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.
A new method to measure lead isotopes in the ocean with an outstanding precision
- Published on Friday, 06 March 2015 15:55
A new method for the determination of seawater lead (Pb) isotope compositions and concentrations was developed, which combines and optimizes previously published protocols for the separation and isotopic analysis of this element. It involves 1 to 2 L of seawater, double spike, magnesium hydroxide coprecipitation, anion exchange chromatography and thermal ionization mass spectrometry. Ratios involving the minor 204Pb isotope are a factor of five more precise than previously published data, yielding uncertainties better than ±3‰. Results are presented on GEOTRACES intercalibration samples and a first depth profile from the eastern South Atlantic Ocean.
Figure: Methodology to separate and analyse Pb isotopes and concentrations from seawater samples using a 207Pb-204Pb double spike and thermal ionisation mass spectrometry (TIMS). Click here to view the figure larger.
How to constrain the biogeochemical cycle of cobalt in the surface Western Atlantic Ocean?
- Published on Tuesday, 24 February 2015 16:17
Cobalt (Co) is an important micronutrient for many species living in the surface waters (bacteria, cyanobacteria, different types of phytoplancton...). Interestingly, the Co requirements vary between the different species and these variations are influencing the dissolved Co distribution in the surface waters. This is clearly demonstrated by the set of data published by Dulaquais and co-authors (2014, see reference below) along a GEOTRACES north-south section in the western Atlantic Ocean (GA02). This work also shows that recycling sustains the biological requirement for cobalt in subtropical domains, and that both atmospheric and Amazon inputs affect the Co distribution.
Figure: Interpolated concentrations of dissolved cobalt overlaid with phosphate (µM; white contours) in the upper 1000 m of the West Atlantic during the GA02 section. Click here to view the figure larger.
New neodymium data in the North East Atlantic Ocean allow progressing on the behaviour of this geochemical tracer
- Published on Monday, 23 February 2015 09:47
High-resolution vertical profiles of neodymium (Nd) concentrations and isotopic compositions were measured at the eastern part of the US GEOTRACES North Atlantic Zonal Transect (GA03, Gulf of Cadiz – Mauritanian Shelf – Cape Verde Islands). This allowed documenting impacts of different environmental settling on the tracer's behaviours: the Mediterranean Outflow Waters (MOW), the Saharan dust plume, the Mauritanian margin with nepheloid layers and an Oxygen Minimum Zone (OMZ).
Distinguishing water masses in this oceanic area was a difficult task due to the relative uniformity of their Nd isotopic composition. Except in the Gulf of Cadiz, where MOW displays distinctively more radiogenic values than the surrounding waters (indicating the advection from the western North Atlantic Central Water from the West Atlantic).
Other striking features are: highest Nd concentrations below the Saharan dust plume with non radiogenic Nd; first documented release of mostly scavenged Nd within an OMZ; and, a prominent benthic nepheloid layer at the bottom of the Mauritanian margin, which favours the release of non radiogenic Nd. Thorough treatments of these data allow disentangling horizontal transports from biogeochemical processes in this area.
Figure: Map of the cruise track and stations with a section along GA03 (Cape Verde Islands – Mauritanian Shelf – Gulf of Cadiz, from left to right) showing measured Nd concentrations (colour shading) overlain by the ratio of expected to actual Nd concentrations (iso-lines). Values >1 indicate excess of Nd with respect to water mass mixing, which is particularly the case within the OMZ at ~500m between section distance 0 and ~2500km. Click here to view the figure larger.
5 minutes to improve Ocean Research
- Published on Thursday, 19 February 2015 14:31
Please take part in this short (5 minutes) survey on the GEOTRACES Intermediate Data Product 2014:
Your contribution will help us to improve the data product for the next release, expected in 2017.
Want to learn more about GEOTRACES Intermediate Data Product? Click here
- What drives the silicon budget in the Bay of Bengal? The isotope composition clues...
- How iron isotopes offer a new window on the oceanic biogeochemical cycling of iron
- Radium quartet reveals no less than four main processes along the GEOTRACES North Atlantic Ocean section (30°N)
- When direct mapping of diatoms reveals unexpected fate of trace metals in the twilight zone
- Iron isotopes in the Equatorial Pacific Ocean: when the dissolved phases are heavier than the particulate ones