REIMAGINATION: REconstructing and understanding the IMplications of surface 14C AGe changes In the North Atlantic for overturning circulaTION
The research aim was to constrain changes to North Atlantic Meridianal Overturning (AMOC) in order to understand its role in abrupt climate change and to improve chronologies for North Atlantic sediment record through high-resolution radiocarbon records of the surface North Atlantic from 10-50 ka.
Rather than using radiocarbon as a dating tool, we used it as a tracer of ocean circulation and air-sea gas exchange to investigate potential mechanisms for the abrupt climate changes seen in the North Atlantic over the last deglaciation.
Tiny shells of single-celled marine organisms (foraminifera) were measured for radiocarbon content from thirteen sediment cores over the past 20,000 years. Age models for the cores were based on correlating the percent of polar planktonic foraminifera to the Greenland ice core δ18O record and refined with thorium normalization. The radiocarbon reservoir ages (the difference between the age of the atmosphere and the carbon in the ocean surface water) was calculated. The data show consistent and large reservoir age increases of more than 1000 years from the last glacial maximum into Heinrich Stadial 1 (HS1), dropping abruptly back to approximately modern reservoir ages before the onset of the Bolling-Allerod. An intermediate complexity earth system model cGENIE was used to investigate the potential drivers of these reservoir age changes. The project found that sea ice, circulation and CO2 all play important roles in setting the reservoir age. Using these records, we showed that that Laurentide Heinrich Events were a response to stadial conditions, rather than their root cause.
Dr Andrea Burke (University of St Andrews) was PI with Co-I’s Prof. William Austin and Dr James Rae (St Andrews) and Prof. Paula Reimer and Dr Maarten Blaauw (QUB) and Postdoctoral research fellow Rosanna Greenop.
Impact of Research
1. The research impact for the public and policy makers focussed on understanding of climate tipping points such as rapid AMOC shifts and evaluate the chances of AMOC shutdown in the future.
2. Climate change education was delivered to high school students and teachers through Geobus which provides teaching and resources in the earth and environmental sciences to high schools across Scotland and the North of England.
3. A Science Taster Day for girls with the theme ‘Ocean circulation and climate change’ on 4 May. Form 4 students took part in experiments demonstrating the effects of salinity and temperature on ocean circulation, examined fossils dredged from the North Sea, learned to identify species of microscopic marine organisms that preferentially live in warm or cool ocean water and discussed how these can be used to understand past climate change. They also toured the 14CHRONO Centre AMS radiocarbon dating facilities.
Burke A, Greenop R, Rae J, Rees-Owen R, Reimer P, Heaton T. Dating rapid climate change in the North Atlantic during Heinrich Stadial 1. Proceedings of the EGU General Assembly Conference Abstracts, 2020, 18942.
Missiaen L, Waelbroeck C, Pichat S, Jaccard SL, Eynaud F, Greenop R, Burke A, 2019. Improving North Atlantic marine core chronologies using 230Th normalization. Paleoceanography and Paleoclimatology 34: 1057-73.
Ivanovic RF, Gregoire LJ, Wickert AD, Valdes PJ, Burke A, 2017. Collapse of the North American ice saddle 14,500 years ago caused widespread cooling and reduced ocean overturning circulation. Geophysical Research Letters 44: 383-92.
In addition to PI and co-Is the following project partners contributed to the project:
Charlotte Bryant (CB, NERC/BGS)
Siwan Davies (SD, Swansea)
Tim Heaton (TH, Sheffield)
David Hodell (DH, Cambridge)
Lloyd Keigwin (LK, WHOI)
Jesper Olsen (JO, Aarhus)
Sune Rasmussen (SR, Copenhagen)
Tine Rasmussen (TR, Troms)
Andy Ridgwell (AR, Bristol)
David Thornalley (DT, UCL)
Antje Voelker (AV, Lisbon)
Claire Waelbroeck (CW, LSCE)