NOCS graduate school projects: Understanding spatial and temporal variability in carbonate chemistry

Toby Tyrrell, Eric Achterberg

Suitable for graduates with degrees in: Oceanography/Marine Science, Chemistry, Physics, Mathematics or Engineering

Rationale

We need to better understand ocean acidification and the ocean carbon sink, and therefore the processes driving spatial and temporal variations in carbonate chemistry. Several very large datasets of carbonate chemistry measurements have recently been released or are currently in advanced preparation. A large database of ~3 million measurements of surface ocean pCO2 has been produced by Takahashi and co-authors (Takahashi et al., 2009), and an even larger database (SOCAT) is in the process of compilation. The GLODAP database of dissolved inorganic carbon (DIC) and alkalinity measurements (Key et al., 2004) is now supplemented by others such as CARINA. Other datasets are being collected or collated within the projects EPOCA, Defra-pH and MEECE. These large datasets, together with recent NOCS datasets, represent a new resource for assessing hypotheses about spatiotemporal variations in ocean acidification and carbon uptake, such as where are they progressing slowest and where fastest?

Methodology

In this PhD project a combination of dataset analysis, modelling and observational data collection work will be undertaken. New data will be collected at sea in one or more areas of particular interest for carbonate chemistry, possibly including one of the ocean acidification pelagic cruises. Matlab and other packages will be used to plot and analyse these and other datasets to investigate different hypotheses as to the most important drivers of carbonate chemistry. Data and location-specific models will be compared, to further test hypotheses.

Training

You will be trained in methods and techniques for the analysis of carbonate chemistry in seawater. These will include measurements of DIC and alkalinity on both VINDTA and Apollo systems. You will participate in one or more ocean-going research cruises during which you will collect carbonate chemistry samples. You will be trained in techniques for local box or 1D modelling combining ecosystem dynamics and biogeochemical (including carbon) cycling. By the end of the PhD you will have been trained in and become familiar with work practices both in state-of-the-art laboratories and on research vessels.

Wider Implications

Generating improved understanding of the processes that control the carbonate chemistry of surface seawater, your work will lead to major improvements in our understanding of both: (1) ocean acidification, and (2) CO2 exchange between the atmosphere and the ocean. This work will help identify which geographical areas of the ocean will be most at risk from ocean acidification, and also the degree to which the future ocean carbon sink will dampen the rise in atmospheric CO2 levels.

Background Reading

T Takahashi et al. (2009) Climatological mean and decadal change in surface ocean pCO2, and net sea–air CO2 flux over the global oceans. Deep Sea Research Part II, 56: 554-577.
Key, R.M., A. Kozyr, C.L. Sabine, K. Lee, R. Wanninkhof, J. Bullister, R.A. Feely, F. Millero, C. Mordy, T.-H. Peng. 2004. A global ocean carbon climatology: Results from GLODAP. Global Biogeochemical Cycles, Vol. 18, GB4031.
Zeebe Re & Wolf-Gladrow D (2001) CO2 in Seawater: Equilibrium, Kinetics, Isotopes. Elsevier
Merico A, Tyrrell T, Cokacar T. (2006) Is there any relationship between phytoplankton seasonal dynamics and the carbonate system? Journal of Marine Systems, 59: 120-142 .
Findlay, H. S., Tyrrell, T., Bellerby, R. G. J., Merico, A., and Skjelvan, I.: Carbon and nutrient mixed layer dynamics in the Norwegian Sea, Biogeosciences, 5, 1395-1410, doi:10.5194/bg-5-1395-2008, 2008.

For enquiries about this project, please contact t.tyrrell@noc.soton.ac.uk.

This Project involves the disciplines of Chemical oceanography

University of Southampton, Web site.


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