Project: GEOTRACES InterCalibration

An international intercalibration effort has been assigned a high priority during the initial phase of GEOTRACES to ensure that results from different cruises, and from different labs, can be compared in a meaningful way.

While the original data from the Intercalibration cruises are not available online, consensus values for the SAFe and North Atlantic GEOTRACES Reference Seawater Samples are available from the GEOTRACES Program Office: Standards and Reference Materials

The ultimate goal for the intercalibration component of the international GEOTRACES program is to achieve the best accuracy possible (lowest random and systematic errors) for the suite of GEOTRACES' Trace Elements and Isotopes (TEI) as a prelude to the sampling program, and continuing effort throughout the sampling and analysis program. To achieve this goal, there will be two primary efforts:

(1) Evaluate and develop GEOTRACES sample acquisition, handling, and storage protocols during initial Intercalibration Cruises;

(2) Identify existing GEOTRACES primary standards and certified reference materials (CRMs) for the TEI suite (and where needed, producing reference materials or primary standards), including the establishment of GEOTRACES Baseline Stations that can be used to evaluate accuracy from sampling to analysis (to facilitate intercalibration for TEIs that do not have CRMs).

Tentative schedule of Intercalibration events:
• June - July 2008. 1st Intercalibration cruise (Sargasso Sea): evaluate sampling apparati and handling methods (diss and part), collect and distribute intercalibration samples, sample storage experiments, establish Baseline Station at BATS
• Dec. 2008. Second Intercalibration workshop (AGU): evaluate and interpret intercalibration results, planning for 2nd cruise
• Spring 2009. 2nd Intercalibration cruise (eastern North Pacific): final testing of complete sampling system and procedures, intercalibrate with other (non-US) sampling systems, speciation + total TEI intercalibration, determine the time to occupy one GEOTRACES station (for cruise planning purposes)
• Jan.-Feb 2010. Third Intercalibration workshop: finalize complete intercalibration results, begin assembling GEOTRACES User Manuals

GEOTRACES intercalibration cruise 1 June 2008
GEOTRACES completed the first Intercalibration cruise from June 8 to July 12, 2008 to collect intercalibration water and particle samples. This intercalibration exercise aimed to provide reference materials that could be distributed to the international community and reference profiles of Trace Elements and their Isotopes to ensure compatibility and consistency of GEOTRACES data.

GEOTRACES intercalibration cruise 2 May 2009
The second intercalibration cruise is planned for May 2009 in the eastern North Pacific and will include sampling near the North Pacific SAFe Station at 30°N, 140°W.

If you are interested in participating in this exercise, note that selected samples for intercalibration will also be available after the cruise. For general information about the intercalibration effort please contact Greg Cutter.