Phytoplankton who lives at the surface of the oceans is the 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 the phytoplankton development is thus a major issue for the 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 the photosynthesis will improve the capacity of the ocean to absorb CO2. However, thanks to studies on 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:
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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 is available to download after registration here: https://geotraces.webodv.awi.de/login
Below you can find a list of science highlights of main GEOTRACES discoveries on iron research:
New trace metal data in the Seas of Japan and Okhotsk
Nakaguchi and colleagues realized full-depth and section distributions of traces metals collected from the Seas of Japan and Okhotsk.
Confrontation of two models to constrain the hydrothermal iron contribution to the Southern Ocean export production
Tagliabue and his co-workers compare the hydrothermal dissolved iron simulated by both models.
Dust deposition rates extracted from a data-assimilation model of the aluminium oceanic cycle
Xu and Weber developed a data-assimilation model of the aluminum oceanic cycle.
Specific features characterize the dissolved iron distribution in the North Western Indian Ocean
Venkatesh Chinni and Sunil Kumar Singh propose dissolved iron profiles along two meridional transects realized during spring and fall seasons between the Arabian Sea and the sub-tropical western Indian Ocean…
Icebergs as sources of trace metals to the ocean: which impact?
Earth’s Ice Sheets are known to release significant quantities of lithogenic particles into the ocean every year, but how does this material affect trace metal availability in the ocean?
Volcanic emissions in the Southern Ocean: an efficient and unexpected source of iron for this remote area
This study suggests that volcanic emission can represent a significant source of bioavailable iron to open ocean anaemic ecosystems.
List of publications
Scroll down to view the list of GEOTRACES publications on dissolved iron: