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A Lagrangian study of the contribution of the Canary coastal upwelling to the nitrogen budget of the open North Atlantic

Abstract.

"The Canary Current System (CanCS) is a major eastern boundary upwelling system (EBUS), known for its high nearshore productivity and for sustaining a large fishery. It is also an important but not well quantified source of nitrogen to the adjacent oligotrophic subtropical gyre of the North Atlantic. Here, we use a Lagrangian modeling approach to quantify this offshore transport and investigate its timescales, reach and contribution to the fueling of productivity in the offshore regions. In our Lagrangian model, we release nearly 10 million particles off the northwestern African coast and then track all those that enter the nearshore region and upwell along the coast between 14 and 35∘ N. We then follow them as they are transported offshore, also tracking the biogeochemical[...]"

 

Source: Biogeosciences
Authors: Derara Hailegeorgis et al.
DOI: https://doi.org/10.5194/bg-18-303-2021

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The role of environmental factors in the long-term evolution of the marine biological pump

Absract.

"The biological pump—the transfer of atmospheric carbon dioxide to the ocean interior and marine sediments as organic carbon—plays a critical role in regulating the long-term carbon cycle, atmospheric composition and climate. Despite its centrality in the Earth system, the response of the biological pump to biotic innovation and climatic fluctuations through most stages of Earth’s history has been largely conjectural. Here we use a mechanistic model of the biological carbon pump to revisit the factors controlling[...]"

 

Source: Nature Geoscience
Authors: Mojtaba Fakhraee et al.
DOI: https://doi.org/10.1038/s41561-020-00660-6

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Glacial deep ocean deoxygenation driven by biologically mediated air–sea disequilibrium

Abstract.

"Deep ocean deoxygenation inferred from proxies has been used to support the hypothesis that a lower atmospheric carbon dioxide during glacial times was due to an increase in the strength of the ocean’s biological pump. This relies on the assumption that surface ocean oxygen (O2) is equilibrated with the atmosphere such that any O2 deficiency observed in deep waters is a result of organic matter respiration, which consumes O2 and produces dissolved inorganic carbon. However, this assumption has been shown to be imperfect because of disequilibrium. Here we used an Earth system[...]"

 

Source: Nature Geoscience 
Authors: Ellen Cliff et al.
DOI: https://doi.org/10.1038/s41561-020-00667-z

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Increased carbon capture by a silicate-treated forested watershed affected by acid deposition

Abstract.

"Meeting internationally agreed-upon climate targets requires carbon dioxide removal (CDR) strategies coupled with an urgent phase-down of fossil fuel emissions. However, the efficacy and wider impacts of CDR are poorly understood. Enhanced rock weathering (ERW) is a land-based CDR strategy requiring large-scale field trials. Here we show that a low 3.44 t ha−1 wollastonite treatment in an 11.8 ha acid-rain-impacted forested watershed in New Hampshire, USA, led to cumulative carbon capture by carbonic acid weathering of 0.025–0.13 t CO2 ha−1 over 15 years. Despite a 0.8–2.4 t CO2 ha−1 logistical carbon penalty from mining, grinding, transportation[...]"

 

Source: Biogeosciences
Authors: Lyla L. Taylor et al.
DOI: https://doi.org/10.5194/bg-18-169-2021

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Effects of Experimental Ocean Acidification on the Larval Morphology and Metabolism of a Temperate Sparid, Chrysoblephus laticeps

Abstract.

"Ocean acidification is predicted to have widespread impacts on marine species. The early life stages of fishes, being particularly sensitive to environmental deviations, represent a critical bottleneck to recruitment. We investigated the effects of ocean acidification (∆pH = −0.4) on the oxygen consumption and morphometry during the early ontogeny of a commercially important seabream, Chrysoblephus laticeps, up until flexion. Hatchlings appeared to be tolerant to hypercapnic conditions, exhibiting no difference in oxygen consumption or morphometry between treatments, although the yolk reserves were marginally reduced in the low-pH treatment. The preflexion stages appeared[...]"

 

Source: MDPI
Authors: Cuen Muller et al.
DOI: https://doi.org/10.3390/oceans2010002

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Os isotopic composition of western Aleutian adakites: Implications for the Re/Os of oceanic crust processed through hot subduction zones

Abstract.

"Constraining the behaviour of Re and Os during eclogite melting is required to understand the Re and Os budget and 187Os/188Os of recycled slabs produced at warm subduction zones. It is particularly relevant to early Earth history, a period during which slab melting could have prevailed over dehydration due to higher mantle temperatures. There are however currently few constraints on Re and Os mobility during slab melting. Accordingly, we measured Os, Re and 187Os/188Os in primitive submarine lavas (Mg# ˃ 0.6) from the western Aleutian Arc. These include strongly adakitic rocks shown[...]"

 

Source: Science Direct
Authors: Rachel Bezard et al.
DOI: https://doi.org/10.1016/j.gca.2020.10.009

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Limited iodate reduction in shipboard seawater incubations from the Eastern Tropical North Pacific oxygen deficient zone

Abstract.

"The relative abundance of the inorganic iodine species, iodide and iodate, are applied to characterize both modern and ancient marine oxygen deficient zones (ODZs). However, the rates and mechanisms responsible for in situ iodine redox transformations are poorly characterized, rendering iodine-based redox reconstructions uncertain. Here, we provide constraints on the rates and mechanisms of iodate reduction in the Eastern Tropical North Pacific (ETNP) offshore ODZ using a shipboard tracer–incubation method. Observations of iodate reduction from incubations[...]"

 

Source: Science Direct
Authors: D.S. Hardisty et al.
DOI: https://doi.org/10.1016/j.epsl.2020.116676

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Sensitivity of 21st-century projected ocean new production changes to idealized biogeochemical model structure

Abstract.

"While there is agreement that global warming over the 21st century is likely to influence the biological pump, Earth system models (ESM) display significant divergence in their projections of future new production. This paper quantifies and interprets the sensitivity of projected changes in new production in an idealized global ocean-biogeochemistry model. The model includes two tracers that explicitly represent nutrient transport, light- and nutrient-limited nutrient uptake by the ecosystem (new production), and export via sinking organic particles. Globally, new production declines with warming due to reduced surface nutrient availability, as expected. However, the magnitude[...]"

 

Source: Biogeosciences
Authors: Genevieve Jay Brett et al.
DOI: https://doi.org/10.5194/bg-2020-479

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Simulating shrubs and their energy and carbon dioxide fluxes in Canada's Low Arctic with the Canadian Land Surface Scheme Including biogeochemical Cyc

Abstract.

"The Arctic is warming more rapidly than other regions of the world leading to ecosystem change including shifts in vegetation communities, permafrost degradation and alteration of tundra surface-atmosphere energy and carbon (C) fluxes, among others. However, year-round C and energy flux measurements at high-latitude sites remain rare. This poses a challenge for evaluating the impacts of climate change on Arctic tundra ecosystems and for developing and evaluating process-based models, which may be used to predict regional and global energy and C feedbacks to the climate system. Our study used 14 years of seasonal eddy covariance (EC) measurements of carbon dioxide (CO2), water and energy fluxes and winter soil chamber CO2 flux measurements at a dwarf-shrub tundra site underlain by continuous permafrost in Canada's Southern Arctic ecozone to evaluate the incorporation[...]"

Source: Biogeosciences
Authors: Gesa Meyer et al.
DOI: https://doi.org/10.5194/bg-2020-458


A transient swing to higher oxygen levels in the atmosphere and oceans at ~1.4 Ga

Abstract.

"The mid-Proterozoic (1.8–0.8 Ga) may have witnessed persistent and predominant anoxia at the Earth’s surface. However, recent studies suggest that there was a period around ~1.4 Ga where oxygen levels might have been transiently elevated, both in the atmosphere and oceans. In order to shed light on this debated topic, we analyzed rare earth elements plus Y (REY) and Cr isotope profiles of the carbonate rocks from the ~1.44-Gyr-old Tieling Formation consisting of the lower Daizhuangzi (DZZ) and upper Laohuding (LHD) Members at the Jixian section, North China. The DZZ samples are characterized by middle REE enriched, hump-shaped REY distribution patterns, while those of the LHD Member display[...]"

 

Source: Science Direct
Authors: Wei Wei et al.
DOI: https://doi.org/10.1016/j.precamres.2020.106058

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