A cartoon model for the Kerguelen Axis: modelling variable ice-states and predator-prey interactions
Merel Bedford1*, Elizabeth Fulton2, Jessica Melbourne-Thomas1,3, Stuart Corney1, Andrew Constable1,3
1 Antarctic Climate and Ecosystems CRC, Hobart, Tasmania, Australia
2 Commonwealth Scientific and Industrial Research Organisation, Hobart, Tasmania, Australia
3 Australian Antarctic Division, Kingston, Tasmania, Australia
So-called “cartoon” models provide a useful means to test representations and parameterisations of complex ecosystem components, which can then be implemented in larger modelling frameworks including biogeochemical and higher order foodwebs (end-to-end models). We have developed a cartoon model for a representative Antarctic marine ecosystem, specifically for the Kerguelen Axis region in the Indian Sector of the Southern Ocean, using the open-source agent-based modelling framework NetLogo. This model is designed to be a test domain for an implementation of the Atlantis model for a broader region of the Indian Sector.
There have only been limited attempts, to date, to model the full Antarctic ecosystem – including lower and higher trophic levels – and key habitat drivers. Our model incorporates the physical and dynamic status of the Kerguelen Axis, through light calculations based on local latitude and longitude; ice-states; mixed layer depths and sea-ice processes (habitat and primary productivity). All trophic levels (phytoplankton to top predators) are represented in the model, where we have used patch-variables for phytoplankton; matrices for the foraging species (krill and fish); and individual-based representations for predator species (penguins, seals and whales). The model also allows for depletion of fish and krill through fishing activities.
We present results from a set of simple scenarios for change in seasonal sea-ice habitats, in particular changes in ice extent and the timing of sea ice advance and retreat. We also evaluate some of the lessons learnt in representing diverse Southern Ocean taxa in a cartoon model framework, including implications for full representations and parameterisations in larger end-to-end models.