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 model of the oceanic aluminium distribution
- Published on Tuesday, 26 August 2014 14:23
Taking into account most of the parameters that govern any trace element's oceanic behaviour is a challenge, given their number and complexity.
Marco van Hulten and co-workers (2014, see reference below) propose here the most complete model ever written for the oceanic aluminium (Al) distribution. In addition to atmospheric input -which was the only term constraining the Al distribution in a preceding model, see van Hulten et al., 2013-, circulation, sediment re-suspension and biological incorporation by diatoms are considered in this new scheme.
These new sources and sinks are significantly improving the simulated distribution, more specifically a sediment source of Al in the bottom waters of the Northern Atlantic and the velocity fields.
Figure: The dissolved aluminium concentration (nM) of a global model simulation of aluminium. The circles are the observations. The sources in the model comprise the release of Al from dust and from resuspended deep-ocean sediments, the latter depending on the bottom Si concentration. Al is removed by reversible scavenging by biogenic silica. (This figure may be reused, changed and redistributed according to Creative Commons BY-SA. Click here to view the figure larger.)
GEOTRACES recommends reading...
- Published on Tuesday, 26 August 2014 08:59
- Achterberg, E. P. (2014). Grand challenges in marine biogeochemistry. Frontiers in Marine Science, 1, 7. doi:10.3389/fmars.2014.00007
Introduction: The ocean plays a central role in our earth's climate system and also provides a range of important ecosystem services, including food, energy, transport, and nutrient cycling. Marine biogeochemistry focuses on the study of complex biological, chemical, and physical processes involved in the cycling of key chemical elements within the ocean, and between the ocean and the seafloor, land and atmosphere...
- Banse, K. M. (2014). Assessing ocean changes without data centers? Frontiers in Marine Science, 1. doi:10.3389/fmars.2014.00029
Introduction: How may we know that the ocean has or has not changed on the half-century time scale, if data points through time from in-situ measurements are not available because we, the observing scientists, did not and still often do not deposit our observations in data centers?
Impact of volcanic ash on marine algae and the global carbon cycle
- Published on Thursday, 24 July 2014 08:38
Volcanic ash fertilization of iron-limited phytoplankton in remote marine waters has been suggested to perturb global biogeochemical cycles and climate. For example, ash from the Pinatubo (Philippines) eruption in 1991 was suggested to have fertilized vast areas of the iron-limited Southern Ocean - potentially causing the drawdown in atmospheric carbon dioxide observed subsequently. However, until recently the impact of volcanic ash on phytoplankton communities in the Southern Ocean had never been directly tested.
Browning and co-authors conducted over 20 experiments in the South Atlantic and Southern Ocean where they added small quantities of volcanic ash to natural phytoplankton communities incubated in bottles. The responses they observed led to two important findings: (i) they conclusively demonstrated for the first time that volcanic ash deposition events strongly stimulated phytoplankton in the Southern Ocean; and (ii) at several experimental locations phytoplankton responded significantly to supply of volcanic ash, but not to iron only. This latter finding could be particularly important as it suggests phytoplankton at these sites may have been limited by another micronutrient other than iron. Manganese concentrations at these sites were amongst some of the lowest ever recorded in seawater and Browning and co-authors therefore suggested that the enhanced response to ash may have likely been a result of relieving manganese (co)limitation.
Both of these findings could both have important implications for our understanding of marine biogeochemistry in the Southern Ocean. Firstly, the Southern Atlantic and Drake Passage, where the experiments were conducted, are areas highly prone to ash deposition from explosive volcanic eruptions in South America - suggesting that ash-driven fertilization and potential carbon export from these waters could be an important control on the biogeochemistry of the region. Secondly, if manganese is (co)limiting marine algae in these waters, addition of this element alongside iron might be critical for stimulating phytoplankton blooms in the region.
Figure: Maps showing the sites where experiments were conducted, highlighting the nutrient concentrations measured in seawater (warmer colors represent higher nutrient concentrations) and the response of phytoplankton to iron and ash additions (warmer colors represent larger phytoplankton responses). For (d-e) sites where the phytoplankton response was statistically significant (relative to bottles where no treatment was made) are shown with black outlines. Please click here to view the figure larger.
A geochemical-physical coupled approach to study phytoplankton plume dynamics off the Crozet Islands (Southern Ocean)
- Published on Wednesday, 23 July 2014 12:06
Interaction of the currents with the sediments deposited on the margins of the Crozet Islands (Southern Ocean) contributes to the supply of iron and other micronutrients to marine waters. This natural fertilization feeds a phytoplankton bloom that was object of study of the KEOPS 2 GEOTRACES process study.
Sanial and co-authors (2014, see reference below) combined three independent methods - including geochemical and physical methods. This allowed them to assess the origin of the natural iron fertilization and the rates and times scale of the offshore transport in the phytoplankton bloom of Crozet. Shelf-water contact ages were determined using radium isotopes and were compared to in situ drifter data and modeling data based on altimetry.
This work highlights the key role played by the horizontal transport in the natural iron fertilization and provides constraints on the transit time of surface waters between the shelf and offshore waters.
Figure: Ages of surface waters derived from a Lagrangian model based on altimetry data. The drifter launched offshore Crozet Islands followed the numerical plume deduced from the model. White circles show the location of radium samples. Please click here to view the figure larger.
- The distribution of dissolved iron in the West Atlantic Ocean
- Successful completion of French GEOVIDE cruise in the North Atlantic Ocean
- Dissolved iron sources in the North Atlantic Ocean quantified
- AGU Fall 2014 - GEOTRACES Special Sessions
- Undocumented cadmium, zinc and copper sink in oxygen minimum zones