Ocean Fertilization Research Articles

Wintertime productivity and carbon export potential across the Agulhas Current system

The Agulhas Current plays a major role in heat and salt exchange between the Indian and Atlantic Oceans, yet little is known of its influence on ocean fertility. To investigate carbon production and export potential in the Agulhas Current system, we measured net primary production (NPP), nitrate and ammonium uptake, N2 fixation, and nitrification along a transect of the current and adjacent subtropical subgyre (33.4°S–35.7°S) in winter when nutrient supply, and thus productivity, should be highest. Phytoplankton biomass was lowest in the current core, increasing into the subgyre as surface nitrate declined, and was dominated by nanoplankton (2.7–10 μm; 62 ± 5.1% of total biomass). NPP and nitrate uptake were generally high across the transect and increased from the current core into the subgyre; the rates were dominated by picoplankton (<2.7 μm; 53–93%) in the current core and nanoplankton elsewhere (63–69%). On average, euphotic zone nitrification supplied 7.6 ± 6.4% of the nitrate consumed by phytoplankton and N2 fixation was also low (2.1 ± 1.3% of new production); we thus consider nitrate uptake a reasonable proxy for new production, at least in winter. Nitrate uptake was highest at the southern edge of the current core, consistent with current-associated (sub)mesoscale mixing enhancing the upward nutrient supply. The fraction of NPP available for export (i.e., the f-ratio) was high across the transect, ranging from 0.44 to 0.69. Our data thus indicate that both total and new production are elevated across the Agulhas Current system in winter and suggest that the (sub)mesoscale dynamics associated with the current system may enhance carbon production and export in the otherwise oligotrophic southwest Indian Ocean.

The response of the ocean carbon cycle to artificial upwelling, ocean iron fertilization and the combination of both

The response of the ocean carbon cycle to artificial upwelling, ocean iron fertilization and the combination of both

An exceptional phytoplankton bloom in the southeast Madagascar Sea driven by African dust deposition

Abstract Rising surface temperatures are projected to cause more frequent and intense droughts in the world's drylands. This can lead to land degradation, mobilization of soil particles, and an increase in dust aerosol emissions from arid and semi-arid regions. Dust aerosols are a key source of bio-essential nutrients, can be transported in the atmosphere over large distances, and ultimately deposited onto the ocean's surface, alleviating nutrient limitation and increasing oceanic primary productivity. Currently, the linkages between desertification, dust emissions and ocean fertilization remain poorly understood. Here, we show that dust emitted from Southern Africa was transported and deposited into the nutrient-limited surface waters southeast of Madagascar, which stimulated the strongest phytoplankton bloom of the last two decades during a period of the year when blooms are not expected. The conditions required for triggering blooms of this magnitude are anomalous, but current trends in air temperatures, aridity, and dust emissions in Southern Africa suggest that such events could become more probable in the future. Together with the recent findings on ocean fertilization by drought-induced megafires in Australia, our results point toward a potential link between global warming, drought, aerosol emissions, and ocean blooms.

Early engagement will be necessary for atmospheric methane removal field trials

Abstract Atmospheric methane removal (AMR) refers to a suite of emerging technologies and practices that destroy atmospheric methane. There is growing interest in AMR field trials to better understand the risks and benefits of various approaches. Building on rights-based rationales from international law and core principles of environmental justice, we argue that AMR field trials should not proceed before meaningful public engagement occurs. We also draw preliminary lessons from ocean fertilization and solar radiation management (SRM) cases to highlight the significance of involving members of the public in conversation about climate intervention technologies in early stages of the research and development process. While we emphasize that engagement is not a checkbox for gaining social license, these cases illustrate how neglecting public engagement can be unnecessarily detrimental to proposed research. We further point to an enhanced weathering experiment to highlight how early engagement can foster ethical processes and outcomes, which enhance alignment of research with societal values. While empirical evidence does not yet support the argument that engagement always results in the outcomes researchers desire, it does always result in justice enhancing outcomes and should therefore be pursued regardless. We advocate for diverse engagement approaches based on the nature of the technology, with a focus on collaboration with impacted communities, the public, and international interdisciplinary researchers. To ensure responsible research practices, the article calls for the development of comprehensive governance frameworks and ethical guidelines for field trials.

Next steps for assessing ocean iron fertilization for marine carbon dioxide removal

There are many potential approaches to marine carbon dioxide removal (mCDR), of which ocean iron fertilization (OIF) has the longest history of study. However, OIF studies to date were not primarily designed to quantify the durability of carbon (C) storage, nor how wise OIF might be as an mCDR approach. To quantify C sequestration, we introduce a metric called the “centennial tonne,” defined as 1,000 kg of C isolated from atmospheric contact for on average at least 100 years. We present the activities needed to assess OIF from a scientific and technological perspective, and additionally, how it might be responsibly studied and potentially deployed. The five activities include: field studies in the Northeast Pacific; improved modeling for field studies, data assimilation and predictions at larger scales; improvements in monitoring, reporting and verification (MRV) for C, and also MRV for tracking ecological and environmental impacts; and developing new iron sources and their delivery, to increase efficiencies and reduce costs. The fifth activity is to understand whether public and community support exists for OIF, and what governance structures might support further research and possible deployment of OIF. This article is written by a multidisciplinary experts group called Exploring Ocean Iron Solutions (ExOIS) that is organized around a responsible code of conduct. Of the mCDR approaches, OIF has the potential to be low cost, scalable, and rapidly deployable. Reducing CO2 emissions must lead the way, but there is also an urgency to decide under what conditions and whether OIF might be deployed or not.

Design and Implementation of Iron-Based Electrochemical System for Simultaneous Carbon Capture and Hydrogen Gas Recovery

The catastrophic results of climate change and energy crisis, such as the rise in wildfires, floods, and ecosystem disruptions highlight the critical need of urgent and innovative global-scale solutions for carbon dioxide (CO2) removal (CDR). Ocean-based CDR methods, leveraging the ocean's capacity as a large sink to sequester up to 30% of emissions, offer a great promise. Yet, implementing and testing marine CO2 removal (mCDR) techniques such as ocean iron fertilization (OIF) or ocean alkalinity enhancement (OAE) face significant challenges. To overcome these challenges, a novel self-operating electrochemical technology is designed and presented in this work. The proposed technology, namely electrochemical OIF (EOIF), does not only combine OIF and OAE, but also recovers hydrogen gas (H2) from seawater, offering a promising solution for achieving quantifiable and transparent large-scale mCDR. The EOIF design s focused on employing Fe/Fe-producing anodes to eliminate the production of acids at the anode in traditional electrochemical OAE systems and replace it with Fe release, where the cathode can be made from naturally abundant cost-effective materials, such as carbon. The obtained results show that the EOIF system can be implemented to increase both the concentration of ferrous iron (Fe+2) by 0-0.5 mg/L, and the seawater pH by 8% (i.e., 25% decrease in the hydrogen ions concentration). It also offers the flexibility to optimize the release of iron (Fe+2/Fe+3) by adjusting the magnitude of the electric current in the systems, as well as by optimizing the electrode material and geometry. In certain ocean regions, enhanced iron concentrations stimulate the naturally occurring biological carbon pump (BCP), leading to increased phytoplankton growth, CO2 uptake, and subsequent export of carbon to the deep ocean. Simultaneously, the system increases seawater alkalinity and the buffer capacity, enhancing CO2 solubility and storage in the shallow ocean through the solubility pump. The techno-economic assessment shows that the combined advantages of the EOIF system can lower the mCDR cost by more than 95% compared to the traditional methods. The obtained measurements demonstrate the scalability of EOIF and its ability to operate using solar energy at a lower cost. Overall, the proposed EOIF technology offers a practical, effective, and sustainable solution for addressing climate change and energy recovery on a large-scale.

Sea Level Modulation of Atlantic Nitrogen Fixation Over Glacial Cycles

AbstractN2 fixation in low‐latitude surface waters dominates the input of fixed nitrogen (N) to the global ocean, sustaining ocean fertility. In the Caribbean Sea, higher foraminifera‐bound (FB‐)δ15N indicates a decline in N2 fixation during ice ages, but its cause and broader implications are unclear. Here, we report three additional Atlantic FB‐δ15N records, from the subtropical North and South Atlantic gyres (MSM58‐50 and DSDP Site 516) and the equatorial Atlantic (ODP Site 662). Similar glacial and interglacial δ15N in the equatorial Atlantic suggests a stable δ15N for the nitrate below the gyre thermoclines. The North Atlantic record shows a FB‐δ15N rise during the ice ages, resembling a previously published FB‐δ15N record from the South China Sea. The commonality among the FB‐δ15N records is that they resemble sea level‐driven variation in regional shelf area, with high FB‐δ15N (inferred reduction in N2 fixation) during periods of low shelf area. The South China Sea shows the largest δ15N signal, the subtropical North Atlantic shows less, and the South Atlantic shows the least, the same ordering as the ice age reductions in continental shelf area in the different regions. Reduced shelf sedimentary denitrification would have increased the nitrogen‐to‐phosphorus ratio of the nutrient supply to open ocean surface waters, leading to decreased N2 fixation and thus higher gyre thermocline nitrate δ15N, explaining the higher FB‐δ15N of peak ice ages. These observations identify shelf sediment denitrification as an important regional driver of modern N2 fixation and imply strong basin‐scale coupling of fixed nitrogen losses and inputs.

Oceanic anoxic event 3 in Arctic Canada—Arc volcanism and ocean fertilization drove anoxia

The global extent of the Late Cretaceous oceanic anoxic event 3 (OAE 3) remains uncertain. It is not considered to have extended into the Boreal Realm. To test this, we examined Late Cretaceous organic- and metal-rich black mudstones of the Smoking Hills Formation in Arctic Canada. New high-precision U-Pb zircon ages indicate that deposition of the Smoking Hills Formation (88.535−78.230 Ma) was temporally coincident with OAE 3, indicating a much broader global expression of this event than previously thought. OAE 3 was likely manifest throughout the proto−Arctic Ocean (now Arctic Canada). Abundant bentonite layers and cryptotephra within the Smoking Hills Formation have rare earth element (REE) patterns that are consistent with ashfall derived from Cretaceous arc volcanism. Anomalously high organic matter content in the Smoking Hills Formation, as compared to underlying and overlying units, suggests that ocean fertilization led to enhanced productivity and metal drawdown. A peak in arc volcanism may have been a key driver of the OAE 3 event. We also explored the potential use of cadmium as a geochemical marker of volcanism and show that high volcanogenic metal loading could affect the use of Cd and other proxies for marine productivity (e.g., Zn, Cu).

Electrochemical ocean iron fertilization and alkalinity enhancement approach toward CO2 sequestration

Achieving net-zero emissions by 2050 requires the development of effective negative emission techniques, including ocean-based approaches for CO2 sequestration. However, the implementation and testing of marine CO2 removal (mCDR) techniques such as ocean iron fertilization (OIF) or ocean alkalinity enhancement (OAE) face significant challenges. Herein, a novel self-operating electrochemical technology is presented that not only combines OIF and OAE, but also recovers hydrogen gas (H2) from seawater, hence offering a promising solution for achieving quantifiable and transparent large-scale mCDR. Experimental results show that the electrochemical OIF (EOIF) can not only increase the concentration of ferrous iron (Fe+2) by 0–0.5 mg/L, but also significantly increases the seawater pH by 8% (i.e., a 25% decrease in the hydrogen ions concentration). The release of iron (Fe+2/Fe+3) can be regulated by adjusting the magnitude of the electric current and its form (e.g., pulsed current and polarity reversal), as well as by optimizing the electrode material and geometry. In certain ocean regions, enhanced iron concentrations stimulate the naturally occurring biological carbon pump (BCP), leading to increased phytoplankton growth, CO2 uptake, and subsequent export of carbon to the deep ocean. Simultaneously, the system increases seawater alkalinity and the buffer capacity, enhancing CO2 solubility and storage in the shallow ocean through the solubility pump. The obtained measurements demonstrate the scalability of EOIF and its ability to operate using solar energy at a lower cost. Overall, the proposed EOIF technology offers a practical, effective, and sustainable solution for addressing climate change on a large scale.

A Cost Model for Ocean Iron Fertilization as a Means of Carbon Dioxide Removal That Compares Ship‐ and Aerial‐Based Delivery, and Estimates Verification Costs

AbstractWe present a cost model for implementing a deployment scale effort for conducting ocean iron fertilization (OIF) for marine‐based carbon dioxide removal (CDR). The model incorporates basic oceanographic parameters critical for estimating the effective export of newly fixed CO2 into biomass that is stimulated by Fe addition to an Fe‐limited region of the Southern Ocean. Estimated costs can vary by nearly 100‐fold between best‐case and worst‐case scenarios, with best‐case values of $7/net tonne C captured versus worst‐case $1,500/net tonne C captured, without accounting for verification costs. Primary oceanographic factors that influence cost are the net primary productivity increases achieved via OIF, the amount of C exported into the deep ocean, and the amount of CO2 ventilated back to the atmosphere. The model compares ship‐based versus aerial delivery of Fe to the ocean, and estimates aerial delivery can be 30%–40% more cost effective; however, the specific requirements for aerial delivery require additional research and development. The model also estimates costs associated with verification and environmental monitoring of OIF. These costs increase $/net tonne C captured by 3–4‐fold. Best, intermediate, and worst cases for aerial delivery and ship delivery are $21, $83, $2,033, and $24, $94, $4,691, respectively, inclusive of verification costs. The primary goal of this model is to demonstrate the variability in cost of OIF as a CDR method, and to better understand where additional research is needed to determine the major factors that may make OIF a tractable, nature‐based CDR method.

Implementation of marine CO2 removal for climate mitigation: The challenges of additionality, predictability, and governability

Achieving net zero CO2 emissions requires gigatonne-scale atmospheric CO2 removal (CDR) to balance residual emissions that are extremely difficult to eliminate. Marine CDR (mCDR) methods are seen increasingly as potentially important additions to a global portfolio of climate policy actions. The most widely considered mCDR methods are coastal blue carbon and seaweed farming that primarily depend on biological manipulations; ocean iron fertilisation, ocean alkalinity enhancement, and direct ocean capture that depend on chemical manipulations; and artificial upwelling that depends on physical manipulation of the ocean system. It is currently highly uncertain which, if any, of these approaches might be implemented at sufficient scale to make a meaningful contribution to net zero. Here, we derive a framework based on additionality, predictability, and governability to assess implementation challenges for these mCDR methods. We argue that additionality, the net increase of CO2 sequestration due to mCDR relative to the baseline state, will be harder to determine for those mCDR methods with relatively large inherent complexity, and therefore higher potential for unpredictable impacts, both climatic and non-climatic. Predictability is inherently lower for mCDR methods that depend on biology than for methods relying on chemical or physical manipulations. Furthermore, predictability is lower for methods that require manipulation of multiple components of the ocean system. The predictability of an mCDR method also affects its governability, as highly complex mCDR methods with uncertain outcomes and greater likelihood of unintended consequences will require more monitoring and regulation, both for risk management and verified carbon accounting. We argue that systematic assessment of additionality, predictability, and governability of mCDR approaches increases their chances of leading to a net climatic benefit and informs political decision-making around their potential implementation.

The Late Maastrichtian Rørdal Member (Denmark): a remarkable window of climatic, environmental and biotic changes at orbital timescales

Abstract The Late Maastrichtian Rørdal Member of the Møns Klint Formation is a remarkable lithological unit of the Danish Basin, characterized by chalk–marl cyclicity, standing out from pure Maastrichtian white chalk within the Chalk Group. A cyclostratigraphic analysis across this unit suggests a control by orbital precession and a strong amplitude modulation of the precession by the 405 kyr eccentricity cycle. Oxygen isotope data from bulk carbonate, benthic foraminifera and brachiopods indicate a prominent cooling commencing at the base of the unit, with maximum cooling aligned with a 405 kyr amplitude modulation maximum. This unit thus represents a rare example of a climatic cooling associated with a 405 kyr insolation maximum. However, geochemical and calcareous nannofossil data support lower productivity levels across the unit, in contradiction to an expected ocean fertilization accompanying enhanced continental weathering as the source of the clay material. An alternative model of deposition for this lithological unit is thus proposed via dense water cascading favoured by a sea-level low, subsequent restriction of the Chalk Sea and associated gravity currents responsible for the resuspension of fine clastic deposits from the margins of the Baltic Shield.

Halophytes/Saline Water/Deserts/Wastelands Nexus as a Scalable Climate Mitigation including Freshwater Impacts

Climate change is rapidly exacerbating and adding to major-to-existential issues associated with freshwater availability and utilization. The massive, thus far untapped saline/salt water/ocean—wastelands/deserts—Halophytes resources nexus can, at scale and profitably, provide major climate change mitigation and greatly alleviate most extant freshwater issues. Approaches include ocean fertilization and saline/seawater agriculture on deserts and wastelands to sequester massive amounts of CO2 and methane and for food, freeing up some 70% of the freshwater now utilized by current agriculture for direct human use. This also enables the production of huge amounts of biofuels and biomass-based chemical feedstock employing the massive capacity of cheap saline/seawater and cheap deserts and wastelands. Overall, saline/seawater can, uniquely, at the scale of the climate and freshwater issues, without desalinization, profitably, utilizing extant technologies, some 40% of the land that is deserts/wastelands, and the 97% of the water that is saline/seawater rapidly, seriously, address land, freshwater, food, energy, and climate.

Numerical analysis of air–water two-phase upflow in artificial upwelling of deep ocean water by airlift pump

Artificial upwelling by the use of airlift pump is regarded as an effective way in utilizing deep ocean water and actualizing ocean fertilization. This paper focuses on numerical analysis of steady air–water two-phase flow in a vertical pipe of an airlift system based on one-dimensional multi-fluid model. The depth distributions of 6 physical quantities such as volumetric fractions and axial velocities of two phases, air density and pressure are calculated by solving the governing equations or by integrating the vector form of nonhomogeneous ordinary differential equation for two-phase flow interval. Upon successful verification of the present numerical model through a comparison with precedent theoretical and experimental results in case of a vertical pipe with length of 7.86 m, the model is extended to the case of artificial upwelling from water depth of 2000 m. The effects of submerged depth of air–water mixer on the pumped amount of water and the depth distributions of 6 physical quantities are considered.

Assessing the Ecological Implications of Ocean Iron Fertilization: Insights from Post-Eruption Volcanic Processes

This study proposes the usage of post-eruption volcanic processes as a natural analog for assessing the potential impacts of man-made iron fertilization on ocean ecosystems. Data is compiled from the 14 most explosive volcanic eruptions since 1884 to establish correlations between climate temperature anomalies and phytoplankton growth induced by volcanic tephra fallout in addition to other post-eruption variables. Through a comparative analysis of the contrasting strengths of these relationships using a student t-test for statistical significance, multivariable regression analysis, and linear regression interpretation, the scale of ocean iron fertilization is quantified. Two well-documented modern volcanic eruptions in Hawaii and Iceland are additionally employed as case studies to provide a comprehensive understanding of micro phenomenons occurring post-eruption. Rapid algae growth is demonstrated in High Nutrient Low Chlorophyll regions (HNLC), where long-term growth can be sustained for up to six months. Statistical results isolate the effect of stratospheric injection from ocean iron fertilization, demonstrating the effectiveness of tephra ash fallout in inducing regional phytoplankton growth. In all, these findings contribute to a comprehension of the potential ecological consequences of iron fertilization efforts, an approach to assess environmental implications without direct experimentation.

Instabilities Across the Agulhas Current Enhance Upward Nitrate Supply in the Southwest Subtropical Indian Ocean

AbstractThe Agulhas Current, like other western boundary currents (WBCs), transports nutrients laterally from the tropics to the subtropics in a subsurface “nutrient stream.” These nutrients are predominantly supplied to surface waters by seasonal convective mixing, to fuel a brief period of productivity before phytoplankton become nutrient‐limited. Episodic mixing events characteristic of WBC systems can temporarily alleviate nutrient scarcity by vertically entraining deep nutrients into surface waters. However, our understanding of these nutrient fluxes is lacking because they are spatio‐temporally limited, and once they enter the sunlit layer, the nutrients are rapidly consumed by phytoplankton. Here, we use a novel application of nitrate Δ(15–18), the difference between the nitrogen and oxygen isotope ratios of nitrate, to characterize three (sub)mesoscale events of upward nitrate supply across the Agulhas Current in winter: (1) mixing at the edges of an anticyclonic eddy, (2) inshore upwelling associated with a submesoscale meander of the Agulhas Current, and (3) overturning at the edge of the current core driven by submesoscale instabilities. All three events manifest as upward injections of high‐Δ(15–18) nitrate into the thermocline and surface where nitrate Δ(15–18) is otherwise low; these entrainment events are not always apparent in the other co‐collected data. The dynamics driving the nitrate supply events are common to all WBCs, implying that nutrient entrainment facilitated by WBCs is quantitatively significant and supports productivity in otherwise oligotrophic subtropical surface waters. A future rise in energy across WBC systems may increase these nutrient fluxes, partly offsetting the predicted stratification‐induced decrease in subtropical ocean fertility.

Treaty Regime of Ocean Fertilization: gaps and solutions

Treaty Regime of Ocean Fertilization: gaps and solutions

Natural ocean iron fertilization and climate variability over geological periods.

Marine primary producers are largely dependent on and shape the Earth's climate, although their relationship with climate varies over space and time. The growth of phytoplankton and associated marine primary productivity in most of the modern global ocean is limited by the supply of nutrients, including the micronutrient iron. The addition of iron via episodic and frequent events drives the biological carbon pump and promotes the sequestration of atmospheric carbon dioxide (CO2 ) into the ocean. However, the dependence between iron and marine primary producers adaptively changes over different geological periods due to the variation in global climate and environment. In this review, we examined the role and importance of iron in modulating marine primary production during some specific geological periods, that is, the Great Oxidation Event (GOE) during the Huronian glaciation, the Snowball Earth Event during the Cryogenian, the glacial-interglacial cycles during the Pleistocene, and the period from the last glacial maximum to the late Holocene. Only the change trend of iron bioavailability and climate in the glacial-interglacial cycles is consistent with the Iron Hypothesis. During the GOE and the Snowball Earth periods, although the bioavailability of iron in the ocean and the climate changed dramatically, the changing trend of many factors contradicted the Iron Hypothesis. By detangling the relationship among marine primary productivity, iron availability and oceanic environments in different geological periods, this review can offer some new insights for evaluating the impact of ocean iron fertilization on removing CO2 from the atmosphere and regulating the climate.

Layout optimization for underwater nozzle array of air-lifted artificial upwelling system based on discrete particle swarm algorithm

Artificial upwelling (AU) is widely recognized as a geoengineering tool to enhance oceanic fertility and stimulate the earth's capability of self-healing. Several air-lifted AU systems have been established to promote seaweed growth and facilitate carbon sequestration, for instance, in Norway and China. However, few researchers have addressed the critical issue of optimizing the layout of the underwater nozzle array (UNA), a key component of the air-lifted AU system. In this paper, we propose a novel method to optimize the layout of UNA by introducing and improving the discrete particle swarm optimization (DPSO) algorithm to guide the optimal nozzle positions. Furthermore, we develop the nutrient transport efficiency model to evaluate the performance of the AU system and apply it to investigate a typical AU system, namely the one in Aoshan Bay, China. Our results demonstrate that the proposed DPSO algorithm outperforms the conventional particle swarm optimization algorithm and the nutrient transport efficiency under the optimized UNA layouts was improved by an average of 14.5% to 35.0% compared to randomly generated layouts. These findings suggest that our optimization method could serve as a scientific reference for the engineering design of AU.

Survey of Frontier Technological Approaches to Mitigate Climate Change

Climate change with its’ increasingly serious and wide spectrum adverse impacts is the Issue of the Age. Climate change impacts have advanced to where mitigation solutions are now required for CO2 removal from the atmosphere along with planetary albedo/ other safe geoengineering approaches in addition to ever lower cost green energy generation and energy storage/ conversion/ conservation/ efficiency. There are extensive ongoing efforts involving all of these climate mitigation approaches. This work is a survey of additional frontier technologies, concepts and alternatives not yet deployed or nascent which could greatly augment the ongoing climate mitigation efforts across the spectrum. Particularly potentially efficacious approaches wrt cost and effectiveness include Halophytes, LENR, high altitude wind, geothermal utilizing abandoned oil and gas wells, ocean fertilization, white roofs and white roads and utilization of weak force nuclear batteries to extract the some 85% of the energy still present in nuclear waste.