Field observation
A measurement tied to a stated method, place, period and intervention or natural analogue.
Regional evidence atlas
Ocean iron fertilisation: Three regions. Three carbon pathways.
Each ocean system changes the biological response, export pathway, atmospheric accounting and observation design. Comparison does not rank locations.
Broad scientific context
HNLC describes a regional oceanographic condition, not an individual project area.
Macronutrients can remain abundant while iron often constrains phytoplankton growth. Boundaries, mechanisms and seasonal expression vary.
02Subarctic North Pacific
01Equatorial Pacific
03Southern Ocean
Broad scientific context only: not HNLC boundaries, maritime boundaries, project sites or permission areas.
Side-by-side evidence
Different questions control each pathway.
Field studies differ by region, season, experiment design, initial conditions and observation period.
| Question | Equatorial Pacific | Subarctic North Pacific | Southern Ocean |
|---|---|---|---|
| Evidence base | IronEx field experiments plus Galápagos natural iron-plume observations; response and rapid transport are directly observed | SEEDS/SEEDS-II and SERIES field experiments plus Line P/OSP observations; repeat outcomes diverge | SOIREE, EisenEx, SOFeX North/South, EIFEX, SAGE and LOHAFEX deliberate experiments; natural analogues at Kerguelen, Crozet and South Georgia |
| Central MRV question | Can biological and carbonate signals be separated from advection, ENSO, upwelling and an evolving matched reference? | What fraction crosses the permanent thermocline or winter ventilation depth rather than being grazed, respired or diluted? | How do deep export, winter ventilation, air–sea equilibration and non-local nutrient effects combine in a net atmospheric account? |
| Ecological uncertainty | Community succession, grazing, silica, toxin pathways, oxygen-minimum-zone and downstream nutrient effects | Seed stock, grazing, Pseudo-nitzschia/toxin pathways, silica and food-web redistribution | Light and silica limitation, grazing, trace gases, protected food webs, benthic effects and displaced productivity |
| Operational reality | Fast moving-patch and downstream-corridor sampling across ENSO and seasonal states | Open-ocean ship time, comparable seasonal repeats, taxonomy/toxin laboratories and long export follow-up | Long transit, narrow weather windows, deep instruments, recovery cruises and winter or multi-season observation |
| Governance sensitivity | High-seas IronEx evidence and Ecuador’s protected Galápagos context have distinct geographic and legal contexts | OSP and SEEDS sites are high seas; Canadian and Japanese scientific leadership does not create site jurisdiction | New Zealand, French/TAAF and SGSSI protected regimes, the South Georgia dispute, and Antarctic/CCAMLR geography have distinct contexts |
Primary evidence: Coale et al. (1996) ↗ · Tsuda et al. (2003) ↗ · Boyd et al. (2004) ↗ · Boyd et al. (2000) ↗ · Gervais et al. (2002) ↗ · Coale et al. (2004) ↗ · Bishop et al. (2004) ↗ · Buesseler et al. (2005) ↗ · Smetacek et al. (2012) ↗ · Peloquin et al. (2011) ↗ · Martin et al. (2013) ↗.
Source: linked regional studies and scientific guidance. Experiment-specific observations and research design implications. Studies differ in place, season, dose, duration, method and follow-up; comparison cannot rank regions
01Field experiments & natural analogue
Equatorial Pacific
A moving patch in a rapidly changing ocean.
- Primary research issue
- The IronEx II patch travelled roughly 1,500 km in 19 days. A coordinate is not a stable experimental boundary.
Subarctic North Pacific
Community composition determines the export pathway.
- Primary research issue
- Western and northeast subarctic experiments cannot be collapsed into one regional response; their communities, seasons and physical settings differ.
Southern Ocean
Deep particles are one step in a longer atmospheric account.
- Primary research issue
- Deep particle observations do not alone quantify additional atmospheric CO₂ uptake, later re-emission, nutrient displacement or life-cycle emissions.
Seven detailed records
Experiments, observatories and natural analogues.
Each context follows the evidence from oceanography and phytoplankton through carbon fate, measurement, operations, risk and governance.
01Natural analogue + mesoscale field experiments
Galápagos & eastern equatorial Pacific
Sustained island-and-current iron supply around Galápagos contrasts with geographically separate IronEx pulses in open-ocean equatorial waters.
Equatorial PacificRead the evidence context →02Mesoscale field experiment + long-term observatoryOcean Station Papa & SERIES
SERIES followed an induced diatom bloom through decline, while Line P and Ocean Station Papa provide a rare multi-decadal baseline for physical, chemical and ecological change.
Subarctic North PacificRead the evidence context →03Repeat mesoscale field experimentsSEEDS & SEEDS-II
Two Japan-led experiments near the same season and location produced sharply different outcomes, exposing the importance of seed stock, grazing and physical state.
Subarctic North PacificRead the evidence context →04Direct field counterevidenceSAGE · New Zealand
SAGE relieved physiological iron stress but produced only a modest bloom, no material particulate-carbon accumulation and a carbonate signal confounded by mixing.
Southern OceanRead the evidence context →05Natural iron-fertilisation analogueKerguelen Plateau
KEOPS traces a recurrent plateau bloom from sustained natural iron supply through community succession, carbonate chemistry and seasonally variable export.
Southern OceanRead the evidence context →06Natural analogue + deep-export observationsCrozet Plateau
CROZEX connects a naturally fertilised bloom to seasonal export, deep sediment traps and seafloor delivery—and reveals how island-specific resting spores shape the result.
Southern OceanRead the evidence context →07Recurring natural analogue + deep trapsSouth Georgia
A recurring diatom-rich bloom, island and glacial iron sources, repeat cruises and deep traps make South Georgia an unusually rich carbon-fate research context.
Southern OceanRead the evidence context →Evidence classes
Evidence scale and measurement window.
Model output
A result conditional on model structure, forcing, parameterisation and scenario assumptions.
Unresolved evidence
Evidence may be sparse, conflicting or not comparable across places, seasons and observation windows.