Franziska Kersten

Name:             Franziska Kersten
Institute:          Alfred Wegener Institute
Department:     Marine Geology and Paleontology
Phone:            +49-(0)471-4831-1570
Email:              Franziska.Kersten(at)awi.de
Web link: http://www.awi.de/en/research/research_divisions/geosciences

PhD-project title: Changes of deep water carbonate ion concentrations in the Southern Ocean over the past glacial/interglacial cycles

During the Last Glacial Maximum (LGM) the atmospheric CO2 concentration was about 80-100 ppm lower than during interglacial times. It is a matter of debate what is causing these glacial-interglacial CO2 variations.

The CYCLOPS ocean geochemistry model indicates that an increase in whole ocean alkalinity alone could produce a 35 ppm decrease in atmospheric CO2 values (Sigman, McCorkle and Martin, 1998). Higher ocean alkalinity leads towards higher carbonate ion concentrations. Carbonate ions react with CO2 and form bicarbonate ions, effectively reducing surface water CO2.

In this project, the connection between carbonate chemistry, deep ocean alkalinity and atmospheric CO2 concentrations will be further investigated. For this purpose a newly developed proxy for past carbonate ion concentrations will be applied on sediment cores from the Australian sector of the Southern Ocean. B/Ca ratios will be measured on benthic foraminifera (following Yu and Elderfield, 2007), in order to reconstruct the changes in carbonate ion concentrations of deep and intermediate water masses since the LGM.

Start of doctoral thesis: 1.10.2008

Thesis Committee:

Supervisor: Prof. Dr. R. Tiedemann (AWI)

Co-Supervisor: Dr. F. Lamy (AWI)

Further members: Dr. T. Bickert (Marum Bremen), Dr. S. Steph (AWI)

References

Fischer, Schmitt, Lüthi, Stocker, Tschumi, Parekh, Joos, Köhler, Völker, Gersonde, Babante,

LeFloch, Ranyaud and Wolff (2010): The role of Southern Ocean processes in orbital and millennial CO₂ variations-A synthesis. Quat. Sci. Rev. 29, 193-205

Siegenthaler, Stocker, Monnin, Lüthi, Schwander, Stauffer, Raynaud, Barnola, Fischer,

Masson-Delmotte and Jouzel (2005): Stable Carbon cycle-climate relationship during the late Pleistocene. Science 310, 1313-1317

Sigman, Hain, Haug (2010): The polar ocean and glacial cycles in atmospheric CO₂ concentration. Nature 466, 47-55

Presentations:

Upcoming:

Franziska Kersten, R. Tiedemann and F. Lamy, The capacity of the Southern Ocean as a CO2 sink during Glacials -a B/Ca based reconstruction of deep and intermediate water [CO₃^2-], International Conference on Paleoceanography, 28.8.-3.9.2010. (Poster)

Expeditions:

“Polarstern” cruise ANT XXVI-2 (27.11.2009-27.01.2010, Punta Arenas to Wellington), Chief Scientist: Rainer Gersonde