The problem: The global oceans are absorbing one third of the anthropogenic emissions of carbon dioxide (CO2) (Sabine et al. 2004), thus strongly reducing the rate of climate change. Substantial year-to-year variation has been observed in the CO2 uptake by the North Atlantic Ocean (Watson et al. 2009). There is much scientific debate on whether regional and global ocean CO2 uptake has increased, remained constant or decreased in recent decades (for example Le Quéré et al. 2007; Ballantyre et al. 2012). Understanding the processes controlling oceanic CO2 uptake and how these may change in the future is essential. The formation of intermediate and deep water masses plays an important role in removing ‘anthropogenic' carbon from the atmosphere. In the Southern Ocean, newly formed intermediate water transports large amounts of anthropogenic carbon to the deep ocean, whilst uptake of anthropogenic carbon by bottom water remains poorly quantified (Sabine et al. 2004). A key uncertainty is the extent to which CO2 dissolved in seasonally ice covered surface waters can equilibrate with the atmosphere, before the water leaves the surface. Furthermore, the role of sea ice in carbonate chemistry is poorly understood (Bakker et al. 2008).

The research: This PhD project aims to quantify natural and anthropogenic carbon transport across deep sections in the Atlantic sector of the Southern Ocean, its long-term variation, and the role of intermediate and deep waters. The student will place these results in the context of physical processes and the overturning circulation of the Southern Ocean. The student will use chemical analyses, data analysis, carbon synthesis products (GLODAP, CARINA (cdiac.ornl.gov/oceans), SOCAT (www.socat.info)), and modelling. The student may also study carbonate chemistry data from the Rothera Oceanographic and Biological Time Series (RaTS, www.antarctica.ac.uk//staff-profiles/webspace/mmm/RaTS/RaTS.html). This will be a joint project between the University of East Anglia and the British Antarctic Survey (BAS, www.antarctica.ac.uk/). The student will benefit from (inter-)national collaborations, such as CarboChange (carbochange.b.uib.no/), SOCAT and planning of a Southern Ocean Observing System (www.scar.org/soos/).

Requirements, training and opportunities: We seek an enthusiastic, pro-active team player with strong scientific interests and self-motivation. She/he will have at least a 2.1 honours degree in physics, chemistry, mathematics, computing, or a branch of environmental science. Good numerical ability and experience in chemical analysis are an advantage. He/she will participate in at least one oceanographic cruise, subject a successful BAS medical and sea survival course, and will spend several weeks per year working at the British Antarctic Survey. The student will be enrolled in the UEA Science Graduate School (www.uea.ac.uk/sci/gradschool/training/) and will attend BAS student days. The candidate will acquire transferable skills, such as such as project planning, handling and visualization of data, execution of fieldwork, effective collaboration, scientific writing, and oral communication, while participating in research of global significance.

Bakker, D.C.E., Hoppema, M., Schröder, M., Geibert, W., Baar H. J.W. de (2008) A rapid transition from ice covered CO2–rich waters to a biologically mediated CO2 sink in the eastern Weddell Gyre. Biogeosciences, 5: 1373-1386. doi:10.5194/bg-5-1373-2008.

Ballantyre AP, Alden CB, Miller JB, Tans PP, White JWC (2012) Increase in observed net carbon dioxide uptake by land and oceans during the past 50 years. Nature 488:70-73. doi:10.1038/nature11299.

Le Quéré C, Rödenbeck C, Buitenhuis ET, Conway TJ, Lagenfelds R, Gomez A, Labuschagne C, Ramonet M, Nakazawa T, Metzl N, Gillett N, Heimann M (2007) Saturation of the Southern Ocean CO2 sink due to recent climate change. Science 316:1735-1738. doi:10.1126/science.1136188.

Sabine, C.L., R.A. Feely, N. Gruber, R.M. Key, K. Lee, J.L. Bullister, R. Wanninkhof, C.S. Wong, D.W.R. Wallace, B. Tilbrook, F.J. Millero, T.H. Peng, A. Kozyr, T. Ono, A.F. Rios (2004) The oceanic sink for anthropogenic CO2. Science 305: 367-371. doi:10.1126/science.1097403.

Watson AJ, Schuster U, Bakker DCE, Bates N, Corbière A, González-Dávila M, Friedrich T, Hauck J, Heinze C, Johannessen T, Körtzinger A, Metzl N, Olaffson J, Oschlies A, Pfeil B, Olsen A, Oschlies A, Santano-Casiano JM, Steinhoff T, Telszewski M, Ríos A, Wallace DWR, Wanninkhof RH (2009) Tracking the variable North Atlantic sink for atmospheric CO2. Science 326(5958):1, http://www.antarctica.ac.uk/ 391-1393. doi:10.1126/science.1177394.