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  • 1
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation. Experimental evidence suggests that if these trends ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Ecosystem processes are important determinants of the biogeochemistry of the ocean, and they can be profoundly affected by changes in climate. Ocean models currently express ecosystem processes through empirically derived parameterizations that tightly link key geochemical tracers to ocean physics. The explicit inclusion of ecosystem processes in models will permit ecological changes to be taken into account, and will allow us to address several important questions, including the causes of observed glacial–interglacial changes in atmospheric trace gases and aerosols, and how the oceanic uptake of CO2 is likely to change in the future. There is an urgent need to assess our mechanistic understanding of the environmental factors that exert control over marine ecosystems, and to represent their natural complexity based on theoretical understanding. We present a prototype design for a Dynamic Green Ocean Model (DGOM) based on the identification of (a) key plankton functional types that need to be simulated explicitly to capture important biogeochemical processes in the ocean; (b) key processes controlling the growth and mortality of these functional types and hence their interactions; and (c) sources of information necessary to parameterize each of these processes within a modeling framework. We also develop a strategy for model evaluation, based on simulation of both past and present mean state and variability, and identify potential sources of validation data for each. Finally, we present a DGOM-based strategy for addressing key questions in ocean biogeochemistry. This paper thus presents ongoing work in ocean biogeochemical modeling, which, it is hoped will motivate international collaborations to improve our understanding of the role of the ocean in the climate system.
    Type of Medium: Electronic Resource
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  • 3
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    In:  Supplement to: Hauck, Judith; Völker, Christoph; Wolf-Gladrow, Dieter A; Laufkötter, Charlotte; Vogt, Meike; Aumont, Olivier; Bopp, Laurent; Buitenhuis, Erik Theodoor; Doney, Scott C; Dunne, John; Gruber, Nicolas; Hashioka, Taketo; John, Jasmin; Le Quéré, Corinne; Lima, Ivan D; Nakano, Hideyuki; Séférian, Roland; Totterdell, Ian J (2015): On the Southern Ocean CO2 uptake and the role of the biological carbon pump in the 21st century. Global Biogeochemical Cycles, 29(9), 1451-1470, https://doi.org/10.1002/2015GB005140
    Publication Date: 2023-01-13
    Description: We use a suite of eight ocean biogeochemical/ecological general circulation models from the MAREMIP and CMIP5 archives to explore the relative roles of changes in winds (positive trend of Southern Annular Mode, SAM) and in warming- and freshening-driven trends of upper ocean stratification in altering export production and CO2 uptake in the Southern Ocean at the end of the 21st century. The investigated models simulate a broad range of responses to climate change, with no agreement ona dominance of either the SAM or the warming signal south of 44° S. In the southernmost zone, i.e., south of 58° S, they concur on an increase of biological export production, while between 44 and 58° S the models lack consensus on the sign of change in export. Yet, in both regions, the models show an enhanced CO2 uptake during spring and summer. This is due to a larger CO 2 (aq) drawdown by the same amount of summer export production at a higher Revelle factor at the end of the 21st century. This strongly increases the importance of the biological carbon pump in the entire Southern Ocean. In the temperate zone, between 30 and 44° S all models show a predominance of the warming signal and a nutrient-driven reduction of export production. As a consequence, the share of the regions south of 44° S to the total uptake of the Southern Ocean south of 30° S is projected to increase at the end of the 21st century from 47 to 66% with a commensurable decrease to the north. Despite this major reorganization of the meridional distribution of the major regions of uptake, the total uptake increases largely in line with the rising atmospheric CO2. Simulations with the MITgcm-REcoM2 model show that this is mostly driven by the strong increase of atmospheric CO2, with the climate-driven changes of natural CO2 exchange offsetting that trend only to a limited degree (~10%) and with negligible impact of climate effects on anthropogenic CO2 uptake when integrated over a full annual cycle south of 30° S.
    Keywords: File content; Uniform resource locator/link to file; Uniform resource locator/link to image
    Type: Dataset
    Format: text/tab-separated-values, 27 data points
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  • 4
    Publication Date: 2020-02-06
    Description: The Ocean Model Intercomparison Project (OMIP) focuses on the physics and biogeochemistry of the ocean component of Earth system models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6). OMIP aims to provide standard protocols and diagnostics for ocean models, while offering a forum to promote their common assessment and improvement. It also offers to compare solutions of the same ocean models when forced with reanalysis data (OMIP simulations) vs. when integrated within fully coupled Earth system models (CMIP6). Here we detail simulation protocols and diagnostics for OMIP's biogeochemical and inert chemical tracers. These passive-tracer simulations will be coupled to ocean circulation models, initialized with observational data or output from a model spin-up, and forced by repeating the 1948–2009 surface fluxes of heat, fresh water, and momentum. These so-called OMIP-BGC simulations include three inert chemical tracers (CFC-11, CFC-12, SF6) and biogeochemical tracers (e.g., dissolved inorganic carbon, carbon isotopes, alkalinity, nutrients, and oxygen). Modelers will use their preferred prognostic BGC model but should follow common guidelines for gas exchange and carbonate chemistry. Simulations include both natural and total carbon tracers. The required forced simulation (omip1) will be initialized with gridded observational climatologies. An optional forced simulation (omip1-spunup) will be initialized instead with BGC fields from a long model spin-up, preferably for 2000 years or more, and forced by repeating the same 62-year meteorological forcing. That optional run will also include abiotic tracers of total dissolved inorganic carbon and radiocarbon, CTabio and 14CTabio, to assess deep-ocean ventilation and distinguish the role of physics vs. biology. These simulations will be forced by observed atmospheric histories of the three inert gases and CO2 as well as carbon isotope ratios of CO2. OMIP-BGC simulation protocols are founded on those from previous phases of the Ocean Carbon-Cycle Model Intercomparison Project. They have been merged and updated to reflect improvements concerning gas exchange, carbonate chemistry, and new data for initial conditions and atmospheric gas histories. Code is provided to facilitate their implementation.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
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  • 5
    Publication Date: 2017-08-28
    Description: Iron limits phytoplankton growth and hence the biological carbon pump in the Southern Ocean1. Models assessing the impacts of iron on the global carbon cycle generally rely on dust input and sediment resuspension as the predominant sources2, 3. Although it was previously thought that most iron from deep-ocean hydrothermal activity was inaccessible to phytoplankton because of the formation of particulates4, it has been suggested that iron from hydrothermal activity5, 6, 7 may be an important source of oceanic dissolved iron8, 9, 10, 11, 12, 13. Here we use a global ocean model to assess the impacts of an annual dissolved iron flux of approximately 9×108 mol, as estimated from regional observations of hydrothermal activity11, 12, on the dissolved iron inventory of the world’s oceans. We find the response to the input of hydrothermal dissolved iron is greatest in the Southern Hemisphere oceans. In particular, observations of the distribution of dissolved iron in the Southern Ocean3 (Chever et al., manuscript in preparation; Bowie et al., manuscript in preparation) can be replicated in our simulations only when our estimated iron flux from hydrothermal sources is included. As the hydrothermal flux of iron is relatively constant over millennial timescales14, we propose that hydrothermal activity can buffer the oceanic dissolved iron inventory against shorter-term fluctuations in dust deposition.
    Type: Article , PeerReviewed
    Format: text
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  • 6
    Publication Date: 2017-12-12
    Description: Highlights: • Strong intraseasonal variability of near shore plankton in Peru upwelling system. • Chlorophyll variability is driven by the intraseasonal coastally trapped waves. • Chlorophyll anomalies propagate poleward at speed of high order CTW mode. • Intraseasonal wind impacts mainly the northern shelf variability and at 20–30 days. Abstract The impact of intraseasonal coastal-trapped waves on the nearshore Peru ecosystem is investigated using observations and a regional eddy-resolving physical-ecosystem coupled model. Model results show that intraseasonal variability over the period 2000–2006 represents about one fourth of the total surface chlorophyll variance and one third of the carbon export variance on the Peruvian shelf. Evidence is presented that subsurface nutrient and chlorophyll intraseasonal variability are mainly forced by the coastally trapped waves triggered by intraseasonal equatorial Kelvin waves reaching the South American coast, and propagate poleward along the Peru shore at a speed close to that of high order coastal trapped waves modes. The currents associated with the coastal waves induce an input of nutrients that triggers a subsequent phytoplankton bloom and carbon export. The impact of the local wind-forced intraseasonal variability on the ecosystem is of a similar order of magnitude to that remotely forced in the northern part of the Peru shelf on [50–90] day time scales and dominates over the entire shelf on [20–30] day time scales.
    Type: Article , PeerReviewed
    Format: text
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  • 7
    Publication Date: 2014-08-27
    Description: Reactive haemophagocytic syndrome is a life-threatening disease for which factors influencing the outcome remain unclear. We sought to identify determinants of early mortality in patients with reactive haemophagocytic syndrome by conducting a non-interventional retrospective multicentre study in three tertiary care teaching hospitals over a 6-year period. The medical files of 162 patients fulfilling our diagnostic criteria of haemophagocytic syndrome were reviewed. Patients were classified according to 30-d outcome following diagnosis. Thirty-three patients (20·4%) died within 30 d. Clinical features at diagnosis associated with 30-d death in univariate analysis were older age ( P  = 0·004), underlying lymphoma ( P  = 0·04), lower platelet count ( P  = 0·001) and elevated aspartate aminotransferase and lactate dehydrogenase ( P  = 0·04 both). The use of etoposide as a first-line treatment tended to be associated with a better outcome ( P  = 0·079). In multivariate analyses, increasing age, decreasing platelet count, underlying lymphoma and no etoposide in the management were associated with a poorer prognosis ( P  = 0·03, 0·01, 0·003 and 0·04, respectively). These prognostic factors could help to identify those patients more severely affected by reactive haemophagocytic syndrome, who should benefit from aggressive supportive care, combined with specific treatment of the precipitating factor.
    Print ISSN: 0007-1048
    Electronic ISSN: 1365-2141
    Topics: Medicine
    Published by Wiley-Blackwell
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  • 8
    Publication Date: 2015-11-26
    Description: Satellite data and models suggest oceanic productivity is reduced in response to less nutrient supply under warming. In contrast, anthropogenic aerosols provide nutrients and exert a fertilizing effect, but its contribution to evolution of oceanic productivity is unknown. We simulate the response of oceanic biogeochemistry to anthropogenic aerosols deposition under varying climate from 1850 to 2010. We find a positive response of observed chlorophyll to deposition of anthropogenic aerosols. Our results suggest that anthropogenic aerosols reduce the sensitivity of oceanic productivity to warming from −15.2±1.8 to −13.3±1.6 Pg C y −1 °C −1 in global stratified oceans during 1948–2007. The reducing percentage over the North Atlantic, North Pacific and Indian oceans reaches 40, 24 and 25%, respectively. We hypothesize that inevitable reduction of aerosol emissions in response to higher air-quality standards in the future might accelerate the decline of oceanic productivity per unit warming.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
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  • 9
    Publication Date: 2015-11-06
    Description: We use a suite of eight ocean biogeochemical/ecological general circulation models from the Marine Ecosystem Model Intercomparison Project and Coupled Model Intercomparison Project Phase 5 archives to explore the relative roles of changes in winds (positive trend of Southern Annular Mode, SAM) and in warming- and freshening-driven trends of upper ocean stratification in altering export production and CO2 uptake in the Southern Ocean at the end of the 21st century. The investigated models simulate a broad range of responses to climate change, with no agreement on a dominance of either the SAM or the warming signal south of 44°S. In the southernmost zone, i.e., south of 58°S, they concur on an increase of biological export production, while between 44 and 58°S the models lack consensus on the sign of change in export. Yet in both regions, the models show an enhanced CO2 uptake during spring and summer. This is due to a larger CO2(aq) drawdown by the same amount of summer export production at a higher Revelle factor at the end of the 21st century. This strongly increases the importance of the biological carbon pump in the entire Southern Ocean. In the temperate zone, between 30 and 44°S, all models show a predominance of the warming signal and a nutrient-driven reduction of export production. As a consequence, the share of the regions south of 44°S to the total uptake of the Southern Ocean south of 30°S is projected to increase at the end of the 21st century from 47 to 66% with a commensurable decrease to the north. Despite this major reorganization of the meridional distribution of the major regions of uptake, the total uptake increases largely in line with the rising atmospheric CO2. Simulations with the MITgcm-REcoM2 model show that this is mostly driven by the strong increase of atmospheric CO2, with the climate-driven changes of natural CO2 exchange offsetting that trend only to a limited degree (∼10%) and with negligible impact of climate effects on anthropogenic CO2 uptake when integrated over a full annual cycle south of 30°S.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
    Format: application/pdf
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  • 10
    Publication Date: 2016-10-05
    Description: Accurate projections of marine particle export production (EP) are crucial for predicting the response of the marine carbon cycle to climate change, yet models show a wide range in both global EP and their responses to climate change. This is, in part, due to EP being the net result of a series of processes, starting with net primary production (NPP) in the sunlit upper ocean, followed by the formation of particulate organic matter and the subsequent sinking and remineralisation of these particles, with each of these processes responding differently to changes in environmental conditions. Here, we compare future projections in EP over the 21st century, generated by four marine ecosystem models under the high emission scenario Representative Concentra- tion Pathways (RCP) 8.5 of the Intergovernmental Panel on Climate Change (IPCC), and determine the processes driving these changes. The models simulate small to modest decreases in global EP between −1 and −12 %. Models differ greatly with regard to the drivers causing these changes. Among them, the formation of particles is the most uncertain process with models not agreeing on either magnitude or the direction of change. The removal of the sinking particles by remineralisation is simulated to increase in the low and intermediate latitudes in three models, driven by either warming-induced increases in remineralisation or slower particle sinking, and show insignificant changes in the remaining model. Changes in ecosystem structure, particularly the relative role of diatoms matters as well, as diatoms produce larger and denser particles that sink faster and are partly protected from remineralisation. Also this controlling factor is afflicted with high uncertainties, particularly since the models differ already substantially with regard to both the initial (present-day) distribution of diatoms (between 11–94 % in the Southern Ocean) and the diatom contribution to particle formation (0.6–3.8 times higher than their contribution to biomass). As a consequence, changes in diatom concentration are a strong driver for EP changes in some models but of low significance in others. Observational and experimental constraints on ecosystem structure and how the fixed carbon is routed through the ecosystem to produce export production are urgently needed in order to improve current generation ecosystem models and their ability to project future changes.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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