International collaborations in ocean modelling

By Neil Malan, PhD Student, SAEON Egagasini Node

Ocean general circulation models are big, not to mention complicated. With even small regional simulations needing to run on supercomputers, creating tens terabytes of data and utilising hundreds of thousands of lines of code, there is no one person who knows how every part of these models works.

Because of this complexity this type of modelling, as with atmospheric and climate modelling, has evolved into an international community effort, with much collaboration in both analysis and the development of model code taking place at institutes across the globe.

In the course of my PhD studies, although being based at SAEON and the University of Cape Town, I have had the opportunity to collaborate with two international institutions, the Nansen Environmental and Remote Sensing Centre (NERSC) in Bergen, Norway and the GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany. I have been lucky enough this year to travel to both these institutes to spend time working with the people who develop the ‘flavours’ of the two ocean models I am using in my PhD work.

The first stop was a two-week visit to Kiel to work with Prof. Arne Biastoch and Dr Jonathan Durgadoo on analyses of their Agulhas Current region model, based on the European NEMO model framework. These two weeks of productive analysis work was followed by a trip to attend an ocean physics summer school, organised by the German Physics Society. This intense week of lectures and activities was attended by 70 PhD students from across the world, and taught by some top researchers in the field of ocean dynamics. Between the official lectures and many informal discussions over coffee I learnt a massive amount and made some valuable contacts.

Snapshot from HYCOM

After a few weeks back in Cape Town I am now in Norway on a five-week research visit at NERSC. The goal of this visit is to run some sensitivity studies from which we can optimise the Agulhas Current model configuration in HYCOM. Although one can log into the supercomputer, run jobs and email and Skype with collaborators from anywhere with an internet connection, nothing beats being able to quickly chat to the person in the next desk about an idea or problem. I am very lucky to be working with Annette Saumelsen and Francois Counillion, who have an impressive knowledge of the ins and outs of the HYCOM system.

Assessing the Agulhas Current’s response to change

Using the data from both of these ocean models, as well as available satellite and in-situ observations, will allow us to gain an understanding of how the Agulhas Current drives the circulation of the waters on the continental shelf of South Africa’s east coast, and how this could change the physical environment in which ecosystems exist. With changes being observed in the Agulhas Current’s core and variability over the last few decades, the development of models that can accurately represent the effects of the current on our waters will allow us to assess what the response of the system will be to change.

These research visits were made possible through the support of the Nansen Tutu Centre, the SPACES programme and SAEON.

Participants in the ocean physics summer school organised by the German Physics Society