Polar Iron in marine applications. These applifations were especially Appkications in SEEDS-1, where they reached a maximum value of Sedwick said the expedition will include work conducted as part of 23 NSF-funded projects that address a range of scientific questions.

Iron in marine applications -

Standing in the pit, Kaplan spotted what he was looking for: a layer of fine gray silt deposited by ice sheets roughly 20, years ago. Dozens of intriguing samples have made their way home with him, stowed in his suitcase or shipped in a duct-taped cardboard box.

As he scraped the dark gray sediment into a plastic bag, he felt a rush of anticipation. Proposed in by the late oceanographer John Martin, the hypothesis suggests that flurries of dust — swept from cold, dry landscapes like the glacial outwash where Kaplan now stood, trowel in hand — played a crucial role in the last major ice age.

When this dust landed in the iron-starved Southern Ocean, Martin argued, the iron within it would have fertilized massive blooms of diatoms and other phytoplankton.

Single-celled algae with intricate silica shells, diatoms photosynthesize, pulling carbon from the atmosphere and transforming it to sugar to fuel their growth. Going a step further, Martin proposed that using iron to trigger diatom blooms might help combat global warming.

Strangelove accent. In , concerns about possible environmental impacts of iron fertilization, such as toxic algal blooms and damaged marine ecosystems, prompted the United Nations Convention on Biological Diversity to place a moratorium on all large-scale ocean fertilization experiments.

The problem with that, many scientists now contend, is that the most fundamental questions about iron fertilization—if it can sequester enough carbon to alter climate, and what its environmental consequences would be—remain unanswered.

As atmospheric carbon levels soar past parts per million, some researchers believe that the freeze on iron fertilization experiments should be reconsidered, Buesseler among them.

Whether people ever decide to pursue iron fertilization to combat climate change or not, scientists still need to understand the environmental impacts of iron-rich dust and ash from natural sources like volcanoes, and from manmade pollutants, says Vicki Grassian, a physical chemist at the University of California, San Diego.

To meet that challenge, labs around the world are studying how iron affects climate and ocean health. Their work spans the scales, from the tiny crystalline structure of iron-peppered nanoparticles to large-scale simulations of global climate. Ultimately, scientists hope to understand the role of iron dust in marine systems, says Kristen Buck, a chemical oceanographer at the University of South Florida.

To learn how iron fertilization might work in the future, some researchers are looking at the past, in paleoclimate records such as ice cores and deep-sea sediments. Three billion years ago the ocean was chock-full of iron, ancient mineral deposits show.

Iron was plentiful when life first evolved, and the metal was incorporated into a long list of essential cellular functions. Animals need iron to transport oxygen in their blood and to break down sugar and other nutrients for energy. Plants need iron to transfer electrons during photosynthesis and to make chlorophyll.

It started disappearing from the seas more than 2. When this happened, dissolved iron rapidly linked up with the newly plentiful oxygen atoms, forming iron oxides such as hematite, a common mineral that contains a form of the element known as iron III.

They require a different form, iron II , which more readily dissolves and is absorbed by cells. Hematite has another downside: It sinks. Over billions of years, layer upon layer fell to the sea floor, forming iron ore deposits hundreds to thousands of feet deep.

Meanwhile, iron in the waters above diminished to barely detectable levels—an average liter of seawater contains roughly 35 grams of salt, but only on the order of a billionth of a gram of iron. In roughly a third of the ocean, iron is so rare that its absence can hinder the growth of diatoms and other phytoplankton.

Unless, of course, a gust of wind delivers a plume of iron particles. Standing in the freshly excavated gravel pit in Patagonia, Kaplan was directly upwind of the Southern Ocean—close to where Martin proposed that ice age dust had helped to fertilize the ocean some 20, years ago.

It was the perfect place to test whether those iron-rich glacial sediments would have made a good fertilizer for diatoms. Researchers already knew that there was more dust-borne iron during the last ice age, much of it freed by melting glaciers. But no one had yet rigorously tested whether the iron was in the form that diatoms can absorb, Kaplan says.

Kaplan scraped up the dark gray silt and brought it back to Columbia, where he handed it off to then-graduate student Elizabeth Shoenfelt Troein, who is now a postdoctoral fellow at the Massachusetts Institute of Technology. Shoenfelt Troein flew out to the Stanford Synchrotron Radiation Lightsource in Menlo Park, California.

There, along with her adviser Benjamin Bostick and fellow graduate student Jing Sun, she spent many long nights zapping the sediment with high-powered X-rays to reveal its mineral composition. Only certain types of minerals yield dust that is rich in soluble forms of iron, including iron II , the kind that diatoms can easily digest, as Grassian and colleagues described in in the Annual Review of Physical Chemistry.

Winds blowing off the Sahara are one of the most important sources of iron dust in the ocean, supplying more than 70 percent of dissolved iron to the Atlantic, another group has found.

But there are several other paths by which iron II makes its way to the oceans, including rivers, hydrothermal vents, volcanoes and glacial outwash plains like the one where Kaplan found his sample in Patagonia. The glacial sediment contained far more iron II than samples deposited during non-glacial periods from the same region, Shoenfelt Troein found.

When glaciers grind down bedrock, the resulting freshly ground sediments tend to contain more iron II than sediments produced from weathering by wind and water, which are richer in iron III , Winckler says. Back at Columbia, Shoenfelt Troein fed the iron II —rich, glacial sediment to a common species of diatom, Phaeodactylum tricornutum , and the diatoms reproduced 2.

This would translate into a roughly fivefold increase in carbon uptake compared with the non-glacial sediment, the team calculated. When the team looked at marine sediment cores from several glacial and interglacial periods spanning , years, Winckler, Shoenfelt Troein and colleagues found that dust from the glacial periods contained 15 to 20 times more iron II than did dust from the current interglacial period.

That suggests that the potency of glacial sediment led to a self-reinforcing cycle, in which higher rates of iron fertilization in the oceans reduced carbon in the air, leading to colder temperatures, which in turn, grew glaciers, the team reported in the Proceedings of the National Academy of Sciences in It also suggests that not all iron is equal when it comes to fertilization, and that freshly mined, fine-ground iron might be more effective than other forms, Winckler says.

In most of the geoengineering experiments in the s and early s, scientists mixed a powdered form of iron called ferrous sulfate with acidic water and fed the liquid off the back of a ship, says David Emerson, a geomicrobiologist at the Bigelow Laboratory for Ocean Sciences in Maine.

Emerson recently proposed using aircraft to distribute a fine iron dust produced by iron-eating bacteria, called biogenic oxide. This form is composed of iron nanoparticles bound to organic compounds, and would likely stay suspended longer than ferrous sulfate in the sunlit surface waters where diatoms grow, he says.

However, no DA was found during EisenEx and SERIES, even though Pseudo-nitzschia were dominant Gervais et al. However, phytoplankton samples used to estimate DA production have sometimes been stored for a long time before the analysis, for example, 12 years in IronEx-2 and 4 years in SOFeX-S Silver et al.

Trick et al. Nevertheless, discernable changes in DA production were found in IronEx-2 and SOFeX-S experiments Silver et al.

However, large uncertainties remain as Trick et al. Here again, existing research indicates that the processes involved need to be better understood in the natural environment before the ramifications of aOIF can be fully understood. Whether aOIF is a viable carbon removal strategy is still under debate Boyd et al.

The production of climate-relevant gases such as N 2 O , DMS, and HVOCs, which is influenced by the remineralization of sinking particles that follows OIF-induced blooms; the decline in oxygen inventory; and the production of DA are particularly important to understand.

These processes can directly and indirectly modify the effectiveness of carbon sequestration, with either positive or negative effects. Therefore, monitoring declines in oxygen content and production of climate-relevant gases and DA to evaluate the effectiveness of aOIF as a geoengineering approach is essential.

The processes discussed here represent the current state of knowledge concerning aOIF side effects. The direct and indirect environmental consequences remain largely unresolved due to the inconsistent and highly uncertain outcomes of the experiments conducted so far, as well as our poor understanding of the processes involved under both nOIF and aOIF conditions Chisholm et al.

However, considering the increasing evidence for the necessity to keep warming at or below 1. Figure 9 Assessment framework for scientific research involving ocean fertilization OF modified from Resolution LC-LP.

To prevent pollution of the sea from human activities, the international Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter London Convention, was amended in In , contracting parties to the London Convention adopted the Protocol to the London Convention London Protocol, In , several commercial companies e.

As discussed earlier, these small-scale experiments have left many unanswered scientific questions regarding both the effectiveness and the potential impacts of aOIF Lawrence, ; Buesseler and Boyd, This resolution prohibited ocean fertilization activities until such time that specific guidance could be developed to justify legitimate scientific research.

In the meantime, there was a call to develop an assessment framework for ocean fertilization experiments to assess, accurately, scientific research proposals Resolution LC-LP. This framework demands preliminary scientific research prior to any aOIF experimentation.

Monitoring is also required as an integral component of all approved i. intended geoengineering benefits ACE CRC, This means that large-scale i. Scientific aOIF research has focused on improving our understanding of the effectiveness, capacity, and risks of OIF as an atmospheric CO 2 removal strategy both in the future and the past in particular glacial periods.

Although the first aOIF experiments took place more than 20 years ago, the legal and economic aspects of such a strategy in terms of the international laws of the sea and carbon offset markets are not yet clear ACE CRC, Nonetheless, previous small-scale aOIF experiments have demonstrated a considerable potential for easily and effectively reducing atmospheric CO 2 levels.

Accordingly, physical—biogeochemical—ecological models and nOIF experiments long-term have been conducted in an effort to overcome some of the limitations of short-term aOIF experiments e. These results suggest that the amount of carbon sequestration resulting from aOIF represents only a modest offset, i.

The nOIF experiments have also produced much higher carbon sequestration rates than the small-scale aOIF experiments Morris and Charette, Furthermore, the results from nOIF experiments do not support the potential negative impacts proposed for OIF experiments, even at larger scales Belviso et al.

However, these nOIF results do not guarantee that aOIF as a geoengineering approach is able to achieve the high effectiveness associated with carbon sequestration and enables a simple scaling up as a prediction tool, because the nOIF experiments differ from the aOIF experiments in the mode of iron supply.

In particular, nOIF is a continuous and slow process and its iron source is based on the upwelling of iron-rich subsurface waters to the surface layer, whereas aOIF is intended to be episodic, with massive short-term iron additions Blain et al.

In addition, in nOIF it is difficult to accurately identify iron sources due to the complexity of the system, whereas in aOIF there is quantitative and qualitative information about iron additions and sources Blain et al.

Contrary to the results of aOIF experiments in the SO e. There is also a broad swath of hypotheses in the fields of pelagic ecology—biogeochemistry that can be tested with OIF experiments using the correlations between temperature, CO 2 concentrations, and dust over the past four glacial—interglacial cycles on the one hand and bottle experiments showing iron limitation of phytoplankton growth in HNLC regions on the other.

Therefore, it is important to continue undertaking small-scale studies to obtain a better understanding of natural processes in the SO as well as to assess the associated risks and so lay the groundwork for evaluating the potential effectiveness and impacts of large-scale aOIF as a geoengineering solution to anthropogenic climate change.

It is therefore of paramount importance that future aOIF experiments continue to focus on the effectiveness and capacity of aOIF as a means of reducing atmospheric CO 2 , but they should also carefully consider the location i.

They should build on the results of previous aOIF experiments to develop our understanding of the magnitude and sources of uncertainties and provide confidence in our ability to reproduce results.

The first consideration for a successful aOIF experiment is the location. The dominance of diatoms in phytoplankton communities plays a major role in increasing the biological pump because diatom species can sink rapidly as aggregates or by forming resting spores to efficiently bypass the intense grazing pressure of mesozooplankton e.

Previous aOIF experiments have shown that silicate concentration and mesozooplankton stocks i. Therefore, to obtain the greatest possible carbon export flux in response to iron addition, aOIF experiments should be designed in regions with high silicate concentrations and low grazing pressure.

It will be important to conduct initial surveys to measure the degree of grazing pressure in HNLC regions with high silicate concentrations such as in the subarctic NP e. In selecting sites for aOIF, it is also important to distinguish the iron-fertilized patch from the surrounding unfertilized waters to easily and efficiently observe iron-induced changes Coale et al.

Ocean eddies provide an excellent setting for aOIF experimentation because they tend to naturally isolate interior waters from the surrounding waters. Eddy centers tend to be subject to relatively slow current speeds, with low shear and high vertical coherence, providing ideal conditions for tracing the same water from the surface to below the winter MLD, while simultaneously minimizing lateral stirring and advection Smetacek et al.

Finding an appropriate eddy setting in a study area should be a high priority consideration when designing an aOIF experiment Smetacek and Naqvi, Mesoscale eddies can be reliably identified and tracked with satellite sea surface height anomalies Smetacek et al.

The second consideration for a successful aOIF experiment is timing, which includes when an experiment starts.

PP in the SO, a representative HNLC region, is subject to co-limitation by micro- or macronutrients i. To the south of the SO PF, phytoplankton blooms usually occur during early summer i. Weekly and monthly climatological maps of chlorophyll a concentrations derived from satellite data could provide the necessary information for determining the timing of blooms in the SO PF Westberry et al.

Prior to December, phytoplankton growth is mainly limited due to light availability Mitchell et al. The grazing pressure of mesozooplankton on large diatoms was also a major limiting factor in diatom production Schultes et al.

Considering the key factors i. Sources are Gall et al. How long. The third consideration for a successful aOIF experiment is the duration. Although the first 2 weeks have a decisive effect on the development and demise of the bloom, it has been suggested that most aOIF experiments did not cover the full response times from onset to termination Boyd et al.

For example, SOIREE and SEEDS-1 had relatively short observation periods 13 days and saw increasing trends in PP throughout the experiments Fig.

This indicates that short experimental durations may not be sufficient for detecting the full influence of aOIF on PP and the ecosystem Figs. SOFeX-S also resulted in relatively low export production despite the high PP due to the experimental duration being insufficient to cover the termination of the phytoplankton bloom.

However, SERIES, SEEDS-2, EIFEX, and LOHAFEX did fully monitor all phases of the phytoplankton bloom from onset to termination. EIFEX, the third-longest aOIF experiment, at 39 days, was the only one that observed iron-induced deep export production between day 28 and 32 Table 5 and Fig.

Furthermore, long-term observations covering the later stage of bloom development during nOIF experiments resulted in much higher C:Fe export efficiencies compared to the short-term aOIF Blain et al. Based on previous aOIF experiments, it would, therefore, be important to detect the full phase of a phytoplankton bloom to determine accurately the amount of iron-induced POC exported out of the winter ML.

The observation period is, therefore, an important consideration with regard to budget and effectiveness estimates. In addition, autonomous observation platforms are essential to monitor post-assessment of effectiveness, capacity, and risks of aOIF for at least 12 months after experiment termination.

First, the chemical form for iron addition should be acidified iron sulfate, which is less expensive and more bioavailable than other iron compounds. As a consequence of expansion and dilution, previous aOIF experiments also produced similar results to this model study.

Therefore, it would be more appropriate to fertilize a large area e. For example, in SOIREE it was found that four additions of iron at intervals of about 3 days led to persistently high levels of both dissolved and particulate iron within the ML, with a rapid reduction at the end of the experiment, combined with an increase in the concentration of iron-binding ligands Bowie et al.

In both EIFEX and SOFeX-S, it was also found that multiple iron II infusions in particular, two infusions with intervals of 13 days in EIFEX and four infusions with intervals of 4 days in SOFeX-S allowed iron to persist in the ML longer than its expected oxidation kinetics.

The relatively low oxidation rates were related to a combination of photochemical production; slow oxidation; and, possibly, organic complexation Croot et al.

Blain et al. Large amounts of iron addition at one time can lead to a substantial loss of artificially added iron. The fifth consideration for a successful aOIF experiment is the effective tracing of the fertilized patch, including the detection of carbon sequestration Buesseler and Boyd, The first step in tracing a fertilized patch is to investigate in advance the development and fate of natural blooms appearing as chlorophyll patches using satellite data from pre-experiment investigations.

All aOIF experiments used physical tracers to follow the iron-fertilized patches, in particular GPS- and Argos-equipped drifting buoys that provide the tracked positions of a fertilized patch as a passive system moving with local currents.

GPS- and Argos-equipped drifting buoys should be released before fertilization to provide a baseline , and ensuing aOIF experiments should be carried out in the region described by the drifting buoys deployed. Drifting buoys are, however, not perfect representations of water motion and due to the effects of winds are likely to escape a fertilized patch within a few days to a week regardless of how deep their drogues are Watson et al.

An inert chemical tracer, such as SF 6 , would also be an excellent option for following the fertilized patch after iron addition.

Previous aOIF experiments have shown that the SF 6 measurements based on underway sampling systems can be used to accurately determine time-dependent vertical and lateral transport of iron-fertilized patches.

Direct measurements of carbon export fluxes to determine the effectiveness of aOIF should be conducted by deploying an NBST at two depths: 1 just below the in situ MLD to detect increases in iron-induced POC in the surface layer along with the calibration of the water-column-based Th method and 2 at the winter MLD to detect iron-induced carbon export fluxes below winter MLD Bidigare et al.

Sinking-particle profiling systems e. Repeat casts with UVPs mounted on the rosette could also serve a similar purpose providing a photographic history of the water column Martin et al. Future aOIF experiments would benefit from these technological advances, enabling a more efficient tracing of the carbon export flux and particle size and composition at higher vertical and temporal resolution than has been possible in the past.

Hence, the application of an NBST system and water-column-based Th method to direct flux estimates, combined with autonomous sinking-particle profilers of a transmissometer and an UVP, will enable the quantitative and qualitative evaluation of the effectiveness of aOIF and direct observation of iron-induced carbon export fluxes after artificial iron additions.

What concerns. The sixth consideration for a successful aOIF experiment is the monitoring of possible side effects. However, there is little quantitative and qualitative information regarding possible side effects following the previous aOIF experiments.

Therefore, the future monitoring of these potential side effects is a prerequisite to evaluate accurately the effectiveness of an aOIF experiment in the future. In summary, to maximize the effectiveness of aOIF experiments in the future, we suggest a design that incorporates several conditions.

Figure 11 Schematic diagram of the Korean Iron Fertilization Experiment in the Southern Ocean KIFES representing the experiment target site eddy structure and survey methods underway sampling systems, multiple sediment traps, sub-bottom profilers, sediment coring systems, and satellite observations.

The KIFES design entails a 5-year project plan modeled on the EIFEX program that found deep carbon by conducting an aOIF experiment in the center of an eddy structure Fig. The KIFES project would include a preliminary environmental survey both outside and inside the center of an eddy structure formed in the SO PF, a scientific aOIF experiment, and an assessment of the full KIFES project.

In this section, we introduce the major goals, objectives, and main tasks of KIFES. Main tasks. First preliminary hydrographic survey to provide a foundational understanding of oceanographic conditions in the SO PF. inside the center of an eddy structure prior to KIFES.

Conduction of the KIFES scientific aOIF experiment in the center of an eddy structure during the early summertime Fig. To conduct a scientific aOIF experiment in the center of an eddy structure formed in the SO PF.

Integrated assessment of the KIFES project. The interests of the KIFES project will be all laid out in the detailed investigation of the biogeochemical effects of scientific aOIF in the SO and in aOIF as a possible geoengineering method to mitigate the climate change effects we will face in the future.

A continuation of the next aOIF experiment would provide fundamental information and guidelines for future scientific aOIF experiments in HNLC regions, in addition to improving our understanding of SO pelagic ecology—biogeochemistry. The risks and side effects of aOIF should be thoroughly investigated to calm international concerns.

Finally, we emphasize that international cooperation is essential for a project as organizationally and scientifically complex as KIFES and that we seek to improve our knowledge and provide a positive outlook for the Earth's future. To test Martin's hypothesis, a total of 13 scientific aOIF experiments have been conducted in HNLC regions during the last 25 years.

These aOIF experiments have resulted in increases in PP and drawdowns of macronutrients and DIC. In most experiments, the phytoplankton group has tended to shift from small-sized to large-sized plankton cells mostly diatom-dominated. However, their effectiveness in enhancing export production has not been confirmed, except for EIFEX.

Likewise, the possible environmental negative side effects in response to iron addition, such as decline in oxygen content and the production of climate-relevant gases and toxic DA, could not be fully evaluated due to the widely differing outcomes, with large uncertainties depending on aOIF experimental conditions and settings.

In particular, the monitoring of N 2 O , DMS, and HVOCs is essential to determine the effectiveness of aOIF as a geoengineering approach, because these potential trace gas emissions can directly and indirectly modify the carbon reduction benefits resulting from aOIF.

Therefore, the validation and suitability of aOIF for the mitigation of rapidly increasing atmospheric CO 2 levels are a subject of vigorous debate. To maximize the effectiveness of aOIF, future aOIF experiments should be conducted by carefully considering the major factors including the methods for iron addition, tracing methods, measurement parameters, location, timing, and experimental duration, under international aOIF regulations.

JEY, KCY, KK, and INK made contributes to the concept, design, and preparation of the manuscript. AMM contributed advise on explanations, content, and English.

JEY and INK wrote the manuscript. All authors discussed the results and commented on the manuscript. We thank two reviewers and Victor Smetacek Alfred Wegener Institute for their valuable comments on the manuscript. We thank Eunsil Kim Sangmyung University for her help in drawing Fig.

Thanks to all the people who contributed to the scientific OIF experiments. This research was a part of the project titled the Korean Iron Fertilization Experiment in the Southern Ocean KOPRI, PM funded by the Ministry of Oceans and Fisheries, Korea.

This work was partly supported by the National Research Foundation of Korea NRF grant funded by the Korea government MSIP no.

Alison M. Macdonald was supported by NOAA grant no. NA11OAR and internal WHOI funding. The last two authors Il-Nam Kim and Kitae Kim act as co-corresponding authors for this work. Edited by: S. Naqvi Reviewed by: Victor Smetacek and two anonymous referees.

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