Late Holocene intensification of the westerly winds at the

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TitleLate Holocene intensification of the westerly winds at the subantarctic Auckland Islands (51° S), New Zealand. AbstractThe 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 millennialand 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 C/N, 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 evidenceforincreasedwindstrengthfrom∼1600to900yrBP at subantarctic latitudes that is broadly consistent with previous studies of climate-driven vegetation change at the Auckland Islands. Comparison with a SHWW reconstruction us
ing similar proxies from Fiordland suggests a northward migrationoftheSHWWoverNewZealandduringtheﬁrsthalf 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 OscillationAcknowledgementsThe authors gratefully acknowledge support from a Royal Society of New Zealand Marsden Fast Start (#UOO1118) and New Zealand Antarctic Research Institute (NZARI 2014-7) funding to Christopher M. Moy. Seismic data were processed using an academic licence for GLOBE Claritas by BenRossandAndrewR.Gorman.NCEPReanalysisdataprovided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their website at http://www.esrl.noaa.gov/psd/. We would like to thank Bruce Hayward for help with identiﬁcation of benthic foraminifera, Thomas Max at NIWA for analysing foraminifer stable isotopes, and Robert Van Hale, Kim Currie, and Chris Aebig at the University of Otago for analysing the isotopic composition of water, particulates, and sediment. We thank Claudia Aracena and an anonymous reviewer for helpful comments on an earlier version of the manuscript. We also thank Patricio Moreno for providing pollen data from Lago Cipreses, and Rolf Kilian for providing MA-1 δ18O data. Special thanks to the crew and scientiﬁc party on Auckland Islands cruises 14PL001 and 15PL001, the Young Blake Expedition members, and Bob Dagg, whose coring expertise was fundamental to the achievement of this work.

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1st AuthorBrowne, I.M.AuthorBrowne, I.M.Moy, C.M. Riesselman, C.R.Neil, H.L.Curtin, L.G. Gorman, A.R. Wilson, G.SYear2017JournalClimate of the PastVolume13Number10Pages1301-1322DOI10.5194/cp-13-1301-2017

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TypeArticleCitationBrowne, I.M., Moy, C.M., Riesselman, C.R., Neil, H.L., Curtin, L.G., Gorman, A.R., and Wilson, G.S. (2017). Late Holocene intensification of the westerly winds at the subantarctic Auckland Islands (51° S), New Zealand. Climate of the Past, 13(10): 1301-1322 Subject fieldPaleo

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