Q&A: Erratic Profiles
November 2019 Newsletter
The data above come from a profiling CTD, deployed in sea conditions that caused approximately 1-meter ship heave. Two things stick out – relatively unchanging salinity data during the downcast, and noisy data during the upcast (shown in light blue and pink).
Can you identify the cause of this problem?
The figure above shows a zoomed-in view of 200 – 240 meters depth. Ship heave is shown in the oscillations in descent rate. If you look closely, a “bump” in salinity and temperature corresponds almost perfectly with each motion of the ship. This is a clear indication that the pump isn’t working – when a CTD has a functional pump, the temperature and conductivity sensors have a consistent flow of water regardless of descent rate and sea conditions. The resulting pumped data are smooth, with minimal effect from ship heave.
Without a pump, the flow of water is dependent on the motion of the CTD package, where a faster descent rate will force more water through the plumbing. Data from the downcast are usually less affected, as the downward motion of the CTD package causes some flow through the plumbing. On the upcast however, water easily becomes entrained in the CTD’s plumbing, and may be unchanging, or will have a strong correlation with ship heave.
Read our Troubleshooting Guide for profiling CTDs to learn more troubleshooting techniques.
Related Posts
Featured Posts
Webinar on Fathom Software in Partnership with the Marine Technology Society
We were excited to partner with the Marine Technology Society (MTS https://www.mtsociety.org/) to bring you a webinar to walk through our new software. We’re excited to release Fathom – the latest in software innovation at Sea-Bird Scientific (SBS). Heather Eberhart,...
Moored pH Systems
Our Moored pH Systems Ocean pH plays a critical role in the health of the global ocean due to the short timescales relevant to biological activity. With recent studies highlighting the impacts of acidification on the carbon cycle as well as on coral, shellfish,...
Oceanology International 2024
We hope to see you at #Oi24 We are excited to return to Oceanology International 2024 again in London, UK from March 12-14. Overview Oceanology International brings together 500+ exhibitors in the only event that links the three key players in the industry:...
Science and Technology
Platform
Contact Us