University of Plymouth PEARL https://pearl.plymouth.ac.uk 04 University of Plymouth Research Theses 01 Research Theses Main Collection 2017 Holocene sea-level changes in the Falkland Islands: new insights into accelerated sea-level rise in the 20th Century Newton, Thomas Lee http://hdl.handle.net/10026.1/9650 University of Plymouth All content in PEARL is protected by copyright law. Author manuscripts are made available in accordance with publisher policies. Please cite only the published version using the details provided on the item record or document. In the absence of an open licence (e.g. Creative Commons), permissions for further reuse of content should be sought from the publisher or author. Holocene sea-level changes in the Falkland Islands: new insights into accelerated sea- level rise in the 20th Century Thomas L. Newton A thesis submitted to Plymouth University in partial fulfilment for the degree of DOCTOR OF PHILOSOPHY School of Geography, Earth and Environmental Sciences Faculty of Science and Technology Plymouth University April 2017 Copyright This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with its author and that no quotation from the thesis and no information derived from it may be published with the author’s prior consent. Author Declaration At no time during the registration for the degree of Doctor of Philosophy has the author been registered for any other university award without prior agreement of the Graduate Committee. This study was financed with the aid of a studentship from the School of Geography, Earth and Environmental Sciences, Plymouth University. During the course of study relevant scientific seminars, conferences and workshops were attended, at which work was often presented. External institutions were visited for training purposes. Word count: 67,416 Author: Thomas L. Newton Signature: Date: 11/04/2017 i Additional funding awards: Natural Environment Research Council (NERC). Radiocarbon Facility Allocation Number 1694.0413 (£20,804) International Union for Quaternary Research (INQUA) Financial support to attend XIX INQUA 2015 (£995) Conferences and presentations: Newton, T.,(2013) ‘Testate amoebae as precise sea-level indicators’ February 2013, Phunch Seminar, University of Plymouth. Newton, T., Gehrels, W. R., Daley, T.J, Bentley, M.J., Long, A.J. and Milne G.A. (2014) ‘Holocene sea-level changes in the Falkland Islands’ April 2014, Poster presentation: European Geophysical Union General Assembly, Vienna. Newton, T. Gehrels, W.R., Daley, T.J. (2014) ‘Reconstructing sea-level change using testate amoebae: A case study from the Falkland Islands’ Oral presentation: Postgraduate Research Conference, University of Plymouth. May 2014 Newton, T., Gehrels, W. R., Daley, T.J., Bentley, M.J. , Long, A.J. and Milne G.A. (2014) ‘Holocene sea-level changes in the Falkland Islands’ (July 2014) Poster presentation: UK Sea Level IGCP / INQUA CMP Working Group Field Meeting, SW Ireland. Newton, T. (2014) ‘Reconstructing sea-level changes from low energy intertidal sediments’ (August 2014) Invited seminar and workshop: Instituto Nacional de Ecologia y Cambio Climatico (INECC) Mexico City, Mexico. Newton, T., Gehrels, W.R., Daley, T.J. (2014) ‘Reconstructing Holocene sea-level changes in the Falkland Islands’ (August, 2014) Invited Seminar: El departamento de geomagnetismo y exploracion geofisica, Universidad Nacional Autónoma de México (UNAM). Newton, T. Gehrels, W.R., Daley, T.J. (2015) ‘Holocene and recent sea-level changes in the Falkland Islands: testing the Greenland melt hypothesis.’(June 2015) Oral presentation: Workshop on Global Sea-Level Variability and Change, Palma de Mallorca, Spain. Newton, T. Gehrels, W.R., Daley, T.J. (2015) ‘Holocene and recent sea-level changes in the Falkland Islands: testing the Greenland melt hypothesis.’(August 2015) Oral presentation: XIX INQUA congress 2015, Nagoya Japan. Newton, T., Gehrels, W.R., Daley, T.J. (2015) ‘Seasonal distributions of salt-marsh testate amoebae: implications for sea-level studies’ (August 2015) Poster presentation: XIX INQUA congress 2015, Nagoya Japan. ii ABSTRACT Holocene sea-level changes in the Falkland Islands: new insights into accelerated sea-level rise in the 20th Century Thomas L. Newton This thesis investigates sea-level changes in order to test the hypothesis that the main contribution to early 20th century sea-level rise was Northern Hemisphere land-based ice melt. Multiproxy sea-level reconstructions were established for the Falkland Islands, a location where models suggest sea-level rise from Northern Hemisphere ice melt produces the largest signal. The Falklands reconstruction indicated sea levels in the early 20th century accelerated compared to the long-term rate, synchronous with accelerations observed globally. The magnitude of the acceleration in the Falklands reconstruction was greater than Northern Hemisphere rates, consistent with the spatial pattern from a Northern Hemisphere melt source, but likely less than in New Zealand and Australia. It is therefore not possible rule out other contributions to the observed sea-level acceleration. The Falklands reconstruction indicated a rapid sea-level jump around 8.4 ka BP, synchronous with a jump observed in the Northern Hemisphere, which has been attributed to the sudden drainage of Laurentide proglacial lake Agassiz-Ojibway associated with the 8.2 ka BP climatic downturn. A maximum estimate of 0.89 ± 0.22 m for this jump in the Falklands is considerably less than estimates from Northern Hemisphere records. This difference could indicate additional contributions from the Southern Hemisphere are being recorded in the Northern Hemisphere signal. This thesis also focused on developing testate amoebae as sea-level indicators. In the Falklands, testate amoebae transfer functions were able to reconstruct sea level with precision (±0.08 m) comparable to diatoms (±0.07 m). However, preservation issues were indicated in the fossil testate amoebae assemblages which limits their use as tools for sea-level reconstruction. In addition, contemporary distributions of salt-marsh testate amoebae were investigated over one annual cycle. Seasonal variations in the live assemblages were observed to be asynchronous between taxa. Variations in the death assemblages were also observed which were correlated with variations in the live assemblages. This observation suggests the commonly applied assumption in palaeoenvironmental studies that analysing the death population negates temporal bias is invalid. Further research is required to investigate the impact these observed variations have on reconstructive performance. iii ACKNOWLEDGEMENTS First and foremost I’d like to thank my supervisory team, Prof. Roland Gehrels and Dr. Tim Daley for having belief in me to begin with, and for their continued support over the duration of my PhD studies. Roland, it was, after all, you who first piqued my interest in sea-level studies. On a similar note, I wish to thank my secondary school and A-level geography and geology teacher John Payne who first inspired me to pursue my interests in these fields. More broadly, I’d like to thank the staff, and the Department of Geography as a whole, at Plymouth University without whom this PhD would not have been possible. I am grateful for the assistance of the South Atlantic Environmental Research Institute for providing lab space in the Falkland Islands, Margarita Caballero and Paola Massyel for hosting me in Mexico, INQUA for providing financial support to attend the Japan congress, and Tom Hill hosting me at the Natural History Museum, London. This work was supported by the NERC Radiocarbon Facility NRCF010001 (allocation number 1694.0413). I would personally like to thank, in no particular order, Katie Head, Rich Hartley, Will Blake, Dan Charman, Tom Hill, Paola Massyel, Margarita Caballero, Rob Barnett, Ralph Fyfe, James Smith, Geoff Millward, Emma Edwards, Emma Rice, Francis Rowney, Glenn Milne, Kurt Lambeck, Andrew Parnell, Antony Long, Mike Bentley, Margot Saher, Jamie Quinn and Arthur Guinness for their generous assistance, contribution of data and/or insightful discussions at various stages of my PhD studies. Finally I wish to give my sincere, indiscriminate thanks to my friends, new and old, and family who have supported me with their company, kept me sane, and in good spirits throughout what has been a challenge of a lifetime – you know who you are. Cheers! iv Contents Copyright ............................................................................................................................... i Author Declaration ................................................................................................................. i Additional funding awards: ................................................................................................. ii Conferences and presentations: ........................................................................................ ii ABSTRACT ........................................................................................................................... iii ACKNOWLEDGEMENTS .................................................................................................... iv Index of Tables .................................................................................................................... ix Index of Figures ..................................................................................................................