Hydrothermal iron flux variability following rapid sea level changes

Middleton, Jennifer L.; Langmuir, C. H.; Mukhopadhyay, Sujoy; McManus, Jerry F; Mitrovica, J. X.

doi:10.1002/2016gl068408

Cited by 49 publications

(59 citation statements)

References 42 publications

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“…They showed that the peaks in these fluxes lag the two previous maxima in the rate of sea-level decrease by about 15 kyr. Middleton et al [49] found that sediments from 26 • N on the Mid-Atlantic Ridge document an increase in elemental fluxes (Fe, Cu) in hydrothermal systems concomitant with the most rapid sea-level decrease leading to the last glacial maximum. Relatively short lags between peaks in rate of sea-level change and peaks in melt flux are consistent with our models forced with the sea-level reconstruction of the Middle and Upper Pleistocene.…”

Section: Discussionmentioning

confidence: 99%

Consequences of glacial cycles for magmatism and carbon transport at mid-ocean ridges

Cerpa

Jones

Katz

2019

Earth and Planetary Science Letters

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Magmatism and volcanism transfer carbon from the solid Earth into the climate system. This transfer may be modulated by the glacial/interglacial cycling of water between oceans and continental ice sheets, which alters the surface loading of the solid Earth. The consequent volcaniccarbon fluctuations have been proposed as a pacing mechanism for Pleistocene glacial cycles. This mechanism is dependant on the amplitude and lag of the mid-ocean ridge response to sea-level changes. Here we develop and analyse a new model for that response, eliminating some questionable assumptions made in previous work. Our model calculates the carbon flux, accounting for the thermodynamic effect of mantle carbon: reduction of the solidus temperature and a deeper onset of melting. We analyse models forced by idealised, periodic sea level and conclude that fluctuations in melting rate are the prime control on magma and carbon flux. We also discuss a model forced by a reconstruction of eustatic sea level over the past 800 kyr. It indicates that peak-to-trough variations of magma and carbon flux are up to about 20% and 10% of the mean flux, respectively. Peaks in mid-ocean ridge emissions lag peaks in sea-level forcing by less than about 20 kyr and the lag could well be shorter. The amplitude and lag are sensitive to the rate of melt segregation. The lag is much shorter than the time it takes for melt to travel vertically across the melting region.

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Section: Discussionmentioning

confidence: 99%

Consequences of glacial cycles for magmatism and carbon transport at mid-ocean ridges

Cerpa

Jones

Katz

2019

Earth and Planetary Science Letters

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“…The seafloor bathymetry, primarily determined by oceanic crustal thickness, suggests a sensitivity of mid-ocean ridge volcanism to sea level changes on Milankovitch timescales (e.g., Crowley et al, 2015;Lund & Asimow, 2011;Schindlbeck et al, 2018;Tolstoy, 2015). A peak of hydrothermal activity~15 ka after the last glacial maximum on the Mid-Atlantic Ridge (Middletone et al, 2016), Juan de Fuca Ridge (Costa et al, 2017), and at the East Pacific Rise (Lund et al, 2016) has been interpreted as the delayed melt formation following the hydrostatic pressure minimum.…”

Section: Journal Of Geophysical Research: Solid Earthmentioning

confidence: 99%

Magmatic Forcing of Cenozoic Climate?

et al. 2020

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Established theories ascribe much of the observed long-term Cenozoic climate cooling to atmospheric carbon consumption by erosion and weathering of tectonically uplifted terrains, but climatic effects due to changes in magmatism and carbon degassing are also involved. At timescales comparable to those of Milankovitch cycles, late Cenozoic building/melting of continental ice sheets, erosion, and sea level changes can affect magmatism, which provides an opportunity to explore possible feedbacks between climate and volcanic changes. Existing data show that extinction of Neo-Tethyan volcanic arcs is largely synchronous with phases of atmospheric carbon reduction, suggesting waning degassing as a possible contribution to climate cooling throughout the early to middle Cenozoic. In addition, the increase in atmospheric CO 2 concentrations during the last deglaciation may be ascribed to enhanced volcanism and carbon emissions due to unloading of active magmatic provinces on continents. The deglacial rise in atmospheric CO 2 points to a mutual feedback between climate and volcanism mediated by the redistribution of surface masses and carbon emissions. This may explain the progression to higher amplitude and increasingly asymmetric cycles of late Cenozoic climate oscillations. Unifying theories relating tectonic, erosional, climatic, and magmatic changes across timescales via the carbon cycle offer an opportunity for future research into the coupling between surface and deep Earth processes. Plain Language Summary Among the most fascinating contemporary developments in theEarth Sciences is the idea that plate tectonics and climate changes are coupled through complex cycles. More than four decades of study have revealed tantalizing examples of relationships between processes near the Earth's surface and deeper within. Accounting for such a surface-deep Earth process coupling has improved our understanding of major climate and tectonic events for virtually all timescales. So far, however, the role of magmatism was overlooked. Magmatism exerts a strong influence on the amount of greenhouse gasses in the atmosphere because of volcanic outgassing. In turn, tectonic and climatic changes control the transfer of rocks, water, and ice masses at the Earth surface and within the Earth's interior, thereby affecting the production, transfer, and eruption of magmas. Unravelling the interactions between surface and deep Earth processes accounting for magmatism will help managing natural resources and mitigating natural hazards. Even more importantly, understanding how climate is naturally related to plate tectonics and magmatism will allow scientists to assess the anthropogenic perturbations to the Earth system and anticipate ongoing and future climate changes.

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“…Along with higher dust flux, 15 N∕ 14 N ratios from planktonic foraminifera in SO sediment cores have been interpreted as higher productivity and more efficient nutrient utilization in the LGM compared to the PI (Martínez-García et al, 2014). Meanwhile, Middleton et al (2016) and Lund et al (2016) proposed that hydrothermal flux may have been higher during the LGM due to lower water column pressure on hydrothermal vents. Numerous modeling efforts have studied effects of iron fertilization on the LGM carbon cycle.…”

Section: 1002/2016pa003077mentioning

confidence: 99%

Combined Effects of Atmospheric and Seafloor Iron Fluxes to the Glacial Ocean

et al. 2017

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Changes in the ocean iron cycle could help explain the low atmospheric CO2 during the Last Glacial Maximum (LGM). Previous modeling studies have mostly considered changes in aeolian iron fluxes, although it is known that sedimentary and hydrothermal fluxes are important iron sources for today's ocean. Here we explore effects of preindustrial‐to‐LGM changes in atmospheric dust, sedimentary, and hydrothermal fluxes on the ocean's iron and carbon cycles in a global coupled biogeochemical‐circulation model. Considering variable atmospheric iron solubility decreases LGM surface soluble iron fluxes compared with assuming constant solubility. This limits potential increases in productivity and export production due to surface iron fertilization, lowering atmospheric CO2 by only 4 ppm. The effect is countered by a decrease in sedimentary flux due to lower sea level, which increases CO2 by 15 ppm. Assuming a 10 times higher iron dust solubility in the Southern Ocean, combined with changes in sedimentary flux, we obtain an atmospheric CO2 reduction of 13 ppm. The high uncertainty in the iron fluxes does not allow us to determine the net direction and magnitude of variations in atmospheric CO2 due to changes in the iron cycle. Our model does not account for changes to iron‐binding ligand concentrations that could modify the results. We conclude that when evaluating glacial‐interglacial changes in the ocean iron cycle, not only surface but also seafloor fluxes must be taken into account.

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Hydrothermal iron flux variability following rapid sea level changes

Cited by 49 publications

References 42 publications

Consequences of glacial cycles for magmatism and carbon transport at mid-ocean ridges

Consequences of glacial cycles for magmatism and carbon transport at mid-ocean ridges

Magmatic Forcing of Cenozoic Climate?

Combined Effects of Atmospheric and Seafloor Iron Fluxes to the Glacial Ocean

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