|
My research focus is the development and application of new geochemical and isotopic tracers in marine geochemistry, paleoceanography and paleoclimate, with particular focus on radiogenic isotope systems (Ar, Sr, Nd, Hf, Pb). Although these tracers have been widely used in solid-earth geochemistry, they represent a relatively new but promising suite of tracers in the low-temperature environment. I utilize them to decipher past changes in ocean circulation patterns, continental weathering, and ice sheet evolution on million-year to millennial time scales. Below some selected projects I am working on.
If you are interested to join the MAGIC isotope geochemistry group at Imperial College London (for research experience as an undergraduate student, a PhD, or a postdoctoral research position), please do not hesitate to get in touch.
1) History of the Antarctic Ice Sheets - Looking Back Into the Future?
The East Antarctic Ice Sheet (EAIS) is up to 4 km thick, and covers an area larger than the United States. Together with the roughly eight times smaller West Antarctic Ice Sheet (WAIS), a water mass is locked up on Antarctica that if melted would be equivalent to a sea level rise of ~60 m.
 From the study of marine sediments we know that today's situation on Antarctica with a stable EAIS and a potentially unstable WAIS is just a snapshot in the Cenozoic glacial history, which has been characterized by the transition from an ice-free "Greenhouse world" more than 40 million years ago, to the present "Icehouse world" with ice caps on both poles.
The record of Ice-Rafted Debris (IRD = glacially eroded material incorporated in icebergs and released to the ocean floor when the icebergs melt) around Antarctica opens a window to explore the history of past glacial activity on Antarctica. This can be done by matching the chemical signature of IRD from marine sediment cores with known Antarctic geology. This way, we have a powerful way to fingerprint, which parts of the Antarctic continent produced icebergs back in time, in turn revealing where and when the ice sheet reached the coast, and what the discharge dynamics were.
Collaborators : Trevor Williams, Sidney R. Hemming, Elizabeth Pierce, Steven L. Goldstein (L-DEO/Columbia University); Stefanie Brachfeld (Montclair University); Martin Roy (UQAM); Bruno Tremblay (McGill), Alan Haywood, Daniel Hill, Aisling Dolan (Leeds), IODP Expedition 318 participants.
This research is supported by the National Science Foundation, the NERC UK IODP, the European Comission (IRG), and the Grantham Institute for Climate Change.
 WILKES LAND IODP EXPEDITION 318
From 4 January to 9 March 2010 I was aboard the drill ship Joides Resolution on IODP expedition 318 to Wilkes Land, Antarctica. The goal was to drill the glacial history of East Antarctica and the greenhouse - icehouse transiton some 34 million years ago ... and we succeeded!
I reported from this expedition in my blog: https://www2.imperial.ac.uk/blog/wilkeslandiodpexpedition/
We also had a professional videographer onboard, who produced weekly video summaries for Ocean Leadership, which can be found on YouTube: http://www.youtube.com/playlist?list=PL8AC7E48053CB639C
2) The Ocean's Role in Climate Change Unraveled by Cold Water Corals
The deep ocean contains a large fraction of the carbon in the coupled ocean-atmosphere system. Therefore small changes in ocean circulation have the potential to profoundly affect the climate system. From the study of marine sediment cores we know that such changes happened in the past – some very rapidly and on short time-scales (decades), and others more gradually and on longer time-scales (millions of years).
 Deep-sea corals offer two main advantages over sedimentary cores when trying to investigate recent and historical changes in the deep ocean: they can be dated radiometrically, and their skeletons record high–resolution information on past environmental conditions.
Together with my collaborators L. Robinson (WHOI) and J. Adkins (Caltech) I use deep-sea corals to constrain past water mass configurations and past ocean ventilation rates from coupled neodymium-radiocarbon analyses on directly dated scleractinian corals. Despite the unique nature of cold water corals as climate recorders, their potential has not yet been fully realized.
To get some impression on deep-sea coral sampling in the Southern Ocean, check out the following link from a cruise I participated in in 2008 (NBP0805).
For impressions from our 2011 coral sampling expedition in the Southern Ocean check out my blog 'Pretty Corals and Rocky Seas' and our official website 'Drake Passage Corals'.
This research is supported by the National Science Foundation, the Natural Environment Research Council, and the European Comission (IRG).
3) Marine Biogeochemical Cycles of Trace Elements and Their Isotopes
Trace elements play an important role in the ocean as nutrients, as tracers of processes now and in the past, and as contaminants. Their biogeochemical cycling has direct implications for research in such diverse areas as the carbon cycle, climate change, ocean ecosystems and environmental contamination.
 GEOTRACES (www.geotraces.org) is an international study of the global marine biogeochemical cycles of trace elements and their isotopes. Its mission is to identify processes and quantify fluxes that control the distributions of key trace elements and their isotopes in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions.
Together with K. Pahnke (L-DEO), I organised the intercalibration phase of this program for Nd isotopes and rare earth elements (REE). Guidlines for sampling and analytical methods are available on the international GEOTRACES webpage (cookbook).
Last year t he major field program kicked off, and we had the firs t UK GEOTRACES cruise in the South Atlantic UK GEOTRACES. Watch out for exciting results ...
This research is supported by the National Science Foundation and the Natural Environment Research Council.
| 
