RESEARCH ARTICLE Climatically Modulated Dust Inputs from New Zealand to 10.1029/2020PA003949 the Southwest Pacific Sector of the Southern Ocean Over Key Points: the Last 410 kyr • We present an SW Pacific Ocean lithogenic flux record for the last 410 Yi Wu1,2,3 , Andrew P. Roberts2 , Katharine M. Grant2, David Heslop2 , ka that covaries with the Antarctic Brad J. Pillans2, Xiang Zhao2 , Eelco J. Rohling2 , Thomas A. Ronge4 , and sub-Antarctic dust records 5 6 7 • Westerly wind-transported material Mingming Ma , Paul P. Hesse , and Alan S. Palmer from New Zealand is the most likely 1 dust source over glacial-interglacial Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Innovation Academy cycles of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences, Guangzhou, China, • Silt-sized sediment was well sorted 2Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia, 3Southern Marine by bottom currents, which were Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China, 4Alfred Wegener Institut more energetic in interglacials than 5 glacials Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany, School of Geographical Sciences, Fujian Normal University, Fuzhou, China, 6Department of Earth and Environmental Sciences, Macquarie University, Sydney, ACT, Australia, 7School of Agriculture and Environment, Massey University, Palmerston North, New Zealand Supporting Information: Supporting Information may be found in the online version of this article. Abstract Eolian mineral dust is an active agent in the global climate system. It affects planetary albedo and can influence marine biological productivity and ocean-atmosphere carbon dynamics. This Correspondence to: makes the understanding of the global dust cycle crucial for constraining the dust/climate relationship, Y. Wu, which requires long-term dust emission records for all major dust sources. Despite their importance, the [email protected] sources of atmospheric dust deposited in the Southern Ocean remain poorly constrained. Eolian dust in the Pacific sector of the Southern Ocean is generally assumed to originate from Australia, with minor Citation: contributions from New Zealand. Here, we present a high-resolution elemental record of terrestrial inputs Wu, Y., Roberts, A. P., Grant, K. M., Heslop, D., Pillans, B. J., Zhao, X., for the past 410 kyr from marine sediment core PS75/100-4 recovered from east of South Island, New et al. (2021). Climatically modulated Zealand. Sediment∼ grain size is slightly finer than that of loess deposits from South Island, New Zealand, dust inputs from New Zealand to and is coarser than that of marine sediments in the Tasman Sea to the west of New Zealand, which the Southwest Pacific sector of the Southern Ocean over the last 410 kyr. indicates that the dust originated mainly from New Zealand and not only from Australia. Core PS75/100- 2 2 Paleoceanography and Paleoclimatology, 4 records lithogenic mass accumulation rates ranging from 0.01 to 0.69 g/cm /kyr ( 0.20 g/cm /kyr 36, e2020PA003949. https://doi. average), with variations over a factor of 3–4 over glacial versus∼ interglacial timescales∼ for the past 410 org/10.1029/2020PA003949 kyr. Our geochemical data correlate well ∼with the Southern Ocean and Antarctic eolian dust records and Received 10 APR 2020 suggest a westerly wind-supplied dust signal from New Zealand. Our findings, therefore, suggest that New Accepted 2 MAR 2021 Zealand should be considered an important long-term regional dust source in global dust cycle models. 1. Introduction The global mineral dust cycle is a key part of the climate system (An et al., 1991; Guo et al., 2002; Hovan et al., 1989; Lambert et al., 2008; Lamy et al., 2014; Liu, 1985; Maher et al., 2010; Mahowald et al., 2006; Martínez-García et al., 2011; Prospero et al., 2002; Rea, 1994; Rea et al, 1985, 1998; Shao et al., 2011). Dust changes the radiative properties of the atmosphere by scattering and absorbing solar and terrestrial radi- ation, and influences climate both directly and through cloud-nucleation processes (Köhler et al., 2010; Lohmann & Feichter, 2005; Maher et al., 2010; Masson-Delmotte et al., 2010; Rohling et al., 2012). Dust deposition onto the ocean surface may also affect climate indirectly by supplying iron as a micronutri- ent to Fe-limited waters, thereby fertilizing phytoplankton productivity, which results in atmospheric CO2 drawdown (Jickells et al., 2005; Kohfeld & Harrison, 2001; Martin et al., 1991; Martínez-García et al., 2014; Moore et al., 2013; Shoenfelt et al., 2018, 2019; Tagliabue et al., 2017). Global dust fluxes were generally greater ( 2–5 times) during glacials than during interglacials throughout most regions and varied spatially (e.g., Kohfeld∼ & Harrison, 2001; Maher et al., 2010 and references therein). This makes it important to obtain atmospheric dust records for all of the world's major dust source regions over glacial-interglacial (G-IG) timescales to understand the role of the dust cycle in long-term climate © 2021. American Geophysical Union. forcing. Mid-latitude arid regions, such as the Sahara and Sahel, the Middle East, and the Asian interior All Rights Reserved. in the Northern Hemisphere, and the Namib Desert, Patagonia, and Australian deserts in the Southern WU ET AL. 1 of 19 Paleoceanography and Paleoclimatology 10.1029/2020PA003949 a Australia Hemisphere, are major eolian dust source areas. Based on model results b Chatham Rise using modern data (1979–2013), Neff and Bertler (2015) found that Pata- 45 OS gonian dust dominates the Atlantic and Indian sectors of the Southern BountyTrough Ocean and that New Zealand, like Australia, is a potentially significant dust source to the Pacific sector of the Southern Ocean (Figure S1). The PS75/59-2 PS75/76-2 60 OS largest dust emissions are often simulated from Australia and Pata- gonia (Albani et al., 2012; Ginoux et al., 2001; Li et al., 2008; Wagener et al., 2008). Joussaume (1993), and Li et al. (2008) argued that Australia is the largest Southern Hemisphere dust source, and geochemical data indicate that Australian dust has been deposited in Antarctica (De Deck- EDC 75 OS ker et al., 2010; Revel-Rolland et al., 2006; Vallelonga et al., 2002). Other authors have argued that Patagonia is the dominant Southern Hemi- sphere dust source (Delmonte et al., 2004; Grousset et al., 1992; McCon- 120EO 180EO 120WO nell et al., 2007). Furthermore, Patagonia possibly contributed more dust during glacial periods due to the expanded continental shelf around the b Falkland Plateau during glacial sea level lowstands (Basile et al., 1997; 35OS Hikurangi Lunt & Valdes, 2002; Walter et al., 2000). Channel North There is a lack of consensus between observations and model simula- E26.1 Island 40OS tions about the relative importance of these dust sources in terms of Tasman 1123 Sea CHAT 16K temporal and spatial dust production variations. This produces major South uncertainties and gaps in understanding of the response and role of dust Can (594) Island PS75/100-4 MD97-2120 45 OS in global climate change, particularly from Southern Hemisphere dust 1119 STF Ota sources, which limits modeling of the role of dust in climate change (Li l 1122 e et al., 2008). In a review of airborne dust, global climate, and ocean bio- n Bounty Channel n a geochemistry, Maher et al. (2010) concluded that much of the Southern h C O r 50 S Hemisphere is severely under-represented with respect to knowledge of e d n Campbell dust inputs for both terrestrial and marine settings and that Southern a l o Plateau S ACC Ocean data are sparse. We here present grain-size and high-resolution BC scanning X-ray fluorescence (XRF) records for a marine sediment core W +D C O AC 55 S from east of New Zealand to investigate potential dust inputs from New Zealand into the Southern Ocean over several G-IG cycles. 160OE 170EO 180OE 170WO Figure 1. Location maps for studied sediment core PS75/100-4 (red 2. Methods circle). (a) Black circles mark core sites discussed in the text: Southern Ocean Pacific Sector cores PS75/76-2 (55°31.71′S, 156°8.39′W; 3,742 m We studied piston core PS75/100-4 (Figure 1; 45°45.41′S, 177°8.93′E; water depth) and PS75/59-2 (54°12.90S, 125°25.53′W; 3,613 m water 2,498 m water depth; 14.77 m in length). This core was retrieved during depth); Antarctic EDC ice core (76°6′S, 123°21′E); (b) Deep Sea Drilling RV Polarstern cruise ANT-XXVI/2 in 2010 from the southern Chatham Project (DSDP) Site 594 (45°31.41′S, 174°56.88′E; 1,204 m water depth); core MD97-2120 (45°32.06′S, 174°55.85′E; 1,210 m water depth), as a Rise, east of South Island, New Zealand (Gersonde, 2011). reoccupation of DSDP Site 594; Ocean Drilling Program (ODP) Site 1119 (44°45.332′S, 172°23.598′E; 396 m water depth); ODP Site 1122 (46°34.781′S, 177°23.610′W; 4,432 m water depth), located on Bounty 2.1. XRF Scanning Count Fan (indicated by the gray zone); ODP Site 1123 (41°47.2′S, 171°29.9′W; 3,290 m water depth); core CHAT 16K (42°32.00′S, 178°29.92′E; 1,408 m Continuous U-channel samples (2 × 2 cm square cross-section and water depth); and Tasman Sea core E26.1 (28 cm in length; 40°17′S, length from 50 to 100 cm; Weeks et al. [1993]) were obtained from the 168°20′E; 910 m water depth). Black lines in (b) indicate locations of the archive halves of the core and were subjected to XRF core scanning using main submarine channels (Solander, Bounty, and Hikurangi Channels) through which sediment is transported around New Zealand.