University of Tasmania, Australia

Ocean-Atmosphere interaction in the Antarctic Circumpolar Current

In December 2008 we deployed 8 EM-APEX profiling floats at the northern edge of the Kerguelen Plateau in the southern Indian Ocean, as part of the international SOFINE experiment. EM-APEX are a recent advancement on standard Argo floats, built by Webb Research Corporation, that use electro-magnetic techniques to measure profiles of ocean velocity. They transfer data across the Iridium satellite phone system, enabling much larger data transfers, and allowing the floats to be controlled remotely.

Our EM-APEX floats have returned more than 2000 profiles of temperature, salinity and horizontal velocity to 1600 metres depth across the northern Kerguelen Plateau, with 2-5 metre vertical spacing, and 4 profiles per day per float.

This extremely highly resolved dataset presents the opportunity to learn a great deal about upper ocean dynamics in the Southern Ocean where few observations are found. Not only does EM-APEX data reveal the changes to the upper ocean but also allows us to diagnose the cause of the change. We can distinguish between the various possible processes, such as lateral advection, inertial pumping or vertical mixing. The student will use these data to investigate aspects of upper ocean dynamics, including

• the evolution of the surface mixed layer in response to surface atmospheric fluxes and the relative roles of ocean processes in distributing the inputs
• the penetration of near-inertial energy into the ocean interior from atmospheric storm events
• surface wave statistics