High-frequency Antarctica climate oscillations during the mid-Pliocene Warm Period

The West Antarctic Ice Sheet (WAIS) is thought to be highly vulnerable to global warming. With this in mind, we analyzed sediments from the Ross Sea during the mid-Pliocene warm period (mPWP), the last period when atmospheric CO₂ levels were comparable to those of today. Using IODP site 1524 cores, we analyzed the organic carbon (OC) and total nitrogen contents and δ¹³C-OC values. The ~ 300,000-year interval between the Kaena top magnetic reversal (3.032 Ma) and the Mammoth bottom reversal (3.330 Ma) reveals 21 glacial beds characterized by strongly negative δ¹³Corg values (~ -28‰) and low OC-contents (<0.3 dw-dry weight-%). In contrast, interglacial layers exhibit δ¹³C values around ~ -25‰ and a consistent OC-content of ~0.6 dw% .We propose   the organic carbon deposited during glacial intervals was predominantly refractory carbon, eroded from continental rocks, whereas the interglacial intervals displayed a stronger contribution from marine primary productivity and/or terrestrial fluxes. Assuming the robustness of the paleomagnetic stratigraphy, the number of glacial beds within the mPWP interval indicates a frequency of approximately 14,000 years per glacial pulses, which is notably more dynamic than the obliquity-paced oscillations reported in previous studies.