Dive into the liquid world of oceanography

SAEON Intern Amy Harding-Goodman will study the track of a lagrangian mooring which broke away from its anchor on the Agulhas Plateau in November last year, to further understand the pathway and dynamics of the Agulhas Return Current. Amy engaged in oceanographic monitoring.

In my oceanography honours year at the University of Cape Town , which was funded by SAEON, I have been privileged to acquire a number of new skills and knowledge from some of the top scientists in the field. These will assist me in applying the many available resources in South Africa to doing good research in the field of oceanography.

The first half of the oceanography honours programme involved a number of modules that provided us with the skills to do a research project. To kickstart the year, we were familiarised with information that empowered us to make use of free internet-based resources that collate global observations as well as satellite data. One can use these data with ease in order to answer many scientific questions regarding the ocean. Useful resources include AVISO, NVODS and Climate Explorer. We also became more proficient with the use of Ocean Data View (ODV) which is a simple, yet powerful program allowing one to view data pictorially.

Satellite skills

As the year progressed we were also equipped with satellite skills. Using Bilko we can now make use of satellite data which are essential for better understanding meso-scale processes in the ocean. This is of particular interest for me as I may be able to use altimetry data to expand my understanding of the Agulhas Return Current, which is the area of study for my thesis project.

Other computer skills gained include an introduction to a programming language MatLab, as well as an introduction to Ocean Modelling. These were challenging to come to terms with, but I feel that although I don't have a full grasp of them yet I am more familiar with the concepts behind them and can thus better understand scientific papers that use these tools.

A particularly useful module we did was in conjunction with applied marine masters students. The course gave an overview of the science behind the environment, emphasising interdisciplinary systems sciences. This multidisciplinary way of thinking, I feel, is essential to fully understand any process that one is studying. This course was comprising also of a number of fieldtrips. These included a trip to Cape Point Nature Reserve Weather Station and a walk up Table Mountain with underprivileged learners, to whom we were given the opportunity to pass on our knowledge.

The opportunity to give several presentations throughout the year has improved my communication skills, which are fundamental for communicating one’s research to fellow researchers and the public. I found that when presenting to a wide range of scientists, it is not only important to know about what you are presenting but also to have a broader knowledge of the topic.

Overall I feel that the first half of this year has equipped me to handle my own research project which I am now keen to explore.

Tracking the Agulhas Return Current with a lagrangian mooring

My thesis project is a study of a lagrangian mooring which broke away from its anchor on the Agulhas Plateau in November last year. Since December the mooring has been floating freely within the Agulhas Return Current, where it is currently measuring surface velocities, air pressure, surface temperature, etc.

Using this data set, the project will look at the path taken by the mooring and the role of the underlying sea floor in steering this flow. Readings from a number of sensors onboard the mooring will provide information on how the physical properties of the Agulhas Return Current change over a period of time, and more importantly with distance east away from the retroflection region.

The project will be divided into two sections. Section 1 aims to study the character of the Agulhas Return Current from the retroflection region along its pathway east to its “assumed” terminus at the south-east Indian Ridge. It is well documented that along its course the Agulhas Return Current is topographically influenced, resulting in a number of meanders in its path. The impact the sea floor has on the velocity, transport and variability of the Agulhas Return Current remains poorly understood.

In addition, the impact these generated meanders have in recirculating Agulhas Water into the subtropical gyre needs to be further explored. Using ARGO, drifter, as well as historical datasets and altimetry (and possibly SODA model output) the character and structure/ dynamics of the Agulhas Return Current will be defined (water mass properties, dynamic height, core location/speed) and its pathway investigated along its entire course.

Section 2 will build on Section 1 by studying the drift of the loose mooring. It is intended that data relayed by this mooring will provide detail into the pathway of the Agulhas Return Current and the in-situ change in the Agulhas Return Current's thermo-haline properties with distance east. How the pathway of this mooring compares to other lagrangian equipment (i.e. ARGO) will be a key study. Furthermore, how the Agulhas Return Current changes as it gradually progresses and dissipates with distance away from the retroflection region will be determined from data recorded by the mooring.

Section 1 is essential in order to define the Agulhas Return Current. This is necessary to identify the exact location of the mooring in relation to the core of the Agulhas Return Current and to establish whether the mooring deviates at any one-time from the core during its lifespan.