CTD Rosette SOP

HelpDesk
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1

Hi,

I am trying to find any documentation related to how discrete water samples are collected during CTD Rosette profiles. Specifically, how long does the Rosette stop at a depth before firing bottles?

Thank you,
Kristen Fogaren

2

Hi Kristen,

I’m currently at sea, so it’s taking a little while to track down the documents. However, the discrete sampling document (on Alfresco, but requiring a login for some reason) doesn’t specify the pause before sampling. On the RCA cruises, we roughly follow the JGOFS protocol of pausing for 1-2 minutes before firing, then resuming the upcast when the CTD sensors come back online. On shallow casts it’s closer to 1 minute, and on deeper casts we wait for ~1-2 minutes.

Let me know if you need more details!

-Mike Vardaro

3

Hi Kristin,

We (EA) also do not have a formal protocol on waiting before firing bottles. The bottle closure times are available in scanned PDF copies of the CTD sampling logs, as well being recorded in the Discrete Sample logs. All of the CTD data is available from R2R if you want to match up the bottle closure times with the complete record.

For the Discrete Sample logs, the Niskin bottle number is in the “Niskin/Bottle Position” column and the bottle closure time is in the “CTD Bottle Closure Time [UTC]” column. Note, we routinely fire 2 bottles per depth.

Cheers,
Chris

4

@fogaren,

CGSN also doesn’t have a set soak time, but we typically soak for at least one minute. There may be some exceptions when we wait longer (for example during OSNAP Calibration Dips – CalDips – on Irminger Sea Array cruises). This should be noted in our CTD logs which are available in Alfresco.

Thanks,
Sheri N. White
OOI/CGSN Data Team