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Description

The Labrador Sea is a key location for the Earth's climate system, because it contributes a major component of the Atlantic meridional overturning circulation (AMOC). Due to intense surface air–sea heat exchange, dense ocean mixed layers are created, forming Labrador Sea Water (LSW), which ventilates the intermediate depths of the North Atlantic and beyond. Various studies have revealed considerable spatial and temporal variability, associated with the formation and meridional transport of this water mass, over the past few decades. Yet, crucially, its longer-term history remains largely unknown.

This project focuses on the reconstruction of multidecadal-centennial scale variability in surface water conditions and deep ocean hydrography of the LSW over the past 10 kyrs (the Holocene), in order to determine its contribution to meridional overturning and its potential role in amplifying global climate variability.

The project will use existing cores (Fig. 1) recovered from within the Labrador Sea at Eirik Drift and the southeast Labrador Sea Slope (Hamilton Spur and Orphan Knoll), as well as along the eastern continental margin of North America (Laurentian Slope and off Cape Hatteras). A multi-proxy approach will be employed, including micropalaeontological (e.g. faunal assemblages), stable isotopic (oxygen and carbon), geochemical (e.g. Mg/Ca traceelement palaeothermometry) and sedimentological (e.g. sortable silt current speed proxy) proxies to record (i) upper ocean conditions in the Labrador Sea and (ii) intermediate depth hydrography and palaeocurrent strength of LSW as it feeds the south-flowing deep western boundary current (DWBC). The project will explore the causal link and phasing between different generated proxy records and between these records and other records of North Atlantic climate variability and climate forcings. The generated proxy records will be further complemented by undertaking a data-model integration with existing/on-going modelling studies of Holocene LSW variability.

Training:

The student will be trained in high-resolution quantitative palaeoclimate reconstruction. This
will include micropalaeontology (e.g. faunal assemblages), stable isotope geochemistry
(oxygen and carbon), trace element geochemistry (e.g. Mg/Ca palaeothermometry) and
sedimentology (e.g. sortable silt current speed proxy). Additional, training will be given in
data-model integration through the examination of existing CMIP5 - Coupled Model
Intercomparison Project Phase 5 -simulations. It is also envisaged that the student would be
able to gain sea-going experience.

Background reading:

Hall, I. R., K. P. Boessenkool, S. Barker, I. N. McCave, and H. Elderfield (2010), Surface
and deep ocean coupling in the subpolar North Atlantic during the last 230 years,
Paleoceanogr., 25.
Moffa-Sánchez P., Born A., Hall I.R., Thornalley D.J.R., Barker S. (2014) Solar forcing of
North Atlantic climate over the last millennium, Nature Geoscience, 7, 275–278,
doi:10.1038/ngeo2094.
Moffa-Sánchez P., Hall I.R., Barker S., Thornalley D.J.R., Yashayaev I. (2014) Surface
ocean changes in the eastern Labrador Sea over the last millennium
Paleoceanography, 10.1002/2013PA002523.

Contact details

Prof Ian Hall
hall@cardiff.ac.uk