Ocean Fertilization

Ocean Fertilization
Overview
Model Requirements for Simulation of Fertilization
Examples of observations that Models will simulate
Example of Model Simulation of Carbon Export
Fertilization Research Issues

Ocean Fertilization

CO₂ is emitted into the atmosphere by centers of fossil fuel use (eg. power generation facilities) and all diffuse sources of CO₂ (eg. transportation). Uptake of CO₂ by the ocean is enhanced through stimulation by fertilizers of the biological pump (photosynthetic carbon uptake by phytoplankton and downward transport of carbon as sinking organic matter).

Overview

Remotely sensed surface chlorophyll and solar irradience. The color scale for chlorophyll is logarithmic over 3 orders of magnitude with magenta and red representing low and high extremes in concentration, respectively. Solar irradience is linearly scaled (from Bishop et al., 1997).
The equatorial Pacific, sub arctic pacific and Southern Ocean are high-nutrient low-chlorophyll (HNLC) areas which may support higher plant biomass if micro-nutrients such as Fe were added.
Lowest plant biomass is found where sunlight is abundantly available. Such regions are referred to as oligotrophic. The oligotrophic subtropical gyres are low-nutrient low-chlorophyll (LNLC) regions and may respond to additions of Fe and P. (N would come from stimulation of nitrogen fixing blue-green algae or added along with Fe and P).
Sequestration options for both HNCL and LNLC waters will be evaluated by the Center.

Model Requirements for Simulation of Fertilization

Simulating the impacts of ocean fertilization and its effectiveness as a carbon sequestration strategy requires model parameterizations of processes occurring over a wide range of temporal and spatial scales.
Initial food-web response will be parameterized based on process studies (e.g. JGOFS, IRONEX). These parameterizations will be built into an ecosystem model (and a remineralization model) that can be evaluated with in situ and satellite observations.
Missing are data needed to go from short term to long term models. Our goal is an ecosystem model embedded in an OGCM which will accurately predict the long-term effectiveness and large-scale biogeochemical consequences of ocean fertilization.

Examples of Observations that Models Will Simulate

Seasonal variability of particulate organic carbon (POC) and chlorophyll pigments along the 1600 km long 'line P' transect near 50N from the continental margin (at 126W) to Ocean Station PAPA (OSP at 145W). We aim to simulate the seasonal cycles of such observables.
POC was computed from transmissometer data (Bishop, 1999; Bishop et al., 1999, in press).
Two other cruises in February 1996 and February 1997 revealed even lower POC (and chlorophyll) concentrations in deep waters.
The deep cholorphyll data are the first reported for deep waters and were obtained through analysis of Multiple Unit Large Volume in situ Filtration System (MULVFS) samples. Data from Thibault el al., 1999.
With funding from NOPP, NOAA and The Center, LBNL is developing the means to determine POC, PIC and other carbon system parameters using low-cost long-lived autonomous profiling vehicles in collaboration with Russ Davis at Scripps.

Example of Model Simulation of Carbon Export

Zonally averaged export of carbon below the 100 m depth horizon (in mol C/m²/yr) as a function of latitude and month of year, as simulated by the LLNL OGCM and ocean biogeochemistry model.
We will use our assembled expertise and new data sets to refine this model so that it can be used to evaluate changes in carbon export and storage that can be achieved with iron fertilization.

Fertilization Research Issues

Food-web dynamics. No ocean fertilization study has been long lived enough to follow the effects of iron fertilization through the food web, and hence determine the potential for long term carbon sequestration.
How does the ratio of nutrients in the fertilizer "mix" influence the species composition of the phytoplankton and the fate of the productivity of the ecosystem? Does the efficiency of the biological carbon pump increase with fertilization?

We know that N and P are important limiting factors in the oligotrophic LNLC oceans and that Fe is important in the HNLC areas where N and P are in excess (Martin et al. 1991). More recently, the importance of iron has been postulated to be significant throughout the world's oceans (in LNLC areas) through its regulation of the nitrogen cycle.

Would nitrogen fixers bloom if Fe and P were supplied? How would the ecosystem respond if they did? If N fixers did responded, how would this impact the global N cycle?

Carbon Cycle Dynamics. When organic carbon is delivered to the deep-sea it is consumed by bacteria and regenerated as dissolved carbon dioxide. The process consumes oxygen. Will an increase in carbon export result in anoxia in deep ocean waters? If so, where?

Silicon dynamics. Silicon is an essential nutrient for the growth of marine diatoms, and this group of species is considered to be very significant in food webs which have high fish yields (e.g. coastal upwelling areas), and in ecosystems which deposit significant carbon in the deep sea. Information on silicon dynamics is important to the mode of carbon export.

Calcium carbonate dynamics. The production of particulate and dissolved organic carbon (POC and DOC) by phytoplankton in seawater consumes CO₂ and has the net effect of increasing the relative transport rates of CO₂ from the atmosphere into the ocean. On the other hand, formation of particulate inorganic carbon (PIC) by calcareous phytoplankton (coccolithophores) and microzooplankton (e.g. foraminifera and pteropods) in seawater increases the CO₂ in the water as carbonates form and thus counter-acts the effects of organic matter production.

A major unknown is whether or not fertilization of HNLC or LNLC waters will change the balance of organic and inorganic carbon fixation and export.

Model parameterization. We require a biogeochemical model with multiple nutrient limitation, (Fe, P, Si, light...), prediction of dissolved and particulate (organic and inorganic) carbon pools, nitrogen fixation, carbon export, with realistic remineralization without geographically dependent parameters.

This depends on physical models that adequately represent mixed layer and intermediate water processes.

Model simulations of LNLC waters and climate induced circulation changes. No model simulations have focused on investigating the sequestration efficiency of LNLC waters. Nor has any study explored the impact of climate induced circulation changes on the efficacy of carbon sequestration.

Monitoring. Costs effective technologies for monitoring sequestration effects must be developed.

Environmental Policy Links. Knowledge, tools, standards, and policies on global manipulations do not, as yet, exist and must be developed.

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Ocean Fertilization
	CO₂ is emitted into the atmosphere by centers of fossil fuel use (eg. power generation facilities) and all diffuse sources of CO₂ (eg. transportation). Uptake of CO₂ by the ocean is enhanced through stimulation by fertilizers of the biological pump (photosynthetic carbon uptake by phytoplankton and downward transport of carbon as sinking organic matter).
Overview
	Remotely sensed surface chlorophyll and solar irradience. The color scale for chlorophyll is logarithmic over 3 orders of magnitude with magenta and red representing low and high extremes in concentration, respectively. Solar irradience is linearly scaled (from Bishop et al., 1997). The equatorial Pacific, sub arctic pacific and Southern Ocean are high-nutrient low-chlorophyll (HNLC) areas which may support higher plant biomass if micro-nutrients such as Fe were added. Lowest plant biomass is found where sunlight is abundantly available. Such regions are referred to as oligotrophic. The oligotrophic subtropical gyres are low-nutrient low-chlorophyll (LNLC) regions and may respond to additions of Fe and P. (N would come from stimulation of nitrogen fixing blue-green algae or added along with Fe and P). Sequestration options for both HNCL and LNLC waters will be evaluated by the Center.
Model Requirements for Simulation of Fertilization
	Simulating the impacts of ocean fertilization and its effectiveness as a carbon sequestration strategy requires model parameterizations of processes occurring over a wide range of temporal and spatial scales. Initial food-web response will be parameterized based on process studies (e.g. JGOFS, IRONEX). These parameterizations will be built into an ecosystem model (and a remineralization model) that can be evaluated with in situ and satellite observations. Missing are data needed to go from short term to long term models. Our goal is an ecosystem model embedded in an OGCM which will accurately predict the long-term effectiveness and large-scale biogeochemical consequences of ocean fertilization.
Examples of Observations that Models Will Simulate
Seasonal variability of particulate organic carbon (POC) and chlorophyll pigments along the 1600 km long 'line P' transect near 50N from the continental margin (at 126W) to Ocean Station PAPA (OSP at 145W). We aim to simulate the seasonal cycles of such observables. POC was computed from transmissometer data (Bishop, 1999; Bishop et al., 1999, in press). Two other cruises in February 1996 and February 1997 revealed even lower POC (and chlorophyll) concentrations in deep waters. The deep cholorphyll data are the first reported for deep waters and were obtained through analysis of Multiple Unit Large Volume in situ Filtration System (MULVFS) samples. Data from Thibault el al., 1999. With funding from NOPP, NOAA and The Center, LBNL is developing the means to determine POC, PIC and other carbon system parameters using low-cost long-lived autonomous profiling vehicles in collaboration with Russ Davis at Scripps.
Example of Model Simulation of Carbon Export
	Zonally averaged export of carbon below the 100 m depth horizon (in mol C/m²/yr) as a function of latitude and month of year, as simulated by the LLNL OGCM and ocean biogeochemistry model. We will use our assembled expertise and new data sets to refine this model so that it can be used to evaluate changes in carbon export and storage that can be achieved with iron fertilization.
Fertilization Research Issues
Food-web dynamics. No ocean fertilization study has been long lived enough to follow the effects of iron fertilization through the food web, and hence determine the potential for long term carbon sequestration. How does the ratio of nutrients in the fertilizer "mix" influence the species composition of the phytoplankton and the fate of the productivity of the ecosystem? Does the efficiency of the biological carbon pump increase with fertilization? We know that N and P are important limiting factors in the oligotrophic LNLC oceans and that Fe is important in the HNLC areas where N and P are in excess (Martin et al. 1991). More recently, the importance of iron has been postulated to be significant throughout the world's oceans (in LNLC areas) through its regulation of the nitrogen cycle. Would nitrogen fixers bloom if Fe and P were supplied? How would the ecosystem respond if they did? If N fixers did responded, how would this impact the global N cycle? Carbon Cycle Dynamics. When organic carbon is delivered to the deep-sea it is consumed by bacteria and regenerated as dissolved carbon dioxide. The process consumes oxygen. Will an increase in carbon export result in anoxia in deep ocean waters? If so, where? Silicon dynamics. Silicon is an essential nutrient for the growth of marine diatoms, and this group of species is considered to be very significant in food webs which have high fish yields (e.g. coastal upwelling areas), and in ecosystems which deposit significant carbon in the deep sea. Information on silicon dynamics is important to the mode of carbon export. Calcium carbonate dynamics. The production of particulate and dissolved organic carbon (POC and DOC) by phytoplankton in seawater consumes CO₂ and has the net effect of increasing the relative transport rates of CO₂ from the atmosphere into the ocean. On the other hand, formation of particulate inorganic carbon (PIC) by calcareous phytoplankton (coccolithophores) and microzooplankton (e.g. foraminifera and pteropods) in seawater increases the CO₂ in the water as carbonates form and thus counter-acts the effects of organic matter production. A major unknown is whether or not fertilization of HNLC or LNLC waters will change the balance of organic and inorganic carbon fixation and export. Model parameterization. We require a biogeochemical model with multiple nutrient limitation, (Fe, P, Si, light...), prediction of dissolved and particulate (organic and inorganic) carbon pools, nitrogen fixation, carbon export, with realistic remineralization without geographically dependent parameters. This depends on physical models that adequately represent mixed layer and intermediate water processes. Model simulations of LNLC waters and climate induced circulation changes. No model simulations have focused on investigating the sequestration efficiency of LNLC waters. Nor has any study explored the impact of climate induced circulation changes on the efficacy of carbon sequestration. Monitoring. Costs effective technologies for monitoring sequestration effects must be developed. Environmental Policy Links. Knowledge, tools, standards, and policies on global manipulations do not, as yet, exist and must be developed.