Day 5: First CTD cast

After experiencing some electrical problems last night, Jason II is back on deck for repairs. While we wait for the next dive, the geochemists on board are keeping themselves entertained with the CTD (below).

CTD alone

CTD is the abbreviated term for a sensor that measures conductivity (from which we can calculate salinity), temperature, and depth of seawater. It also measures the concentration of particles suspended in the water.

The sensor itself is mounted at the bottom of the frame pictured above. The rosette of bottles mounted on the frame are used to collect water samples to pair with the CTD measurements.

Here we are casting the CTD:

CTD cast

The CTD is gradually lowered deeper and deeper into the water, while the data it collects are streamed in real-time in the computer lab.

CTD data

Based on these data, we select depths at which to collect water samples on the way back up. As the CTD is slowly hoisted back up through the water column, a subset of bottles collects water at each selected sampling depth. The bottles are triggered to fill remotely from on board the ship.

The water samples and CTD data will help us better understand the characteristics of the hydrothermal plumes of water overlying Loihi Seamount. This will provide us with a broader physical and geochemical context for the fine-scale work that we’re doing at the hydrothermal vents, and tell us something about how Loihi relates to the surrounding ocean.

–Cat Wolner, NSF


Photo credits: Cat Wolner


One thought on “Day 5: First CTD cast

  1. Pingback: Day 10: Bugs + rocks | zetahunters

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