Late Quaternary changes in the Westerly Winds over the Southern Ocean

Late Quaternary changes in the Westerly Winds over the Southern Ocean

Start date
30 September, 2013
End date
31 March, 2017
Fieldwork, Isla Hermite, Cape Horn
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.

mapSHW
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.

 

 

core44
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.