Climate variability at the Middle Pleistocene Transition 900 kyr ago (CLIM900K)
Lead Research Organisation:
University College London
Department Name: Geography
Abstract
The prolongation and intensification of glacial cycles over the course of the Middle Pleistocene Transition (MPT; ~1.25-0.65 Ma) remains one of the major unsolved mysteries of Quaternary ice ages. Within the MPT, the interval from Marine Isotope Stage (MIS) 25 to 21 (~0.965-0.850 Ma) is thought to represent a fundamental shift in the mode of glacial cycles, with the appearance of a 100-kyr glacial cycle culminating in the first major Northern Hemisphere glaciation, but there is considerable uncertainty over the extent of ice volume increase. Moreover, while prominent debates centre on the causes of the transition, we are still lacking an adequate description and understanding of the evolution of climate variability over this interval. We propose to provide a comprehensive assessment of orbital- and millennial-scale climate changes during MIS 25-21, through joint pollen and foraminiferal isotopic and Mg/Ca analyses at unprecedented resolution from Site U1385 on the Portuguese Margin, a key location for linking changes in the ocean, atmosphere and biosphere. Results will transform our understanding of the magnitude of ice volume increase, the interaction of orbital- and millennial-scale variability and its role in glaciation and deglaciation, and impacts on plant biodiversity during this interval and will provide a benchmark for future studies on the transition into the 100-kyr world.
Planned Impact
Who and how will benefit from this research?
Our impact is through public engagement:
Climate change is a topic that is not only a concern of the scientific community but also of the public, media and policy makers. Our proposed development of a museum exhibit at the Sedgwick Museum, Cambridge on 'Quaternary ice ages and the first major Northern Hemisphere glaciation', communicating the key concepts of our research, will contribute to increasing public awareness and understanding of climate science issues.
Our impact is through public engagement:
Climate change is a topic that is not only a concern of the scientific community but also of the public, media and policy makers. Our proposed development of a museum exhibit at the Sedgwick Museum, Cambridge on 'Quaternary ice ages and the first major Northern Hemisphere glaciation', communicating the key concepts of our research, will contribute to increasing public awareness and understanding of climate science issues.
Publications
Bajo P
(2020)
Persistent influence of obliquity on ice age terminations since the Middle Pleistocene transition
in Science
Liautaud P
(2020)
Detection of significant climatic precession variability in early Pleistocene glacial cycles
in Earth and Planetary Science Letters
Menviel L
(2020)
An ice-climate oscillatory framework for Dansgaard-Oeschger cycles
in Nature Reviews Earth & Environment
Zhao Y
(2020)
Evolution of vegetation and climate variability on the Tibetan Plateau over the past 1.74 million years.
in Science advances
| Description | The prolongation and intensification of glacial cycles over the course of the Middle Pleistocene Transition (MPT; ~1.25-0.65 million years ago [MA]) remains one of the major unsolved mysteries of Quaternary ice ages. Within the MPT, a fundamental shift in the mode of glacial cycles is thought to have occurred during Marine Isotope Stage (MIS) 25 to 22 (~0.960-0.860 Ma) with the appearance of the first prolonged glacial cycle that culminated in major Northern Hemisphere glaciation. However, we are still lacking an adequate description and understanding of the evolution of climate variability over this interval and the causes that led to the increase in ice volume. Our project (CLIM900K) contributes a comprehensive assessment of climate changes during MIS 25-22 by generating records of changes in ice volume, surface ocean conditions, iceberg discharges, deep-sea oxygenation and carbon storage, and western Iberian vegetation from Site U1385 on the Portuguese Margin, and Sites U1308 and 980/981/982 from the central North Atlantic, key locations for linking changes in the ocean, cryosphere and biosphere. Key findings include: (1) Our proxy records reveal a sustained interval of iceberg discharges, cold North Atlantic conditions and expansion of semi-desert vegetation communities reflecting increased aridity over western Iberia during the interval of ice volume increase in MIS 22. Earlier glacial intervals recorded in U1385 and U1308 do not contain such sustained intervals of changes. The ice-rafted detritus (IRD) at Site U1308 during MIS 22-24 is dominated by silicate minerals (quartz) with only a few grains of detrital carbonate, indicating the lack of massive surges through Hudson Strait (Heinrich events). At Sites 980/981/982 near the Rockall Plateau at 55.5°N, a major increase in sediment input and IRD marks a major expansion of the British-Irish and European Ice Sheets. (2) Our records show a prominent increase in millennial-scale variability and activation of the bipolar seesaw at the MIS 25-24 transition. It is possible that a combination of astronomical configuration (low obliquity, high precession) and abrupt changes in the bipolar seesaw may have played a role in the descent to glacial conditions. (3) During MIS 22, our records suggest a diminution of millennial-scale variability, indicating climate regimes of greater stability associated with large ice sheets. (4) A significant stepped reduction in glacial Atlantic deep-water oxygenation occurred at ~960-900 ka that coincided with increased continental ice volume and a major disruption of the ocean thermohaline circulation. Our paleo-oxygen results support a scenario of decreasing deep-water oxygen concentrations, increased respired carbon storage, and a reduction in glacial pCO2 across this critical interval. |
| Exploitation Route | Our project addresses fundamental questions on glacial cycles and the operation of the climate system. As such it is of interest to climate scientists in general, by delivering better constraints on links between key parameters in the climate system and by describing the mode and tempo of climate variability during the transition into the 100-kyr world. Climate change is a topic that is not only a concern of the scientific community of palaeoclimate and global change scientists, including the IPCC, but also of the public and media. The proposed project aims and findings will be of potential interest to the scientifically-minded portion of the public. |
| Sectors | Environment |
| Description | Public Engagement Family Events: Fossil Pollen Grains |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Public/other audiences |
| Results and Impact | On December 14th and 21st 2019, the PDRA Dr V. Margari (with assistance from the PI and his PhD students) organised and ran two family events at the Sedgwick Museum of Earth Sciences in Cambridge. The theme was "Fossil Pollen Grains and what they can teach us about changes in past vegetation and climate". We used specially-made 3D pollen models to demonstrate the variety of pollen types and light microscopes to observe fossil pollen grains and explain how they are identified. The event also included a craft activity making pollen grains to decorate a Christmas tree. Both events were part of the Pathways to Impact of the project. The events were attended by 90 people (45 children) in total. The children were delighted and asked several questions. Every family attending completed a feedback form providing extremely complimentary comments. Another planned public engagement activity to have a stand on the Sedgwick Museum's "Super Science Saturday" as part of the Cambridge Science Festival on 14 March 2020 was cancelled due to COVID-19. |
| Year(s) Of Engagement Activity | 2019 |
| URL | https://www.museums.cam.ac.uk/events/fossil-pollen |