IAP-24-008

Investigating past changes in Greenland melting and its impacts on ocean circulation as a key to the future.

The transformation of warm and salty surface waters in the North Atlantic into cold and dense deep waters, plays a key role in regional and global climate change. This process, referred to as the Atlantic Meridional Overturning Circulation (AMOC), is crucial for the re-distribution of heat, nutrients and gasses across the globe. For example, in the North Atlantic it contributes towards the northward transport of heat to higher latitudes, which helps maintain the relatively mild climate in NW Europe. This overturning is projected to weaken in the 21st century as a response to increased meltwater from polar regions and warming of the surface waters due to the increasing atmospheric CO2 levels [IPCC, 2019].
Over the last 60 years, melting of Greenland and Arctic ice has increased the flux of freshwater reaching the North Atlantic [Bamber et al., 2018]. Yet, the limited temporal span of oceanographic data (70 years) means that there are still large uncertainties surrounding the future sensitivity of AMOC to freshwater forcing. The East Greenland Current is a key ocean current that acts as the main conduit of Arctic freshwater and sea-ice southward to the subpolar North Atlantic [Agaard and Carmack 1989] and can weaken the formation of deep waters in the Labrador Sea with knock on consequences for the strength of the AMOC [Yang et al., 2016].
The aim of this PhD project is to address this crucial gap in our knowledge by extending ocean measurements of the properties of the East Greenland Current System and its effects on deepwater formation across the current interglacial, the Holocene. To do this, exceptional sedimentary and biological archives will be used including marine sediment cores located along the East Greenland Coast [e.g. Dyke et al., 2017, Perner et al., 2015] and in the Eastern Labrador Sea [Moffa-Sanchez et al., 2014 and 2015, Moffa-Sanchez and Hall 2017]. The cores from the East Greenland margin will enable the reconstruction of meltwater run-off and iceberg fluxes in the EGC. The Eastern Labrador Sea core will be used to reconstruct surface and deep Subpolar North Atlantic responses to the freshwater input across the Holocene. This project will benefit from close collaboration with project partner Prof Camilla Andresen based at the Geological Survey of Denmark and Greenland (GEUS), including secondments to GEUS in Copenhagen.

The student will use a suite of sedimentary, chemical and biological proxies on exceptional marine sediment cores. Proxies such as trace metal (e.g. Mg/Ca) and stable isotope
chemistry in foraminiferal calcite alongside foraminiferal assemblage counts will be used to reconstruct past ocean conditions such as temperature and salinity. Ice rafted debris
composition and counts will give an indication of provenance and amount of land ice reaching the ocean. Bottom flow speed records of sortable silt mean grain size will be used
to reconstruct the strength of the densest deep AMOC currents.

Year 1

Review of existing literature relating to the AMOC and its response to freshwater forcing and the North Atlantic climate. Laboratory training for the sampling and processing of marine sediment cores for grain size analysis and training in the identification of foraminifera. Presentation of initial research and results at national meetings/workshops (e.g. Quaternary Research Association Annual Postgraduate Symposium, September 2026).

Year 2

Preparation and analysis of inorganic chemistry in foraminifera including oxygen isotopes, and trace metals with particular focus on Mg/Ca as a temperature proxy. Data analysis and interpretation of the datasets. Secondment to GEUS, Copenhagen to visit Prof Andresen (Autumn 2026). Presentation of the results at national meetings/workshops (e.g. Quaternary Research Association Annual Postgraduate Symposium, September 2027).
Production of paper 1

Year 3

Continued data analysis and interpretation. Production of paper II. Presentation of the results at the European Geophysical Union Meeting (Vienna, April 2027).

Year 3.5

Production of paper III. Writing and submission of thesis.

This project will provide the student with a wide range of skills in paleoceanographic reconstructions using geochemical, micropaleontological and physical proxies from marine
sediment cores. The student will be trained in micropaleontological identification, and geochemical analysis of marine sediments in the state-of-the-art laboratories of the
Geography Department at Durham University. Additional training will be provided through visits to NERC radiocarbon and stable isotope facilities, including training on core chronology development using different mathematical approaches.
The student will also benefit from close collaboration with the Marine Geology group of GEUS (Project Partner C. Andresen) and the project will involve an extended visit to
Copenhagen to samples cores stored there and receive training in sediment core analysis. Participation on a research cruise will also be sought through project partners/collaborators and opportunities for data and climate model integration may be pursued.
The student will be a member of the dynamic Sea Level, Ice and Climate Research Cluster in Geography at Durham (https://www.dur.ac.uk/geography/slic/). The student will also
participate in a broad range of skills training provided in-house at Durham through the award-winning Durham Centre for Academic Development (DCAD) (thesis writing, writing for publication, presentation skills, enterprise skills etc.) and from the range of environmental science training provided as part of the IAPETUS Doctoral Training Partnership framework.
Through project collaborators/supervisors the student will have the opportunity to develop a network of national and international collaborators in the general study area. The student will also attend and contribute to the programme of regular departmental seminars and discussion groups as well as National and International conferences to support their general development as a scientist. The student will be encouraged to write scientific papers for publication during their PhD. This will be a major benefit to their career, and they will be well supported through this process by the experienced supervisory team.