scholarly journals Microstructure and composition of marine aggregates as co-determinants for vertical particulate organic carbon transfer in the global ocean

2019 ◽  
Author(s):  
Joeran Maerz ◽  
Katharina D. Six ◽  
Irene Stemmler ◽  
Soeren Ahmerkamp ◽  
Tatiana Ilyina
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Global Ocean ◽  
Co2 Uptake ◽  
Diatom Frustule ◽  
Marine Aggregates ◽  
Carbon Pump ◽  
The Impact ◽  
Biological Carbon Pump ◽  
Sinking Velocity

Abstract. Marine aggregates are the vector for biogenically bound carbon and nutrients from the euphotic zone to the interior of the oceans. To improve the representation of this biological carbon pump in the global biogeochemical HAMburg Ocean Carbon Cycle (HAMOCC) model, we implemented a novel Microstructure, Multiscale, Mechanistic, Marine Aggregates in the Global Ocean (M4AGO) sinking scheme. M4AGO explicitly represents the size, microstructure, heterogeneous composition, density, and porosity of aggregates, and ties ballasting mineral and particulate organic carbon (POC) fluxes together. Additionally, we incorporated temperature-dependent remineralization of POC. We compare M4AGO with the standard HAMOCC version, where POC fluxes follow a Martin curve approach with linearly increasing sinking velocity with depth, and temperature-independent remineralization. Minerals descend separately with a constant speed. In contrast to the standard HAMOCC, M4AGO reproduces the latitudinal pattern of POC transfer efficiency which has been recently constrained by Weber et al. (2016). High latitudes show transfer efficiencies of ≈ 0.25 ± 0.04 and the subtropical gyres show lower values of about 0.10 ± 0.03. In addition to temperature as a driving factor, diatom frustule size co-determines POC fluxes in silicifiers-dominated ocean regions while calcium carbonate enhances the aggregate excess density, and thus sinking velocity in subtropical gyres. In ocean standalone runs and rising carbon dioxide (CO2) without CO2 climate feedback, M4AGO alters the regional ocean-atmosphere CO2 fluxes compared to the standard model. M4AGO exhibits higher CO2 uptake in the Southern Ocean compared to the standard run while in subtropical gyres, less CO2 is taken up. Overall, the global oceanic CO2 uptake remains the same. With the explicit representation of measurable aggregate properties, M4AGO can serve as a testbed for evaluating the impact of aggregate-associated processes on global biogeochemical cycles, and, in particular, on the biological carbon pump.

scholarly journals Microstructure and composition of marine aggregates as co-determinants for vertical particulate organic carbon transfer in the global ocean

2020 ◽  
Vol 17 (7) ◽  
pp. 1765-1803 ◽  
Author(s):  
Joeran Maerz ◽  
Katharina D. Six ◽  
Irene Stemmler ◽  
Soeren Ahmerkamp ◽  
Tatiana Ilyina
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Global Ocean ◽  
Co2 Uptake ◽  
Diatom Frustule ◽  
Marine Aggregates ◽  
Carbon Pump ◽  
The Impact ◽  
Biological Carbon Pump ◽  
Sinking Velocity

Abstract. Marine aggregates are the vector for biogenically bound carbon and nutrients from the euphotic zone to the interior of the oceans. To improve the representation of this biological carbon pump in the global biogeochemical HAMburg Ocean Carbon Cycle (HAMOCC) model, we implemented a novel Microstructure, Multiscale, Mechanistic, Marine Aggregates in the Global Ocean (M4AGO) sinking scheme. M4AGO explicitly represents the size, microstructure, heterogeneous composition, density and porosity of aggregates and ties ballasting mineral and particulate organic carbon (POC) fluxes together. Additionally, we incorporated temperature-dependent remineralization of POC. We compare M4AGO with the standard HAMOCC version, where POC fluxes follow a Martin curve approach with (i) linearly increasing sinking velocity with depth and (ii) temperature-independent remineralization. Minerals descend separately with a constant speed. In contrast to the standard HAMOCC, M4AGO reproduces the latitudinal pattern of POC transfer efficiency, as recently constrained by Weber et al. (2016). High latitudes show transfer efficiencies of ≈0.25±0.04, and the subtropical gyres show lower values of about 0.10±0.03. In addition to temperature as a driving factor for remineralization, diatom frustule size co-determines POC fluxes in silicifier-dominated ocean regions, while calcium carbonate enhances the aggregate excess density and thus sinking velocity in subtropical gyres. Prescribing rising carbon dioxide (CO2) concentrations in stand-alone runs (without climate feedback), M4AGO alters the regional ocean atmosphere CO2 fluxes compared to the standard model. M4AGO exhibits higher CO2 uptake in the Southern Ocean compared to the standard run, while in subtropical gyres, less CO2 is taken up. Overall, the global oceanic CO2 uptake remains the same. With the explicit representation of measurable aggregate properties, M4AGO can serve as a test bed for evaluating the impact of aggregate-associated processes on global biogeochemical cycles and, in particular, on the biological carbon pump.

scholarly journals Global database of ratios of particulate organic carbon to thorium-234 in the ocean: improving estimates of the biological carbon pump

2020 ◽  
Vol 12 (2) ◽  
pp. 1267-1285 ◽  
Author(s):  
Viena Puigcorbé ◽  
Pere Masqué ◽  
Frédéric A. C. Le Moigne
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Mixed Layer Depth ◽  
Sediment Traps ◽  
Data Repository ◽  
The South ◽  
South Indian ◽  
Wide Range ◽  
Carbon Pump ◽  
Biological Carbon Pump

Abstract. The ocean's biological carbon pump (BCP) plays a major role in the global carbon cycle. A fraction of the photosynthetically fixed organic carbon produced in surface waters is exported below the sunlit layer as settling particles (e.g., marine snow). Since the seminal works on the BCP, global estimates of the global strength of the BCP have improved but large uncertainties remain (from 5 to 20 Gt C yr−1 exported below the euphotic zone or mixed-layer depth). The 234Th technique is widely used to measure the downward export of particulate organic carbon (POC). This technique has the advantage of allowing a downward flux to be determined by integrating the deficit of 234Th in the upper water column and coupling it to the POC∕234Th ratio in sinking particles. However, the factors controlling the regional, temporal, and depth variations of POC∕234Th ratios are poorly understood. We present a database of 9318 measurements of the POC∕234Th ratio in the ocean, from the surface down to >5500 m, sampled on three size fractions (∼>0.7 µm, ∼1–50 µm, ∼>50 µm), collected with in situ pumps and bottles, and also from bulk particles collected with sediment traps. The dataset is archived in the data repository PANGAEA® under https://doi.org/10.1594/PANGAEA.911424 (Puigcorbé, 2019). The samples presented in this dataset were collected between 1989 and 2018, and the data have been obtained from published papers and open datasets available online. Unpublished data have also been included. Multiple measurements can be found in most of the open ocean provinces. However, there is an uneven distribution of the data, with some areas highly sampled (e.g., China Sea, Bermuda Atlantic Time Series station) compared to some others that are not well represented, such as the southeastern Atlantic, the south Pacific, and the south Indian oceans. Some coastal areas, although in a much smaller number, are also included in this global compilation. Globally, based on different depth horizons and climate zones, the median POC∕234Th ratios have a wide range, from 0.6 to 18 µmol dpm−1.

scholarly journals The Ballast Effect of Lithogenic Matter and its Influences on the Carbon Fluxes in the Indian Ocean

2018 ◽  
Author(s):  
Tim Rixen ◽  
Birgit Gaye ◽  
Kay-Christian Emeis ◽  
Venkitasubramani Ramaswamy
Keyword(s):  
Organic Matter ◽  
Indian Ocean ◽  
Organic Carbon ◽  
Deep Sea ◽  
Carbon Fluxes ◽  
Co2 Uptake ◽  
Surface Ocean ◽  
Carbon Pump ◽  
The Indian Ocean ◽  
The Impact

Abstract. Data obtained from long-term sediment trap experiments in the Indian Ocean were analysed in conjunction with satellite-derived observations and results obtained from a box model to study the influence of primary production and the ballast effect on organic carbon flux into the deep sea. The results are used to better understand the associated impacts on the CO2 uptake of the organic carbon pump. In line with other findings derived from global data sets, our results suggest that a preferential export of organic matter in slower-sinking particles reduces the transfer efficiency of exported organic matter in high-productive systems compared with low-productive regions. The resulting enhanced respiration of organic matter maintains the high nutrient availability in the surface ocean and thus the high productivity during the summer and winter bloom in the Arabian Sea. In turn, mineral ballast is essential for the transport of organic matter and nutrients into the deep sea. The additional lithogenic ballast effect can increase organic carbon fluxes by 60 %. Our model results indicate that lithogenic ballast enhances the CO2 uptake of the organic carbon pump by increasing the amount of nutrients utilised by the organic carbon pump to bind CO2. By enhancing the export of organic matter into the deep sea, the ballast effect increases the residence time of these nutrients in the ocean. They lose the attached CO2 if they are introduced into the surface ocean at higher latitude, where the lack of light prevents photosynthesis in winter. Considering the impact of the lithogenic ballast effect on the organic carbon export into the deep sea and the enhanced mobilisation of lithogenic matter due to land-use changes, it is assumed that humans influence the CO2 uptake of the organic carbon pump, which might hold relevance for the discussion about the anthropogenic CO2 uptake of the ocean.

scholarly journals Global database of oceanic particulate organic carbon to <sup>234</sup>Th ratios: Improving estimates of the biological carbon pump

2020 ◽  
Author(s):  
Viena Puigcorbé ◽  
Pere Masqué ◽  
Fréderic A. C. Le Moigne
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Mixed Layer Depth ◽  
Sediment Traps ◽  
Data Repository ◽  
The South ◽  
South Indian ◽  
Wide Range ◽  
Carbon Pump ◽  
Biological Carbon Pump

Abstract. The ocean's biological carbon pump (BCP) plays a major role in the global earth carbon cycle. A fraction of the photosynthetically fixed organic carbon produced in surface waters is exported below the sunlit layer in the form of settling particles (e.g. marine snow). Since the seminal works on the BCP, global estimates of the global strength of the BCP have improved but large uncertainties remain (from 5 to 20 GtC yr−1 exported below the euphotic zone or mixed layer depth). The 234Th technique is widely used to measure the downward export of particulate organic carbon (POC). This technique has the advantage to allow a downward flux to be determined by integrating the deficit of 234Th in the upper water column and coupling it to an estimate of the POC/234Th ratio in sinking matter. However, the factors controlling the regional, temporal and depth variations of POC/234Th ratios are poorly understood. We present a database of 9110 measurements of the POC/234Th ratio in the ocean, from the surface down to > 5500 m, sampled on three size fractions (~ > 0.7 μm, ~ 1–50 μm, ~ > 50 μm), collected with in situ pumps and bottles, and also from bulk particles collected with sediment traps. The dataset is archived on the data repository PANGAEA® (https://www.pangaea.de/) under https://doi.pangaea.de/10.1594/PANGAEA.902103 (Puigcorbé, 2019). The samples presented in this dataset were collected between 1989 and 2016 and the data have been obtained from published papers and open datasets available online. Unpublished data has also been included. Most of the open ocean provinces are represented by multiple measurements. However, there is an uneven distribution of the data, with some areas highly sampled (e.g, China Sea, Bermuda Atlantic Time Series station) compared to some others that are not well represented, such as the southeastern Atlantic, the south Pacific and the south Indian oceans. Some costal areas, although in a much smaller number, are also included in this global compilation. Globally, based on different depths horizons and climate zones, the median POC/234Th ratios have a wide range, from 0.6 to 18 μmol dpm-1.

Biogeochemical and ecological features of sinking particulate matter in the deep Ionian Sea (E. Mediterranean) during a 10-year time series study: impacts of atmospheric and oceanographic variabilities on carbon production and sequestration

2021 ◽  
Author(s):  
Alexandra Gogou ◽  
Constantine Parinos ◽  
Spyros Stavrakakis ◽  
Emmanouil Proestakis ◽  
Maria Kanakidou ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Organic Carbon ◽  
Carbon Cycle ◽  
Atmospheric Deposition ◽  
Water Column ◽  
Particulate Organic Carbon ◽  
Nutrient Dynamics ◽  
Ionian Sea ◽  
Ecological Features ◽  
The Impact

&lt;p&gt;Biotic and abiotic processes that form, alter, transport, and remineralize particulate organic carbon, silicon, calcium carbonate, and other minor and trace chemical species in the water column are central to the ocean&amp;#8217;s ecological and biogeochemical functioning and of fundamental importance to the ocean carbon cycle. Sinking particulate matter is the major vehicle for exporting carbon from the sea surface to the deep sea. During its transit towards the sea floor, most particulate organic carbon (POC) is returned to inorganic form and redistributed in the water column. This redistribution determines the surface concentration of dissolved CO&lt;sub&gt;2&lt;/sub&gt;, and hence the rate at which the ocean can absorb CO&lt;sub&gt;2&lt;/sub&gt; from the atmosphere. The ability to predict quantitatively the depth profile of remineralization is therefore critical to deciphering the response of the global carbon cycle to natural and human-induced changes.&lt;/p&gt;&lt;p&gt;Aiming to investigate the significant biogeochemical and ecological features and provide new insights on the sources and cycles of sinking particulate matter, a mooring line of five sediment traps was deployed from 2006 to 2015 (with some gap periods) at 5 successive water column depths (700, 1200, 2000, 3200 and 4300 m) in the SE Ionian Sea, northeastern Mediterranean (&amp;#8216;NESTOR&amp;#8217; site). We have examined the long-term records of downward fluxes for Corg, N&lt;sub&gt;tot&lt;/sub&gt;, &amp;#948;&lt;sup&gt;13&lt;/sup&gt;Corg and &amp;#948;&lt;sup&gt;15&lt;/sup&gt;N&lt;sub&gt;tot&lt;/sub&gt;, along with the associated ballast minerals (opal, lithogenics and CaCO&lt;sub&gt;3&lt;/sub&gt;), lipid biomarkers, Chl-a and PP rates, phytoplankton composition, nutrient dynamics and atmospheric deposition. &amp;#160;&lt;/p&gt;&lt;p&gt;The satellite-derived seasonal and interannual variability of phytoplankton metrics (biomass and phenology) and atmospheric deposition (meteorology and air masses origin) was examined for the period of the sediment trap experiment. Regarding the atmospheric deposition, synergistic opportunities using Earth Observation satellite lidar and radiometer systems are proposed (e.g. Cloud&amp;#8208;Aerosol Lidar with Orthogonal Polarization - CALIOP, Moderate Resolution Imaging Spectroradiometer - MODIS), aiming towards a four&amp;#8208;dimensional exploitation of atmospheric aerosol loading (e.g. Dust Optical Depth) in the study area.&lt;/p&gt;&lt;p&gt;Our main goals are to: i) develop a comprehensive knowledge of carbon fluxes and associated mineral ballast fluxes from the epipelagic to the mesopelagic and bathypelagic layers, ii) elucidate the mechanisms governing marine productivity and carbon export and sequestration to depth and iii) shed light on the impact of atmospheric forcing and deposition in respect to regional and large scale circulation patterns and climate variability and the prevailing oceanographic processes (internal variability).&lt;/p&gt;&lt;p&gt;Acknowledgments&lt;/p&gt;&lt;p&gt;We acknowledge support of this work by the Action &amp;#8216;National Network on Climate Change and its Impacts &amp;#8211; &lt;strong&gt;CLIMPACT&lt;/strong&gt;&amp;#8217;, funded by the Public Investment Program of Greece (GSRT, Ministry of Development and Investments).&lt;/p&gt;

scholarly journals Estimation of the Particulate Organic Carbon to Chlorophyll-a Ratio Using MODIS-Aqua in the East/Japan Sea, South Korea

2020 ◽  
Vol 12 (5) ◽  
pp. 840 ◽  
Author(s):  
Dabin Lee ◽  
SeungHyun Son ◽  
HuiTae Joo ◽  
Kwanwoo Kim ◽  
Myung Joon Kim ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Chlorophyll A ◽  
Primary Productivity ◽  
Seasonal Variability ◽  
Japan Sea ◽  
Global Ocean ◽  
Phytoplankton Communities

In recent years, the change of marine environment due to climate change and declining primary productivity have been big concerns in the East/Japan Sea, Korea. However, the main causes for the recent changes are still not revealed clearly. The particulate organic carbon (POC) to chlorophyll-a (chl-a) ratio (POC:chl-a) could be a useful indicator for ecological and physiological conditions of phytoplankton communities and thus help us to understand the recent reduction of primary productivity in the East/Japan Sea. To derive the POC in the East/Japan Sea from a satellite dataset, the new regional POC algorithm was empirically derived with in-situ measured POC concentrations. A strong positive linear relationship (R2 = 0.6579) was observed between the estimated and in-situ measured POC concentrations. Our new POC algorithm proved a better performance in the East/Japan Sea compared to the previous one for the global ocean. Based on the new algorithm, long-term POC:chl-a ratios were obtained in the entire East/Japan Sea from 2003 to 2018. The POC:chl-a showed a strong seasonal variability in the East/Japan Sea. The spring and fall blooms of phytoplankton mainly driven by the growth of large diatoms seem to be a major factor for the seasonal variability in the POC:chl-a. Our new regional POC algorithm modified for the East/Japan Sea could potentially contribute to long-term monitoring for the climate-associated ecosystem changes in the East/Japan Sea. Although the new regional POC algorithm shows a good correspondence with in-situ observed POC concentrations, the algorithm should be further improved with continuous field surveys.

scholarly journals Impact of hydrothermalism on the ocean iron cycle

2016 ◽  
Vol 374 (2081) ◽  
pp. 20150291 ◽  
Author(s):  
Alessandro Tagliabue ◽  
Joseph Resing
Keyword(s):  
Southern Ocean ◽  
Oxidation Kinetics ◽  
State Of The Art ◽  
Section Data ◽  
Trace Element Chemistry ◽  
Carbon Pump ◽  
Climatic Impacts ◽  
The Impact ◽  
Biological Carbon Pump

As the iron supplied from hydrothermalism is ultimately ventilated in the iron-limited Southern Ocean, it plays an important role in the ocean biological carbon pump. We deploy a set of focused sensitivity experiments with a state of the art global model of the ocean to examine the processes that regulate the lifetime of hydrothermal iron and the role of different ridge systems in governing the hydrothermal impact on the Southern Ocean biological carbon pump. Using GEOTRACES section data, we find that stabilization of hydrothermal iron is important in some, but not all regions. The impact on the Southern Ocean biological carbon pump is dominated by poorly explored southern ridge systems, highlighting the need for future exploration in this region. We find inter-basin differences in the isopycnal layer onto which hydrothermal Fe is supplied between the Atlantic and Pacific basins, which when combined with the inter-basin contrasts in oxidation kinetics suggests a muted influence of Atlantic ridges on the Southern Ocean biological carbon pump. Ultimately, we present a range of processes, operating at distinct scales, that must be better constrained to improve our understanding of how hydrothermalism affects the ocean cycling of iron and carbon. This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’.

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