Changes in the carbon cycle of the Southern Ocean during glacial / interglacial climate transitions have been directly linked to major changes in atmospheric CO2 and greenhouse gas climate forcing (Sarmiento and Toggweiler 1984). Martin et al. (1990) demonstrated that iron deficiency limits phytoplankton productivity in the Southern Ocean. The Southern Ocean plankton ecology system has the largest inventory of pre-formed nutrients in the global oceans and thus is considered to be a region with a large potential for climate feedback through changes in net community production (NCP) (Sigman et al. 2010; 2013). The rate of iron delivery to the photic zone combined with upper ocean stratification regulates primary production in the Southern Ocean. These discoveries motivated major multi-agency interdisciplinary projects in the region (JGOFS, SOFEX and GASEX) yet we still lack an ability to constrain NCP estimates better than a factor of 2x. Therefore it is essential to understand the integrated dynamics of ocean, ice and atmosphere interactions to quantify the magnitude and uncertainties of carbon fluxes, and to carry out climate prediction scenarios. Key questions that must be addressed include: 1) Will warming and acceleration of glacial melt increase surface buoyancy and stratification, thereby reducing iron input to the surface ocean? 2) Will glacial melt deliver more atmospheric iron stored for millennia in the ice, and fresh water buoyancy to the surface ocean, thus increasing productivity? 3) Will stronger winds and reduced sea ice lead to deeper mixing and coastal upwelling delivering more iron to the system? These system-level questions are directly relevant to the high-level goals defined by NASA's Carbon Cycle and Ecosystems Roadmap as focused by NASA's Ocean Biology and Biogeochemistry Program and motivate NASA's PACE advanced hyperspectral ocean color satellite mission.

 

Quantitative knowledge of the rates of NCP in time and space are essential for addressing key global ocean carbon cycle questions, including understanding the role of the biological pump on atmospheric CO2. Understanding the contemporary ocean is required for creating coupled models that can predict future interactions and feedback between fossil fuel CO2 emissions, climate, ocean ecosystem structure, and biogeochemical cycles. The time and space quantification of net primary production (NPP) and NCP at global scales, including robust estimates at seasonal to interannual time scales, is a fundamental rationale for NASA's Pre-Aerosol-Cloud-Ecosystems (PACE) mission. However, our ability to assess these important carbon cycle parameters from satellite data remains quite limited and new approaches and data sets are desperately needed. Here we propose the “Scoping for Interdisciplinary Coordinated Experiment of the Southern Ocean Carbon Cycle (ICESOCC)” project to implement a broad community consensus process to create a detailed report that will specify an interdisciplinary and international field campaign to develop improved capability for measuring seasonal variations in NCP and subsurface ventilation at the scale of the entire Southern Ocean south of 30°S. Our overarching goal is to foster the development of operational capability integrating satellite, land based and ocean observations and robust data assimilation models for quantifying seasonal and interannual changes in NCP, including explicit satellite-derived details in time and space, thereby providing essential monitoring of this critical region. This approach will contribute to prognostic climate model simulations based on a more realistic understanding of contemporary processes that must be incorporated in advanced, data assimilating, coupled physical – biogeochemical models.