Wed 04 Jun 17:30: Temporal Dynamics of Island Biodiversity
Understanding how quickly, where, and why biodiversity is changing remains a key question in ecology. Observations show that the pace of change varies widely across different regions. Palaeoecological research contributes valuable insights by revealing long-term patterns and helping to interpret the effects of drivers such as human activity and erosion.
Drawing on examples from islands around the world, we examine how biodiversity has shifted significantly, particularly following human settlement and other environmental pressures. Our findings suggest that islands colonised within the past 1500 years tend to experience more rapid ecological changes than those settled earlier. We also explore the long-term introduction and spread of non-native species, along with the resulting trends in biotic homogenisation.
These examples show how standardised palaeoecological records can help create a more complete understanding of long-term changes in island ecosystems.
- 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 21 May 17:30: Mid-Holocene climate and environmental changes revealed by subfossil wood from eastern England
To better understand current climate trends and extremes and their potential environmental impacts, annually resolved and absolutely dated proxy archives are required, but their quality and quantity decrease drastically back in time with only a few such records available before the Common Era. In this talk, we will learn from living and relict trees about climate and environmental conditions in eastern England and beyond from the present back to the mid-Holocene. I will introduce a vast, yet rapidly disappearing archive of thousands of exceptionally well-preserved subfossil oak and yew trunks in eastern England. Using dendrochronological, radiocarbon and isotopic dating, we anchor oak and yew tree-ring chronologies between 5,200 and 4,200 years ago. We further develop an eco-physiological model based on yew tree-ring stable carbon and oxygen isotopes to reconstruct mid-Holocene hydroclimate variability. We show that contrary to today’s climate-growth relationships, relatively dry soil and atmospheric conditions in the mid-Holocene favoured yew growth, while higher groundwater tables and wetter soils reduced ring width formation. We propose that yew woodlands disappeared around 4,200 years ago due to the combined effects of rapid sea-level rise in the North Sea, a prolonged negative phase of the North Atlantic Oscillation, and significant riverine flooding. These hydroclimatic and biogeographic changes in eastern England, together with independent evidence from pollen records and lake sediments, shed new lights on the yet debated 4.2 ka climate anomaly, typically associated with extreme drought in central Asia. Intriguingly, our new subfossil Fenland record implies unusually humid and stormy conditions for the North Atlantic/European region during this period.
- 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 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.