Deglacial changes in dust flux in the eastern equatorial Pacific

McGee, David; Marcantonio, Franco; Lynch‐Stieglitz, Jean

doi:10.1016/j.epsl.2007.02.033

Cited by 87 publications

(87 citation statements)

References 71 publications

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“…Another maximum also occurs between 20 and 15 ka, during the late glacial/early deglaciation. The higher flux of eolian dust inferred from the C 26 -alcohol record during the last glacial period is consistent with recent studies of dust deposition measuring 232 Th fluxes in marine cores from the central and eastern equatorial Pacific (27)(28)(29) (Fig. 1).…”

Section: Resultssupporting

confidence: 77%

Eastern Equatorial Pacific productivity and related-CO ₂ changes since the last glacial period

Calvo

Pelejero

Pena

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Understanding oceanic processes, both physical and biological, that control atmospheric CO 2 is vital for predicting their influence during the past and into the future. The Eastern Equatorial Pacific (EEP) is thought to have exerted a strong control over glacial/interglacial CO 2 variations through its link to circulation and nutrientrelated changes in the Southern Ocean, the primary region of the world oceans where CO 2 -enriched deep water is upwelled to the surface ocean and comes into contact with the atmosphere. Here we present a multiproxy record of surface ocean productivity, dust inputs, and thermocline conditions for the EEP over the last 40,000 y. This allows us to detect changes in phytoplankton productivity and composition associated with increases in equatorial upwelling intensity and influence of Si-rich waters of subAntarctic origin. Our evidence indicates that diatoms outcompeted coccolithophores at times when the influence of Si-rich Southern Ocean intermediate waters was greatest. This shift from calcareous to noncalcareous phytoplankton would cause a lowering in atmospheric CO 2 through a reduced carbonate pump, as hypothesized by the Silicic Acid Leakage Hypothesis. However, this change does not seem to have been crucial in controlling atmospheric CO 2 , as it took place during the deglaciation, when atmospheric CO 2 concentrations had already started to rise. Instead, the concomitant intensification of Antarctic upwelling brought large quantities of deep CO 2 -rich waters to the ocean surface. This process very likely dominated any biologically mediated CO 2 sequestration and probably accounts for most of the deglacial rise in atmospheric CO 2 .marine productivity | molecular biomarkers | paleoceanography

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Section: Resultssupporting

confidence: 77%

Eastern Equatorial Pacific productivity and related-CO ₂ changes since the last glacial period

Calvo

Pelejero

Pena

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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“…(1b)). Dust sources have 232 Th concentrations in a narrow range of the average for the upper continental crust (McGee et al, 2007). A recent study determined an end-member concentration for Th in East Asian aerosol dust of 14.6 ± 0.2 ppm (Serno et al, submitted for publication), making it simple to apply a [Th] litho with confidence for estimating dust fluxes (Eq.…”

Section: Tablementioning

confidence: 99%

Quantifying lithogenic inputs to the North Pacific Ocean using the long-lived thorium isotopes

Hayes

Anderson

Fleisher

et al. 2013

Earth and Planetary Science Letters

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Dissolved 232 Th is added to the ocean though the partial dissolution of lithogenic materials such as aerosol dust in the same way as other lithogenically sourced and more biologically important trace metals such as Fe. Oceanic 230 Th, on the other hand, is sourced primarily from the highly predictable decay of dissolved 234 U. The rate at which dissolved 232 Th is released by mineral dissolution can be constrained by a Th removal rate derived from 230 Th: 234 U disequilibria, assuming steady-state. Calculated fluxes of dissolved 232 Th can in turn be used to estimate fluxes of other lithogenically sourced dissolved metals as well as the original lithogenic supplies, such as aerosol dust deposition, given the concentration and fractional solubility of Th (or other metals) in the lithogenic material. This method is applied to 7 water column profiles from the Innovative North Pacific Experiment (INOPEX) cruise of 2009 and 2 sites from the subtropical North Pacific. The structure of shallow depth profiles suggests rapid scavenging at the surface and at least partial regeneration of dissolved 232 Th at 100-200 m depth. This rapid cycling could involve colloidal Th generated during mineral dissolution, which may not be subject to the same removal rates as the more truly dissolved 230 Th. An additional deep source of 232 Th was revealed in deep waters, most likely dissolution of seafloor sediments, and offers a constraint on dissolved trace element supply due to boundary exchange.

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“…Dust has, for example, been demonstrated to be a driver of ocean productivity through additions of principally Fe and Si (though other elements are also important) in settings, such as the Southern Ocean, that are otherwise very depleted in these elements (Boyd et al, 2004;Duce and Tindale, 1991;Martin et al, 1994). The role of dust in sedimentary systems is apparent in oceanic settings remote from continents where significant dust mantles the ocean floor (Hesse, 1994;McGee et al, 2007;Rea, 1994). Copious dust transport and deposition marked the glacial cycles of the Quaternary Period, resulting in accumulation of loess downwind of cold climate regions, most notably in China where loess deposits of up to 100 m date from this time, but also in Eurasia, North America, Northern Europe, southern South America and New Zealand (Maher et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Trace elements and metal pollution in aerosols at an alpine site, New Zealand: Sources, concentrations and implications

Marx

Lavin

Hageman

et al. 2014

Atmospheric Environment

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Atmospheric aerosol samples were collected at a remote site in New Zealand's Southern Alps. Collected samples were found to be a mixture of New Zealand and Australian sourced sediment, using their trace element signatures. Aerosol concentrations and the relative contribution of different sources was found to be a function of specific air-mass trajectories influencing the study site, dust entrainment rates in source areas and rainfall. Results show that Australian dust is a major source of particulate matter in New Zealand, particularly in remote alpine locations; however, locally derived dust is also important. Metal pollutants, including Pb, Cu and Sn, were enriched in the samples by approximately 15 times and up to >100 times expected natural concentrations, confirming that metal pollution is a ubiquitous component of the atmosphere, even in relatively remote locations. Moreover, pollutants were highly enriched in otherwise clean air, i.e. during and following rainfall. Additionally, high concentrations of elements naturally enriched in sea water, e.g. Sr, Ba and Rb, were deposited alongside mineral dust, reflecting the oceanic origin of air influencing the site and the role of sea spray in contributing aerosol to the atmosphere. These elements experienced the greatest enrichment during rainfall, implying sea spray and pollution become relatively important during otherwise clean air conditions. AbstractAtmospheric aerosol samples were collected at a remote site in New Zealand's Southern Alps. Collected samples were found to be a mixture of New Zealand and Australian sourced sediment, using their trace element signatures. Aerosol concentrations and the relative contribution of different sources was found to be a function of specific air-mass trajectories influencing the study site, dust entrainment rates in source areas and rainfall.Results show that Australian dust is a major source of particulate matter in New Zealand, particularly in remote alpine locations; however, locally derived dust is also important. Metal pollutants, including Pb, Cu and Sn, were enriched in the samples by approximately 15 times and up to >100 times expected natural concentrations, confirming that metal pollution is a ubiquitous component of the atmosphere, even in relatively remote locations. Moreover, pollutants were highly enriched in otherwise clean air, i.e. during and following rainfall.Additionally, high concentrations of elements naturally enriched in sea water, e.g. Sr, Ba and Rb, were deposited alongside mineral dust, reflecting the oceanic origin of air influencing the site and the role of sea spray in contributing aerosol to the atmosphere. These elements experienced the greatest enrichment during rainfall, implying sea spray and pollution become relatively important during otherwise clean air conditions.2

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Deglacial changes in dust flux in the eastern equatorial Pacific

Cited by 87 publications

References 71 publications

Eastern Equatorial Pacific productivity and related-CO ₂ changes since the last glacial period

Eastern Equatorial Pacific productivity and related-CO ₂ changes since the last glacial period

Quantifying lithogenic inputs to the North Pacific Ocean using the long-lived thorium isotopes

Trace elements and metal pollution in aerosols at an alpine site, New Zealand: Sources, concentrations and implications

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Deglacial changes in dust flux in the eastern equatorial Pacific

Cited by 87 publications

References 71 publications

Eastern Equatorial Pacific productivity and related-CO 2 changes since the last glacial period

Eastern Equatorial Pacific productivity and related-CO 2 changes since the last glacial period

Quantifying lithogenic inputs to the North Pacific Ocean using the long-lived thorium isotopes

Trace elements and metal pollution in aerosols at an alpine site, New Zealand: Sources, concentrations and implications

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Product

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Eastern Equatorial Pacific productivity and related-CO ₂ changes since the last glacial period

Eastern Equatorial Pacific productivity and related-CO ₂ changes since the last glacial period