FY 2010

Ship-based repeat hydrography: A strategy for a sustained global programme

Fukasawa, M., N. Gruber, M. Hood, G.C. Johnson, A. Körtzinger, C. Sabine, B. Sloyan, K. Stansfield, and T. Tanhua

IOC Technical Series 89, IOCCP Report Number 17, ICPO Publication 142, M. Hood (ed.), Intergovernmental Oceanographic Commission of UNESCO and the International CLIVAR Project Office, 48 pp (2010)

Executive Summary

Ship-based hydrography is the only method for obtaining high-quality measurements with high spatial and vertical resolution of a suite of physical, chemical, and biological parameters over the full ocean water column, and in areas of the ocean inaccessible to other platforms. Global hydrographic surveys have been carried out approximately every decade since the 1970s through research programs such as GEOSECS, TTO/SAVE, WOCE / JGOFS, and CLIVAR. It is time to consider how future surveys can build on these foundations to create a coordinated network of sustained ship-based hydrographic sections that will become an integral component of the ocean observing system.

This white paper provides scientific justification and guidelines for the development of a regular and coordinated global survey. Two types of surveys are required to meet scientific objectives: (1) a global decadal survey conducted such that each full ocean basin is observed over an approximately synoptic time-period (< 3 years), and (2) a sub-set of the decadal survey lines sampled at high-frequency (repeats every 2-3 years). Given the end date of the present sampling programs, a coordinated global survey should begin before 2012 to maintain continuity.

While it is essential to maintain a repeat hydrography program firmly linked to national, regional and international research programs, some elements of coordination and implementation could benefit from a more pro-active oversight structure. These include the development of a sustained international coordination body for an interdisciplinary repeat hydrography program that is independent of any single time-limited research program (for example, following the model of Argo or OceanSITES); and a single, international information and communications forum to facilitate field program planning, to set experimental standards and methods, and to underpin data sharing / synthesis activities, including international data management activities.

Thirteen countries currently participate in the global repeat hydrographic program. The cost of repeat hydrographic sections currently implemented is estimated to be approximately US $10 Million dollars per year. New resources will be required for maintenance of lines, upgrading of the data assembly center network, joint synthesis activities, and international coordination activities.