Phytoplankton which lives at the surface of the oceans is responsible of half of the Earth oxygen production, through photosynthesis. In addition, it is fixing dissolved carbon (CO2) of atmospheric origin as solid particles which, when dying, are falling as detritus in the abyss and the sediment. This mechanism called the “Biological Carbon Pump” is an important sink for the anthropogenic CO2. Understanding the processes leading to phytoplankton development is thus a major issue for present-day climate modelling and the prediction of our future climate.
Iron (as other trace metals) is essential for the photosynthesis success of most of the phytoplanktonic species. However, its abundance in the marine waters is extremely low and its absence is limiting the phytoplankton development in roughly half of the world’s oceans. This led to the development of studies of artificial ocean iron fertilization, the hypothesis being that stimulating photosynthesis will improve the capacity of the ocean to absorb CO2. However, thanks to studies on the iron distribution and fate it is now proved that artificial ocean iron fertilization will never produce the expected result as photosynthesis continues to be limited due to the complexity of processes at play in surface waters. Such results prevent wasting money in useless operations.
Thus, to understand the carbon pump functioning or to test geoengineer’s hypothesis, studying the oceanic iron cycle is essential. This includes: understanding the iron sources to the ocean, its sinks, its distribution, etc. GEOTRACES is elucidating these questions, as well as, producing high-quality data and representing it on an electronic Atlas that helps to easily convey the information.
Find below a summary of main GEOTRACES findings and products on iron research:
Atlas
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Atlantic Ocean:
Pacific Ocean:
3D scenes showing the distribution of dissolved iron in the Atlantic and the Pacific. In warm colours (red, orange, etc.) you can view high concentrations of dissolved iron. The diversity of hydrothermal iron inputs is identified along Mid Oceanic Ridges in the two basins. Important release of dissolved iron from the sediments are indicated along the African, South American, Asian and Peruvian coasts.
Data
Data is available to download after registration here: https://geotraces.webodv.awi.de/login
Discoveries include:
Below you can find a list of science highlights of main GEOTRACES discoveries on iron research:
Science Highlights
Iron and zinc isotopes disentangle the anthropogenic, natural and wildfire sources of aerosols over the North and Equatorial Pacific Ocean
Bunnell and co-authors analysed aerosol iron and zinc isotopic compositions along the North Pacific GEOTRACES GP15 section (Alaska-Tahiti).
Science Highlights
Biological production of ligands influences iron chemistry in hydrothermal systems
For the first time, siderophores and siderophore-producing microbes were determined in 11 distinct hydrothermal plume environments.
Science Highlights
Substantial trace metal input from the 2022 Hunga Tonga-Hunga Ha’apai eruption into the South Pacific Ocean
Zhang and co-workers investigate the impact of the 2022 eruption on the biogeochemistry of the South Pacific Gyre.
Science Highlights
Iron limitation also affects the twilight zone
Li and co-workers established the distribution and uptake of siderophores along the Pacific meridional section (GP15 GEOTRACES cruise)…
Science Highlights
Long distance dissolved iron transport in the North-East Pacific revealed by multiple tracers and an ocean circulation model
Sieber and co-authors have made extensive use of the multi-tracer approach, coupled to an oceanic circulation model…
Science Highlights
North-South section of bioactive cadmium, nickel, zinc, copper and iron along GEOTRACES transect GP19 in the Pacific Ocean
Zheng and his colleagues propose the first full sections of the simultaneous dissolved distributions of five nutrient-type trace metals in the western South Pacific Ocean.
List of publications
Scroll down to view the list of GEOTRACES publications on dissolved iron: