Roger Stevens

Investigation of ice edge controls

Supervisors: Dr Petra Heil (ACE CRC), Dr Kelvin Michael (IASOS) and Dr Steve Rintoul (CSIRO)

Background

In the Antarctic the seasonal advance and retreat of the sea-ice edge presents the largest variability within the polar climate system at annual time scales. Further, the seasonal translation of the ice edge is not spatially uniform, instead maximum and minimum positions vary with longitude. Improved knowledge about the physical processes that control the ice edge is important, as the ice edge is a prime location for the occurrence of algal blooms and plankton assemblages. Because of the temperature gradient and changes in surface drag the equatorward ice edge is a location, where large flux adjustments are required in current generation, coupled ice-ocean models. Hence detailed knowledge of the ice-edge control mechanisms will lead towards improved skill of numerical forecasting and climate models as well as opportunities for improved ecosystem modelling.

Objective

The aim of this study is to separate between thermodynamic and dynamic controls of the ice-edge position, and to assess how the ice-edge location responds within past and future climate scenarios.

The project will assess the relative contributions of sea-ice growth (thermodynamic processes) and of ice advection (dynamic process) to the ice-edge advance, and how these may change in changing climate forcing.

To separate the importance of the various processes, a number of forcing parameters will be investigated: E.g., how do winds impact on the north-south movement of the ice edge? How does wave-ice interaction influence the ice-edge position? How persistent are seasonal extreme locations of the ice-edge, and what are the dominant processes in maintaining the annual maximum ice-edge position?

Key Data Sets

Output from a stand-alone sea-ice model and from a coupled model will be available to be analysed for variability patterns of the Antarctic ice-edge position. Atmospheric reanalysis fields and oceanic observations are available to study past conditions. Coupled simulations will be used to investigate the ice edge under future scenarios.

Using statistical tools (e.g., Fourier transforms, Empirical Orthogonal Functions (EOFs)) and sensitivity studies, mechanisms of ice-edge control will be investigated. This will involve dividing the Antarctic sea-ice zone into sub-regions to isolate competing mechanisms.

The student will be encouraged to learn about numerical analysis and modelling techniques and could participate in a sea-ice observation campaign aboard a research vessel.