A continuous record of particulate mineral dust from the new Beyond EPICA Oldest Ice Core: paleoclimatic implications of variability in dust physical and optical properties

Particulate mineral dust is a critical part of the Earth’s climate system, modulating radiative balance and providing a crucial source of micronutrients to surface oceans. In ice cores, mineral dust also serves as a key proxy for past atmospheric dynamics - controlling dust mobilization and transport - as well as hydroclimate variability, which affects the atmospheric residence time of dust in addition to emission strength in the source regions. Previous studies, including those from the 800,000-year EPICA Dome C ice core, have demonstrated a close coupling between dust particle number concentrations in ice cores and glacial-interglacial climate variability, with consistently higher dust concentrations during cold glacial periods. The new Beyond EPICA-Oldest Ice Core (BE-OIC: 75º 18’ S, 122º 27’ W) extends the existing ice core particulate dust record back through the Mid-Pleistocene Transition (MPT), providing new constraints on this enigmatic period in Earth’s climate history.

We present the first continuous record of particulate mineral dust particle size and particle number distributions from the new BE-OIC, spanning from 700,000 years BP through the Mid-Pleistocene Transition. Physical characteristics of individual dust grains were measured online by the University of Bern during the Continuous Flow Analysis measurement campaign at the British Antarctic Survey using dual Classizer One Single Particle Extinction and Scattering instruments (EOS) and an Abakus laser particle sensor (Klotz GmbH), enabling characterization of particle concentration, dust size but also its refractive index over a wide range of diameters (0.2–10 µm). The latter is crucial as it allows us for the first time to resolve the submicrometer mode in the number size distribution.

Consistent with earlier work on the EDC ice core, the new BE-OIC record shows elevated dust concentrations during glacial periods both before, during and post MPT. However, the amplitude of glacial-interglacial variability is reduced relative to the past 800,000 years. In addition, modal particle diameters in the number size distribution are smaller during glacials compared to interglacials, indicating enhanced contributions from long-distance dust transport during the colder climate states. We investigate the processes that lead to dust size and number changes, including how reduced glacial intensity pre-MPT may have impacted dust source regions and the atmospheric lifetimes of dust particles. Together, these observations indicate changes in dust source-to-sink dynamics that have implications for biogeochemical cycles in the Southern Ocean and atmospheric dynamics during the MPT.