The purpose of our voyage

Pings, Dopplers and Wiggles

The purpose of our voyage is two-fold. The first is recovery - we are recovering moorings that were lowered into Jackson Bay a year ago. On each mooring are two Acoustic Doppler Current Profiler (ADCP) instruments which measure the speed of the water going past.

The ADCP sends out a high frequency sound or 'ping' which bounces off particles in the ocean and is reflected back. How long it takes for a 'ping' to come back to the instrument determines the speed of the water going past, and this gives us measurements of the ocean currents.

Other instruments along the mooring measure temperature, salinity and pressure. These readings can tell us about the density of the water. Even though scientists know that density increases the deeper you are in the water, there are lots of changes or 'wiggles' in density that tell us about what is happening in the ocean.

The second task to be carried out is a series of surveys down the Moeraki Canyon on the West Coast. We'll start at the head of the Canyon, the shallowest part at around 200m, and make our way down to over 3000m.

The CTD is the primary research tool for oceanographers (it’s used to measure the Conductivity, Temperature and Depth of the ocean). At the heart of the CDT are probes which measure pressure, temperature, conductivity, and dissolved oxygen. From temperature and conductivity, we can calculate salinity (how salty the ocean is).

CTD instrument used for sampling

Around the outside of the CTD are bottles which collect water samples at different water depths when they are ‘fired’ (activated) by the computer. Later those water samples are filtered and calibrated (in other words, the water is analysed).

Why do we measure water?

Collecting this data means we are able to learn about water movement (transport) along the West Coast region. Try to imagine transport like the motorway that you drive your car on. Each car can travel a different pathway along a journey - these have on-ramps, places to exit and regions where there will always be congestion. Scientists will use the data to characterise these transport pathways.

Ocean water flows like a motorway - with roads going in different directions

Why the West Coast?

Rivers in this region are among the biggest in New Zealand. The data we get back from the moorings will be used to understand where fresh water that runs off the land ends up and to what extent that could affect marine productivity.