Date: Mon, 22 Jul 1996 15:09:16 +1000 From: Brian GriffithsACE-1 Data Workshop Report of the Seawater Processes Working Group Most of the Discoverer's oceanographic and hydrocarbon data was in the CODIAC data base prior to the workshop. None of the Southern Surveyor oceanographic data was available due to the lack of post-cruise data processing personnel in Hobart. This has now been rectified, and the data is expected to be available by November 1996. The Discoverer/Southern Surveyor intercomparison station at 47o 55S, 147 o 25E will be critical in cross-calibrating the two data sets. There was agreement to write a Overview paper which would describe the surface oceanography for the two major legs (Trans-Pacific and Tasmanian) covered during the experiment. Bates and Quinn would take the lead in the Trans-Pacific leg, with emphasis on water mass and gyre boundaries and frontal regions encountered along the track that could affect aircraft measurements. Griffiths would take the lead in the surface oceanography around Tasmania, with emphasis on when the ships were in which water masses. This section would include estimates of the sea-air fluxes of NH3, DMS, and possibly CO2 and hydrocarbons. A biology section could include surface chlorophyll, nutrients, phytoplankton speciation, production, and grazing rates, all of which may affect DMS production. The potential authors include Griffiths, Clementson, Parslow, Tilbrook (CSIRO), Bates, Quinn, Feely (PMEL), Curran/Jones (JCU), Greene (TAMU), and possibly others. One link between ship and aircraft data sets were identified during the discussion. North of New Zealand, there was a correlation between DMS measured on Disco and methyl iodide measured on the C-130. During Lagrangian A and B, concentrations of propene and ethene dropped markedly as the aircraft crossed from warmer, subtropical waters into the cooler subantarctic/polar waters. This led to a decision to try and get a water mass specific relationship between sea surface temperature and chlorophyll-a to look for further correlations with aircraft-sampled, "biological" data. It became clear that satellite sea surface temperature images under the aircraft tracks would be very useful in identifying the water masses that the aircraft was flying over. Brian Griffiths will try and match cloud-free images from the CSIRO archive to aircraft tracks, and make these available in the data base as gif images. He will also oversee the prepartion of the SST image with both ships cruise tracks, and the aircraft tracks during Lagrangian A and B on it for use in the ACE-1 data report. The DMS flux modelling will proceed using regional averages of DMS in the water and atmosphere from each ship during the various time periods. This will need to be a cooperative effort between Bates and Curran/Jones. Other factors that can be factored in to understanding differences in flux rates will include phytoplankton species abundances, zooplankton grazing rates, and mixed layer depths, nutrients, and temperatures (Griffiths/Greene) There is the potential for comparison of upwelling radiances, continuous spectral optical depth, and ocean colour measured by John Porter on the C-130 with data sets from both Discoverer and Southern Surveyor. Porter obtained radiance data on flights 10, 18-21, and 28. This comparison should be pursued between Porter, Parslow (CSIRO) and Quinn. Brian Griffiths CSIRO Divison of Fisheries Hobart. ------------------------------------------------------------------------------ Brian Griffiths CSIRO Division of Fisheries, GPO Box 1538, Hobart, Tasmania, Australia 7001 Australian telephone and fax: (002) 325-338 and (002) 325-000 International telephone and fax: +61-02-325-338 and +61-02-325-000