Variability and trends of heat and carbon uptake and storage

Objectives

WP6 quantifies the uptake of heat and carbon in the Southern Ocean and the subsequent transport and storage of these two quantities in the ocean’s interior using a combination of observations and models. Thus, this WP integrates and synthesises the insights and improved process-level understanding developed in WP1 through WP5. We focus on the anthropogenic perturbations of these two quantities, i.e., the so-called “excess” heat and “anthropogenic” CO2 components. The combined analysis of carbon and heat is of high diagnostic value, since they share many similarities, but also important differences. Namely, while the transport and storage of these two tracers are tightly connected, the near-surface boundary conditions of them are very different, leading to a spatial and temporal decoupling. A particular focus of this WP is the determination of the sensitivity of this uptake and storage to changes in the state of the Southern Hemisphere climate system, ranging from seasonal to multi-decadal time-scales. While much of the work will concentrate on the Atlantic Sector of the Southern Ocean, this WP will take a pan-Southern Ocean view as well.

To reach these objectives, WP6 will use observations from a large range of in situ and remote-sensing platforms including ships, XBTs, deep-profiling and more conventional autonomous platforms, and satellites. It will combine these observations with statistical as well as a wide-range of numerical models in order (i) to establish the seasonal to annual budgets for heat and carbon and (ii) to investigate sensitivities to change in atmospheric winds, to representation of the upper and bottom boundary layer, and to changes in surface buoyancy fluxes (including changes in sea-ice regime). The newly gained observations in the Atlantic sector (WP1-4) will also be used to assess the ability of the new generation of climate models (phase 6 of CMIP) to represent Southern Ocean heat and carbon uptake and storage and place the uncertainty range of each model, as an emergent constraint to weight climate models in their future prediction of heat and carbon storage.

Tasks

  • Task 6.1: Seasonal to annual carbon and heat budgets of the Atlantic Sector of the Southern Ocean [Lead: T. Kansow (AWI); participant: N. Gruber (ETHZ)]
  • Task 6.2: Interannual to decadal variations and trends in the carbon and heat budgets of the Southern Ocean [Lead: N. Gruber (ETHZ); participant: T. Kansow (AWI); T. Roy (ECOCEANA)]
  • Task 6.3: Projected trends in carbon and heat flux and storage over Southern Ocean water masses [Lead: T. Roy (ECOCEANA); participant: N. Gruber (ETHZ)]

Partners

WP leaders: N. Gruber (ETHZ, lead) and T. Kansow (AWI, co-lead)

Other participants: T. Roy (ECOCEANA)