I am pleased to announce three PhDs being advertised in the IAPETUS DTP that I am involved with.
These are for 2024 entry, with a closing deadline of January 5th 2024. Information on how to apply here.
#1. Palaeoglacier and Palaeoclimate reconstructions in the Chilean and Argentinian Lake District, Patagonia
Rationale
During past glaciations, the Patagonian Ice Sheet stretched from ~38°S to 55°S, with terrestrial outlet piedmont lobes forming at low elevations above sea level in the northern sector. Reconstruction of the Patagonian Ice Sheet through different and rapidly changing climate states provides insights into past climatic change in a data-sparse area of the globe, forming an important proxy for changes in hemispheric atmospheric and oceanic systems (Davies et al., 2020). This includes insights into the contraction and expansion of the Southern Westerly Winds during significant palaeoclimate transitions; these winds bring moisture and precipitation to the Andes and are a key control on palaeoglaciation (Kaplan et al., 2020; Reynout et al., 2019; Moreno et al. 2014; Leger et al., 2021). Today, these winds are one of the most important climatic controls in the Southern Andes and are driving major changes in ocean currents in West Antarctica. However, large uncertainties in latitudinal extent and long-term dynamics make it challenging to contextualise recent change in this major atmospheric circulation system. Inconsistent model simulations of the past westerly winds with varied predictions for the location of the westerlies (Harrison et al., 2015) challenges our ability to make high-confidence future predictions. Palaeoglacier reconstruction in the northern sector of the former Patagonian Ice Sheet therefore offers opportunities for new insights into past changes in atmospheric and oceanic circulation.
In the Chilean and Argentinian Lake District, in the Valdivia, Bueno and Collon Cura hydrological basins (~39°S), there are small glaciers on volcanoes. However, little is known about the mass balance sensitivities, landsystems and behaviours of these small present-day glaciers, which are likely to be very different from the more well-studied glaciers further south. In this region, there is also limited data on past glacier extent, and chronologies are greatly lacking (Davies et al., 2020). Large piedmont moraines attest to former outlet lobes of the Patagonian Ice Sheet extending to low elevations, but the timing is poorly constrained. Past climate modes, such as the Southern Annular Mode, Antarctic Cold Reversal, Younger Dryas and “Little Ice Age”, may have influenced palaeoglaciers here. Whilst there is growing data on palaeoglacier fluctuations further south (Leger et al., 2020; Martin et al., 2022, Kaplan et al. 2020), Late Glacial and Holocene ice dynamics here in particular have high uncertainty (Davies et al., 2020). This limits our ability to utilise the latitudinal range provided by the former Patagonian Ice Sheet. These glaciers therefore have important and unrealised potentials as proxies for palaeoclimate, bringing insights into large scale climatic reorganisations during different climate states.
Research Questions
Major research questions include,
1) What was the style and manner of the former Patagonian Ice Sheet at ~39°S, and how did this differ from other Patagonian glacial landsystems?
2) What was the timing of the local glacial maximum and palaeoglacier advances in this area?
3) What were the climatic controls forcing palaeoglacier fluctuations?
Aims and Objectives
This project aims to reconstruct the style and manner, timing, and climatic controls on palaeoglacier advances during the Last Glacial Maximum, Late Glacial and Holocene in the Lake District of northern Patagonia.
Objective 1. Apply geomorphological mapping and sediment-landform analyses to constrain past glacier behaviour in east-west transects across the former Patagonian Ice Sheet, prioritising the Valdivia, Bueno and Collon Cura catchments (~39°S).
Objective 2. Apply chronological techniques to constrain the timing of palaeoglacier fluctuations.
Objective 3. Reconstruct the climatic conditions forcing palaeoglacier fluctuations using numerical ice-flow modelling of the glaciers in these catchments, forced by palaeo climate data and GCM outputs.
#2. Implications of climate change for geomorphological process and hazard cascades in glaciated catchments of central Patagonia
Glaciers in mountainous regions such as the Patagonian Andes are currently experiencing accelerated rates of recession in response to a rapidly changing climate. Transition from ‘glacial’ to ‘paraglacial’ conditions is typically characterised by destabilisation of mountainsides, liberation of large volumes of sediment, changes in proglacial meltwater routing, the development/expansion of proglacial lakes and changes in sediment flux to proglacial rivers systems. Newly developed process chains have the potential to generate hazards in the form of landslides, catastrophic mass flows (aluviones) and rapid changes to the fluvial and groundwater system as well as riparian vegetation. The Aysén region of Chile has recently experienced slope instability generated by glacier recession and intense rainfall events generating recent aluviones and floods which have resulted in loss of life and infrastructure.
Models of paraglaciation based on reconstructions of palaeo landforms and deposits do not necessarily allow the identification of complex and transient process cascades. Focussed studies of contemporary deglaciation and paraglacial processes can be used to generate models which can be used both to identify and mitigate the impacts of resulting hazards.
This project aims to (1) Test existing models of paraglacial process chains and (2) Develop new models for paraglacial response to deglaciation.
This study will focus on two locations in Aysén which contain a number of hazards and associated risk to local communities: (1) the Rio Mosco at Villa O’Higgins, which flanks the northern sector of the Southern Patagonian Icefield, and (2) the Exploradores valley, which flanks the northern border of the Northern Patagonian Icefield. The Rio Mosco drains a rapidly deglaciating environment catchment, subject to large scale hillslope failures and associated enhanced sediment supply to the fluvial system. The Exploradores valley has recently experienced rapid changes in the proglacial landscape as well as a range of hazards associated with deglaciation including, rock slope failures, aluviones, and glacial lake outburst floods.
Project objectives:
(1) Quantification of rates of ice-marginal and proglacial landscape change.
(2) Measurement water and sediment flux from the river catchments.
(3) Meteorological measurements including precipitation and temperature.
(4) Groundwater levels and fluxes.
#3. Antarctic palaeo-ice streams and their pan-Antarctic glacial geological record
Satellite measurements and direct observations demonstrate that Antarctica is losing mass at an increasing rate (Shepherd et al., 2018). Recent IPCC predictions suggest that under a worst-case scenario it could contribute significantly to sea-level rise by 2100. Ice streams are fast flowing corridors of ice that exert a critical control on the overall mass balance of the Antarctic Ice Sheet, both today and in the past. This is because they can efficiently transport mass from the grounded interior of the ice sheet to the floating ice shelves where ice becomes vulnerable to basal melting, the primary way in which mass is lost from Antarctica. Understanding the evolution of the Antarctic Ice Sheet and its ice streams since the Last Glacial Maximum provides insights on processes that will control the future Antarctic contribution to sea level change. Additionally, robust data on the patterns and timing of deglaciation are essential to test the numerical ice sheet models that are used to make predictions of sea level rise.
As the seafloor around Antarctica is mapped in increasing detail it reveals an abundance of landforms that are the fingerprint of past ice sheet and ice stream behaviours. These include locations and directions of ice streaming, maximum extents, and their pattern and style of deglaciation (Graham et al., 2016; Larter et al., 2019; Wise et al., 2017). Alongside this landform record geological samples from marine and terrestrial settings have been analysed to provide chronological controls on the timing of deglaciation around Antarctica (Bentley et al., 2014). Taken together these empirical datasets can constrain the patterns and timing of past ice sheet change. Similarly, ice sheet models can simulate deglaciation of Antarctica through time. Comparing the simulated deglaciation scenarios with the empirical data allows these models to be evaluated such that models that accurately reconstruct “known” past ice sheet behaviour can be considered more likely to make accurate predictions of future change.
Livingstone et al. (2012) compiled evidence for the existence of former ice streams in Antarctica but since this effort there has been significant improvement in data availability and quality with much of the recent mapping being undertaken in efforts to constrain behaviour of specific sectors of the ice sheet such as the Ross and Amundsen Seas (e.g., Greenwood et al., 2018; Klages et al., 2015). Similarly, Bentley et al. (2014) compiled existing chronological data into a database and used it to reconstruct the ice sheet margin at 5000-year intervals. However, since this contribution there has been a significant volume of new data produced. While chronological data has been used in ice sheet model evaluation for Antarctica (e.g., Pittard et al., 2022) the landform record remains underutilised despite increasing awareness of its potential (Ely et al., 2021). A new pan-Antarctic record of glacial landforms, combined with updated geochronological constraints, would enable deglacial behaviour of Antarctica and its ice streams to be investigated in order to make a significant advance in understanding past scales, rates and processes of change. Crucially, the development of such a dataset would enable significant advances in our ability to assess ice sheet model simulations of Antarctic deglaciation on timescales longer than centuries.
The overall aim of this project is to develop a pan-Antarctic landform record and to use it to better understand the behaviour of the ice sheet during deglaciation.
Objectives
The main objectives are:
– Produce the first pan-Antarctic map of sub-glacial and ice marginal landforms.
– Combine this with internally consistent chronological data to investigate rates and patterns of ice margin retreat in different ice sheet sectors.
– Use the new landform record to evaluate model simulations to explore drivers of observed behaviour (e.g., still-stands, rapid retreat) and/or predict past ice sheet behaviour in areas where landform record is incomplete.
