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.
Special Issue devoted to the U.S. GEOTRACES North Atlantic Transect is published!
- Published on Friday, 22 May 2015 09:13
Everything you always wanted to know about trace elements and isotopes (TEI) distribution in the North Atlantic... but were afraid to ask
Many answers could be find in the Deep Sea Research Part II special issue dedicated to the results of the US GEOTRACES section cruise GA03: a beautiful water mass analysis settled the frame to no more than 24 other studies of a wide range of isotopes (from the hydrogen to the protactinium ones) and of the diverse distributions of many trace elements, with some focus on their role on the diazotrophic species activity... This is among the most exciting issues of this month (at least!)...don't waste time, get it, open it, read it!
|Deep Sea Research Part II: Topical Studies in Oceanography
Volume 116, Pages 1-342 (June 2015)
GEOTRACES GA-03 - The U.S. GEOTRACES North Atlantic Transect
Edited by Edward A. Boyle, Robert F. Anderson, Gregory A. Cutter, Rana Fine, William J. Jenkins and Mak Saito
Intermediate Data Product 2014 version 2 and DOI - Available!
- Published on Thursday, 21 May 2015 12:26
The corrected and updated of the GEOTRACES Intermediate Data Product 2014 (IDP2014) is now available. The new version (version 2) of the digital data is now available in four formats (ASCII, Excel, netCDF, and ODV) from www.bodc.ac.uk/geotraces/data/idp2014/.
For further details on the revisions made please click here. Please also remember to clear your cache so as to ensure the correct files can be accessed.
The IDP2014 should also be cited in the following way:
Mawji, E., et al., The GEOTRACES Intermediate Data Product 2014, Mar. Chem. (2015), http://dx.doi.org/10.1016/j.marchem.2015.04.005.
This citation text is included in the new download agreement document available here.
Insights into Particle Cycling from Thorium and Particle Data
- Published on Thursday, 21 May 2015 14:37
Phoebe Lam and Olivier Marchal (2015, see reference below) propose to describe, with the same model, the dynamics of particles in the oceanic water column and its effects –on four different tracers characterized by very distinct sources and sinks. The considered tracers are: Particulate Organic Carbon (POC) (a biogenic compound), barium (Ba) (an authigenic mineral), titanium (Ti) (mainly lithogenic), and thorium isotopes (a particle-reactive radionuclide). Thorium isotopes are used for the estimation of exchange rates between small and large particles and for the estimation of particle settling velocities. Lessons learned from thorium isotopes may be applied to understand other classes of particle tracers such as POC, Ba, and Ti.
- The separation of oceanic particles in two distinct classes (small, suspended particles and large, sinking particles), which interact throughout the water column via aggregation and disaggregation processes, remains a useful description of particle cycling, provided its limitations are fully appreciated.
- The simple models currently used in marine particle research (small particles are suspended and interact with seawater, large particles are removed by sinking, small and large particles interact throughout the water column, ...) allow one to reproduce the observed vertical distributions of a range of chemical substances in the ocean, such as POC, Ba, Ti, and 230Th, in spite of their distinct sources and sinks as well as reactivities.
Figure: Schematic depiction of the biological carbon pump, emphasizing the important particle dynamics processes: aggregation (red arrows ), sinking (black arrows), disaggregation (dark blue arrows), and remineralization (light blue arrows). Particles in the small, suspended size fraction (brown) comprise phytoplankton, authigenic particles, and lithogenic particles and do not sink or sink very slowly. Particles in the large, sinking size fraction (green) comprise fecal material and aggregates of smaller particles and do sink. Aggregation can be abiotic or mediated by zooplankton packaging through fecal pellet production. Click here to view the figure larger.
Shallow methylmercury production in the marginal sea ice zone of the central Arctic Ocean
- Published on Wednesday, 20 May 2015 19:10
Understanding persistent high levels of mercury in arctic biota has been an elusive goal for nearly two decades. Little is known about where exactly inorganic Hg inputs into the Arctic generate the toxic methylmercury (MeHg) form that bioaccumulates in biota. Lars-Eric Heimbürger and colleagues (2015, see reference below) present the first full-depth high resolution profiles (> 5200 m-depth) of total mercury (tHg) and MeHg in the central Arctic Ocean (79-90°N). MeHg maxima occur in the pycnocline waters, although noticeably shallower than in the other oceans (150 m in the Arctic versus roughly 1000 m in the Atlantic). These shallow maxima are probably due to the accumulation of settling biogenic particles slowed down by the strong density barrier of the arctic pycnocline, which in turn will favor their microbial degradation and MeHg production. The shallow MeHg maxima likely result in enhanced biological uptake at the base of the marine food web, yielding elevated MeHg levels in Arctic wildlife. For this study the authors developed a new double isotope-dilution MeHg detection method with exceptional precision and low detection limit. These new findings will be guiding future Arctic Hg research, notably the international Arctic GEOTRACES multi-ship survey planned for summer 2015 by American, Canadian and German teams.
Figure: Total mercury (tHg) and methylmercury (MeHg) profiles in picomoles per litre (pM) at the coastal influenced open water Laptev Sea station (PS78/280:79°N; brown triangles), the open water Amundsen Basin station at the sea ice edge (PS78/273:81°N; red dots), the > 75% sea ice covered Makarov Basin station (PS78/245:85°N; green squares), and the permanently sea ice-covered North Pole station (PS78/218:90°N, purple diamonds). The white line indicates the sea ice extent during the time of sampling. The blue line shows the general oceanic circulation of intermediate and Atlantic waters after Rudels, 2012. Click here to view the figure larger.
- Submarine Groundwater Discharge as a major source of nutrients in the Mediterranean Sea
- GEOTRACES Marine Particles Special Issue Published!
- Join GEOTRACES webinar series!
- Two GEOTRACES works question the present ocean chemical elements budgets
- GEOTRACES Japanese Cruise in the South Pacific Ocean - Short report