Wed 21 May 17:30: Mid-Holocene climate and environmental changes revealed by subfossil wood from eastern England
Abstract not available
- Speaker: Tatiana Bebchuk, University of Cambridge
- Wednesday 21 May 2025, 17:30-19:00
- Venue: Latimer Room, Clare College.
- Series: Quaternary Discussion Group (QDG); organiser: sr632.
Wed 07 May 17:30: Detecting reversible retreat and readvance of the Antarctic Ice Sheet during the Holocene
Several lines of geological evidence from both the marine and terrestrial record tell us that the Antarctic Ice Sheet was much bigger than present at the Last Glacial Maximum. Determining how it has changed in both thickness and extent since then, in particular whether it has undergone any major fluctuations in the last few thousand years, is important for validating ice sheet and glacial-isostatic adjustment models that are used to project future sea level rise.
In this talk, I will present an overview of the emerging evidence for large-scale reversible retreat of the Antarctic Ice Sheet during the mid to late Holocene period. I will discuss the methods with which we can further investigate this phenomenon and present a case study from the Amundsen Sea sector illustrating how cosmogenic nuclide measurements in subglacial bedrock reveal regrowth of the Pine Island-Thwaites Glacier system from a smaller than present configuration in the Holocene. Direct evidence for reversible retreat from this and other locations in Antarctica is urgently needed in order to understand what drives regrowth of ice sheets in warm climates and the conditions under which ongoing retreat could be reversed.
- Speaker: Joanne Johnson, British Antarctic Survey
- Wednesday 07 May 2025, 17:30-19:00
- Venue: Harker 1, Department of Earth Sciences, Downing Street.
- Series: Quaternary Discussion Group (QDG); organiser: sr632.
Wed 04 Jun 17:30: Island timelines to quantify biodiversity change
Abstract not available
- Speaker: Sandra Nogué Bosch, Autonomous University of Barcelona
- Wednesday 04 June 2025, 17:30-19:00
- Venue: Latimer Room, Clare College.
- Series: Quaternary Discussion Group (QDG); organiser: wb350.
Wed 18 Jun 17:30: Rock magnetic estimation of past precipitation from topsoil calibration - recent studies in Europe and India
Several rock magnetic parameters have been demonstrated to be related to climate. The concept behind magnetic enhancement is that during soil formation, specific iron minerals are formed depending on soil properties, which depend on amongst others precipitation and temperature. In the mid-latitudes, mainly magnetite and maghemite are formed, and these minerals represent a proxy for ‘soil formation intensity’ in some regions, which is driven by i.a. precipitation. While most studies focus on Eurasian Chernozems due to their rather simple stratigraphy and formation processes, other soil types such as luvisols also show elevated magnetic properties in topsoils in relation to climate.
In this presentation, I will provide a short overview of the concept of using magnetic proxies for (paleo)climate studies. Further, first data from ongoing studies in Europe and India will be presented and discussed in a climate perspective. At this point magnetic properties of last interglacial soils appear clearly stronger than Holocene soil properties, suggesting a wetter than recent last interglacial.
- Speaker: Christian Zeeden, Leibniz Institute for Applied Geophysics
- Wednesday 18 June 2025, 17:30-19:00
- Venue: Latimer Room, Clare College.
- Series: Quaternary Discussion Group (QDG); organiser: wb350.
Wed 07 May 17:30: Detecting reversible retreat and readvance of the Antarctic Ice Sheet during the Holocene
Several lines of geological evidence from both the marine and terrestrial record tell us that the Antarctic Ice Sheet was much bigger than present at the Last Glacial Maximum. Determining how it has changed in both thickness and extent since then, in particular whether it has undergone any major fluctuations in the last few thousand years, is important for validating ice sheet and glacial-isostatic adjustment models that are used to project future sea level rise.
In this talk, I will present an overview of the emerging evidence for large-scale reversible retreat of the Antarctic Ice Sheet during the mid to late Holocene period. I will discuss the methods with which we can further investigate this phenomenon and present a case study from the Amundsen Sea sector illustrating how cosmogenic nuclide measurements in subglacial bedrock reveal regrowth of the Pine Island-Thwaites Glacier system from a smaller than present configuration in the Holocene. Direct evidence for reversible retreat from this and other locations in Antarctica is urgently needed in order to understand what drives regrowth of ice sheets in warm climates and the conditions under which ongoing retreat could be reversed.
- Speaker: Joanne Johnson, British Antarctic Survey
- Wednesday 07 May 2025, 17:30-19:00
- Venue: Latimer Room, Clare College.
- Series: Quaternary Discussion Group (QDG); organiser: sr632.
Wed 12 Feb 17:30: Climate-ice sheet interactions in the long-term past and their importance for the long-term future
The simulation of the last deglaciation (about 20.000 years before present to present) represents a hitherto unsolved challenge for comprehensive state-of-the-art climate models. During my presentation, I will introduce our novel coupled atmosphere-ocean-vegetation-ice sheet-solid earth model that is used to simulate the transient climate. An ensemble of transient model simulations successfully captures the main features of the last deglaciation, as depicted by proxy estimates. In addition, our model simulates a series of abrupt climate changes, which can be attributed to different drivers that will be discussed throughout the presentation. I will furthermore show, how the model can be applied for simulations of the long-term future. The future simulations show, that parts of the Antarctic ice sheet become unstable even under low-emission scenarios, with significant implications for the modelled climate response. Sensitivity experiments additionally show that, the Greenland ice sheet may exhibit multiple steady-states under pre-industrial climate conditions. This has significant implications for a potential regrowth, once disintegrated entirely.
- Speaker: Marie-Luise Kapsch (Max Planck Institute for Meteorology)
- Wednesday 12 February 2025, 17:30-19:00
- Venue: Latimer Room, Clare College.
- Series: Quaternary Discussion Group (QDG); organiser: wb350.