Irminger Sea calibration CTDs

Dear OOI helpdesk,

I’m working with the OOI Irminger Sea MMP data. It seems there is an issue with the conductivity, where in each deployment the resulting salinity starts far to low, increases to normal levels in a month or two and then continues showing normal variability. I would like to try and correct these initial parts of the record. Are the shipboard CTDs done at the MMP/HYPM location available and if yes, where can I find them?

Many thanks,
Femke de Jong

Thank you for bringing this to our attention. A similar issue has been noted in the Argentine Basin MMP data, and we are looking into it.

CTDs are conducted when moorings are deployed and recovered for instrument data validation, and the CTD and water sampling data are available in Alfresco (username: guest, password: guest).

For the Irminger Sea cruises, navigate here to see folders for each deployment cruise:
OOI > Global Irminger Sea Array > Cruise Data

Under the cruise of interest, go to the Ship Data folder. There will be a ctd folder with the shipboard CTD data. There is also a Water Sampling folder which has the CTD sampling logs and a Discrete Summary spreadsheet with all of the water sampling analysis data. (See this write up about the Discrete Summary spreadsheets on the OOI website)

Please let us know if you have any trouble finding what you need.

Thanks and stay safe,
Sheri White
OOI/CGSN Data Team

Thank you, Sheri.
There is a treasure trove of (meta)data there. This will be very helpfull!


Dear Sheri,

Do you know if the CTD data in the “process” folder has already been calibrated with the salinity samples?

Most of the CTD data looks fine, but it appears that the conductivity and thus salinity in the CTD profiles in the 2019 cruise (AR 35-05) are off. I see this is also flagged as an issue in the cruise report, where it states that further investigation is needed. Maybe you discovered what the issue was (glass Ccell broken?), but the data doesn’t appear to be fixable. Just wanted to make a note for others looking into this.


Femke (@fdejong),

We do not typically do a correction of the CTD cast data from the water samples. The process folder under the ctd folder is directly from the ship. But we provide the data for researchers to do the corrections themselves.

If we do correct the CTD data, it would be placed under the Water Sampling folder in a folder called ctd_proc.

The Irminger 6 (AR 35-05) cruise was a difficult one from a CTD standpoint. We were primarily focussed on the failure of the pylon (which prevented firing of the Niskin bottles), but as noted in the Cruise Report, there were other issues as well. We do not have any further information on those issues at this time.

Thanks and stay safe,
OOI/CGSN Data Team

Thank you Femke,

I am reaching out to Seabird to see if they can assist with this issue. MMP CTD’s are returned to Seabird after each deployment for refurbishment and re-calibration. I will update this conversation with any details that I find.

John Lund

Excellent, thank you.