Table of Contents

• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

This dataset was collected as part of a Chief Scientist Training Cruise, May-June 2014. The focus of this research was 'Tracking Saharan dust deposition in the Northwest Atlantic using Th isotopes'. This dataset is GEOTRACES-compliant.

Water sampling followed GEOTRACES protocols from a standard Niskin Bottle CTD/Rosette (Anderson et al. 2012). 4-5 L water samples were drained or filtered directly from Niskin bottles using Teflon-lined tygon tubing, acidified at sea with ultra-pure 6 molar hydrochloric acid, and analyzed at on-shore at MIT. Analysis involved Fe hydroxide co-precipitation, acid digestion, anion exchange chromatography and isotope dilution inductively-coupled plasma mass spectrometry. Laboratory methods were slightly modified from Anderson et al. (2012) as described by Hayes et al (2015).

References:

Anderson, R. F., M. Q. Fleisher, L. F. Robinson, R. L. Edwards, J. Hoff, S. B. Moran, M. M. Rutgers van der Loeff, A. L. Thomas, M. Roy-Barman, and R. Franois (2012), GEOTRACES intercalibration of 230Th, 232Th, 231Pa, and prospects for 10Be, Limnol. Oceanogr. Methods, 10, 179-213.

Hayes, C. T., R. F. Anderson, S. L. Jaccard, R. François, M. Q. Fleisher, M. Soon, and R. Gersonde (2013), A new perspective on boundary scavenging in the North Pacific Ocean, Earth Planet. Sci. Lett., 369-370(0), 86-97, doi:http://dx.doi.org/10.1016/j.epsl.2013.03.008.

Owens, S. A., K. O. Buesseler, and K. W. W. Sims. "Re-evaluating the 238 U-salinity relationship in seawater: implications for the 238 U-234 Th disequilibrium method." Marine Chemistry 127.1 (2011): 31-39.

Th isotope concentrations are derived from measured Th-232/Th-229 and Th-230/Th-229 ratios as determined by mass spectrometry. The Th-229 spike at MIT was calibrated against a gravimetric Th standard as well as an artificial seawater standard called SWSTD 2010-1, described by Anderson et al. (2012).  Corrections for ingrowth of Th-230 from dissolved U-234 during sample storage were made based on measured salinity and the U-salinity relationship of Owens et al. (2011).

The dissolved “excess” Th-230 (Th_230_D_XS) is derived by subtracting from the measured dissolved Th-230 the component sourced from the partial dissolution of lithogenic material based on measured dissolved Th-232 and a lithogenic Th-230/232 atom ratio of 4 x 10-6, as described by Hayes et al. (2013).

BCO-DMO Processing:
- added conventional header with dataset name, PI name, version date
- renamed parameters to BCO-DMO standard
- changed longitude from positive to negative values

Cruise AE1410 was supported by UNOLS and NSF. The sample analysis was supported by the W.O. Crosby post-doctoral fellowship from MIT to Christopher Hayes.

NSF Award Abstract:
Overview:
This grant will support a CST cruise on the R/V Atlantic Explorer from Barbados to Bermuda in May and June 2014. Chief Scientist Training (CST) cruises are part of an educational initiative designed for young US oceanographers, from senior graduate students to junior faculty, to increase their participation in seagoing research by educating them about the capabilities and opportunities provided by the UNOLS research fleet. In addition to providing sampling opportunities for individual research, a CST cruise is specifically organized to teach cruise participants how to successfully plan and execute a research cruise, from proposal to post-cruise reporting. Cruise participants will be selected based on the feasibility of their proposed Intellectual Merit: The ship track covers a oceanographically important transitional area in the western subtropical Atlantic, and thus the participants will be able to obtain scientifically valuable data in addition to gaining valuable skills and training that will help them to plan and execute successful cruises in their future careers.

Broader Impacts:
The CST cruise will help develop future expertise in the US oceanographic community by reducing the barriers to participation of young scientists in seagoing research, particularly those scientists from non ship-operator institutions. The activities proposed will help to disseminate information about the research opportunities that are provided by NSF and the UNOLS research fleet. The training and workshop activities are projected to increase the number and breadth of future proposals requesting ship support as well as to improve the quality of execution and success of funded cruises. The CST cruise opportunity will also help to broaden the geographic representation of the research community that is involved in ship-based scientific studies as well as increase the diversity of this community.