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

Patterson, Desmond B; Farley, Kenneth A.; Norman, Marc D.

doi:10.1016/s0016-7037(99)00077-0

Cited by 60 publications

(72 citation statements)

References 29 publications

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“…For the Red Sea dataset, Helium-4 ( 4 He) measurements were carried out on annual growth bands of a Porites lutea coral collected in the northern Red Sea from the Ras Mohammad National park at the southern tip of Sinai Peninsula (27 • 43 N, 34 • 07 E). Previous studies have established 4 He to be an effective proxy for mineral dust in deep-sea sediments and corals (Mukhopadhyay and Kreycik, 2008;Patterson et al, 1999;Winckler et al, 2005). …”

Section: Paleodata Descriptionmentioning

confidence: 99%

Observed 20th century desert dust variability: impact on climate and biogeochemistry

et al. 2010

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Abstract. Desert dust perturbs climate by directly and indirectly interacting with incoming solar and outgoing long wave radiation, thereby changing precipitation and temperature, in addition to modifying ocean and land biogeochemistry. While we know that desert dust is sensitive to perturbations in climate and human land use, previous studies have been unable to determine whether humans were increasing or decreasing desert dust in the global average. Here we present observational estimates of desert dust based on paleodata proxies showing a doubling of desert dust during the 20th century over much, but not all the globe. Large uncertainties remain in estimates of desert dust variability over 20th century due to limited data. Using these observational estimates of desert dust change in combination with ocean, atmosphere and land models, we calculate the net radiative effect of these observed changes (top of atmosphere) over the 20th century to be −0.14 ± 0.11 W/m 2 (1990-1999 vs. 1905-1914). The estimated radiative changeCorrespondence to: N. M. Mahowald (mahowald@cornell.edu) due to dust is especially strong between the heavily loaded 1980-1989 and the less heavily loaded 1955-1964 time periods (−0.57 ± 0.46 W/m 2 ), which model simulations suggest may have reduced the rate of temperature increase between these time periods by 0.11 • C. Model simulations also indicate strong regional shifts in precipitation and temperature from desert dust changes, causing 6 ppm (12 PgC) reduction in model carbon uptake by the terrestrial biosphere over the 20th century. Desert dust carries iron, an important micronutrient for ocean biogeochemistry that can modulate ocean carbon storage; here we show that dust deposition trends increase ocean productivity by an estimated 6% over the 20th century, drawing down an additional 4 ppm (8 PgC) of carbon dioxide into the oceans. Thus, perturbations to desert dust over the 20th century inferred from observations are potentially important for climate and biogeochemistry, and our understanding of these changes and their impacts should continue to be refined.

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Section: Paleodata Descriptionmentioning

confidence: 99%

Observed 20th century desert dust variability: impact on climate and biogeochemistry

et al. 2010

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“…Volcanic ashes from subduction-related volcanic arcs are known to be effectively helium-free in comparison to continental dust (Patterson et al, 1999; Supplementary Information, Section 2.3). We therefore determined the 232 Th concentration in the volcanic endmember ( 232 Th volcanic EM ) to be 2.3 ppm based on the y-intercept of the regression line of the INOPEX samples (Fig.…”

Section: He Terr and 232 Th Approachesmentioning

confidence: 99%

“…Since East Asian dust is the only source of 4 He to the marine sediments (Patterson et al, 1999;Winckler et al, 2005Winckler et al, , 2008 …”

Section: He Terr and 232 Th Approachesmentioning

confidence: 99%

Eolian dust input to the Subarctic North Pacific

Serno

Winckler

Anderson

et al. 2014

Earth and Planetary Science Letters

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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, 4 He, 232 Th 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 230 Th-normalization technique, our proxies yield a consistent pattern of uniform dust fluxes of 1-2 g/m 2 /yr across the Subarctic North Pacific. Elevated eolian dust fluxes of 2-4 g/m 2 /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/m 2 /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.

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“…By analyzing biotic proxies like the foraminifer assemblages at ODP Site 807, Zhang et al [50] found that the increase of surface productivity in the central WPWP was not related to other ways of the nutrients supply, and then deduced the effect of the influx of Asian dust. Furthermore, Patterson et al [51] and Winckler et al [52] reconstructed the history of aeolian dust input deposition at ODP Site 806 using the flux of 4 He and 232 Th, respectively. The results suggested that the Asian dust is an important source for sediments on the Ontong Java Plateau and the dust input responds to the climate change in glacial cycles.…”

Section: Provenance Of Clay Mineralsmentioning

confidence: 99%

Late quaternary glacial cycle and precessional period of clay mineral assemblages in the western pacific warm pool

Liu

Zhou

2012

Chin. Sci. Bull.

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Variability of clay mineral assemblages in the Western Pacific Warm Pool (WPWP) over the past 370 ka shows the prominent glacial-interglacial cyclicity. Smectite (62%-91%) is the dominant clay mineral, with decreased contents during interglacials while increased in glacials. In contrast, variations in chlorite (4%-21%), illite (4%-12%), and kaolinite (2%-10%) share a similar pattern with higher contents during interglacials than glacials, mirroring to that of smectite. The results indicate that the smectite-dominated clay minerals derive mainly from the river detrital inputs of New Guinea. The glacial-interglacial cycle of clay mineral assemblages well correspond to the fluctuation of sea level. When the sea level was low, the river materials can travel more easily across the narrow shelf off the island of New Guinea, inject directly into the subsurface currents flowing westwards, then merge into the Equatorial Undercurrent (EUC), and eventually deposit on the central part of WPWP. Precessional periods of the smectite content indicate the intensity of mechanical erosion in its provenance of New Guinea, responding to the river runoff and precipitation, and this could also be linked to the meridional migration of the Intertropical Convergence Zone (ITCZ).

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

Cited by 60 publications

References 29 publications

Observed 20th century desert dust variability: impact on climate and biogeochemistry

Observed 20th century desert dust variability: impact on climate and biogeochemistry

Eolian dust input to the Subarctic North Pacific

Late quaternary glacial cycle and precessional period of clay mineral assemblages in the western pacific warm pool

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