Welcome to GEOTRACES
GEOTRACES is an international programme which aims to improve the understanding of biogeochemical cycles and large-scale distribution of trace elements and their isotopes in the marine environment. Scientists from approximately 35 nations have been involved in the programme, which is designed to study all major ocean basins over the next decade.
GEOTRACES Sections. For more information please click here. In red: Planned Sections. In yellow: Completed Sections. In black: Sections completed as GEOTRACES contribution to the IPY. Download the map.
The distribution of dissolved iron in the West Atlantic Ocean
- Published on Wednesday, 09 July 2014 13:16
Iron (Fe) is an essential trace element for marine life. Extremely low Fe concentrations limit primary production and nitrogen fixation in large parts of the oceans and consequently influence ocean ecosystem functioning. In a publication published on 30 June in Plos ONE, Rijkenberg and co-authors present dissolved Fe (DFe) values measured at an unprecedented high intensity (1407 samples) along the longest full ocean depth transect (17500 kilometers) covering the entire western Atlantic Ocean.
DFe measurements along this transect revealed details about the supply and cycling of Fe. External sources of Fe identified included off-shelf and river supply, hydrothermal vents and aeolian dust. Nevertheless, vertical processes, such as the recycling of Fe resulting from the remineralization of sinking organic matter and the removal of Fe by scavenging, dominated the distribution of DFe. Iron recycling and lateral transport of DFe from the eastern tropical North Atlantic Oxygen Minimum Zone (OMZ) were important sources of DFe to the northern West Atlantic Ocean.
Finally, this study showed that the North Atlantic Deep Water (NADW), the major driver of the so-called oceanic conveyor belt, contains excess DFe relative to phosphate after full biological utilization and is therefore an important source of Fe for biological production in the global ocean.
Figure: The distribution of DFe along the 17500 km long full depth transect in the western Atlantic Ocean. Click here to view the figure larger.
Successful completion of French GEOVIDE cruise in the North Atlantic Ocean
- Published on Tuesday, 08 July 2014 20:28
The GEOVIDE cruise (GA01) has been successfully completed on 30 June, after 47 days of sailing in the North Atlantic from Lisbon (Portugal) to St John's (Newfoundland, Canada).
The North Atlantic is a key region for Earth climate and oceanic circulation, being a major area of the Merdional Overturning Circulation (MOC), which characteristics and variability have been studied since 2002 in the framework of the OVIDE project. Moreover, the Trace Element and Isotope (TEI) cycles are largely unknown in this zone and present very contrasted sources.
GEOVIDE is an international collaborative project that aims to better constrain (i) the uncertainties on water and heat fluxes, notably by adding new tracers and information on export and circulation of deep waters, and (ii) the biogeochemical fluxes and processes.
Forty scientists from 15 laboratories from 7 different countries successfully occupied 78 stations, with a total of 163 classical rosette casts and 53 clean rosette ones. In-situ pumps were deployed 25 times, representing more than 140 hours of pumping. In addition, a mono-corer was deployed 11 times, and 9 plankton nets traits were realized. 60 XBTs were dropped, and 17 floats were deployed. Finally, 140 clean underway surface samples were collected as well as 18 aerosol and 10 rainwater samples.
Figure: R/V Pourquoi pas? during GEOVIDE cruise - © IFREMER
Chief scientists : Géraldine Sarthou (LEMAR-IUEM, Brest, France) and Pascale Lherminier (LPO-IUEM, Brest, France).
Dissolved iron sources in the North Atlantic Ocean quantified
- Published on Wednesday, 02 July 2014 17:37
The relative importance of four different dissolved iron (Fe) sources in the North Atlantic Ocean have been precisely determined for the first time thanks to GEOTRACES.
Using a novel method based on the stable isotopic composition of dissolved Fe, Conway and John (2014, see reference below) have "fingerprinted" different sources of Fe along a section in the North Atlantic Ocean (GEOTRACES GA03 section). This has allowed the scientists to determine precisely the relative contribution of these sources to the North Atlantic Ocean. They found that the dominant sources were Saharan dust, which contributes 71-87 per cent of dissolved iron, followed by North American margin sediments (10-19 per cent). Smaller contributions were observed from the African margins (1-4 per cent) and hydrothermal venting at the Mid-Atlantic Ridge (2-6 per cent).
Since Fe is an essential marine micronutrient for phytoplankton, the scarcity of dissolved Fe in surface waters limits biological productivity over much of the oceans. Thus, changes in Fe inputs from different dissolved Fe sources have important implications for patterns of marine productivity and the global carbon cycle. This study therefore represents a significant contribution to our understanding of how dissolved Fe may influence past and future global change.
Figure: The figure shows the fraction of the seawater-dissolved Fe across the GA03 North Atlantic section that originates from each of four distinct sources : 1. Fe from oxygenated sediments on the North American margin (fnon-red); 2. Fe released by dissolution of atmospheric dust (fdust); 3. Fe from reducing sedimentry porewaters on the West African Margin (fred); and 4. Fe from hydrothermal venting on the Mid-Atlantic Ridge (fhyd). Click here to view it larger.
AGU Fall 2014 - GEOTRACES Special Sessions
- Published on Monday, 23 June 2014 13:14
American Geophysical Union Fall 2014 Meeting
15-19 December - San Francisco, CA, USA
Abstract deadline: 6 August 2014
Trace Element and Isotope Cycling in the Coastal Environment – 40 Years of Innovations
Conveners: Greg Cutter and Pete Sedwick
Trace metals and isotopes in the Eastern Tropical South Pacific: Results of the 2013 US GEOTRACES Zonal Transect and complimentary studies
Conveners: Jim Moffett, Chris German and Martin Frank
Productivity Proxies: New Developments and Records
Conveners: Fatima Abrantes, Bob Anderson and Heather Stoll
Biogeochemical cycling of silicon in coastal transition zones
Conveners: Claudia Ehlert, Patricia Grasse, Daniel J Conley and Mark A Brzezinski
The Biogeochemical Cycling of Mercury in the Coastal and Open Ocean
Conveners: Robert P Mason and Arthur Russell Flegal
Past Ocean Dynamics
Conveners: Joerg Albert Lippold, Luke Skinner and Sam Jaccard
See GEOTRACES full session abstract list.
- Undocumented cadmium, zinc and copper sink in oxygen minimum zones
- Successful GEOTRACES Intermediate Data Product presentation at Goldschmidt 2014
- The impact of the different sources of iron on the ability of the ocean to absorb atmospheric carbon dioxide: reversing the paradigm?
- Special issue call for Papers: 'Biogeochemistry of trace elements and their isotopes' in Marine Chemistry
- GEOTRACES Intermediate Data Product at Goldschmidt 2014