Alex Griffiths – Neodymium isotopic composition of Antarctic water
Antarctic Bottom Water (AABW) plays a key role in the Earth’s climate system by forming the counter-clockwise section of the Meridional Overturning Circulation and, thus, influencing large scale redistribution of heat, nutrients and carbon. The neodymium (Nd) isotopic composition of seawater has been used as proxy to understand circulation changes in the AABW through time. The biogeochemical processes controlling Nd in seawater, however, remain largely unconstrained, and modern observations of Nd isotopes in the AABW are still numerically and geographically limited to west Antarctica. To overcome this limitation, samples were collected for Nd isotopic and rare earth element (REE) analysis off the coast of Wilkes Land (~120°E) in the Australian-Antarctic Basin. The results show no observable “boundary exchange” processes from continental sediments which would affect the Nd isotopic composition and REE concentrations of AABW, even along the Wilkes Land shelf. The Nd isotopic composition for AABW from this study is identical, within error, to previously published values for AABW from the Weddell Sea (εNd = −9.1. ± 0.7) and to areas further east (Adelie Land Bottom water: εNd = −8.9 ± 1.0).
Naomi Pratt – Deep sea corals and deglacial climate change
As the deep ocean is the largest store of carbon on the planet, changes in ocean circulation have the potential to profoundly affect climate. Reconstructing these changes in the past is vital to our understanding of earth system processes and feedbacks in future climate change. This is especially true in the Southern Ocean, thought to be a major source of CO2 since the termination of the last ice age. New ocean records from this region are sparse, as the most commonly used archive for paleoceanography – carbonate from microorganisms – tends to dissolve or be scoured away by strong currents before it can accumulate on the seafloor. This environment however is advantageous to deep sea corals, which can be dated radiometrically, and record high–resolution information on past seawater chemistry. In this talk I will introduce a new collection of subfossil deep sea corals from the southwest Indian Ocean, discuss species diversity and abundance through time, and explore concepts of changing circulation and impacts on deglacial atmospheric CO2 trends.
About the Series
The Grantham Changing Planet seminar series is run by students and staff on the Science and Solutions for a Changing Planet (SSCP) Doctoral Training Partnership. The aim is to complement the diversity of environmental research here at Imperial College London and promote links to the broader community in UK and beyond. It offers the chance to hear the latest in understanding, adapting to and mitigating environmental problems.