Marine dust records as templates to date 1.5 million year old ice

The marine sediment record shows that glacial-interglacial cycles transitioned from regular ~41 kyr year cycles to irregular ~100 kyr cycles approximately 1 million years ago, an event known as the Mid-Pleistocene Transition (MPT). However, the ice core record only extends 800 kyr years into the past, limiting our understanding of this major change in the climate system and thus of fundamental climate forcings and feedbacks. International efforts to recover a 1.5 million year old continuous ice core (Oldest Ice) in Antarctica are underway, with goals of extending the ice core CO2 record into the pre-MPT world and gaining insight into the relationship between greenhouse gases and climate.

The challenge of dating Oldest Ice may be addressed using dated marine records that are known to correlate with Antarctic records over the existing 800 kyr period. In particular, marine dust records along dust transport pathways to Antarctica show strong similarity to Antarctic dust records, with highly elevated dust signals during glacial periods. These marine dust records may be used to date both rapid-drilled, optically logged boreholes as a reconnaissance tool to identify Oldest Ice sites and subsequently recovered Oldest Ice cores. We examine marine dust records from the Southern Ocean that exceed the current ice continuous ice core age as potential templates for dating Oldest Ice. While the records are closely coupled over the post-MPT period, they show less agreement during and before the MPT, where the record located further south and closer to South American dust sources shows more distinct 41 kyr peaks. We explore reasons for this decoupling and describe techniques to facilitate pattern matching between dated marine and undated ice dust records.