Two male elephant seals playing
Two male elephant seals playing in front of a king penguin colony at the beach of Ratmanoff in the Kerguelen islands. Photo: Etienne Pauthenet.

 

What is it you have studied in your Doctoral thesis?

− I explored the distribution of temperature and salinity in the Southern Ocean and took part in a program that equips elephant seals with sensors, to retrieve data in remote places, says Etienne Pauthenet.

− The Southern Ocean is encircling the Antarctic continent. This ocean is remote, battered by persistent strong winds and covered in ice in winter, making its observation logistically complicated with standard research vessels. An unconventional way to get oceanographic data in these regions is to “use" elephant seals as oceanographic platforms. Indeed these animals can dive up to 2000m and cover several thousands of kilometers during their trip at seas, gathering very valuable data along their tracks.

Why is this interesting?

− The Southern Ocean occupies a central place for the global climate system. It mixes and redistributes water masses from the three other basins, the Atlantic, Pacific and Indian Oceans. Understanding its density structure and its global circulation is relevant for the prediction of our changing climate. Yet it is lacking in-situ observations due to its remoteness and the elephant seal program is an effort towards a better observing system.

How can your research be put to further use?

− In my thesis we especially worked on a statistical tool to simplify and visualize the complex 3D structure of the Southern Ocean. This method could be used for objectively identifying water masses and their boundaries. It is useful for inter-model comparison and also comparing models with observations.

− It could also be used to validate new data relatively to a climatology. One of the paper of my thesis used this method to locate objectively an oceanic front in the Indian Ocean. This kind of study could be done in other regions with complex circulation patterns.

What was the most challenging in you work with this?

− The most challenging part for me was to do a PhD in physical oceanography coming from a master of marine biology and ecology. I had to take courses of dynamic meteorology and general circulation that were very hard for my level of mathematics and physics. It was also a challenge to give oral presentations because I get nervous easily. But looking back most of it was pretty fun and I particularly enjoyed playing with the data and exploring the elephant seal tracks.

Close encounter with elephant seals

Did you meet the elephant seals?

− I got the chance to meet them yes! My supervisor Fabien Roquet sent me on a cruise to the Kerguelen Islands where I spent one month catching elephant seals and attaching or retrieving tags from their heads. I was part of a french-australian team contributing to the sampling of ocean properties in remote places, CEBC-CNRS and IMOS. The initial goal of this project is to study the at sea behavior of the animals. But now the seals are also the largest contributors of temperature and salinity data in the high latitudes (south of the latitude 60°South).

− That was an unforgettable experience and definitely the highlight of this PhD. 

How does it feel to have completed your PhD? Will you continue working in this field do you think?

− It feels good! I remember when I started it was impossible to imagine finishing all this work. But step by step I managed to validate the courses, publish papers and teach a little bit. I feel like it went very fast, I can't believe I spent 4 years here. 

− I plan to continue in this field with a post doc in Paris. The subject is the ocean dynamics in the Antarctic coastal polynyas, partly using data gathered by seals.

Etienne Pauthenet will have his PhD defence on November 30 2018.