Archive for geoengineering

The past, present, and future of artificial ocean iron fertilization experiments

Posted by mmaheigan 
· Wednesday, January 23rd, 2019 

Since the beginning of the industrial revolution, human activities have greatly increased atmospheric CO2 concentrations, leading to global warming and indicating an urgent need to reduce global greenhouse gas emissions. The Martin (or iron) hypothesis suggests that ocean iron fertilization (OIF) could be a low-cost effective method for reducing atmospheric CO2 levels by stimulating carbon sequestration via the biological pump in iron-limited, high-nutrient, low-chlorophyll (HNLC) ocean regions. Given increasing global political, social, and economic concerns associated with climate change, it is necessary to examine the validity and usefulness of artificial OIF (aOIF) experimentation as a geoengineering solution.

Figure 1. (a) Global annual distribution of surface chlorophyll concentrations (mg m-3) with locations of 13 aOIF experiments. Maximum and initial values in (b) maximum quantum yield of photosynthesis (Fv/Fm ratios) and (c) chlorophyll-a concentrations (mg m-3) during aOIF experiments. (d) Changes in primary productivity (ΔPP = [PP]post-fertilization (postf) ‒ [PP]pre-fertilization (pref); mg C m-2 d-1). (e) Distributions of chlorophyll-a concentrations (mg m-3) on day 24 after iron addition in the Southern Ocean iron experiment-north (SOFeX-N) from MODIS Terra Level-2 daily image and on day 20 in the SOFeX-south (SOFeX-S) from SeaWiFS Level-2 daily image (white dotted box indicates phytoplankton bloom during aOIF experiments). (f) Changes in nitrate concentrations (ΔNO3– = [NO3–]postf ‒ [NO3–]pref; μM). (g) Changes in partial pressure of CO2 (ΔpCO2 = [pCO2]postf ‒ [pCO2]pref; μatm). The color bar indicates changes in dissolved inorganic carbon (ΔDIC = [DIC]postf ‒ [DIC]pref; μM). The numbers on the X axis indicate the order of aOIF experiments as given in Figure 1a and are grouped according to ocean basins; Equatorial Pacific (EP) (yellow bar), Southern Ocean (SO) (blue bar), subarctic North Pacific (NP) (red bar), and subtropical North Atlantic (NA) (green bar).

A review paper published in Biogeosciences on aOIF experiments provides a thorough overview of 13 scientific artificial OIF experiments conducted in HNLC regions over the last 25 years. These aOIF experiments have demonstrated that iron addition stimulates substantial increases in phytoplankton biomass and primary production, resulting in drawdown of macro-nutrients and dissolved inorganic carbon (Figure 1). Many of the aOIF experiments have also precipitated community shifts from smaller (pico- and nano-) to larger (micro) phytoplankton. However, the impact on the net transfer of CO2 from the atmosphere to below the winter mixed layer via the biological pump is not yet fully understood or quantified and appears to vary with environmental conditions, export flux measurement techniques, and other unknown factors. These results, including possible side effects, have been debated among those who support and oppose aOIF experimentation, and many questions remain about the effectiveness of scientific aOIF, possible side effects, and international aOIF law frameworks. Therefore, it is important to continue undertaking small-scale, scientifically controlled studies to better understand natural processes in the HNLC regions, assess the associated risks, and lay the groundwork for evaluating the potential effectiveness and impacts of large-scale aOIF as a geoengineering solution to anthropogenic climate change. Additionally, this paper suggests considerations for the design of future aOIF experiments to maximize the effectiveness of the technique and begin to answer open questions under international aOIF regulations.

 

Authors:
Joo-Eun Yoon (Incheon National University)
Il-Nam Kim (Incheon National University)
Alison M. Macdonald (Woods Hole Oceanographic Institution)

Filter by Keyword

abundance acidification africa air-sea interactions alkalinity allometry ammonium AMOC anoxia anoxic Antarctic anthropogenic carbon aragonite saturation arctic arsenic Atlantic Atlantic modeling atmospheric CO2 atmospheric nitrogen deposition authigenic carbonates autonomous platforms bacteria BATS benthic bgc argo bioavailability biogeochemical cycles biogeochemical models biogeochemistry biological pump biological uptake biophysics bloom blooms blue carbon bottom water boundary layer buffer capacity CaCO3 calcification calcite carbon-climate feedback carbon-sulfur coupling carbon cycle carbon dioxide carbon sequestration Caribbean CCA CCS changing marine ecosystems changing ocean chemistry chemoautotroph chesapeake bay chl a chlorophyll circulation climate change CO2 coastal darkening coastal ocean cobalt Coccolithophores community composition conservation cooling effect copepod coral reefs currents cyclone DCM decomposers decomposition deep convection deep ocean deep sea coral deoxygenation depth diagenesis diatoms DIC diel migration dimethylsulfide dinoflagellate dissolved inorganic carbon dissolved organic carbon DOC DOM domoic acid dust DVM earth system models ecosystem state eddy Education Ekman transport emissions ENSO enzyme equatorial regions error ESM estuarine and coastal carbon fluxes estuary euphotic zone eutrophication evolution export EXPORTS extreme events extreme weather events faecal pellets filter feeders filtration rates fire fish Fish carbon fisheries floats fluid dynamics fluorescence food webs forams freshening freshwater frontal zone functional role future oceans geochemistry geoengineering GEOTRACES glaciers gliders global carbon budget global warming go-ship grazing greenhouse gas Greenland groundwater Gulf of Maine Gulf of Mexico Gulf Stream gyre harmful algal bloom high latitude human food human impact hurricane hydrothermal hypoxia ice age ice cores ice cover industrial onset inverse circulation iron iron fertilization isotopes jellies katabatic winds kelvin waves krill kuroshio land-ocean continuum larvaceans lateral transport LGM lidar ligands light light attenuation mangroves marine heatwave marine snowfall marshes Mediterranean meltwater mesopelagic mesoscale metagenome metals methane microbes microlayer microorganisms microscale microzooplankton midwater mixed layer mixed layers mixotrophy modeling mode water molecular diffusion MPT multi-decade NASA NCP net community production new technology nitrate nitrogen nitrogen fixation nitrous oxide north atlantic north pacific nutricline nutrient budget nutrient cycling nutrient limitation nutrients OA ocean-atmosphere ocean acidification ocean carbon uptake and storage ocean color ocean observatories ODZ oligotrophic omics OMZ open ocean optics organic particles overturning circulation oxygen pacific paleoceanography particle flux pCO2 PDO peat pelagic pH phenology phosphorus photosynthesis physical processes physiology phytoplankton plankton POC polar regions pollutants prediction primary productivity Prochlorococcus proteins pteropods pycnocline radioisotopes remineralization remote sensing residence time resource management respiration resuspension rivers rocky shore Rossby waves Ross Sea ROV salinity salt marsh satell satellite scale seafloor seagrass sea ice sea level rise seasonal patterns sea spray seaweed sediments sensors shelf system shells ship-based observations shorelines silicate sinking particles size SOCCOM soil carbon southern ocean south pacific spatial covariations speciation SST subduction submesoscale subpolar subtropical sulfate surface surface ocean Synechococcus teleconnections temperate temperature temporal covariations thermocline thermohaline thorium tidal time-series time of emergence top predators total alkalinity trace elements trace metals trait-based transfer efficiency transient features trophic transfer tropical turbulence twilight zone upper ocean upper water column upwelling US CLIVAR validation velocity gradient ventilation vertical flux vertical migration vertical transport volcano water clarity water quality western boundary currents wetlands winter mixing zooplankton

Copyright © 2021 - OCB Project Office, Woods Hole Oceanographic Institution, 266 Woods Hole Rd, MS #25, Woods Hole, MA 02543 USA Phone: 508-289-2838  •  Fax: 508-457-2193  •  Email: ocb_news@us-ocb.org

link to nsflink to noaalink to WHOI

Funding for the Ocean Carbon & Biogeochemistry Project Office is provided by the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA). The OCB Project Office is housed at the Woods Hole Oceanographic Institution.