An international team of scientists have unveiled the sequence of climatic events that ended the penultimate ice age, about 135 thousand years ago.
The findings, published in today’s issue of Nature, help us to better understand the processes that control Earth’s dramatic climate changes at the end of an ice age, and show that, surprisingly, the sequence of events at the end of the ice age before last were very different to those at the termination of the last one.
Dr Jennifer Stanford, lecturer in Physical Geography at Swansea University, contributed to the study, which was led by Dr Gianluca Marino of The Australian National University (ANU), and included researchers from ANU as well as the Universities of Southampton and Swansea in the UK.
Dr Stanford said: “By careful scrutiny of archives that record past climatic changes, we can decipher the complex interplay between the systems that control global temperatures.”
Lead author, Dr. Gianluca Marino, from ANU, said: “During the last million years, Earth’s climate repeatedly fluctuated between ice ages and interglacials. The end of an ice age (glacial termination) is characterised by rapid reorganisations of the continental ice sheets, ocean, and atmosphere. To date, it has only been possible to precisely constrain the chronology of these different events for the termination of the last ice age, about 20 to 10 thousand years ago. But major questions remained whether this applied to all terminations, or only to the last one. We therefore focused on the ending of the before-last ice age (about 140-130 thousand years ago). We used precisely dated cave records and marine sediments from the Mediterranean region to construct in detail the sequence through time of changes in all critical climate parameters.”
Co-author Professor Eelco Rohling, from both ANU and the University of Southampton, adds: “We found that a dramatic collapse of the Northern Hemisphere ice sheets into the North Atlantic Ocean suppressed the ocean circulation and caused global climate impacts. The North Atlantic cooled while the Southern Ocean warmed. The latter destabilised Antarctic land ice, causing a continuation of melting that eventually drove sea level rise to several meters above the present.”
The team concludes: “To our surprise, the sequence of climate events 135 thousand years ago looks very different from what happened at the end of the last ice age, 20 thousand years ago. So, ice-age cycles may superficially look similar to one another, but in detail there are important differences in the relationships between melting of continental ice sheets and global climate changes.”
- The research paper "Bipolar seesaw control on last interglacial sea level" can be found on the Nature website when it is published on 11 June 2015 at http://www.nature.com/
- Dr Jennifer Stanford is a lecturer in Physical Geography at Swansea University and heads the Geography Foundation Year. Her key research interests include sea-level and climate change over millennial to 100,000 yr time-scales.
- For more information about the Geography Department, College of Science, Swansea University and the courses it offers go to http://www.swansea.ac.uk/geography
Picture 1: 'Bergs'. Courtesy of (credit to) Professor Adrian Luckman, Swansea University.
Picture 2: ‘Dr Jennifer Stanford, lecturer in Physical Geography, Swansea University’. Courtesy of (credit to) Swansea University.
Picture 3: ‘Core drilling onboard Joides Resolution’. Courtesy of (credit to) Markus Fingerle.
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