WOCE vertical sampling guidelines (Lynne Talley, 1995) (Modified by Molly Baringer 1997) The Chief scientist should oversee the ultimate choice in vertical sampling, but some guidelines follow as each CTD watch leader will typically specify the bottle positions. The most important guideline is that the sampling be fairly uniform in density space (i.e. at uniform density intervals assuming density is the vertical coordinate). The second most important guideline is that sampling not vary widely between watches or from day to day. Spacing of bottle samples will depend on the exact location, time of year, overall depth, specific water masses targeted, etc. In general these bottles will be adjusted to match obvious salinity or oxygen extrema. However, clustering of bottles near extrema is discouraged partially since an extrema in one property is unlikely to be an extrema in another property, but mostly since this can detract from sampling the full water column. Overall coverage should be maintained. Minimum guidelines: assuming 36 bottles (24 bottles in parentheses) 1) top bottle within sight of the surface 2) bottom bottle within 10 m of the bottom 3) 0-1000 m: no greater than 100 m (150) 4) 1000-3000 m: no greater than 200 m (300) 5) below 3000 m: no greater than 250 m (400) 6) in thermocline: no separation greater than 0.04 sigma theta (0.06) The following sampling scheme assumes that the thermocline is shallow and the maximum depth is between 4500 and 4700 m. Column 2 is the depth we would like to fire bottles following WOCE standards, using a full 36 bottle rosette. Column 3 assumes we only have a 24 bottle rosette and vertical spacing must be reduced. bottle depth assuming only 24 bottles 1 0 0 2 25 50 3 50 100 4 75 150 5 100 200 6 125 275 7 150 350 8 175 475 9 200 600 10 250 750 11 300 900 12 350 1050 13 400 1250 14 500 1550 15 600 1850 16 700 2150 17 800 2450 18 900 2750 19 1000 3125 20 1200 3500 21 1400 3875 22 1600 4250 23 1800 4500 24 2000 5-10 m off bottom 25 2200 26 2400 27 2600 28 2800 29 3000 30 3250 31 3500 32 3750 33 4000 34 4250 35 4500 36 5-20 m above bottom These depths will be approximate and will require judicious adjustment as the water mass features require. We have also found it advantageous to stagger the sampling so that we are not always sampling at exactly the same depths (e.g. 1600 m). This improves contouring and reduces the error incurred if some depths (say 1700m) were never sampled. At the beginning of each cast as the CTD begins its descent towards the bottom, the watch leader will specify target depths for the profile. This should be based on the previous 2-3 casts, staggering the bottles and noting any unusualy features in previous CTD traces for emphasis. We recommend finalizing the bottle positions as the rosette nears the bottom of the cast by considering the density profile and any extrema noted in the current cast. A sheet listing the target "wire out" depths can then be hand carried to the winch operator by someone not involved in monitoring the CTD console and directing the winch operator over the radio. The bottle sampling sheet should then be filled out with the target depths and made available to any water samplers (chemists, etc) so that they may choose their own sampling depths. Notes on The 1997 ACCE Float deployment cruise: During the float deployment cruise, casts will only be taken to 2000 m. A typical bottle spacing would then follow the 36 bottle guidelines above and the sample bottle depths might look like the first column above(i.e. the full water column 36 bottle scheme) truncated at bottle 24 (which is at 2000 m). Note on this float deployment cruise we will likely always sample the bottom (and surface) bottle which will be at 2000 m depth. The float deployment cruise will not have any other chemistry samples being collected during legs 2 and 3 of the float deployment cruise and hence the sample log proceedures need not be strict.