Exploring the Growing Role of Terrestrial Carbon Across North Atlantic Fjords

2020 ◽  
Author(s):  
Craig Smeaton ◽  
William Austin
Keyword(s):  
Organic Carbon ◽  
Marine Environment ◽  
North Atlantic ◽  
Planetary Science ◽  
Terrestrial Environment ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Fjord Sediments

<p>Fjords are recognized as globally significant hotspots for the burial (Smith et al., 2015) and long-term storage (Smeaton et al., 2017) of marine and terrestrially derived organic carbon (OC). By trapping and locking away OC over geological timescales, fjord sediments provide a potentially important yet largely overlooked climate regulation service. The proximity of fjords to the terrestrial environment in combination with their geomorphology and hydrography results in the fjordic sediments being subsidized with organic carbon (OC) from the terrestrial environment. This terrestrial OC (OC<sub>terr</sub>) transferred to the marine environment has traditionally be considered lost to the atmosphere in the form of CO<sub>2</sub> in most carbon (C) accounting schemes yet globally it is estimated that 55% of OC trapped in fjord sediments is derived from terrestrial sources (Cui et al., 2016). So is this terrestrial OC truly lost? Here, we estimate the quantity of OC<sub>terr</sub> held within North Atlantic fjords with the aim of better understanding the recent and long-term role of the terrestrial environment in the evolution of these globally significant sedimentary OC stores. By understanding this subsidy of OC from the terrestrial to the marine environment we can take the first steps in quantifying the terrestrial OC stored in fjords and the wider coastal marine environment.</p><p>Cui, X., Bianchi, T.S., Savage, C. and Smith, R.W., 2016. Organic carbon burial in fjords: Terrestrial versus marine inputs. <em>Earth and Planetary Science Letters</em>, <em>451</em>, pp.41-50.</p><p>Smeaton, C., Austin, W.E., Davies, A., Baltzer, A., Howe, J.A. and Baxter, J.M., 2017. Scotland's forgotten carbon: a national assessment of mid-latitude fjord sedimentary stocks. <em>Biogeosciences</em>.</p><p>Smith, R.W., Bianchi, T.S., Allison, M., Savage, C. and Galy, V., 2015. High rates of organic carbon burial in fjord sediments globally. <em>Nature Geoscience</em>, <em>8</em>(6), p.450.</p><p> </p>

Long-term Aptian marine osmium isotopic record of Ontong Java Nui activity

Geology ◽  
2021 ◽  
Author(s):  
Hironao Matsumoto ◽  
Rodolfo Coccioni ◽  
Fabrizio Frontalini ◽  
Kotaro Shirai ◽  
Luigi Jovane ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Volcanic Eruptions ◽  
Hydrothermal Activity ◽  
Published Data ◽  
Isotopic Data ◽  
Oceanic Plateaus ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Isotopic Records

The early to mid-Aptian was punctuated by episodic phases of organic-carbon burial in various oceanographic settings, which are possibly related to massive volcanism associated with the emplacement of the Ontong Java, Manihiki, and Hikurangi oceanic plateaus in the southwestern Pacific Ocean, inferred to have formed a single plateau called Ontong Java Nui. Sedimentary osmium (Os) isotopic compositions are one of the best proxies for determining the timing of voluminous submarine volcanic episodes. However, available Os isotopic records during the age are limited to a narrow interval in the earliest Aptian, which is insufficient for the reconstruction of long-term hydrothermal activity. We document the early to mid-Aptian Os isotopic record using pelagic Tethyan sediments deposited in the Poggio le Guaine (Umbria-Marche Basin, Italy) to precisely constrain the timing of massive volcanic episodes and to assess their impact on the marine environment. Our new Os isotopic data reveal three shifts to unradiogenic values, two of which correspond to black shale horizons in the lower to mid-Aptian, namely the Wezel (herein named) and Fallot Levels. These Os isotopic excursions are ascribed to massive inputs of unradiogenic Os to the ocean through hydrothermal activity. Combining the new Os isotopic record with published data from the lowermost Aptian organic-rich interval in the Gorgo a Cerbara section of the Umbria-Marche Basin, it can be inferred that Ontong Java Nui volcanic eruptions persisted for ~5 m.y. during the early to mid-Aptian.

scholarly journals Earliest land plants created modern levels of atmospheric oxygen

2016 ◽  
Vol 113 (35) ◽  
pp. 9704-9709 ◽  
Author(s):  
Timothy M. Lenton ◽  
Tais W. Dahl ◽  
Stuart J. Daines ◽  
Benjamin J. W. Mills ◽  
Kazumi Ozaki ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Land Surface ◽  
Atmospheric Oxygen ◽  
Geochemical Data ◽  
Regulatory Regime ◽  
Carbon Burial ◽  
C:P Ratio ◽  
Marine Biomass ◽  
Organic Carbon Burial

The progressive oxygenation of the Earth’s atmosphere was pivotal to the evolution of life, but the puzzle of when and how atmospheric oxygen (O2) first approached modern levels (∼21%) remains unresolved. Redox proxy data indicate the deep oceans were oxygenated during 435–392 Ma, and the appearance of fossil charcoal indicates O2 >15–17% by 420–400 Ma. However, existing models have failed to predict oxygenation at this time. Here we show that the earliest plants, which colonized the land surface from ∼470 Ma onward, were responsible for this mid-Paleozoic oxygenation event, through greatly increasing global organic carbon burial—the net long-term source of O2. We use a trait-based ecophysiological model to predict that cryptogamic vegetation cover could have achieved ∼30% of today’s global terrestrial net primary productivity by ∼445 Ma. Data from modern bryophytes suggests this plentiful early plant material had a much higher molar C:P ratio (∼2,000) than marine biomass (∼100), such that a given weathering flux of phosphorus could support more organic carbon burial. Furthermore, recent experiments suggest that early plants selectively increased the flux of phosphorus (relative to alkalinity) weathered from rocks. Combining these effects in a model of long-term biogeochemical cycling, we reproduce a sustained +2‰ increase in the carbonate carbon isotope (δ13C) record by ∼445 Ma, and predict a corresponding rise in O2 to present levels by 420–400 Ma, consistent with geochemical data. This oxygen rise represents a permanent shift in regulatory regime to one where fire-mediated negative feedbacks stabilize high O2 levels.

scholarly journals Orbital forcing of organic carbon burial in the proto-North Atlantic during oceanic anoxic event 2

2004 ◽  
Vol 228 (3-4) ◽  
pp. 465-482 ◽  
Author(s):  
Marcel M.M. Kuypers ◽  
Lucas J. Lourens ◽  
W. Irene C. Rijpstra ◽  
Richard D. Pancost ◽  
Ivar A. Nijenhuis ◽  
...  
Keyword(s):  
Organic Carbon ◽  
North Atlantic ◽  
Orbital Forcing ◽  
Oceanic Anoxic Event ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event

High rates of organic carbon burial in fjord sediments globally

2015 ◽  
Vol 8 (6) ◽  
pp. 450-453 ◽  
Author(s):  
Richard W. Smith ◽  
Thomas S. Bianchi ◽  
Mead Allison ◽  
Candida Savage ◽  
Valier Galy
Keyword(s):  
Organic Carbon ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Fjord Sediments

A tentative attempt to better trace the late Pleistocene oxygen cycle

2021 ◽  
Author(s):  
Ji-Woong Yang ◽  
Thomas Extier ◽  
Martin Kölling ◽  
Amaëlle Landais ◽  
Gaëlle Leloup ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Late Pleistocene ◽  
Global Ocean ◽  
Geological Time Scale ◽  
Sources And Sinks ◽  
The Earth ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Burial Flux

<p>Atmospheric abundance of oxygen (O<sub>2</sub>) has been co-evolved with different aspects of the Earth system since appearance of oxygenic photosynthesis by cyanobacteria around 2.4 10<sup>9</sup> years before present (Ga). Therefore, much attention has been paid to understand the changes in O<sub>2</sub> and the underlying mechanisms over the Earth’s history. The pioneering work by Stolper et al. (2016) revealed the long-term decreasing trend of O<sub>2</sub> mixing ratios over the last 800,000 years using the ice-core composite record of molar ratios of O<sub>2</sub> and nitrogen (δ(O<sub>2</sub>/N<sub>2</sub>)), implying a slight imbalance between sources and sinks. Over geological time scale, O<sub>2</sub> is mainly controlled by burial and oxidation of organic carbon and pyrite, but also by oxidation of volcanic gases and sedimentary rocks. Nevertheless, the O<sub>2</sub> cycle of the late Pleistocene has not been well understood, partly due to the lack of knowledge about the individual sources and sinks. Since then, Kölling et al. (2019) proposed a simple model to estimate the O<sub>2</sub> release/uptake fluxes due to the pyrite burial/oxidation that predicts up to ~70% of the O<sub>2</sub> decrease of the last 800,000 years could be explained by pyrite burial/oxidation.</p><p>Building on this, we present here our preliminary, tentative attempt for reconstruction of the net organic carbon burial flux over the last 800,000 years by combining available information (including new δ(O<sub>2</sub>/N<sub>2</sub>) data) and assuming constant O<sub>2</sub> fluxes associated with volcanic outgassing and rock weathering. The long-term organic carbon burial flux trend obtained with our new calculations is similar to the global ocean δ<sup>13</sup>C records but also to simulations using a conceptual carbon cycle model (Paillard, 2017). These results partly support the geomorphological hypothesis that the major sea-level drops during the earlier period of the last 800,000 years lead to enhanced organic carbon burial, and that significant changes in the net organic carbon happen around Marine Isotopic Stage (MIS) 13. In addition, we present the long-term decreasing trend of the global biosphere productivity, or gross photosynthetic O<sub>2</sub> flux, reconstructed from new measurements of triple-isotope composition of atmospheric O<sub>2</sub> trapped in ice cores. As the largest O<sub>2</sub> flux, the observed decrease in gross photosynthesis requires to be compensated by parallel reduction of global ecosystem respiration.</p>

scholarly journals Calcification-driven CO2 emissions exceed “Blue Carbon” sequestration in a carbonate seagrass meadow

2021 ◽  
Author(s):  
Bryce Van Dam ◽  
Mary Zeller ◽  
Christian Lopes ◽  
Ashley Smyth ◽  
Michael Böttcher ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Sequestration ◽  
Organic Carbon ◽  
Seagrass Meadow ◽  
Blue Carbon ◽  
Carbonate Sediments ◽  
Seagrass Meadows ◽  
Carbon Burial ◽  
Organic Carbon Burial

Abstract Long-term “blue carbon” burial in seagrass meadows is complicated by other carbon and alkalinity exchanges that shape net carbon sequestration. We measured a suite of such processes, including denitrification, sulfur, and inorganic carbon cycling, and assessed their impact on air-water carbon dioxide exchange in a typical seagrass meadow underlain by carbonate sediments. Contrary to the prevailing concept of seagrass meadows acting as carbon sinks, eddy covariance measurements reveal this ecosystem as a consistent source of carbon dioxide to the atmosphere, at an average rate of 610 ± 990 µmol m-2 hr-1 during our study and 700 ± 660 µmol m-2 hr-1 over an annual cycle. A robust mass-balance shows that net alkalinity consumption by ecosystem calcification explains >95% of the observed carbon dioxide emissions, far exceeding alkalinity generated by net reduced sulfur, iron and organic carbon burial. Isotope geochemistry of porewaters suggests substantial dissolution and re-crystallization of more stable carbonates mediated by sulfide oxidation-induced acidification, enhancing long-term carbonate burial and ultimate carbon dioxide production. We show that the “blue carbon” sequestration potential of calcifying seagrass meadows has been over-estimated, and that in-situ organic carbon burial only offsets a small fraction (<5%) of calcification-induced CO2 emissions. Ocean-based climate change mitigation activities in such calcifying regions should be approached with caution and an understanding that net carbon sequestration may not be possible.

scholarly journals Past climate variations recorded in needle-like aragonites correlate with organic carbon burial efficiency as revealed by lake sediments in Croatia

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ivan Razum ◽  
Petra Bajo ◽  
Dea Brunović ◽  
Nikolina Ilijanić ◽  
Ozren Hasan ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Stable Carbon Isotope ◽  
Climate Variations ◽  
Before Present ◽  
Stable Carbon ◽  
Climate Trends ◽  
Geochemical Proxies ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Burial Efficiency

AbstractThe drivers of organic carbon (OC) burial efficiency are still poorly understood despite their key role in reliable projections of future climate trends. Here, we provide insights on this issue by presenting a paleoclimate time series of sediments, including the OC contents, from Lake Veliko jezero, Croatia. The Sr/Ca ratios of the bulk sediment are mainly derived from the strontium (Sr) and calcium (Ca) concentrations of needle-like aragonite in Core M1-A and used as paleotemperature and paleohydrology indicators. Four major and six minor cold and dry events were detected in the interval from 8.3 to 2.6 calibrated kilo anno before present (cal ka BP). The combined assessment of Sr/Ca ratios, OC content, carbon/nitrogen (C/N) ratios, stable carbon isotope (δ13C) ratios, and modeled geochemical proxies for paleoredox conditions and aeolian input revealed that cold and dry climate states promoted anoxic conditions in the lake, thereby enhancing organic matter preservation and increasing the OC burial efficiency. Our study shows that the projected future increase in temperature might play an important role in the OC burial efficiency of meromictic lakes.

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