Bridget Wade
Bridget Wade did her undergraduate at the University of Leeds (UK) and PhD at the University of Edinburgh (UK). She held positions in the United States and joined University College London as a Professor in 2013. Her research uses microscopic fossils and their chemistry to determine patterns of evolution and extinction, ancient marine temperatures, circulation, productivity and ice sheet dynamics. She has been involved fieldwork in Europe, Australia, Africa, the Caribbean/Gulf of Mexico, and onshore drilling by the International Continental Scientific Drilling Program at Chesapeake Bay Impact Structure and the Tanzania Drilling Project. She had the pleasure of twice sailing on ocean drilling expeditions in the Pacific Ocean, as well as a site survey expedition in the Indian Ocean. She has published over 100 papers and is lead author on a major taxonomic monograph. Honours and awards include The Geological Society Bigsby Medal (2020).
The Oligocene - with ice and a twist
It is well established that a continental-scale ice sheet developed on Antarctica in the early Oligocene (~33.7 million years ago) as evidenced by sea level fall, ice rafted debris in the Southern Ocean and a >1 per mil increase in marine oxygen isotopes. However, the behavior of the young ice sheet and its relation to climate throughout the rest of the Oligocene raises many questions about our understanding of the cryosphere and carbon cycle. Multiple records suggest that the Oligocene Antarctic ice sheet was highly dynamic and unstable, leading to high amplitude sea level fluctuations and like a flickering switch, climate seems to have balanced on the cusp between ‘icehouse’ and ‘greenhouse’ modes for millions of years. But what drove this instability? Through the last twenty years there has been a large increase of Oligocene ocean temperature records which indicate a cooling through the late Eocene and early Oligocene, but the temperature decline appears to be temporary and heterogeneous. The role that oceanic gateways played in the Oligocene climate evolution is also complex, with wide uncertainty in the timing of the effective opening of the Drake Passage. The existing atmospheric carbon dioxide records are arguably less detailed and reliable than for the Eocene and Miocene but suggest another twist, a reduction through the Oligocene. This coincides with deep water warming and ice volume decrease, suggesting long-term climate decoupling. Here I explore and discuss perspectives on the Oligocene icehouse, including an outlook on unresolved questions and future directions.
