scholarly journals Sequestration and subduction of deep-sea carbonate in the global ocean since the Early Cretaceous

Geology ◽  
2018 ◽  
Vol 47 (1) ◽  
pp. 91-94 ◽  
Author(s):  
Adriana Dutkiewicz ◽  
R. Dietmar Müller ◽  
John Cannon ◽  
Sioned Vaughan ◽  
Sabin Zahirovic
Keyword(s):  
Early Cretaceous ◽  
Deep Sea ◽  
Global Ocean

scholarly journals Reviews and syntheses: Hidden forests, the role of vegetated coastal habitats in the ocean carbon budget

2017 ◽  
Vol 14 (2) ◽  
pp. 301-310 ◽  
Author(s):  
Carlos M. Duarte
Keyword(s):  
Carbon Sequestration ◽  
Organic Carbon ◽  
Primary Production ◽  
Deep Sea ◽  
Carbon Budget ◽  
Net Primary Production ◽  
Global Ocean ◽  
Coastal Habitats ◽  
Global Carbon Budget ◽  
Global Carbon

Abstract. Vegetated coastal habitats, including seagrass and macroalgal beds, mangrove forests and salt marshes, form highly productive ecosystems, but their contribution to the global carbon budget remains overlooked, and these forests remain hidden in representations of the global carbon budget. Despite being confined to a narrow belt around the shoreline of the world's oceans, where they cover less than 7 million km2, vegetated coastal habitats support about 1 to 10 % of the global marine net primary production and generate a large organic carbon surplus of about 40 % of their net primary production (NPP), which is either buried in sediments within these habitats or exported away. Large, 10-fold uncertainties in the area covered by vegetated coastal habitats, along with variability about carbon flux estimates, result in a 10-fold bracket around the estimates of their contribution to organic carbon sequestration in sediments and the deep sea from 73 to 866 Tg C yr−1, representing between 3 % and 1∕3 of oceanic CO2 uptake. Up to 1∕2 of this carbon sequestration occurs in sink reservoirs (sediments or the deep sea) beyond these habitats. The organic carbon exported that does not reach depositional sites subsidizes the metabolism of heterotrophic organisms. In addition to a significant contribution to organic carbon production and sequestration, vegetated coastal habitats contribute as much to carbonate accumulation as coral reefs do. While globally relevant, the magnitude of global carbon fluxes supported by salt-marsh, mangrove, seagrass and macroalgal habitats is declining due to rapid habitat loss, contributing to loss of CO2 sequestration, storage capacity and carbon subsidies. Incorporating the carbon fluxes' vegetated coastal habitats' support into depictions of the carbon budget of the global ocean and its perturbations will improve current representations of the carbon budget of the global ocean.

scholarly journals Large deep-sea zooplankton biomass mirrors primary production in the global ocean

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
S. Hernández-León ◽  
R. Koppelmann ◽  
E. Fraile-Nuez ◽  
A. Bode ◽  
C. Mompeán ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Deep Sea ◽  
Large Scale ◽  
Net Primary Production ◽  
Deep Ocean ◽  
Zooplankton Biomass ◽  
Global Ocean ◽  
Global Coupling ◽  
Do So

AbstractThe biological pump transports organic carbon produced by photosynthesis to the meso- and bathypelagic zones, the latter removing carbon from exchanging with the atmosphere over centennial time scales. Organisms living in both zones are supported by a passive flux of particles, and carbon transported to the deep-sea through vertical zooplankton migrations. Here we report globally-coherent positive relationships between zooplankton biomass in the epi-, meso-, and bathypelagic layers and average net primary production (NPP). We do so based on a global assessment of available deep-sea zooplankton biomass data and large-scale estimates of average NPP. The relationships obtained imply that increased NPP leads to enhanced transference of organic carbon to the deep ocean. Estimated remineralization from respiration rates by deep-sea zooplankton requires a minimum supply of 0.44 Pg C y−1 transported into the bathypelagic ocean, comparable to the passive carbon sequestration. We suggest that the global coupling between NPP and bathypelagic zooplankton biomass must be also supported by an active transport mechanism associated to vertical zooplankton migration.

scholarly journals On the time to tracer equilibrium in the global ocean

2008 ◽  
Vol 5 (3) ◽  
pp. 471-506
Author(s):  
F. Primeau ◽  
E. Deleersnijder
Keyword(s):  
Boundary Condition ◽  
Ocean Circulation ◽  
Dirichlet Boundary Condition ◽  
Deep Sea ◽  
Dirichlet Boundary ◽  
Three Dimensional ◽  
Sea Surface ◽  
Global Ocean ◽  
Surface Boundary ◽  
Surface Boundary Condition

Abstract. An important issue for the interpretation of data from deep-sea cores is the time for tracers to be transported from the sea surface to the deep ocean. Global ocean circulation models can help shed light on the timescales over which a tracer comes to equilibrium in different regions of the ocean. In this note, we discuss how the most slowly decaying eigenmode of a model can be used to obtain a relevant timescale for a tracer that enters through the sea surface to become well mixed in the ocean interior. We show how this timescale depends critically on the choice between a Neumann surface boundary condition in which the flux of tracer is prescribed or a Dirichlet surface boundary condition in which the concentration is prescribed. Explicit calculations with a 3-box model and a three-dimensional ocean circulation model show that the Dirichlet boundary condition when applied to only part of the surface ocean greatly overestimate the time needed to reach equilibrium. As a result regional-"injection" calculations which prescribe the surface concentration instead of the surface flux are not relevant for interpreting the regional disequilibrium between the Atlantic and Pacific found in paleo-tracer records from deep-sea cores. For tracers such as δ18O that enter the ocean from melt water, a Neumann boundary condition is more relevant. For tracers that enter the ocean through air-sea gas exchange such as 14C, a prescribed concentration boundary condition can be used to infer relevant timescales, but the Dirichlet Boundary condition must be applied over the entire ocean surface and not only to a patch of limited area. Our three-dimensional model results based on a steady-state modern circulation suggest that the relative disequilibrium between the deep Atlantic and Pacific is on the order of "only" 1200 years or less and does not depend on the size and location of the patch where the tracer is injected.

scholarly journals The global marine phosphorus cycle: sensitivity to oceanic circulation

2006 ◽  
Vol 3 (5) ◽  
pp. 1587-1629 ◽  
Author(s):  
C. P. Slomp ◽  
P. Van Cappellen
Keyword(s):  
Calcium Phosphate ◽  
Primary Production ◽  
Ocean Circulation ◽  
Primary Productivity ◽  
Deep Sea ◽  
Open Ocean ◽  
Depositional Environments ◽  
Global Ocean ◽  
Oceanic Circulation ◽  
Continental Shelves

Abstract. A new mass balance model for the coupled marine cycles of phosphorus (P) and carbon (C) is used to examine the relationships between oceanic circulation, primary productivity, and sedimentary burial of reactive P and particulate organic C (POC), on geological time scales. The model explicitly represents the exchanges of water and particulate matter between the continental shelves and the open ocean, and it accounts for the redox-dependent burial of POC and the various forms of reactive P (iron(III)-bound P, particulate organic P (POP), authigenic calcium phosphate, and fish debris). Steady state and transient simulations indicate that a slowing down of global ocean circulation decreases primary production in the open ocean, but increases that in the coastal ocean. The latter is due to increased transfer of soluble P from deep ocean water to the shelves, where it fuels primary production and causes increased reactive P burial. While authigenic calcium phosphate accounts for most reactive P burial ocean-wide, enhanced preservation of fish debris may become an important reactive P sink in deep-sea sediments during periods of ocean anoxia. Slower ocean circulation globally increases POC burial, because of enhanced POC preservation under anoxia in deep-sea depositional environments and higher primary productivity along the continental margins. In accordance with geological evidence, the model predicts increased accumulation of reactive P on the continental shelves during and following periods of ocean anoxia.

scholarly journals Deep-sea sediments of the global ocean

2020 ◽  
Author(s):  
Markus Diesing
Keyword(s):  
Machine Learning ◽  
Spatial Distribution ◽  
Deep Sea ◽  
Learning Algorithm ◽  
Marine Species ◽  
Global Ocean ◽  
Teaching Management ◽  
Sediment Distribution ◽  
Deep Sea Sediments ◽  
Seafloor Sediment

Abstract. Although the deep-sea floor accounts for more than 70 % of the Earth's surface, there has been little progress in relation to deriving maps of seafloor sediment distribution based on transparent, repeatable and automated methods such as machine learning. A new digital map of the spatial distribution of seafloor lithologies in the deep sea below 500 m water depth is presented to address this shortcoming. The lithology map is accompanied by estimates of the probability of the most probable class, which may be interpreted as a spatially-explicit measure of confidence in the predictions, and probabilities for the occurrence of seven lithology classes (Calcareous sediment, Clay, Diatom ooze, Lithogenous sediment, Mixed calcareous-siliceous ooze, Radiolarian ooze and Siliceous mud). These map products were derived by the application of the Random Forest machine learning algorithm to a homogenised dataset of seafloor lithology samples and global environmental predictor variables that were selected based on the current understanding of the controls on the spatial distribution of deep-sea sediments. The overall accuracy of the lithology map is 69.5 %, with 95 % confidence limits of 67.9 % and 71.1 %. It is expected that the map products are useful for various purposes including, but not limited to, teaching, management, spatial planning, design of marine protected areas and as input for global spatial predictions of marine species distributions and seafloor sediment properties. The map products are available at https://doi.org/10.1594/PANGAEA.911692 (Diesing, 2020).

scholarly journals The Concept of Oceanian Sovereignty in the Context of Deep Sea Mining in the Pacific Region

2021 ◽  
Vol 8 ◽  
Author(s):  
Virginie C. Tilot ◽  
Bleuenn Guilloux ◽  
Klaas Willaert ◽  
Clement Y. Mulalap ◽  
Tamatoa Bambridge ◽  
...  
Keyword(s):  
Deep Sea ◽  
Sustainable Livelihoods ◽  
Well Being ◽  
Global Ocean ◽  
Economic Science ◽  
Suitable Model ◽  
Pacific Region ◽  
Legal Context ◽  
The Pacific ◽  
Island Communities

Based on an interdisciplinary experience addressing traditional dimensions in marine resource management in the Pacific, the socio-ecological interconnectivity between island communities, the ocean realm and the legal context concerning the management of seabed resources (Tilot, 2006, 2010; Tilot et al., 2018, 2021a,b; Mulalap et al., 2020; Willaert, 2020a,b, c; 2021; DOSI, 2021), this paper proposes to discuss the relevance and efficacy of the concept of “Oceanian Sovereignty” (Bambridge et al., 2021) in the context of Deep Sea Mining, from the different legal, environmental, anthropological, social, political, and economic science perspectives. The policies and practices developed in the Pacific in this context could well serve as a suitable model elsewhere to reconcile competing perspectives in addition to sustaining the Human Well-being and Sustainable Livelihoods (HWSL) and the health of the Global Ocean.

scholarly journals On the time to tracer equilibrium in the global ocean

Ocean Science ◽  
2009 ◽  
Vol 5 (1) ◽  
pp. 13-28 ◽  
Author(s):  
F. Primeau ◽  
E. Deleersnijder
Keyword(s):  
Boundary Condition ◽  
Ocean Circulation ◽  
Deep Sea ◽  
Neumann Boundary Condition ◽  
Three Dimensional ◽  
Neumann Boundary ◽  
Sea Surface ◽  
Global Ocean ◽  
Surface Boundary ◽  
Surface Boundary Condition

Abstract. An important issue for the interpretation of data from deep-sea cores is the time for tracers to be transported from the sea surface to the deep ocean. Global ocean circulation models can help shed light on the timescales over which a tracer comes to equilibrium in different regions of the ocean. In this note, we discuss how the most slowly decaying eigenmode of a model can be used to obtain a relevant timescale for a tracer that enters through the sea surface to become well mixed in the ocean interior. We show how this timescale depends critically on the choice between a Neumann surface boundary condition in which the flux of tracer is prescribed, a Robin surface boundary condition in which a combination of the flux and tracer concentration is prescribed or a Dirichlet surface boundary condition in which the concentration is prescribed. Explicit calculations with a 3-box model and a three-dimensional ocean circulation model show that the Dirichlet boundary condition when applied to only part of the surface ocean greatly overestimate the time needed to reach equilibrium. As a result regional-"injection" calculations which prescribe the surface concentration instead of the surface flux are not relevant for interpreting the regional disequilibrium between the Atlantic and Pacific found in paleo-tracer records from deep-sea cores. For tracers that enter the ocean through air-sea gas exchange a prescribed concentration boundary condition can be used to infer relevant timescales if the air-sea gas exchange rate is sufficiently fast, but the boundary condition must be applied over the entire ocean surface and not only to a patch of limited area. For tracers with a slow air-sea exchange rate such as 14C a Robin-type boundary condition is more relevant and for tracers such as δ18O that enter the ocean from melt water, a Neumann boundary condition is presumably more relevant. Our three-dimensional model results based on a steady-state modern circulation suggest that the relative disequilibrium between the deep Atlantic and Pacific is on the order of "only" 1200 years or less for a Neumann boundary condition and does not depend on the size and location of the patch where the tracer is injected.

Environmental predictors of deep-sea polymetallic nodule occurrence in the global ocean

Geology ◽  
2020 ◽  
Vol 48 (3) ◽  
pp. 293-297
Author(s):  
Adriana Dutkiewicz ◽  
Alexander Judge ◽  
R. Dietmar Müller
Keyword(s):  
Ocean Circulation ◽  
Deep Sea ◽  
Circulation Model ◽  
Global Ocean ◽  
Environmental Drivers ◽  
Bottom Current ◽  
Organic Carbon Content ◽  
Environmental Predictors ◽  
Data Set ◽  
Geological Processes

Abstract Polymetallic nodules found on the abyssal plains of the oceans represent one of the slowest known geological processes, and are a source of critical and rare metals for frontier technologies. A quantitative assessment of their occurrence worldwide has been hampered by a research focus on the northeastern Pacific Ocean and the lack of a global open-access data set of nodules. We have compiled a global data set of >10,000 seabed nodule and control samples, and combine it with digital grids of key environmental parameters to generate a predictive machine-learning model of nodule occurrence. In order of decreasing parameter ranking, we find that nodules are associated with very low sedimentation rates (< 0.5 cm/k.y.), moderately high oxygen values (150 and 210 mmol/m3), lithologies of clay followed by calcareous ooze, low summer surface productivity (<300 mgC/m2/day), low benthic biomass concentration (<1 log mgC/m2), water depths >4500 m, and low total organic carbon content (0.3–0.5 wt%). Competing hypotheses for nodule sustention and thus continued growth on the seafloor are the removal of sediment by bottom-water currents and biological activity. Using a high-resolution eddy-resolving ocean circulation model, we find that the bottom-current speeds over nodule fields are too low (<5 cm/s) to remove sediment, implicating the activity of epibenthic megafauna as the most likely mechanism. Our global nodule probability map combined with the assessment of a range of environmental drivers provides an improved basis for decision and policy making in the controversial area of deep-sea exploration.

Application of machine learning to map the global distribution of deep-sea sediments

2020 ◽  
Author(s):  
Markus Diesing
Keyword(s):  
Machine Learning ◽  
Deep Sea ◽  
Learning Algorithm ◽  
Predictor Variable ◽  
Global Ocean ◽  
Predictor Variables ◽  
Maximum Temperature ◽  
Sea Floor ◽  
Deep Sea Sediments ◽  
Calcareous Sediment

<p>The deep-sea floor accounts for >90% of seafloor area and >70% of the Earth’s surface. It acts as a receptor of the particle flux from the surface layers of the global ocean, is a place of biogeochemical cycling, records environmental and climate conditions through time and provides habitat for benthic organisms. Maps of the spatial patterns of deep-sea sediments are therefore a major prerequisite for many studies addressing aspects of deep-sea sedimentation, biogeochemistry, ecology and related fields.</p><p>A new digital map of deep-sea sediments of the global ocean is presented. The map was derived by applying the Random Forest machine-learning algorithm to published sample data of seafloor lithologies and environmental predictor variables. The selection of environmental predictors was initially based on the current understanding of the controls on the distribution of deep-sea sediments and the availability of data. A predictor variable selection process ensured that only important and uncorrelated variables were employed in the model. The three most important predictor variables were sea-surface maximum salinity, sea-floor maximum temperature and bathymetry. The occurrence probabilities of seven seafloor lithologies (Calcareous sediment, Clay, Diatom ooze, Lithogenous sediment, Mixed calcareous-siliceous ooze, Radiolarian ooze and Siliceous mud) were spatially predicted. The final map shows the most probable seafloor lithology and an associated probability value, which may be viewed as a spatially explicit measure of map confidence. An assessment of the accuracy of the map was based on a test set of observations not used for model training. Overall map accuracy was 69.5% (95% confidence interval: 67.9% - 71.1%). The sea-floor lithology map bears some resemblance with previously published hand-drawn maps in that the distribution of Calcareous sediment, Clay and Diatom ooze are very similar. Clear differences were however also noted: Most strikingly, the map presented here does not display a band of Radiolarian ooze in the equatorial Pacific.</p><p>The probability surfaces of individual seafloor lithologies, the categorical map of the seven mapped lithologies and the associated map confidence will be made freely available. It is hoped that they form a useful basis for research pertaining to deep-sea sediments.</p>

Sign in / Sign up

Export Citation Format

Share Document