Blog: Oceanographic drifters and CTD - 13 February
Today was a busy day! We continue to transit southwards but we released three oceanographic drifters at 56 degrees South in the wee hours of the morning then stopped at 58 degrees South for our first sampling station. Through the day, we deployed the CTD (instrument to measure Conductivity, Temperature, and pressure at Depth), zooplankton nets, and a weather balloon, and released another set of drifters. The oceanographers, atmospheric team, plankton team and the marine microbial team were busy into the night processing samples and data.
Here are the highlights from our teams today:
An Argo float is deployed by crew Bruce McIntyre, Shane Harvey and Bryce Barrett. Argo floats profile the temperature and salinity of the ocean, diving down every ten days to 2000 m deep. This single Argo we deployed today joins an array of about 3200 floats cruising the currents of the world’s oceans. All the data collected by Argo floats are publically available in near real-time.
Peter Kuma, University of Canterbury releases the first weather balloon of the voyage with the help of crew Bruce McIntyre and Shane Harvey. The weather balloon has a radiosonde attached which gives us measurements of air temperature, pressure, and relative humidity in the atmosphere. These balloons can fly up to 20 km high, this one got to 16 km.
Crew member Bryce Bennett is pictured here deploying the first CTD of the voyage. The 24 Niskin bottles attached to the CTD rosette are cocked and ready to be closed at various depths throughout the water column. These will collect water samples, which will be filtered or preserved for a whole variety of different analyses by scientists onboard. The CTD measures the water column properties of conductivity (salinity), temperature, and depth (pressure).
Crew member Bryce Bennett deploys a ‘Bongo’ zooplankton net. This frame holds a pair of fine-meshed plankton nets (200μ), and is shaped like a set of bongo drums. The nets were designed this way to avoid having a bridle in front of the net mouth. While plankton are small critters, they can detect the pressure wave generated by a bridle and quite easily escape. This design decreases their ability to see the net coming, and increases our chance of catching them, particularly euphausiids (krill). Today we deployed the Bongos to collect plankton samples from 200 m deep all the way back up to the surface.
Crew member Peter Wall recovers the Continuous Plankton Recorder (CPR). Whenever the ship stops, the CPR must be brought back on board. This instrument records for 450 nautical miles, and we have only gone about 100 since we started this new silk (where the plankton get caught). Scientists will note the location on the silk where the CPR silk stopped when it exited the water, and note a new position further along where the sampling will resume.