A Holocene peat record in the central South Atlantic: an archive of precipitation changes

Peat deposits from the littoral part of the wetland 2nd Pond on Nightingale Island in the central South Atlantic have been analysed to investigate the Holocene climate development on the island and to test a hypothesis about regionally persistent humidity variations. A variety of proxies were analysed - total carbon and nitrogen, biogenic silica, diatoms, amount of organic matter, macrofossils and magnetic susceptibility - and together with the lithology they are interpreted as a record reflecting changes in humidity/precipitation. Early Holocene (10,000-8500 cal. BP) was possibly significantly drier than today, probably caused by a southerly displacement of the Southern Hemisphere Westerlies (SHW) during the Antarctic climate optimum. From 8500 cal. BP and onwards, the climate became generally more humid and surface run-off increased due to higher precipitation, possibly as an effect of increased influence from the SHW as it moved north. During this generally humid period, our data disclose a distinct pattern of recurrent centennial- to millennial-long events of increased precipitation and the results corroborate the only other study in the region with a similar humidity record. The events might represent large-scale climate oscillations in the Southern Hemisphere, such as latitudinal shifts of the SHW, but may also be related to changes in sea surface temperatures.