Previously, I was a post-doctoral researcher in the Geochemistry section at the Alfred-Wegener Institute, Germany. My research focused on understanding the role of the ocean in controlling Earth's climate on glacial-interglacial timescales. I worked as part of the COPTER project, which aimed to quantify the rates of carbon dioxide outgassing from the South Pacific over the last deglaciation.
I used a range of geochemical proxies (e.g. Δ14C, δ11B, δ18O, δ13C) measured on benthic and planktonic foraminifera to reconstruct changes in the carbonate chemistry of South Pacific. I also developed a novel proxy for reconstructing past ocean pH using foraminiferal δ7Li.
A geochemical approach to reconstruct modern dust fluxes and sources to the South Pacific, M. Wengler, F. Lamy, T. Struve, A. Borunda, P. Böning, W. Geibert, G, Kuhn, K. Pahnke, J. Roberts, R. Tiedemann, G. Winckler, Geochimica et Cosmochimica Acta, 264, 205-223, (2019) doi.org/10.1016/j.gca.2019.08.024
Consistently dated Atlantic sediment cores over the last 40 thousand years, C. Waelbroeck, B.C. Lougheed, N. Vazquez Riveiros, L. Missiaen, J. Pedro, T. Dokken, I. Hajdas, L. Wacker, P. Abbott, J.-P. Dumoulin, F. Thil, F. Eynaud, L. Rossignol, W. Fersi, A.L. Albuquerque, H. Arz, W.E.N. Austin, R. Came, A.E. Carlson, J.A. Collins, B. Dennielou, S. Desprat, A. Dickson, M. Elliot, C. Farmer, J. Giraudeau, J. Gottschalk, J. Henderiks, K. Hughen, S. Jung, P. Knutz, S. Lebreiro, D.C. Lund, J. Lynch-Stieglitz, B. Malaizé, T. Marchitto, G. Martínez-Méndez, G. Mollenhauer, F. Naughton, S. Nave, D. Nürnberg, D. Oppo, V. Peck, F.J.C. Peeters, A. Penaud, R. da Costa Portilho-Ramos, J. Repschläger, J. Roberts, C. Rühlemann, E. Salgueiro, M.F.S. Goni, J. Schönfeld, P. Scussolini, L.C. Skinner, C. Skonieczny, D. Thornalley, S. Toucanne, D. Van Rooij, L. Vidal, A.H.L. Voelker, M. Wary, S. Weldeab & M. Ziegler, Scientific Data, 6, 1, (2019), doi.org/10.1038/s41597-019-0173-8
Lithium isotopic composition of benthic foraminifera: A new proxy for paleo-pH reconstruction, J. Roberts, K. Kaczmarek, G. Langer, L.C. Skinner, J. Bijma, H. Bradbury, A.V. Turchyn, F. Lamy, S. Misra, Geochimica et Cosmochimica Acta, 236, (2018), doi.org/10.1016/j.gca.2018.02.038
Disentangling Diagenesis From the Rock Record: An Example From the Permo-Triassic Wordie Creek Formation, East Greenland, J. Roberts, A.V. Turchyn, P.B. Wignall, R. Newton, C.H. Vane, Geochemistry, Geophysics, Geosystems, 19, (2018), doi.org/10.1002/2017GC007259
Deglacial changes in flow and frontal structure through the Drake Passage, J. Roberts, I.N. McCave, E.L. McClymont, S. Kender, C.-D. Hillenbrand, R. Matano, D.A. Hodell, V.L. Peck, Earth and Planetary Science Letters, 474,397-408, (2017), doi.org/10.1016/j.epsl.2017.07.004
Evolution of South Atlantic density and chemical stratification across the last deglaciation, J. Roberts, J. Gottschalk, L.C. Skinner, V.L. Peck, S. Kender, H. Elderfield, C. Waelbroeck, N. Vázquez Riveiros, D.A. Hodell, Proceedings of the National Academy of Sciences,113, 3, 514-519, (2016), doi.org/10.1073/pnas.1511252113
Quantified effects of abundance changes and bioturbation on proxy records in marine sediment cores, J. Roberts, F. Lamy, A. Mackensen, M. Sarnthein, J. Southon, R. Tiedemann, R. Paleoceanography, (in rev.)
Lithium incorporation and isotope fractionation in planktonic foraminifera, part I: The role of pH, K. Kaczmarek, S. Misra, M. Greaves, J. Roberts, M. Raitzsch, J. Bijma, Geochimica et Cosmochimica Acta, (in rev.)
Lithium incorporation and isotope fractionation in planktonic foraminifera, part II: Li/Ca trends across glacial-interglacial transitions, K. Kaczmarek, S. Misra, M. Greaves, J. Roberts, M. Raitzsch, J. Bijma, Geochimica et Cosmochimica Acta, (in rev.)
Deep water formation in the glacial South Pacific and the deglacial release of CO2, J. Roberts, S. Misra, J.B.W. Rae, L.C. Skinner, M. Butzin, H. Grotheer, R. Shuttleworth, G. Mollenhauer, J. Bijma, F. Tiedemann, F. Lamy, (in prep.)
Insights into Glacial Terminations from a South Atlantic Perspective, J. Roberts, University of Cambridge, (2016). doi.org/10.17863/CAM.13432
Recently, I co-led the IODP short-drilling proposal (APL846), in which we proposed to drill a long sequence of sediments from the Falkland Island shelf slope. Our proposal was successful and has now been scheduled for March 2019 to be part of the larger expedition 382 to Iceberg Alley in the Scotia Sea.
I have been involved in a number of research cruises, including JC089 to the Iberian Margin and ANT-XXIX/4 to the South Sandwich Islands. During these cruises, I was involved in mapping of sediments on the seafloor using seismic techniques and retrieval of sediment samples from the bottom of the ocean.
This script provides you with the formulae required to convert foraminifera δ11B into pH.
This file contains 1o x 1o gridded data of pre-industrial alkalinity and dissolved inorganic carbon. This data can be imported directly into Ocean Data View or can be opened in R using the package 'ncdf4'.
This file contains 1o x 1o gridded data of pre-industrial pH. This data can be imported directly into Ocean Data View or can be opened in R using the package 'ncdf4'.
This file contains 1o x 1o gridded data of pre-industrial δ11Bborate. This data can be imported directly into Ocean Data View or can be opened in R using the package 'ncdf4'.
This file contains an excel spreadsheet that can allow you to log counts of anything (foraminifera, IRD etc.). This is a lot quicker than jotting down counts with pen and paper and is particularly useful if you have a keyboard with a numeric keypad.
Here are a set of macros designed by Simon Crowhurst to allow you to rapidly interpolate between data points in Excel. This is very useful for age modelling and provides much of the functionality of Analyseries, but in Excel.
I have added some scripts and files that might be useful for others. Please get in touch if you need any help using them.
