Elsevier

Earth and Planetary Science Letters

Volume 387, 1 February 2014, Pages 252-263
Earth and Planetary Science Letters

Eolian dust input to the Subarctic North Pacific

https://doi.org/10.1016/j.epsl.2013.11.008Get rights and content

Highlights

  • Spatial survey of dust tracers 4Heterr, 232Th and REE in the Subarctic North Pacific.

  • Sedimentary lithogenic components are deconvolved with dust and volcanic endmembers.

  • High dust fluxes in the southwest SNP and constant lower fluxes elsewhere are found.

  • Sedimentary and dissolved Th-based dust fluxes from seawater show good consistency.

  • A constant eolian dust grain size mode at 4 μm over the entire SNP is observed.

Abstract

Eolian dust is a significant source of iron and other nutrients that are essential for the health of marine ecosystems and potentially a controlling factor of the high nutrient-low chlorophyll status of the Subarctic North Pacific. We map the spatial distribution of dust input using three different geochemical tracers of eolian dust, 4He, 232Th and rare earth elements, in combination with grain size distribution data, from a set of core-top sediments covering the entire Subarctic North Pacific. Using the suite of geochemical proxies to fingerprint different lithogenic components, we deconvolve eolian dust input from other lithogenic inputs such as volcanic ash, ice-rafted debris, riverine and hemipelagic input. While the open ocean sites far away from the volcanic arcs are dominantly composed of pure eolian dust, lithogenic components other than eolian dust play a more crucial role along the arcs. In sites dominated by dust, eolian dust input appears to be characterized by a nearly uniform grain size mode at ∼4 μm.

Applying the 230Th-normalization technique, our proxies yield a consistent pattern of uniform dust fluxes of 1–2 g/m2/yr across the Subarctic North Pacific. Elevated eolian dust fluxes of 2–4 g/m2/yr characterize the westernmost region off Japan and the southern Kurile Islands south of 45° N and west of 165° E along the main pathway of the westerly winds. The core-top based dust flux reconstruction is consistent with recent estimates based on dissolved thorium isotope concentrations in seawater from the Subarctic North Pacific. The dust flux pattern compares well with state-of-the-art dust model predictions in the western and central Subarctic North Pacific, but we find that dust fluxes are higher than modeled fluxes by 0.5–1 g/m2/yr in the northwest, northeast and eastern Subarctic North Pacific. Our results provide an important benchmark for biogeochemical models and a robust approach for downcore studies testing dust-induced iron fertilization of past changes in biological productivity in the Subarctic North Pacific.

Introduction

Eolian dust is a major driver in the global climate system through its influence on light scattering and absorption (Harrison et al., 2001, Tegen and Fung, 1994), cloud and precipitation properties (Kaufman et al., 2002, Levin et al., 1996), and the oceanic biogeochemical cycles of carbon and nutrients as a result of delivering micronutrients like iron (Duce and Tindale, 1991, Jickells et al., 2005, Martin, 1990).

The Subarctic North Pacific (SNP) is one of the three principal High Nutrient-Low Chlorophyll (HNLC) regions of the world ocean, together with the equatorial Pacific and Southern Ocean. These regions are characterized by an excess pool of macronutrients delivered to the euphotic zone by mixing that is incompletely consumed during the annual biogeochemical cycle (Falkowski et al., 1998). The incomplete consumption has been explained by a lack of dissolved iron for which eolian dust is suggested to be the primary source in the SNP (e.g., Bishop et al., 2002, Duce and Tindale, 1991, Martin and Fitzwater, 1988, Martin et al., 1989, Rea, 1994). To test this hypothesis under modern conditions and in the past, we need reliable high-resolution dust records that are presently not available. The recent DIRTMAP3 compilation (Maher and Kohfeld, 2009, and references therein) with the addition of data based on surface water concentrations of dissolved aluminum (Measures et al., 2005) and 230Th-normalized 232Th fluxes (Kohfeld and Chase, 2011) show considerable variability in the Holocene spatial pattern of dust input to the SNP, varying between 0.1 and 21.4 g/m2/yr without a clear geographical pattern. Therefore, most studies rely on dust model predictions. Model reconstructions are challenged by the complexity of the topography and local climatic settings of the East Asian dust source regions which can result in over- or under-representations of important sources like the Taklimakan desert (Luo et al., 2003, Tanaka and Chiba, 2006, Yumimoto et al., 2009). Since arid regions in East Asia are proposed to be the dominant dust sources to the SNP (e.g., Duce et al., 1980, Husar et al., 2001, Sun et al., 2001, Tanaka and Chiba, 2006, Uno et al., 2011), with potential minor contributions from North Africa, Middle East and Central Asia (Creamean et al., 2013, Hsu et al., 2012, Tanaka and Chiba, 2006), their complexity can result in uncertainties of model predictions for the SNP.

In this study, we present results from an extensive set of multicorer core-top sediments covering the SNP. In combination with biogenic component and grain size distribution data as well as 230Th-normalized mass accumulation rates (MARs), we reconstruct spatial dust flux patterns from three unique and independent geochemical tracers of dust: 4He, 232Th and rare earth elements (REEs). We use geochemical data from dominant East Asian dust sources for long-range atmospheric transport (Ferrat et al., 2011, McGee, 2009) and from volcanic ash layers from ODP sites in the SNP (Cao et al., 1995a, Cao et al., 1995b) as lithogenic endmembers to determine the sedimentary dust component. We compare the proxy results with each other to verify their potential as dust flux proxies and compare our results to model estimates and published observational data.

Section snippets

Study area and material

Samples from the top one cm were used from 37 multicorer sediment cores recovered during the SO202-INOPEX cruise in 2009 (Fig. 1; Table 1; Gersonde, 2012). The Kamchatka Transect in the northwest SNP consists of stations 1–9, the Alaska Transect in the northeast SNP of stations 23–31 and the Southern Transect of stations 32–45 (Fig. 1). Sediment lithology varies over the cruise track from clay-bearing diatomaceous muds at stations 10–12 in the southern Bering Sea to foraminiferal sands at

Results

All INOPEX core-top data and dust source data are available in Supplementary Datasets 1 and 2 and through PANGAEA (doi.pangaea.de/10.1594/PANGAEA.823124).

Discussion

Determining the eolian dust component in near-land regions of the SNP is a geochemical challenge because a significant fraction of the lithogenic input may originate from other sources. A major source is volcanic ash from the surrounding Kurile, Aleutian, Kamchatka, Alaska and Japan volcanic arcs (Bailey, 1993, Jones et al., 1994, Jones et al., 2000, Maeda et al., 2007, Nakai et al., 1993, Olivarez et al., 1991, Otosaka et al., 2004, Shigemitsu et al., 2007, Weber et al., 1996). Also

Summary and conclusions

This study presents a core-top spatial survey of lithogenic input to the Subarctic North Pacific. We find contributions of eolian dust, IRD, volcanic ash, hemipelagic and riverine material to the lithogenic fraction of the sediments, requiring deconvolution of the different contributions to estimate the eolian dust flux. Grain size distributions and grain size data modeling indicate the presence of a component with an uniform fine grain size mode at ∼4 μm over the entire SNP; however, grain

Acknowledgments

We would like to thank Roseanne Schwartz, Marty Fleisher, Louise Bolge, Linda Baker, Pat Malone and Nichole Anest for laboratory support at LDEO. We are thankful to Youbin Sun and Ryuji Tada for providing dust source samples. The paper was improved by constructive comments by Ryuji Tada, Lucia Korff, 2 anonymous reviewers and the editor, Gideon Henderson.

This work was supported by U.S. National Science Foundation grant OCE1060907 to G.W. and R.F.A. INOPEX samples were obtained during the

References (79)

  • M. Méheust et al.

    Variability in modern sea surface temperature, sea ice and terrigenous input in the sub-polar North Pacific and Bering Sea: Reconstruction from biomarker data

    Org. Geochem.

    (2013)
  • T. Moreno et al.

    Geochemical variations in aeolian mineral particles from the Sahara–Sahel dust corridor

    Chemosphere

    (2006)
  • K. Nagashima et al.

    Orbital- and millennial-scale variations in Asian dust transport path to the Japan Sea

    Palaeogeogr. Palaeoclimatol. Palaeoecol.

    (2007)
  • K. Nagashima et al.

    Millennial-scale oscillations of the westerly jet path during the last glacial period

    J. Asian Earth Sci.

    (2011)
  • S. Nakai et al.

    Provenance of dust in the Pacific Ocean

    Earth Planet. Sci. Lett.

    (1993)
  • A.M. Olivarez et al.

    Geochemistry of eolian dust in Pacific pelagic sediments: Implications for paleoclimatic interpretations

    Geochim. Cosmochim. Acta

    (1991)
  • D.B. Patterson et al.

    4He as a tracer of continental dust: A 1.9 million year record of aeolian flux to the west equatorial Pacific Ocean

    Geochim. Cosmochim. Acta

    (1999)
  • D.K. Rea et al.

    Asian aridity and the zonal westerlies: Late Pleistocene and Holocene record of eolian deposition in the northwest Pacific Ocean

    Palaeogeogr. Palaeoclimatol. Palaeoecol.

    (1988)
  • M. Shigemitsu et al.

    Ba, Si, U, Al, Sc, La, Th, C and 13C/12C in a sediment core in the western subarctic Pacific as proxies of past biological production

    Mar. Chem.

    (2007)
  • T.Y. Tanaka et al.

    A numerical study of the contributions of dust source regions to the global dust budget

    Glob. Planet. Change

    (2006)
  • T. van de Flierdt et al.

    Lead isotopes in North Pacific deep water – implications for past changes in input sources and circulation patterns

    Earth Planet. Sci. Lett.

    (2003)
  • S. VanLaningham et al.

    Glacial–interglacial sediment transport to the Meiji Drift, northwest Pacific Ocean: Evidence for timing of Beringian outwashing

    Earth Planet. Sci. Lett.

    (2009)
  • E.T. Weber et al.

    Causes and implications of the middle rare earth element depletion in the eolian component of North Pacific sediment

    Geochim. Cosmochim. Acta

    (1998)
  • C. Zdanowicz et al.

    Asian dustfall in the St. Elias Mountains, Yukon, Canada

    Geochim. Cosmochim. Acta

    (2006)
  • J.C. Bailey

    Geochemical history of sediments in the northwestern Pacific Ocean

    Geochem. J.

    (1993)
  • P.E. Biscaye et al.

    Asian provenance of glacial dust (stage 2) in the Greenland Ice Sheet Project 2 Ice Core, Summit, Greenland

    J. Geophys. Res., Oceans

    (1997)
  • J.K.B. Bishop et al.

    Robotic observations of dust storm enhancement of carbon biomass in the North Pacific

    Science

    (2002)
  • P.W. Boyd et al.

    Atmospheric iron supply and enhanced vertical carbon flux in the NE subarctic Pacific: Is there a connection?

    Glob. Biogeochem. Cycles

    (1998)
  • L.Q. Cao et al.

    Geochemistry and petrology of volcanic ashes recovered from Sites 881 through 884: A temporal record of Kamchatka and Kurile volcanism

  • L.Q. Cao et al.

    Geochemistry of volcanic ashes recovered from Hole 887A

  • N.R. Catubig et al.

    Global deep-sea burial rate of calcium carbonate during the last glacial maximum

    Paleoceanography

    (1998)
  • J.M. Creamean et al.

    Dust and biological aerosols from the Sahara and Asian influence precipitation in the Western U.S

    Science

    (2013)
  • J. Crusius et al.

    Glacial flour dust storms in the Gulf of Alaska: Hydrologic and meteorological controls and their importance as a source of bioavailable iron

    Geophys. Res. Lett.

    (2011)
  • R.A. Duce et al.

    Atmospheric transport of iron and its deposition in the ocean

    Limnol. Oceanogr.

    (1991)
  • R.A. Duce et al.

    Long-range atmospheric transport of soil dust from Asia to the Tropical North Pacific: temporal variability

    Science

    (1980)
  • P.G. Falkowski et al.

    Biogeochemical controls and feedbacks on ocean primary production

    Science

    (1998)
  • H. Gebhardt et al.

    Paleonutrient and productivity records from the subarctic North Pacific for Pleistocene glacial terminations I to V

    Paleoceanography

    (2008)
  • R. Gersonde

    The expedition of the research vessel “Sonne” to the subpolar North Pacific and the Bering Sea in 2009 (SO202-INOPEX)

    Rep. Polar Mar Res.

    (2012)
  • P. Ginoux et al.

    Sources and distributions of dust aerosols simulated with the GOCART model

    J. Geophys. Res., Atmos.

    (2001)
  • Cited by (66)

    View all citing articles on Scopus
    View full text