Late Quaternary changes in the Westerly Winds over the Southern Ocean

Fieldwork, Isla Hermite, Cape Horn 56°S, February-March 2015

In this NERC-funded project, we are generating Southern Hemisphere Westerlies (SHW) proxy records from each of the three major sectors of the Southern Ocean, focusing on subantarctic islands situated in the core belt of the SHW.

We are applying a novel diatom proxy for past wind strength independently controlled by a range of standard sedimentological and biogeochemical proxies. The new proxy is based on the direct transfer of sea spray across the islands by wind, and its effect on the salinity of west coast lakes and ponds. This works on sub-Antarctic islands where there is a marked west-east conductivity gradient in water bodies across the island. This conductivity gradient determines which diatom communities are present in the lakes and can be used to reconstruct changes in conductivity through time, and hence past relative wind strength.

We have demonstrated that this approach works at Macquarie Island, Marion Island, Campbell Island and in the Cape Horn archipelago.

In 2016-2017, on the Antarctic Circumpolar Expedition (ACE), we will visit Marion, Crozet, Kerguelen, Heard, Macquarie, Diego Ramirez and South Georgia Islands to recover more peat and lake sediment records from the core belt of the SHW. Find our project here.

Circumantarctic map showing the location of the key SHW project lake sites in blue, superimposed on the core SHW belt in the Southern Ocean. Open blue circles show the additional palaeoclimate records we have retrieved from the subantarctic region.

Lake sediment core from Isla Hermite, Cape Horn, 56°S.

Lake sediment and peat cores provide us with an archive of how an environment has changed over time. Within these sediments, we look at geochemical and sedimentological proxies (e.g. ITRAX, SPECIM, C and N isotopes) and biological records (e.g. diatoms, testate amoebae, pollen) of past climate conditions. These enable us to reconstruct changing lake salinity and westerly wind strength back in time, over millennia. These data will be incorporated into GCM models to develop a better mechanistic understanding of the drivers of SHW evolution.

A stratigraphy from KK2, on Marion Island, 46°S, showing the main transitions in diatom species over the last 850 years, diatom-inferred conductivity, and the changes in geochemical parameters.

Project collaborators

Dr. Krystyna Saunders, Australian Nuclear Science and Technology Organisation (ANSTO) and the University of Bern

Dr. Wim Vyverman, Dr. Elie Verleyen, Dr. Wim van Nieuwenhuyze, Department of Biology, Ghent University

Dr. Dan Charman, Dr. Angela Galego-Sala, Dr. Matt Amesbury, Dr. Tom Roland, Department of Geography, Exeter University

Dr. Martin Grosjean, Oeschger Centre for Climate Change Research, University of Bern

Dr. François de Vleeschouwer, ECO lab, Toulouse

Dr. Zicheng Yu, Earth and Environmental Sciences, Lehigh University

Dr. Nathalie van der Putten, Dr. Svante Björck, Department of Geology, Lund University

1. Increases in winds weaken Southern Ocean carbon sink

   A new study of lake sediments from the sub-Antarctic reveals for the first time that increases in westerly winds are likely to reduce the ability of the Southern Ocean to […]

   Read more of: Increases in winds weaken Southern Ocean carbon sink

   

Publications

Hodgson , D. A., and Sime, L. C. 2010. Southern westerlies and CO₂. Nature Geoscience 3, 666-667, doi:10.1038/ngeo970

Saunders, K.M., et al. 2015 A diatom-conductivity transfer function for reconstructing past changes in the Southern Hemisphere westerly winds over the Southern Ocean. Journal of Quaternary Science 30, 464-477

Strother, S.L., et al. 2015. Changes in Holocene vegetation, climate and the intensity of Southern Hemisphere Westerly Winds based on a high-resolution palynological record from sub-Antarctic South Georgia. The Holocene 25, 263-279.

Saunders, K.M., et al. 2012. Late Holocene changes in precipitation in northwest Tasmania and their potential links to shifts in the Southern Hemisphere westerly winds. Global and Planetary Change 92-93, 82-91.