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Volume 13, issue 10
Clim. Past, 13, 1301-1322, 2017
https://doi.org/10.5194/cp-13-1301-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Southern perspectives on climate and the environment from...

Clim. Past, 13, 1301-1322, 2017
https://doi.org/10.5194/cp-13-1301-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 04 Oct 2017

Research article | 04 Oct 2017

Late Holocene intensification of the westerly winds at the subantarctic Auckland Islands (51° S), New Zealand

Imogen M. Browne1,a, Christopher M. Moy1, Christina R. Riesselman1,2, Helen L. Neil3, Lorelei G. Curtin1,b, Andrew R. Gorman1, and Gary S. Wilson1,2,4 Imogen M. Browne et al.
  • 1Department of Geology, University of Otago, Dunedin 9016, New Zealand
  • 2Department of Marine Science, University of Otago, Dunedin 9016, New Zealand
  • 3National Institute of Water and Atmospheric Research (NIWA), Wellington 6021, New Zealand
  • 4New Zealand Antarctic Research Institute (NZARI), Christchurch 8053, New Zealand
  • acurrent address: College of Marine Science, University of South Florida, St. Petersburg, FL 33701, USA
  • bcurrent address: Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA

Abstract. The Southern Hemisphere westerly winds (SHWWs) play a major role in controlling wind-driven upwelling of Circumpolar Deep Water (CDW) and outgassing of CO2 in the Southern Ocean, on interannual to glacial–interglacial timescales. Despite their significance in the global carbon cycle, our understanding of millennial- and centennial-scale changes in the strength and latitudinal position of the westerlies during the Holocene (especially since 5000yrBP) is limited by a scarcity of palaeoclimate records from comparable latitudes. Here, we reconstruct middle to late Holocene SHWW variability using a fjord sediment core collected from the subantarctic Auckland Islands (51°S, 166°E), located in the modern centre of the westerly wind belt. Changes in drainage basin response to variability in the strength of the SHWW at this latitude are interpreted from downcore variations in magnetic susceptibility (MS) and bulk organic δ13C and atomic CN, which monitor influxes of lithogenous and terrestrial vs. marine organic matter, respectively. The fjord water column response to SHWW variability is evaluated using benthic foraminifer δ18O and δ13C, both of which are influenced by the isotopic composition of shelf water masses entering the fjord. Using these data, we provide marine and terrestrial-based evidence for increased wind strength from  ∼ 1600 to 900yrBP at subantarctic latitudes that is broadly consistent with previous studies of climate-driven vegetation change at the Auckland Islands. Comparison with a SHWW reconstruction using similar proxies from Fiordland suggests a northward migration of the SHWW over New Zealand during the first half of the last millennium. Comparison with palaeoclimate and palaeoceanographic records from southern South America and West Antarctica indicates a late Holocene strengthening of the SHWW after  ∼ 1600yrBP that appears to be broadly symmetrical across the Pacific Basin. Contemporaneous increases in SHWW at localities on either side of the Pacific in the late Holocene are likely controlled atmospheric teleconnections between the low and high latitudes, and by variability in the Southern Annular Mode and El Niño–Southern Oscillation.

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Short summary
The westerly winds determine weather patterns and exert an effect on carbon dioxide (CO2) flux in and out of the Southern Ocean, an important sink for atmospheric CO2. Our research reconstructs changes in the westerlies over the past 5000 years, using a marine sediment core record collected from the subantarctic Auckland Islands. Our results indicate an intensification of the westerlies around 1600 years ago, contemporaneous with other records from comparable latitudes across the Pacific Ocean.
The westerly winds determine weather patterns and exert an effect on carbon dioxide (CO2) flux...
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