Polar Climate History

Wed, 14 Jan 2026, 16:00 CEST

Conveners: Antje Voelker & Irina Rogozhina

Polar Climate History is critical for understanding ice sheet dynamics, sea level changes, and the role of polar regions in the global climate system.

Guest speakers:

• Peter Bijl (Utrecht University, The Netherlands)
• Heike Zimmermann (Geological Survey of Denmark and Greenland, Denmark)

Long-term history of the Antarctic Circumpolar Current

Peter Bijl

Tectonic changes on the Southern Hemisphere have shaped the configuration of Southern Ocean surface currents. The separation of both Australia and South America away from Antarctica some time in the Paleogene ultimately provided the boundary conditions for the development of the strongest ocean current on our planet: the Antarctic Circumpolar Current (ACC). Over the past decades, reconstructions from sediment cores, and from numerical model simulations, have developed our collective thinking about the development of Southern Ocean oceanography, from strong subpolar gyre circulation to circumpolar flow to the Antarctic circumpolar current we know today. My own work on this subject, in many multidisciplinary teams, is focused on microfossil-based paleoceanographic reconstructions (notably with organic-walled dinoflagellate cysts), combined with biomarker paleothermometry (TEX86 and UK37), and integration of those with numerical modeling experiments. I will show that the opening of ocean gateways played a crucial but secondary role in the onset of Antarctic glaciation, that the first circumpolar flow of surface water was slow but destroyed the existing subpolar gyres. I will show that subsequent development of the ACC was limited until ~10 million years ago, after which we see paradoxically progressive weakening of latitudinal temperature gradients and the development of Southern Ocean fronts.

Unlocking the seafloor's genetic archive

Heike Zimmermann

Biodiversity is central to the functioning, health, and resilience of marine ecosystems. As climate warming rapidly alters Arctic marine environments, the urgency for long-term ecological baselines has grown. Therefore, studying past ecosystem responses to natural climate variability is essential for interpreting current and future changes. However, many species leave no fossil record (e.g., zooplankton, jellyfish, worm-like fauna), limiting our understanding of past marine ecosystems and our ability to predict future changes. The retrieval of sedimentary ancient DNA (sedaDNA), the molecular traces of past biota from marine sediments, has been revolutionary in this regard. It allows us to trace species in the absence of physical remains, offering a more complete picture of ecosystem responses over time. By analyzing these genetic traces, we can uncover how Arctic species and communities responded to changes in climate, sea ice, and ocean conditions up to geological timescales. This webinar will explore how sedaDNA opens a window into the past, helping us better understand long-term climate – biota dynamics and offering valuable context for predicting the future of Arctic marine biodiversity.