scholarly journals Marine phytoplankton stoichiometry mediates nonlinear interactions between nutrient supply, temperature, and atmospheric CO<sub>2</sub>

2018 ◽  
Vol 15 (9) ◽  
pp. 2761-2779 ◽  
Author(s):  
Allison R. Moreno ◽  
George I. Hagstrom ◽  
Francois W. Primeau ◽  
Simon A. Levin ◽  
Adam C. Martiny
Keyword(s):  
Carbon Cycling ◽  
Ocean Circulation ◽  
Circulation Model ◽  
Nutrient Supply ◽  
Marine Phytoplankton ◽  
Phosphorus Concentration ◽  
Biological Pump ◽  
Carbon Export ◽  
Environmental Model ◽  
The Impact

Abstract. Marine phytoplankton stoichiometry links nutrient supply to marine carbon export. Deviations of phytoplankton stoichiometry from Redfield proportions (106C : 1P) could therefore have a significant impact on carbon cycling, and understanding which environmental factors drive these deviations may reveal new mechanisms regulating the carbon cycle. To explore the links between environmental conditions, stoichiometry, and carbon cycling, we compared four different models of phytoplankton C : P: a fixed Redfield model, a model with C : P given as a function of surface phosphorus concentration (P), a model with C   P given as a function of temperature, and a new multi-environmental model that predicts C : P as a function of light, temperature, and P. These stoichiometric models were embedded into a five-box ocean circulation model, which resolves the three major ocean biomes (high-latitude, subtropical gyres, and tropical upwelling regions). Contrary to the expectation of a monotonic relationship between surface nutrient drawdown and carbon export, we found that lateral nutrient transport from lower C : P tropical waters to high C : P subtropical waters could cause carbon export to decrease with increased tropical nutrient utilization. It has been hypothesized that a positive feedback between temperature and pCO2, atm will play an important role in anthropogenic climate change, with changes in the biological pump playing at most a secondary role. Here we show that environmentally driven shifts in stoichiometry make the biological pump more influential, and may reverse the expected positive relationship between temperature and pCO2, atm. In the temperature-only model, changes in tropical temperature have more impact on the Δ pCO2, atm (∼ 41 ppm) compared to subtropical temperature changes (∼ 4.5 ppm). Our multi-environmental model predicted a decline in pCO2, atm of ∼ 46 ppm when temperature spanned a change of 10 °C. Thus, we find that variation in marine phytoplankton stoichiometry and its environmental controlling factors can lead to nonlinear controls on pCO2, atm, suggesting the need for further studies of ocean C : P and the impact on ocean carbon cycling.

scholarly journals Marine Phytoplankton Stoichiometry Mediates Nonlinear Interactions Between Nutrient Supply, Temperature, and Atmospheric CO<sub>2</sub>

2017 ◽  
Author(s):  
Allison R. Moreno ◽  
George I. Hagstrom ◽  
Francois W. Primeau ◽  
Simon A. Levin ◽  
Adam C. Martiny
Keyword(s):  
Carbon Cycling ◽  
Ocean Circulation ◽  
Negative Relationship ◽  
Nutrient Supply ◽  
Marine Phytoplankton ◽  
Phosphorus Concentration ◽  
Biological Pump ◽  
Carbon Export ◽  
Environmental Model ◽  
The Impact

Abstract. Marine phytoplankton stoichiometry links nutrient supply to marine carbon export. Deviations of phytoplankton stoichiometry from Redfield proportions (106C : 1P) could therefore have a significant impact on carbon cycling, and understanding which environmental factors drive these deviations may reveal new mechanisms that regulate the carbon cycle. To explore the links between environmental conditions, stoichiometry, and carbon cycling, we compared four different models for variations in phytoplankton C : P: a fixed Redfield model, a model with C : P given as a function of surface phosphorus concentration ([P]), a model with C : P given as a function of temperature, and a new multi-environmental model that predicts C : P as a function of light, temperature, and [P]. These stoichiometric models were embedded into a box model of the ocean circulation, which resolves the three major ocean biomes (high-latitude, subtropical gyres, and iron-limited tropical upwelling regions). Contrary to the expectation of a monotonic relationship between surface nutrient drawdown and carbon export, we found that lateral nutrient transport from lower C : P tropical waters to high C : P subtropical waters could cause carbon-export to decrease with increased tropical nutrient utilization. Temperature is thought to be one of the primary drivers of changes in atmospheric pCO2 (pCO2,atm) across glacial/interglacial periods, and it has been hypothesized that a positive feedback between temperature and pCO2,atm will play an important role in anthropogenic climate change, with changes in the biological pump playing at most a secondary role. Here we show that environmentally driven shifts in stoichiometry make the biological pump more influential, and may reverse the expected negative relationship between temperature and pCO2,atm. In the temperature-only model changes in tropical temperature have more impact on the Δ pCO2,atm (~ 41 ppm) compared to subtropical temperature (~ 4.5 ppm). Our multi-environmental model produced a decline in pCO2,atm of ~ 46 when temperature spanned a change of 10 °C. Thus, we find that variation in marine phytoplankton stoichiometry and its environmental controlling factor can lead to counterintuitive controls on pCO2,atm, suggesting the need for further studies of ocean C : P and the impact on ocean carbon cycling.

On the impact of sea ice in a global ocean circulation model

1997 ◽  
Vol 25 ◽  
pp. 111-115 ◽  
Author(s):  
Achim Stössel
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Ocean Circulation ◽  
General Circulation ◽  
Thermohaline Circulation ◽  
Circulation Model ◽  
Deep Ocean ◽  
Global Ocean ◽  
Convective Activity ◽  
The Impact

This paper investigates the long-term impact of sea ice on global climate using a global sea-ice–ocean general circulation model (OGCM). The sea-ice component involves state-of-the-art dynamics; the ocean component consists of a 3.5° × 3.5° × 11 layer primitive-equation model. Depending on the physical description of sea ice, significant changes are detected in the convective activity, in the hydrographic properties and in the thermohaline circulation of the ocean model. Most of these changes originate in the Southern Ocean, emphasizing the crucial role of sea ice in this marginally stably stratified region of the world's oceans. Specifically, if the effect of brine release is neglected, the deep layers of the Southern Ocean warm up considerably; this is associated with a weakening of the Southern Hemisphere overturning cell. The removal of the commonly used “salinity enhancement” leads to a similar effect. The deep-ocean salinity is almost unaffected in both experiments. Introducing explicit new-ice thickness growth in partially ice-covered gridcells leads to a substantial increase in convective activity, especially in the Southern Ocean, with a concomitant significant cooling and salinification of the deep ocean. Possible mechanisms for the resulting interactions between sea-ice processes and deep-ocean characteristics are suggested.

Impact of Accurate Geoid Fields on Estimates of the Ocean Circulation

2007 ◽  
Vol 24 (8) ◽  
pp. 1464-1478 ◽  
Author(s):  
Detlef Stammer ◽  
Armin Köhl ◽  
Carl Wunsch
Keyword(s):  
Ocean Circulation ◽  
General Circulation ◽  
Circulation Model ◽  
Formal Proof ◽  
Meridional Overturning Circulation ◽  
Dynamic Topography ◽  
Model Errors ◽  
Geoid Model ◽  
Meridional Heat Transport ◽  
The Impact

Abstract The impact of new geoid height models on estimates of the ocean circulation, now available from the Gravity Recovery and Climate Experiment (GRACE) spacecraft, is assessed, and the implications of far more accurate geoids, anticipated from the European Space Agency’s (ESA) Gravity and Ocean Circulation Explorer (GOCE) mission, are explored. The study is based on several circulation estimates obtained over the period 1992–2002 by combining most of the available ocean datasets with a global general circulation model on a 1° horizontal grid and by exchanging only the EGM96 geoid model with two different geoid models available from GRACE. As compared to the EGM96-based solution, the GRACE geoid leads to an estimate of the ocean circulation that is more consistent with the Levitus temperature and salinity climatology. While not a formal proof, this finding supports the inference of a substantially improved GRACE geoid skill. However, oceanographic implications of the GRACE model are only modest compared to what can be obtained from ocean observations alone. To understand the extent to which this is merely a consequence of a not-optimally converged solution or if a much more accurate geoid field could in principle play a profound role in the ocean estimation procedure, an additional experiment was performed in which the geoid error was artificially reduced relative to all other datasets. Adjustments occur then in all elements of the ocean circulation, including 10% changes in the meridional overturning circulation and the corresponding meridional heat transport in the Atlantic. For an optimal use of new geoid fields, improved error information is required. The error budget of existing time-mean dynamic topography estimates may now be dominated by residual errors in time-mean altimetric corrections. Both these and the model errors need to be better understood before improved geoid estimates can be fully exploited. As is commonly found, the Southern Ocean is of particular concern.

scholarly journals The impact of wave physics in the CMEMS-IBI ocean system Part A: Wave forcing validation

2019 ◽  
Author(s):  
Romain Rainaud ◽  
Lotfi Aouf ◽  
Alice Dalphinet ◽  
Marcos Garcia Sotillo ◽  
Enrique Alvarez-Fanjul ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Wave Spectrum ◽  
Circulation Model ◽  
Wave Model ◽  
Heat Fluxes ◽  
Wave System ◽  
Peak Period ◽  
Wave Forecast ◽  
High Frequency Waves ◽  
The Impact

Abstract. The Iberian Biscay Ireland (IBI) wave system has the challenge to improve wave forecast and the coupling with ocean circulation model dedicated to western european coast. The momentum and heat fluxes at the sea surface are strongly controlled by the waves and there is a need of using accurate sea state from wave model. This work describes the more recent version of the IBI wave system and highlight the performance of system in comparison with satellite altimeters and buoys wave data. The validation process has been performed for 1-year run of the wave model MFWAM with boundary conditions provided by the global wave system. The results show on the one hand a slightly improvement on significant wave height and peak period, and on the other hand a better surface stress for high wind conditions. This latter is a consequence of using a tail wave spectrum shaped as the Philipps wave spectrum for high frequency waves.

scholarly journals Ocean-sea-ice coupling in a global ocean general circulation model

1997 ◽  
Vol 25 ◽  
pp. 116-120 ◽  
Author(s):  
S. Legutke ◽  
E. Maier-Reimkr ◽  
A. Stössel ◽  
A. Hellbach
Keyword(s):  
Sea Ice ◽  
General Circulation Model ◽  
Ocean Circulation ◽  
General Circulation ◽  
Circulation Model ◽  
Ice Cover ◽  
Ocean General Circulation Model ◽  
Global Ocean ◽  
Ocean General Circulation ◽  
The Impact

A global ocean general circulation model has been coupled with a dynamic thermodynamic sea-ice model. This model has been spun-up in a 1000 year integration using daily atmosphere model data. Main water masses and currents are reproduced as well as the seasonal characteristics of the ice cover of the Northern and Southern Hemispheres. Model results for the Southern Ocean, however, show the ice cover as too thin, and there are large permanent polynyas in the Weddell and Ross Seas. These polynyas are due to a large upward oceanic heat flux caused by haline rejection during the freezing of sea ice. Sensitivity studies were performed to test several ways of treating the sea-surface salinity and the rejected brine. The impact on the ice cover, water-mass characteristics, and ocean circulation are described.

scholarly journals A nested Atlantic-Mediterranean Sea general circulation model for operational forecasting

Ocean Science ◽  
2009 ◽  
Vol 5 (4) ◽  
pp. 461-473 ◽  
Author(s):  
P. Oddo ◽  
M. Adani ◽  
N. Pinardi ◽  
C. Fratianni ◽  
M. Tonani ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
General Circulation Model ◽  
Ocean Circulation ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean Model ◽  
Global Ocean ◽  
Lateral Boundary ◽  
The Mediterranean ◽  
The Impact

Abstract. A new numerical general circulation ocean model for the Mediterranean Sea has been implemented nested within an Atlantic general circulation model within the framework of the Marine Environment and Security for the European Area project (MERSEA, Desaubies, 2006). A 4-year twin experiment was carried out from January 2004 to December 2007 with two different models to evaluate the impact on the Mediterranean Sea circulation of open lateral boundary conditions in the Atlantic Ocean. One model considers a closed lateral boundary in a large Atlantic box and the other is nested in the same box in a global ocean circulation model. Impact was observed comparing the two simulations with independent observations: ARGO for temperature and salinity profiles and tide gauges and along-track satellite observations for the sea surface height. The improvement in the nested Atlantic-Mediterranean model with respect to the closed one is particularly evident in the salinity characteristics of the Modified Atlantic Water and in the Mediterranean sea level seasonal variability.

scholarly journals OSSE for a sustainable marine observing network in the Marmara Sea

2018 ◽  
Author(s):  
Ali Aydoğdu ◽  
Timothy J. Hoar ◽  
Tomislava Vukicevic ◽  
Jeffrey L. Anderson ◽  
Nadia Pinardi ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Lower Layer ◽  
Circulation Model ◽  
Marmara Sea ◽  
Western Basin ◽  
Synthetic Temperature ◽  
Reference Experiment ◽  
Temperature Errors ◽  
Observing System Simulation Experiment ◽  
The Impact

Abstract. An observing system simulation experiment (OSSE) is presented in the Marmara Sea. A high resolution ocean circulation model (FESOM) and an ensemble data assimilation tool (DART) are coupled. The OSSE methodology is used to assess the possible impact of a ferrybox network in the eastern Marmara Sea. A reference experiment without assimilation is performed. Then, synthetic temperature and salinity observations are assimilated along the track of the ferries in the second experiment. The results suggest that a ferrybox network in the Marmara Sea may improve the forecasts significantly. The salinity and temperature errors get smaller in the upper layer of the water column. The impact of the assimilation is negligible in the lower layer due to the strong stratification. The circulation in the Marmara Sea, particularly the Bosphorus outflow, helps to propagate the error reduction towards the western basin where no assimilation is performed. Overall, the proposed ferrybox network can be a good start to design an optimal sustained marine observing network in the Marmara Sea for assimilation purposes.

scholarly journals The effect of tides on dense water formation in Arctic shelf seas

Ocean Science ◽  
2011 ◽  
Vol 7 (2) ◽  
pp. 203-217 ◽  
Author(s):  
C. F. Postlethwaite ◽  
M. A. Morales Maqueda ◽  
V. le Fouest ◽  
G. R. Tattersall ◽  
J. Holt ◽  
...  
Keyword(s):  
Sea Ice ◽  
Ocean Circulation ◽  
General Circulation ◽  
Circulation Model ◽  
Salt Flux ◽  
The Arctic ◽  
Ocean Tides ◽  
Sea Ice Extent ◽  
Salt Budget ◽  
The Impact

Abstract. Ocean tides are not explicitly included in many ocean general circulation models, which will therefore omit any interactions between tides and the cryosphere. We present model simulations of the wind and buoyancy driven circulation and tides of the Barents and Kara Seas, using a 25 km × 25 km 3-D ocean circulation model coupled to a dynamic and thermodynamic sea ice model. The modeled tidal amplitudes are compared with tide gauge data and sea ice extent is compared with satellite data. Including tides in the model is found to have little impact on overall sea ice extent but is found to delay freeze up and hasten the onset of melting in tidally active coastal regions. The impact that including tides in the model has on the salt budget is investigated and found to be regionally dependent. The vertically integrated salt budget is dominated by lateral advection. This increases significantly when tides are included in the model in the Pechora Sea and around Svalbard where tides are strong. Tides increase the salt flux from sea ice by 50% in the Pechora and White Seas but have little impact elsewhere. This study suggests that the interaction between ocean tides and sea ice should not be neglected when modeling the Arctic.

Wave-currents interaction in the Black Sea: new modelling approach for next generation of operational forecasting system.

2021 ◽  
Author(s):  
Salvatore Causio ◽  
Piero Lionello ◽  
Stefania Angela Ciliberti ◽  
Giovanni Coppini
Keyword(s):  
Black Sea ◽  
Ocean Circulation ◽  
Wave Spectrum ◽  
Circulation Model ◽  
Wave Model ◽  
Bias Reduction ◽  
Hydrodynamical Model ◽  
The Black Sea ◽  
Surface Boundary ◽  
The Impact

&lt;p&gt;This study analyzes wave-currents interactions in the Black Sea basin focusing on deep water processes by using a coupled two-ways off-line numerical system, based on the ocean circulation model NEMO v4.0 and the third-generation wave model WaveWatchIII v5.16. The coupling between wave and hydrodynamical models is carried out at hourly frequency. The physical processes taken in consideration are: Stokes-Coriolis force, sea-state dependent momentum flux, wave induced vertical mixing, Doppler shift, and the stability parameter for the computation of effective wind speed.&amp;#160;&lt;/p&gt;&lt;p&gt;The hydrodynamical model is implemented over the Black Sea at the horizontal resolution of about 3km and 31 vertical levels, with closed boundary at the Bosporus Strait. The impact of the Bosporus Strait on the Black Sea dynamics is modeled using a surface boundary condition, taking into account the barotropic transport, which balances the freshwater fluxes on monthly basis (Stanev and Beckers, 1999; Peneva et al., 2001; Ciliberti et al., 2021). Additionally, Mediterranean waters inflow is represented by applying a local damping to high resolution temperature and salinity profiles (Aydogdu et al., 2018) at the Bosporus exit.&lt;/p&gt;&lt;p&gt;The wave model adopts the WW3 implementation of the WAM Cycle4 model physics, with Ultimate Quickest propagation scheme and GSE alleviation, over the same spatial grid as the hydrodynamical model Wind input and dissipation are based on Ardhuin et al. (2010), wave-wave interactions are based on Discrete Interaction Approximation. The wave spectrum is discretized using 24 directional sectors, and 30 frequencies, with 10% increment starting from 0.055Hz. Validation and statistical analysis of the results have been carried out to compare coupled and uncoupled runs, aiming to identify the model set-up to upgrade in the future the near real time operational system.&lt;/p&gt;&lt;p&gt;The evaluation of the coupling impact on significant wave height and temperature shows BIAS reduction, and even slight improvement of RMSE.&lt;/p&gt;

A global circulation model for the asteroid impact simulations

2020 ◽  
Author(s):  
Hakan Sert ◽  
Orkun Temel ◽  
Cem Berk Senel ◽  
Ozgur Karatekin
Keyword(s):  
Ocean Circulation ◽  
Three Dimensional ◽  
Circulation Model ◽  
Co2 Concentration ◽  
Atmospheric Model ◽  
Global Circulation Model ◽  
Asteroid Impact ◽  
Global Circulation ◽  
Impact Simulations ◽  
The Impact

&lt;p&gt;In this study, we present a three-dimensional global circulation model (GCM) to investigate the environmental effects of an asteroid impact on the global Earth system. The model is applied to model the atmospheric response of the Cretaceous&amp;#8211;Paleogene (K&amp;#8211;Pg) extinction event which took place 66 million years ago and resulted in the mass extinction of various animal and plant species. The atmospheric model is developed based on the planetWRF model. First, the paleoclimate model is validated using the proxy data. Then, the sensitivity to atmospheric co2 concentration is investigated. The radiation parameterization scheme of the planetWRF model is modified to include the effect of various climate-active aerosols and gases released after the impact event. The model is also coupled both to a simple one-dimensional ocean mixed layer and a three-dimensional ocean circulation model. Both the atmospheric and oceanic response is investigated.&lt;/p&gt;

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