Scientist Profile: Katy Sheen

I work at the National Oceanography Centre in Southampton, UK as a postdoctoral researcher for the DIMES project. I primarily look at the data that we collect using the vertical microstructure probes (VMP). These data are important as they provides 'on-the spot' estimates of the vertical mixing present in the ocean, in contrast to the time and space averaged values determined from the yearly spread of the tracer (dye). On the James Cook, my main role has been helping to deploy and recover the VMP, and to process the data. It can be a little nerve-racking, making sure that you have programmed the VMP correctly so that it doesn't crash into the sea bed!

Back in the office, I have been looking in detail at what kind of processes cause the variations in mixing that we observe in the VMP data. One source of mixing is the breaking of waves produced from the interaction of bottom currents with bumps in the sea-bed. These waves (internal waves) radiate through the ocean interior along density layers. When the internal waves lose enough energy, they  break, mixing up the water - just like waves breaking on the beach. High levels of ocean mixing are therefore associated with rough topography and strong currents, as in the DIMES region of study. The energy from internal waves contributes to pumping deep ocean waters back to the surface through vertical mixing, powering the global overturning circulation.

Internal waves typically have wavelengths of about 100 m, and information about the internal wave field can be obtained from the temperature, salinity and current velocity data collected by the CTD which is deployed at the same time as the VMP.  (The data obtained by the VMP is on the millimetre scales). These CTD data, along with theoretical ideas about how and when internal waves break, can be used to estimate mixing too. One of my main areas of research is to look at how well mixing estimates from CTD data compare to those measured directly by the VMP.

What do you enjoy about being at sea?

I enjoy working in a completely different environment , especially somewhere as beautiful and remote as the Southern Ocean - it's not a place where many people get the opportunity to visit! It's also a lot of fun meeting the other scientists and crew working on the project and exciting to be involved in such a dynamic and cutting-edge science programme. I normally manage to sneak in some travelling too - this year I spent a week camping in Uruguay before joining the ship in Montevideo.

What do you hope to gain?

Hopefully lots of data, new friends and I'd love to see an ice-berg!