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Changing carbon-to-nitrogen ratios of organic-matter export under ocean acidification

Abstract.

"Ocean acidification (OA) will affect marine biotas from the organism to the ecosystem level. Yet, the consequences for the biological carbon pump and thereby the oceanic sink for atmospheric CO2 are still unclear. Here we show that OA considerably alters the C/N ratio of organic-matter export (C/Nexport), a key factor determining efficiency of the biological pump. By synthesizing sediment-trap data from in situ mesocosm studies in different marine biomes[...]

 

Source: Nature Climate Change 
Authors: Jan Taucher et al.
DOI:https://doi.org/10.1038/s41558-020-00915-5

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Opposite response of strong and moderate positive Indian Ocean Dipole to global warming

Abstract.

"A strong positive Indian Ocean Dipole (pIOD) induces weather extremes such as the 2019 Australian bushfires and African floods. The impact is influenced by sea surface temperature (SST), yet models disagree on how pIOD SST may respond to greenhouse warming. Here we find increased SST variability of strong pIOD events, with strong equatorial eastern Indian Ocean cool anomalies, but decreased variability of moderate pIOD events, dominated by western warm anomalies[...]"

 

Source: Nature Climate Change
Authors: Wenju Cai et al.
DOI: https://doi.org/10.1038/s41558-020-00943-1

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Pelagic microplastics in surface water of the Eastern Indian Ocean during monsoon transition period: Abundance, distribution, and characteristics

Abstract.

"Microplastics (MPs) have been documented in almost all marine environments, including coastal regions, the open ocean, and the deep sea. However, relatively little knowledge was available about MP pollution in the open ocean, especially the Indian Ocean. We conducted field observations at 36 stations in the Eastern Indian Ocean (EIO), using a typical manta trawl with a mesh size of 330 μm for surface water sampling. Ours is the first study to obtained comprehensive and comparable baseline data about MPs in the EIO, including abundance, spatial distribution and characteristics[...]"

 

Source: Science Direct 
Authors: Changjun Li et al.
DOI: https://doi.org/10.1016/j.scitotenv.2020.142629

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11 - Impacts of strong warm ocean currents on development of extratropical cyclones through the warm and cold conveyor belts: A review

Abstract.

"Recent high-resolution observations and numerical simulations have revealed active roles of the ocean in the mid-latitude climate system. In this chapter, we review recent studies on the topic especially focusing on roles of strong oceanic warm currents and associated sea surface temperature (SST) frontal structures in the development of extratropical cyclones, which can cause extreme rainfall/snowfall. Speed of the warm strong ocean currents such as the Kuroshio/Kuroshio Extension and activities of associated mesoscale eddies have strong influence on SST and its meridional[...]"

 

Source: Science Direct
Authors: Hidetaka Hirata et al.
DOI: https://doi.org/10.1016/B978-0-12-818156-0.00014-9

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Quantifying Nitrous Oxide Cycling Regimes in the Eastern Tropical North Pacific Ocean With Isotopomer Analysis

Abstract.

"Nitrous oxide (N2O), a potent greenhouse gas, is produced disproportionately in marine oxygen deficient zones (ODZs). To quantify spatiotemporal variation in N2O cycling in an ODZ, we analyzed N2O concentration and isotopologues along a transect through the eastern tropical North Pacific (ETNP). At several stations along this transect, N2O concentrations reached a near surface maximum that exceeded prior measurements in this region, of up to 226.1 ± 20.5 nM at the coast. Above the σθ = 25.0 kg/m3 isopycnal, Keeling plot analysis revealed two sources[...]"

Source: AGU- Advanced Earth and Space Science
Author: Colette L. Kelly et al.
DOI: https://doi.org/10.1029/2020GB006637

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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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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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