Methane release from the southern Brazilian margin during the last glacial

Portilho-Ramos, Rodrigo Costa; Cruz, Anna Paula Soares; Barbosa, Cátia F; Rathburn, Anthony E.; Mulitza, Stefan; Venancio, Igor Martins; Schwenk, Tilmann; Rühlemann, Carsten; Vidal, Laurence; Chiessi, Cristiano Mazur; Silveira, Carla Semiramis

doi:10.1038/s41598-018-24420-0

Cited by 36 publications

(25 citation statements)

References 64 publications

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“…The investigated section of core GeoB2107‐3 spans the period from 0.85 to 40 cal kyr BP. The age model adopted here is the same as that recently published by Howe, Piotrowski, Noble, et al (), Howe, Piotrowski, Oppo, et al (), Gu et al (), and Portilho‐Ramos et al () using the Marine13 calibration curve (Reimer et al, ), which produced ages similar to those previously published by Hendry et al () using the Marine09 curve (Reimer et al, ). Those age models show a maximum difference of ca.…”

Section: Resultsmentioning

confidence: 72%

“…Radiocarbon analyses were conducted at the Leibniz Laboratory for Radiometric Dating and Stable Isotope Research at the University of Kiel, Germany. The age‐depth model was originally published by Hendry et al (), using the Marine09 calibration curve (Reimer et al, ), and more recently by Howe, Piotrowski, Noble, et al (), Howe, Piotrowski, Oppo, et al (), Gu et al (), and Portilho‐Ramos et al () with the Marine13 calibration curve (Reimer et al, ). All radiocarbon ages were converted into calibrated ages using the online version of the software Calib 7.1 (Stuiver et al, ) and the Marine13 calibration curve (Reimer et al, ), applying a marine reservoir correction (Δ R ) of 35 years (Stuiver et al, ; http://calib.org/marine/getref.php?RefNo¼135).…”

Section: Methodsmentioning

confidence: 99%

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Productivity Evolution in the South Brazilian Bight During the Last 40,000 Years

Pereira

Arz

Pätzold

et al. 2018

Paleoceanog and Paleoclimatol

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Marine productivity largely controls the oceanic uptake of atmospheric carbon dioxide and contributed to the global climate changes that led to the termination of the last glacial cycle. Past changes in marine productivity were presumably associated with disturbances in the Atlantic meridional overturning circulation (AMOC). In the South Atlantic, however, the evolution of marine productivity throughout the last glacial–interglacial cycle is still poorly constrained mainly due to the scarcity of records with high temporal resolution. Here we present high‐resolution records of paleoproductivity and upper‐water‐column properties from the western subtropical South Atlantic covering the last 40,000 years. Our records are based on faunal and stable oxygen isotopic analyses of planktonic foraminifera from a marine sediment core collected from an upwelling region off southeastern South America (27°S). We used the relative abundance of eutrophic planktonic foraminifera (i.e., Globigerinita glutinata and Globigerina bulloides) as proxies of primary productivity. Our findings reveal, for the first time, enhanced primary productivity during Heinrich Stadials along the last glacial, when the AMOC showed reduced strength. Additionally, our results reveal decreased primary productivity over the Last Glacial Maximum, a period of markedly lower sea level; and the Younger Dryas, when the AMOC showed only moderate reductions. The most outstanding productivity decline, however, is depicted at the onset of the Holocene, when the AMOC recovers its strength. We hypothesize that the observed changes were triggered by the dynamics of the Brazil Current primarily driven by disturbances in the AMOC.

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Section: Resultsmentioning

confidence: 72%

Section: Methodsmentioning

confidence: 99%

Productivity Evolution in the South Brazilian Bight During the Last 40,000 Years

Pereira

Arz

Pätzold

et al. 2018

Paleoceanog and Paleoclimatol

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“…For example, Portilho-Ramos et al (2018) describe evidence from foraminiferal stable carbon isotopes that suggests methane hydrate dissociated offshore of Brazil during the LGM. At this location, changes in currents caused warming of bottom water by an estimated 4°C during the LGM (Portilho-Ramos et al, 2018). In the Arctic Ocean,~2°C warmer temperatures are inferred for 1,000-to 2,500-m depth in the Arctic Ocean during the LGM based on Mg/Ca and Sr/Ca values of ostracods (Cronin et al, 2012).…”

Section: Discussionmentioning

confidence: 99%

Sedimentation Controls on Methane‐Hydrate Dynamics Across Glacial/Interglacial Stages: An Example From International Ocean Discovery Program Site U1517, Hikurangi Margin

Screaton

Torres

Dugan

et al. 2019

Geochem Geophys Geosyst

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Dissolved chloride concentrations higher than seawater were observed over a broad depth range in pore water profiles from International Ocean Discovery Program Site U1517 on the Hikurangi Margin. This Cl maximum is not associated with an 87Sr/86Sr anomaly, indicating that it is not caused by hydration reactions during ash alteration. We use a numerical modeling approach to examine possible causes for recent gas hydrate formation that can result in the observed Cl high. Our approach considers sedimentation, sea level, and bottom water temperature (BWT) changes due to glaciation as drivers for the downward migration of the base of gas hydrate stability and gas hydrate formation. The modeling results reveal that lowering of sea level during glaciation can allow methane hydrate dissociation followed by postglacial hydrate formation as sea level rises. However, BWT cooling of 2 °C during glaciation followed by warming during deglaciation would mostly counteract the impacts of sea level change. Bottom water cooling during glaciation is expected in this region and many locations worldwide. As a result, our simulations do not support the previous hypotheses of large‐scale gas hydrate dissociation due to sea level drop during glaciation, which have been proposed as triggers for widespread gas release and slope failure. Such a mechanism is only possible where BWT remains constant or increases during glaciation. Our simulations indicate that sedimentation constitutes the largest factor driving recent methane hydrate formation at Site U1517, and we suggest that sedimentation may play a larger role in gas hydrate dynamics along margins than previously recognized.

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“…For example, gas seepages from the continental shelf of the United Kingdom account for up to 40% of total CH 4 emissions in that area (Judd et al, 1997). In addition, sea-level fluctuations due to glaciation-deglaciation can cause release of CH 4 due to changes in hydrostatic pressure, currents, and bottom water temperatures (Portilho-Ramos et al, 2018). Finally, CH 4 hydrates found in continental margin sediments could also be destabilized by earthquakes (Mienert, Posewang, & Baumann, 1998) and turbidity currents (Shakhova et al, 2014).…”

Section: Methane Emissions From Ancient Ferruginous Oceansmentioning

confidence: 99%

Biogeochemical and physical controls on methane fluxes from two ferruginous meromictic lakes

et al. 2019

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Meromictic lakes with anoxic bottom waters often have active methane cycles whereby methane is generally produced biogenically under anoxic conditions and oxidized in oxic surface waters prior to reaching the atmosphere. Lakes that contain dissolved ferrous iron in their deep waters (i.e., ferruginous) are rare, but valuable, as geochemical analogues of the conditions that dominated the Earth's oceans during the Precambrian when interactions between the iron and methane cycles could have shaped the greenhouse regulation of the planet's climate. Here, we explored controls on the methane fluxes from Brownie Lake and Canyon Lake, two ferruginous meromictic lakes that contain similar concentrations (max. >1 mM) of dissolved methane in their bottom waters. The order Methanobacteriales was the dominant methanogen detected in both lakes. At Brownie Lake, methanogen abundance, an increase in methane concentration with respect to depths closer to the sediment, and isotopic data suggest methanogenesis is an active process in the anoxic water column. At Canyon Lake, methanogenesis occurred primarily in the sediment. The most abundant aerobic methane‐oxidizing bacteria present in both water columns were associated with the Gammaproteobacteria, with little evidence of anaerobic methane oxidizing organisms being present or active. Direct measurements at the surface revealed a methane flux from Brownie Lake that was two orders of magnitude greater than the flux from Canyon Lake. Comparison of measured versus calculated turbulent diffusive fluxes indicates that most of the methane flux at Brownie Lake was non‐diffusive. Although the turbulent diffusive methane flux at Canyon Lake was attenuated by methane oxidizing bacteria, dissolved methane was detected in the epilimnion, suggestive of lateral transport of methane from littoral sediments. These results highlight the importance of direct measurements in estimating the total methane flux from water columns, and that non‐diffusive transport of methane may be important to consider from other ferruginous systems.

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Methane release from the southern Brazilian margin during the last glacial

Cited by 36 publications

References 64 publications

Productivity Evolution in the South Brazilian Bight During the Last 40,000 Years

Productivity Evolution in the South Brazilian Bight During the Last 40,000 Years

Sedimentation Controls on Methane‐Hydrate Dynamics Across Glacial/Interglacial Stages: An Example From International Ocean Discovery Program Site U1517, Hikurangi Margin

Biogeochemical and physical controls on methane fluxes from two ferruginous meromictic lakes

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