Glacial meltwater evolution during the deglaciation of THE Fennoscandian Ice Sheet

Rising global temperatures are likely to lead to an impact on the generation of glacial meltwater, its distribution, and its seasonal evolution on contemporary ice masses (e.g. Kingslake et al., 2017). To better analyse the impacts of this climate-driven increase requires an improved understanding of how meltwater moves from supra- to subglacial settings and its resultant impact on ice sheet dynamics and sediment depositional-erosional processes. The ice-bed interface plays a key role when it comes to understating seasonal and annual meltwater evolution - e.g. potential switches between efficient and distributed subglacial drainage systems (Andrews et al., 2014). Such variations in meltwater availability can provide important internal feedbacks on glacial mass balance and ice velocity across a range of spatial and temporal scales. For example, during episodes of pressurising, a distributed subglacial meltwater drainage system can lead to an increase in ice velocity. The corollary of such an increase in ice velocity is that it could potentially exert a mass balance impact by increasing ice flux, drawing down the ice surface ice below the equilibrium line, making more ice susceptible to surface melting, and generating more meltwater in a positive feedback. These processes need to be robustly understood in order to be effectively integrated into, or used to test, numerical ice sheet models.

Given the difficulty in observing meltwater processes at the contemporary ice-bed interface, geological records can provide the ideal opportunity to investigate past ice sheet meltwater evolution. This project explores the geological record of southern Finland during the deglaciation of the last Fennoscandian ice sheet. The work proposed here will exploit the availability of a 2 m resolution LiDAR digital terrain model to map a dense network of eskers and their associated glaciofluvial deposits. These features likely capture a record of meltwater evolution and ice sheet discharge after the deposition of the Salpausselkä moraine during the Younger Dryas (Stroeven et al., 2016). This is a particularly important time period because it is characterised by an increase in global temperature and concomitant ice sheet retreat, that could represent a proxy for the present. This case study will provide new details on how meltwater availability changed through time and how this relates to other proxy records of environmental change. The mapping will be used to plan a number of fieldwork campaigns to survey the most important landforms. During these campaigns the student will collect geophysical datasets, such as ground-penetrating radar (GPR - frequencies of 50 MHz, 100 MHz and 160 MHz), electrical resistivity tomography, and seismic refraction, along dip and strike profiles. This fieldwork will also allow the student to collect supplemental drone-based photogrammetry, shallow sediment cores and bedrock samples for developing a geochronology, as well as outcrop logging and sampling that can be used to ground-truth geophysical surveys. The student will be equipped with new skills in the collection of geological and geophysical surveying, fieldwork planning, and data management that will be useful for wide range of potential environmental, academic, and industry careers.