This work package focuses on: Exchange between the Southern Ocean and the global ocean.

What are the size, variability and controls on basin-scale heat and carbon transports throughout the Atlantic sector of the Southern Ocean and outwards to the global ocean, and how will these change in the future?

The focus of Work Package 3 is the large-scale circulation in the Atlantic Sector of the Southern Ocean and the role of this region in the global ocean and climate system. WP3 aims to inform the strength, variability, controls and future evolution of the heat and carbon inventory in the region and exports from the study area using a targeted campaign of observations and complementary model analyses. For this purpose we split the study region in two to isolate the upper cell associated with formation and export from the ORCHESTRA region of mode and intermediate waters and the lower cell associated with the formation and export of AABW. It is the formation of these key water masses that is the focus of Work Package 2. WP3 will achieve its aims by:

• Making new climate-quality shipboard, moored and autonomous observations to determine the state of the ocean in the ORCHESTRA study period, and the representative circulation.
• Synthesizing observations with others from the international hydrography, Argo float observing systems and satellite data to determine the evolution of the inventory of heat and carbon and variability in the circulation and exports of heat and carbon.
• We will compare model output with our observations using a suite of bespoke metrics to validate model performance including targeted improvements to model code.
• We will use the outputs from coupled models to determine the relationship between our key metrics with large-scale climate modes, and their evolution into the future.