Halogen Records from the Beyond EPICA Ice Core: Insights from the Holocene to the Mid-Pleistocene Transition

Halogens (Br, I) and their enrichment relative to seawater abundance preserved in polar ice cores are powerful tracers for reconstructing past sea-ice dynamics and marine primary productivity. Within the framework of the Beyond EPICA Oldest Ice (BEOI) project, we present a new halogen concentration record derived from discrete ice core samples. Analytical measurements were performed in Italy (ISP-CNR, Ca’ Foscari University), focusing on the relatively stable climatic conditions of the Holocene and on the Mid-Pleistocene Transition (MPT).

The Holocene record, combined with previously published datasets, provides a critical baseline for understanding the environmental processes and transport mechanisms controlling halogen deposition on the central Antarctic plateau. To validate the halogen signal, we investigate the behaviour of bromine and iodine measured in the Younger Ice section of the BEOI ice core during the Holocene, comparing these records with independent paleoclimatic parameters from earlier studies, including temperature reconstructions (ΔT), stable water isotopes (δD), and sea surface temperatures (SST). These comparisons support the interpretation of halogen variability as a proxy for changes in sea-ice conditions.

While the Holocene analysis aims to constrain the halogen signal using well-established climatic parameters, the primary objective of the Beyond EPICA mission is to extend this approach back to 1.5 million years. As drilling reaches the deepest sections of the BEOI ice core, halogen records offer a unique opportunity to investigate changes in sea-ice dynamics across the MPT, when Earth’s climate system transitioned from a dominant 41-kyr to a 100-kyr glacial cyclicity. Ongoing chemical analyses of the oldest ice will help assess whether sea-ice feedbacks played a causal role in the emergence of the 100-kyr cycles or primarily acted as an amplifier of late-Pleistocene glacial intensification.