The Southern Ocean’s role in glacial cycles: Engine not caboose?

Abstract:

The waters of the worlds’ oceans mingle in the Southern Ocean. The dynamic processes found here play a critical role in earth’s climate engine by impacting ocean-atmosphere CO₂ partitioning through changes to overturning circulation dynamics, winds, sea ice extent, and ultimately the biological pump. Southern Ocean dynamics likely played a critical role in glacial-interglacial climate cycles by influencing atmospheric CO₂ levels. Recent insights on the relative inputs of the processes that contributed to glacial CO₂ sequestration in the deep ocean and outgassing across the last deglaciation have relied on evidence from multiple proxies with a substantial amount of the interpretation relying on oxygen isotopes (δ¹⁸O) in biogenic calcium carbonate records. Cesare Emiliani's pioneering work in the 1950's using the δ¹⁸O in foraminiferal fossils from deep-sea sediments to infer past climate continues be relevant in interpreting glacial-interglacial cycles. Since his work, we have added the ability to use the biomarkers synthesized by Emiliania huxelyi to reconstruct paleo- sea surface temperature. This presentation will present a synthesis of proxies from across the Southern Ocean to examine the critical role this region plays in glaciation and deglaciation, informing the ongoing debate of whether the Southern Ocean was a driver (engine) or follower (caboose).