Resolving Antarctic meltwater events in Southern Ocean marine sediments and exploring their significance using climate models

Dr Alessandro Silvano, Dr Claire Allen, BAS; Dr Louise C Sime, BAS; Dr George Swann, Nottingham University; Professor Melanie Leng, Nottingham University

The principal aim of this project is to better understand the role of the Antarctic ice sheet in global sea level and rapid climate change by reconstructing Antarctic glacial discharge and modelling the impact of these freshwater fluxes on ocean circulation and climate. The project will target marine sediments from ‘iceberg alley’ (Fig.1) to identify intervals of increased Antarctic ice sheet discharge for the Last Interglacial (LIG), and the past millennium.

Last Interglacial (130-120 ka): A lasting enigma in climate research is to establish the source and forcing for the high global mean sea level (GMSL) when the earth was 1-2°C warmer and global sea level was 6 to 9 m higher than present at the peak of the LIG (~127 ka). A GMSL high stand of this amplitude cannot be accounted for by collapse of the Greenland ice sheet, so sights have turned to Antarctica to account for the bulk of the LIG sea level rise (Fig.2).

Historical (~1 ka to present): Existing records of Antarctic glacial discharge either do not include the Anthropocene (Fig.3-green), are at very low resolution (Fig.3-orange) or are from sites on the inner continental shelf where glacial discharge is likely dominated by local glacier conditions (Fig.3-blue & pink). Records of continental-scale ice discharge are urgently needed to resolve historical changes in Antarctic contributions to GMSL and freshwater influence on ocean circulation.

Analyses of LIG and historical sediments from ‘iceberg alley’ in the deep Southern Ocean (Fig.1), will yield an integrated (WAIS & EAIS) record of glacial discharge, more representative of the contributions to GMSL, as well as provide new evidence for models to assess how Antarctic freshwater inputs impact ventilation of deep waters, large-scale ocean circulation and other global climate dynamics.



This project combines proxy and modelling components to impart a truly multi-disciplinary approach.

Proxy component: The project will develop the scope of the silica-based oxygen isotope (δ18O(diatom)) proxy for Antarctic glacial discharge (Pike et al., 2013) by targeting last interglacial and recent sediments from the iceberg alley in the deep Southern Ocean. δ18O(diatom) and other proxies (eg. ice-rafted debris, diatom assemblage composition) will be employed to resolve intervals of Antarctic ice sheet discharge during the LIG and past millennium.

Modelling component: There are multiple benefits that arise from including water tracers in climate models, including (1) the ability to assess relationships between isotopic concentrations and ocean-climate variables, ensuing the most accurate interpretation of stable water isotopic measurement from sediment cores to provide important long-term records of past changes, and (2) representation of water tracers and isotopes within UKESM2 (UK Earth System Model) allows us to gain a better understanding of crucial hydrological processes within the model and better predict how the earth system will respond to Antarctic meltwater events under future climate change. For this project, we will use this facility to track water originating from the Weddell Sea, and how this may imprint on δ18O(diatom).

The results of this project will provide timely evidence of Antarctica’s role in sea level rise and climate change with relevance for a broad range of research themes such as SCAR’s (Scientific Committee on Antarctic Research) INSTANT Scientific Research Programme and the PAGES (Past Global Changes) CLIVASH2k, QUIGS and PALSEA working groups.


British Antarctic Survey

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the British Antarctic Survey.

Specific training will include a broad range of sedimentological, micropaleontological procedures and techniques (including sediment description, classification, sampling, archiving, Southern Ocean diatom taxonomy, diatom oxygen isotope cleaning, preparation and analysis) to produce the relevant proxy records on the selected marine sediment cores. The student will access the National Environmental Isotope Facility for diatom silica stable isotope analyses and will collaborate in the preparation of an application for analytical funding to the NEIFSC. The student will also learn the necessary skills to experiment with relevant model simulations. All relevant training and facilities are available within the network of collaborating researchers and their institutions. The student will benefit from inclusion in both the PICC (Palaeo-Environments, Icesheets and Climate Change) and IDP (Ice Dynamics and Paleoclimate) research teams at the British Antarctic Survey. The student will be encouraged to engage in science meetings, attend science talks and get involved in the BAS student network.


Eligibility & Funding Details: 

Please see for details.


Background Reading: 

> Swann, G.E.A., Pike, J., Snelling, A.M., Leng, M.J., Williams, M.C. (2013) Seasonally resolved diatom δ18O records from the West Antarctic Peninsula over the last deglaciation. Earth and Planetary Science Letters. 364: 12-23.

> Holloway, M.D. , Sime, L.C. , Singarayer, J.S., Tindall, J.C., Valdes, P.J. (2016) Reconstructing paleosalinity from δ18O: Coupled model simulations of the Last Glacial Maximum, Last Interglacial and Late Holocene. Quaternary Science Reviews, 131. 350-364. doi:10.1016/j.quascirev.2015.07.007

> Chadwick, M., Sime, L.C., Allen, C.S., Guarino, V-M., Oliver, K. (Submitted) Model-data comparison of Antarctic winter sea-ice extent and Southern Ocean sea-surface temperatures during Marine Isotope Stage 5e. Earth and Planetary Science Letters.