Increased abyssal ocean density stratification across the Middle Pleistocene Transition
Year: 2026
Type: article
Abstract: . We report basinal and global compilations of deep-water temperature and δ18Oseawater for the past 1.5 million years using tandem oxygen isotopic and Mg/Ca measurements of benthic foraminifera. Across the Middle Pleistocene Transition (MPT), interbasinal gradients suggest North Atlantic deep-water became colder and Pacific deep-water saltier during glacial periods after ~900 thousand years ago. Salinity in source areas increased in the marginal seas around Antarctica by decreased meltwater discharge from ice sheets and increased sea ice extent, which led to increased density stratification of the abyssal ocean. The deep ocean became a more effective carbon trap and lowered glacial atmospheric carbon dioxide, leading to expansion of continental ice sheets and longer glacial cycles. Results support a physical role for abyssal ocean stratification in explaining the MPT. Collectively, our deep ocean stacks lend support to hypotheses proposing that the MPT resulted from a progressive drawdown in glacial atmospheric pCO2, a conclusion that awaits verification from the Beyond EPICA–Oldest Ice core from Antarctica.
Source: Climate of the past
Institutions: University of Cambridge, Queen Mary University of London
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,725
Awards: Participation in IODP Expedition 339, Climate variability at the Middle Pleistocene Transition 900 kyr ago (CLIM900K), North Atlantic Bottom Water Temperature and Ice Volume Records from the Mid-Pleistocene Transition, A reference time scale for the study of Pleistocene orbital and millennial-scale climate variability: IODP Site U1385 ("Shackleton site")
OpenAlex ID: W4414701112