IAP-25-018

Holocene ice sheet-ocean interaction and glacimarine sedimentation in Greenland fjords

The 1.7 million km2 Greenland Ice Sheet is the largest ice mass in the northern hemisphere today with a sea level equivalent of ~7 m. Observations from satellite remote sensing and oceanography over the last few decades show that the ice sheet is undergoing significant changes in many locations with thinning and rapid mass loss. These changes are associated with its marine-terminating outlet glaciers many of which are fast-flowing and are the main pathways through which ice is delivered into the surrounding oceans. Our knowledge of the longer-term (centennial-millennial) history of these outlets, however, is still surprisingly poor for many sectors of the ice sheet and there remain large gaps in knowledge regarding Holocene ice sheet extent and the timing, rate and drivers of its subsequent retreat.

This PhD project will address the above problem by utilising an exceptional suite of marine sediment cores and geophysical data on seafloor geomorphology and sub-surface acoustic stratigraphy collected on the recent ‘Kang-Glac’ research expedition of the RRS Sir David Attenborough to SE Greenland in 2024 (https://www.durham.ac.uk/departments/academic/geography/research/projects/kang-glac/), as well as an earlier dataset from West Greenland. These data are from fjords adjoining marine-terminating outlet glaciers.

The overall scientific goal of this project is to reconstruct the role of ocean forcing in driving Holocene Greenland ice sheet dynamics and to determine the associated processes and patterns of glacimarine sedimentation. There are three main objectives: (1) To investigate core sedimentology and chronology using a range of techniques including radiocarbon and lead-210 dating. (2) To determine foraminiferal abundance and diversity and thereby reconstruct changing oceanographic conditions during the Holocene. (3) To investigate seafloor landform-sediment assemblages, acoustic stratigraphy and sediment thickness and characteristics.

Marine geophysical data comprising multibeam swath bathymetric imagery of seafloor morphology which will allow the reconstruction of former ice sheet extent, flow direction and flow dynamics. The multibeam data are supplemented with shallow acoustic (sub-bottom profiler) data on acoustic stratigraphy and sediment thickness. Sediment coring during the cruises utilised gravity, piston and multi- corers to obtain samples of subglacial, deglacial and postglacial sediments. A large dataset of over twenty sediment cores up to 10 m in length will be available for this project. Core analysis will take place in the Department of Geography, Durham University which is equipped with state of the art laboratory facilities for paleoenvironmental analysis of sediment cores and is supported by a group of highly trained technicians. The student will have access to all of these facilities and support during the PhD. The cores will be analysed for grain size, sedimentary structures, shear strength, and micro- and macrofaunal content. Selected samples will be dated using radiocarbon with samples submitted to the NERC Radiocarbon Facility and Lead-210 dating (done in-house in Durham Geography) to obtain a chronology of ice sheet-ocean interaction, ice sheet retreat and palaeoceanographic change.

Year 1

Analysis and interpretation of marine geophysical data and initial description and analysis of sediment cores. Visit to British Antarctic Survey for meetings with supervisors Dr. Kelly Hogan and Rob Larter.

Year 2

Continued analysis of marine sediment cores and submission of samples for radiocarbon and Lead-210 dating. Visit to British Antarctic Survey for meetings with supervisors Dr. Kelly Hogan and Rob Larter.

Year 3

Completion of all data analysis and interpretation. Commence thesis writing. Visit to British Antarctic Survey for meetings with supervisors Dr. Kelly Hogan and Rob Larter. Presentation of results at national conferences.

Year 3.5

Completion and submission of thesis. Finalise publication of manuscripts. Visit to British Antarctic Survey for meetings with supervisors Dr. Kelly Hogan and Rob Larter. Attend major international conference (e.g., EGU or AGU or INQUA).

The student will receive training in the description, analysis and interpretation of multibeam swath bathymetric datasets, sub-bottom profiler records and marine sediment cores. Broader, transferrable skills training will be provided via Durham University’s award-winning Career and Research Development (CAROD) group with courses, for example, in writing for publication, thesis writing, presentation skills. The student will also benefit from cross-disciplinary training provided through IAPETUS2. The student will be a member of the ‘Sea Level, Ice Sheets and Climate Research Cluster in Geography’. It is also intended that the student will participate in a research cruise during the course of the PhD to experience the hands-on data collection of sediment cores at sea. There will be several possibilities for this through participation in existing scheduled cruises led by either Durham or BAS.