We are expanding the options to interact with the LL speakers during and after their talks by opening dedicated channels on the new Landscapes Live discord server.
Program (Fall 2023):
Thursday, 05 October 2023 at 16:00 CEST
Bethan Davies (Newcastle University)
Accelerating glacier volume loss on Juneau Icefield driven by non-linear processes
Abstract: Large icefields and ice caps in high latitude regions are currently contributing significantly to global sea level rise, with Alaska leading contributions from glaciers. This contribution is likely to accelerate since icefield topography drives a non-linear response to climate change. Here we show that icefield area and volume loss from Juneau Icefield has accelerated exponentially over the last few decades, with catastrophic losses reaching -5.91 ± 0.80 km3 a-1 from 2010-2020. Thinning is now pervasive across the icefield plateau, resulting in glacier fragmentation, especially rapidly after 2005. This glaciological threshold response to a warming climate is underlain by the plateau hypsometry. The non-linear behavior is concerning for the future viability of this icefield and for plateau icefields and ice caps globally, with implications for future projections of sea-level contributions.
Thursday, 10 October 2023 at 16:00 CEST
Todd Ehlers (University of Glasgow)
How Plants Shape Mountains
Abstract: Fascinating interactions between biota, climate, and plate tectonics modulate the Earth’s surface and topographic development. These interactions occur over seconds to millions of years and microns to thousands of kilometers. This talk investigates these interactions and illustrates how state-of-the-art coupled computer models and observed catchment erosion rates from cosmogenic isotopes can be used to understand how vegetation change influences the shape and evolution of mountain topography over seasonal to millennial timescales. I do this by discussing the coupled interactions between paleoclimate, vegetation change, and landscape evolution across the extreme climate and ecological gradient of the Chilean Coastal Cordillera.
Thursday, 26 October 2023 at 16:00 CEST
Dongfeng Li (Peking University)
Modern climate change-driven landscape processes in cryospheric basins: sediment sources, fluxes, and impacts
Thursday, 16 November 2023 at 16:00 CEST
Ryan Venturelli (Colorado School of Mines)
Retreat, Recovery, and Subglacial Radiocarbon: Untangling past [in]stability of the West Antarctic Ice Sheet
Abstract: Reconstructions of past ice sheet behavior enable us to refine physical models that predict how much, how fast, and from where Antarctic ice mass loss will contribute to future sea level rise. Geological constraints on paleo ice thickness obtained from above the modern ice surface (e.g., exposure age data from deglaciated nunataks) and on paleo ice extent obtained outboard from modern margins (e.g., sediment core and geomorphic data from the ice-free continental shelf) have served as the primary tools to decipher the topology of the Antarctic Ice Sheet from the Last Glacial Maximum to present. Recent efforts to recover sediment and bedrock from beneath grounded ice in Antarctica offer insight into the southernmost extent of grounding line retreat, yielding a more complete view of ice dynamics through the last deglaciation. In this talk, I will present results from recent subglacial access efforts that have provided the first direct constraints on a less extensive West Antarctic Ice Sheet in the Holocene compared to today. These new constraints on the timing and extent of grounding line retreat prior to the modern observational record allow for a mechanistic understanding of the drivers of marine ice-sheet evolution, subglacial ecosystem processes, and subglacial Antarctica’s role in global biogeochemical cycling. I will conclude by presenting new geochemical and sampling tools under development to enable future work constraining ice-sheet history. By generating this process-to-paleo perspective on the co-evolution of cryospheric, geologic, biologic, and oceanographic systems and combining it with detailed ice-sheet modeling experiments, we can create the context required to reduce uncertainty in sea-level projections on societally relevant timescales.
Thursday, 30 November 2023 at 16:00 CEST
Kathryn Fitzsimmons (University of Tübingen)
What can dryland sediments tell us about landscapes through time?
Abstract: Almost half of the Earth’s land surface comprises deserts and desert margins. These so-called drylands include substantial swathes of unconsolidated sediment which preserve information about past conditions and interactions between the atmosphere and Earth surface. Under conditions of accelerated global change, desert margins in particular are hypothesized to become increasingly unstable. Since drylands also host some 40% of the world’s human population, this increasing instability will become a central concern for the future. In this lecture I would like to discuss the wealth of information contained within dryland sediments with respect to what they can tell us about landscape and hydroclimate change through time, with a focus on the Australian continent. We will take a look at the evidence for past environments across a range of scales, from interrogating intracrystalline charge within quartz grains for information about provenance and timing of deposition, to examining the morphology of lake margin shorelines and dunefields which provide the key to interactions between landforms, hydroclimate and synoptic-scale climate circulation.
Thursday, 7 December 2023 at 16:00 CEST
Lithospheric flexure controls on geomorphology, hydrology, and river chemistry in the Andean foreland basin
Abstract: Tectonics exerts a strong control over the morphology of Earth’s surface that is apparent in active mountain belts. In lowland areas, subtle processes like lithospheric flexure and isostatic rebound can impact Earth surface dynamics, hydrologic connectivity, and topography, suggesting that geomorphic and hydrologic analyses can shed light on underlying lithospheric properties. Here we examine the effect of lithospheric flexure on the geomorphology, hydrology, and river water chemistry of the Rio Bermejo fluvial system in the east Andean foreland basin of northern Argentina. Results show that proximal to the mountain front, foredeep basin subsidence causes sedimentation along a braided channel belt that is superelevated relative to the surrounding flood basin. During floods, water flows from the superelevated channel into the groundwater reservoir, causing a net loss of discharge with distance downstream. Further downstream, forebulge uplift forces channel narrowing, high lateral migration rates, and incision up to 13 m into older river deposits. This incision locally allows groundwater flow into the river, causing a ~20% increase in river solute load. Groundwater emerges from the forebulge into the backbulge, predominantly as spring-fed channels. Here, channel migration rates decrease, suggesting a switch from net uplift to subsidence that reduces the depth to the groundwater table. This analysis shows that subtle lithospheric flexure can have significant effects on river channel morphology that determine hydrologic flow paths, and ultimately influence geochemical and ecological patterns. We suggest that these effects may elucidate lithospheric properties that are otherwise inferred from bulk geophysical observations.