Preprints
https://doi.org/10.5194/egusphere-2024-603
https://doi.org/10.5194/egusphere-2024-603
07 Mar 2024
 | 07 Mar 2024
Status: this preprint is open for discussion and under review for Climate of the Past (CP).

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

Xiaolei Pang, Antje Helga Luise Voelker, Sihua Lu, and Xuan Ding

Abstract. 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.

Xiaolei Pang, Antje Helga Luise Voelker, Sihua Lu, and Xuan Ding

Status: open (until 11 May 2024)

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Xiaolei Pang, Antje Helga Luise Voelker, Sihua Lu, and Xuan Ding
Xiaolei Pang, Antje Helga Luise Voelker, Sihua Lu, and Xuan Ding

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Short summary
Our research discovered significant seasonal temperature variations in the North Atlantic's mid-latitudes during the early Late Pliocene. This highlights the necessity of using multiple methods to get a full picture of past climates, thus avoiding a biased understanding of the climate system. Moreover, our study reveals that the precession signal, which previously dominate surface temperature records, disappeared with the increased influence of the ice sheets in the Northern Hemisphere.