Repeat Hydrography

Core measurements: text

Core measurements: text


Click here to return to menu with table listings of Level I, II, III measurements by cruise.


Three levels of observations are included in the CO2/CLIVAR hydrographic section program with selection criteria listed in parentheses:


  • Level I core measurements (mandatory on all cruises; suggested standard for international collaborators; measured at highest spatial resolution practical; funded through the omnibus proposal across all cruises).
  • Level II recommended measurements (highly desirable on subset of US cruises; may be collected on coarser station spacing; coordinated with the core effort but funded by separate proposals either on a cruise by cruise basis of by specific measurement).
  • Level III ancillary measurements (on opportunity and space available basis; not to significantly interfere with Level I or II effort; may be regional or specific to individual cruise; extramural funding).


Level I: rationale based on measurements required to directly quantify change in ocean carbon inventory, estimate anthropogenic CO2 empirically, characterize large-scale water mass ventilation rates, constrain  horizontal heat, freshwater, C, N, and O2 transports and/or net divergence,  and provide on-going basis for model evaluation.


DIC dissolved inorganic carbon (DIC)

Total Alkalinity (TAlk)

CTD pressure, temperature, conductivity (salinity)

CTD oxygen (sensor)

Bottle salinity

Nutrients by standard auto analyzer (NO3/NO2, PO4, SiO3)

Dissolved oxygen (O2)

Chlorofluoro carbon tracers CFC-11, -12, -113


Total organic carbon (TOC, DOC and/or POC) 

Total organic nitrogen

Surface underway system: T, S, pCO2

ADCP shipboard

ADCP lowered


Level II: related to large-scale carbon cycle and/or ventilation; specific rationale listed after measurement; possibly on coarser spatial resolution than Level I but on all cruises

pH (internal carbonate system consistency)


discrete pCO2

(internal carbonate system consistency)

14C by AMS (bomb penetration; southern ocean circulation changes; may need to repeat only on 20 year time-scale)


CCl4 and SF6

(to extend range of  age tracers further back in time (CCl4) and into the  future (SF6 )


del 13C of DIC

(independent measure of anthropogenic CO2 uptake and inventory changes)


Fe/trace metals 


(others? Zn? Al for dust? There are three sampling approaches

-on "regular" rosette

-Teflon/plastic water sampler hanging below CTD

-Separate Kevlar wire; separate casts)


CTD transmissometer 

(POC distribution; ambiguity as to calibration; regional?)

More complete surface underway system: nutrients, O2, Chl, DIC, surface skin temperature


Level III: focus on upper ocean biogeochemistry and cycling



Primary production (on deck incubations)

HPLC pigments  (phytoplankton community composition)



Experimental continuous analyzers (as they develop and can go full depth)

del 15N NO3 (nutrient utilization)


18O of H2O


Low level nutrients

Total organic phosphorus (difficult to measure??)

Upper ocean optical profile (similar to AMT line; algorithm development/validation; short cast; needs to be coherent with  biological  sampling)

del 17O of O2  (gross primary production)

methyl halides (linkages to SOLAS)

DMS (linkages to SOLAS)

ADCP (multibeam) (optimized for (biological) particle enumeration)

Last Updated 10/15/2004
Lynne Talley