Vogt Meike

No Thumbnail Available
Last Name
First Name

Search Results

Now showing 1 - 7 of 7
  • Article
    Drivers and uncertainties of future global marine primary production in marine ecosystem models
    (Copernicus Publications on behalf of the European Geosciences Union, 2015-12-07) Laufkötter, Charlotte ; Vogt, Meike ; Gruber, Nicolas ; Aita-Noguchi, M. ; Aumont, Olivier ; Bopp, Laurent ; Buitenhuis, Erik T. ; Doney, Scott C. ; Dunne, John P. ; Hashioka, Taketo ; Hauck, Judith ; Hirata, Takafumi ; John, Jasmin G. ; Le Quere, Corinne ; Lima, Ivan D. ; Nakano, Hideyuki ; Seferian, Roland ; Totterdell, Ian J. ; Vichi, Marcello ; Volker, Chrisoph
    Past model studies have projected a global decrease in marine net primary production (NPP) over the 21st century, but these studies focused on the multi-model mean rather than on the large inter-model differences. Here, we analyze model-simulated changes in NPP for the 21st century under IPCC's high-emission scenario RCP8.5. We use a suite of nine coupled carbon–climate Earth system models with embedded marine ecosystem models and focus on the spread between the different models and the underlying reasons. Globally, NPP decreases in five out of the nine models over the course of the 21st century, while three show no significant trend and one even simulates an increase. The largest model spread occurs in the low latitudes (between 30° S and 30° N), with individual models simulating relative changes between −25 and +40 %. Of the seven models diagnosing a net decrease in NPP in the low latitudes, only three simulate this to be a consequence of the classical interpretation, i.e., a stronger nutrient limitation due to increased stratification leading to reduced phytoplankton growth. In the other four, warming-induced increases in phytoplankton growth outbalance the stronger nutrient limitation. However, temperature-driven increases in grazing and other loss processes cause a net decrease in phytoplankton biomass and reduce NPP despite higher growth rates. One model projects a strong increase in NPP in the low latitudes, caused by an intensification of the microbial loop, while NPP in the remaining model changes by less than 0.5 %. While models consistently project increases NPP in the Southern Ocean, the regional inter-model range is also very substantial. In most models, this increase in NPP is driven by temperature, but it is also modulated by changes in light, macronutrients and iron as well as grazing. Overall, current projections of future changes in global marine NPP are subject to large uncertainties and necessitate a dedicated and sustained effort to improve the models and the concepts and data that guide their development.
  • Article
    Comparing food web structures and dynamics across a suite of global marine ecosystem models
    (Elsevier, 2013-05-16) Sailley, Sevrine F. ; Vogt, Meike ; Doney, Scott C. ; Aita, M. N. ; Bopp, Laurent ; Buitenhuis, Erik T. ; Hashioka, Taketo ; Lima, Ivan D. ; Le Quere, Corinne ; Yamanaka, Yasuhiro
    Dynamic Green Ocean Models (DGOMs) include different sets of Plankton Functional Types (PFTs) and equations, thus different interactions and food webs. Using four DGOMs (CCSM-BEC, PISCES, NEMURO and PlankTOM5) we explore how predator–prey interactions influence food web dynamics. Using each model's equations and biomass output, interaction strengths (direct and specific) were calculated and the role of zooplankton in modeled food webs examined. In CCSM-BEC the single size-class adaptive zooplankton preys on different phytoplankton groups according to prey availability and food preferences, resulting in a strong top-down control. In PISCES the micro- and meso-zooplankton groups compete for food resources, grazing phytoplankton depending on their availability in a mixture of bottom-up and top-down control. In NEMURO macrozooplankton controls the biomass of other zooplankton PFTs and defines the structure of the food web with a strong top-down control within the zooplankton. In PlankTOM5, competition and predation between micro- and meso-zooplankton along with strong preferences for nanophytoplankton and diatoms, respectively, leads to their mutual exclusion with a mixture of bottom-up and top-down control of the plankton community composition. In each model, the grazing pressure of the zooplankton PFTs and the way it is exerted on their preys may result in the food web dynamics and structure of the model to diverge from the one that was intended when designing the model. Our approach shows that the food web dynamics, in particular the strength of the predator–prey interactions, are driven by the choice of parameters and more specifically the food preferences. Consequently, our findings stress the importance of equation and parameter choice as they define interactions between PFTs and overall food web dynamics (competition, bottom-up or top-down effects). Also, the differences in the simulated food-webs between different models highlight the gap of knowledge for zooplankton rates and predator–prey interactions. In particular, concerted effort is needed to identify the key growth and loss parameters and interactions and quantify them with targeted laboratory experiments in order to bring our understanding of zooplankton at a similar level to phytoplankton.
  • Article
    On the Southern Ocean CO2 uptake and the role of the biological carbon pump in the 21st century
    (John Wiley & Sons, 2015-09-23) Hauck, Judith ; Volker, Chrisoph ; Wolf-Gladrow, Dieter A. ; Laufkötter, Charlotte ; Vogt, Meike ; Aumont, Olivier ; Bopp, Laurent ; Buitenhuis, Erik T. ; Doney, Scott C. ; Dunne, John P. ; Gruber, Nicolas ; Hashioka, Taketo ; John, Jasmin G. ; Le Quere, Corinne ; Lima, Ivan D. ; Nakano, Hideyuki ; Seferian, Roland ; Totterdell, Ian J.
    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.
  • Article
    Phytoplankton competition during the spring bloom in four plankton functional type models
    (Copernicus Publications on behalf of the European Geosciences Union, 2013-11-02) Hashioka, Taketo ; Vogt, Meike ; Yamanaka, Yasuhiro ; Le Quere, Corinne ; Buitenhuis, Erik T. ; Aita, M. N. ; Alvain, S. ; Bopp, Laurent ; Hirata, T. ; Lima, Ivan D. ; Sailley, Sevrine F. ; Doney, Scott C.
    We investigated the mechanisms of phytoplankton competition during the spring bloom, one of the most dramatic seasonal events in lower-trophic-level ecosystems, in four state-of-the-art plankton functional type (PFT) models: PISCES, NEMURO, PlankTOM5 and CCSM-BEC. In particular, we investigated the relative importance of different ecophysiological processes on the determination of the community structure, focusing both on the bottom-up and the top-down controls. The models reasonably reproduced the observed global distribution and seasonal variation of phytoplankton biomass. The fraction of diatoms with respect to the total phytoplankton biomass increases with the magnitude of the spring bloom in all models. However, the governing mechanisms differ between models, despite the fact that current PFT models represent ecophysiological processes using the same types of parameterizations. The increasing trend in the percentage of diatoms with increasing bloom magnitude is mainly caused by a stronger nutrient dependence of diatom growth compared to nanophytoplankton (bottom-up control). The difference in the maximum growth rate plays an important role in NEMURO and PlankTOM5 and determines the absolute values of the percentage of diatoms during the bloom. In CCSM-BEC, the light dependency of growth plays an important role in the North Atlantic and the Southern Ocean. The grazing pressure by zooplankton (top-down control), however, strongly contributes to the dominance of diatoms in PISCES and CCSM-BEC. The regional differences in the percentage of diatoms in PlankTOM5 are mainly determined by top-down control. These differences in the mechanisms suggest that the response of marine ecosystems to climate change could significantly differ among models, even if the present-day ecosystem is reproduced to a similar degree of confidence. For further understanding of plankton competition and for the prediction of future change in marine ecosystems, it is important to understand the relative differences in each physiological rate and life history rate in the bottom-up and the top-down controls between PFTs.
  • Article
    Globally consistent quantitative observations of planktonic ecosystems
    (Frontiers Media, 2019-04-25) Lombard, Fabien ; Boss, Emmanuel S. ; Waite, Anya M. ; Vogt, Meike ; Uitz, Julia ; Stemmann, Lars ; Sosik, Heidi M. ; Schulz, Jan ; Romagnan, Jean-Baptiste ; Picheral, Marc ; Pearlman, Jay ; Ohman, Mark D. ; Niehoff, Barbara ; Möller, Klas O. ; Miloslavich, Patricia ; Lara-Lpez, Ana ; Kudela, Raphael M. ; Lopes, Rubens M. ; Kiko, Rainer ; Karp-Boss, Lee ; Jaffe, Jules S. ; Iversen, Morten H. ; Irisson, Jean-Olivier ; Fennel, Katja ; Hauss, Helena ; Guidi, Lionel ; Gorsky, Gabriel ; Giering, Sarah L. C. ; Gaube, Peter ; Gallager, Scott M. ; Dubelaar, George ; Cowen, Robert K. ; Carlotti, François ; Briseño-Avena, Christian ; Berline, Leo ; Benoit-Bird, Kelly J. ; Bax, Nicholas ; Batten, Sonia ; Ayata, Sakina Dorothée ; Artigas, Luis Felipe ; Appeltans, Ward
    In this paper we review the technologies available to make globally quantitative observations of particles in general—and plankton in particular—in the world oceans, and for sizes varying from sub-microns to centimeters. Some of these technologies have been available for years while others have only recently emerged. Use of these technologies is critical to improve understanding of the processes that control abundances, distributions and composition of plankton, provide data necessary to constrain and improve ecosystem and biogeochemical models, and forecast changes in marine ecosystems in light of climate change. In this paper we begin by providing the motivation for plankton observations, quantification and diversity qualification on a global scale. We then expand on the state-of-the-art, detailing a variety of relevant and (mostly) mature technologies and measurements, including bulk measurements of plankton, pigment composition, uses of genomic, optical and acoustical methods as well as analysis using particle counters, flow cytometers and quantitative imaging devices. We follow by highlighting the requirements necessary for a plankton observing system, the approach to achieve it and associated challenges. We conclude with ranked action-item recommendations for the next 10 years to move toward our vision of a holistic ocean-wide plankton observing system. Particularly, we suggest to begin with a demonstration project on a GO-SHIP line and/or a long-term observation site and expand from there, ensuring that issues associated with methods, observation tools, data analysis, quality assessment and curation are addressed early in the implementation. Global coordination is key for the success of this vision and will bring new insights on processes associated with nutrient regeneration, ocean production, fisheries and carbon sequestration.
  • Article
    Spatiotemporal variability and long-term trends of ocean acidification in the California Current System
    (Copernicus Publications on behalf of the European Geosciences Union, 2013-01-14) Hauri, Claudine ; Gruber, Nicolas ; Vogt, Meike ; Doney, Scott C. ; Feely, Richard A. ; Lachkar, Z. ; Leinweber, A. ; McDonnell, Andrew M. P. ; Munnich, M. ; Plattner, Gian-Kasper
    Due to seasonal upwelling, the upper ocean waters of the California Current System (CCS) have a naturally low pH and aragonite saturation state (Ωarag), making this region particularly prone to the effects of ocean acidification. Here, we use the Regional Oceanic Modeling System (ROMS) to conduct preindustrial and transient (1995–2050) simulations of ocean biogeochemistry in the CCS. The transient simulations were forced with increasing atmospheric pCO2 and increasing oceanic dissolved inorganic carbon concentrations at the lateral boundaries, as projected by the NCAR CSM 1.4 model for the IPCC SRES A2 scenario. Our results show a large seasonal variability in pH (range of ~ 0.14) and Ωarag (~ 0.2) for the nearshore areas (50 km from shore). This variability is created by the interplay of physical and biogeochemical processes. Despite this large variability, we find that present-day pH and Ωarag have already moved outside of their simulated preindustrial variability envelopes (defined by ±1 temporal standard deviation) due to the rapidly increasing concentrations of atmospheric CO2. The nearshore surface pH of the northern and central CCS are simulated to move outside of their present-day variability envelopes by the mid-2040s and late 2030s, respectively. This transition may occur even earlier for nearshore surface Ωarag, which is projected to depart from its present-day variability envelope by the early- to mid-2030s. The aragonite saturation horizon of the central CCS is projected to shoal into the upper 75 m within the next 25 yr, causing near-permanent undersaturation in subsurface waters. Due to the model's overestimation of Ωarag, this transition may occur even earlier than simulated by the model. Overall, our study shows that the CCS joins the Arctic and Southern oceans as one of only a few known ocean regions presently approaching the dual threshold of widespread and near-permanent undersaturation with respect to aragonite and a departure from its variability envelope. In these regions, organisms may be forced to rapidly adjust to conditions that are both inherently chemically challenging and also substantially different from past conditions.
  • Article
    Projected decreases in future marine export production : the role of the carbon flux through the upper ocean ecosystem
    (Copernicus Publications on behalf of the European Geosciences Union, 2016-07-14) Laufkötter, Charlotte ; Vogt, Meike ; Gruber, Nicolas ; Aumont, Olivier ; Bopp, Laurent ; Doney, Scott C. ; Dunne, John P. ; Hauck, Judith ; John, Jasmin G. ; Lima, Ivan D. ; Seferian, Roland ; Völker, Christoph
    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 Concentration 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.