Updated Southern Ocean Carbon Trends and their Sensitivity to Methods

The Southern Ocean is highly under-sampled with respect to variables needed to assess trends in air-sea carbon dioxide fluxes. Multiple investigators have made use of sparse measurements of surface ocean partial pressure of CO₂ (pCO₂), but there remains a lack of consensus as to recent trends in the carbon sink here, especially as a transition in the Southern Ocean carbon sink emerges. We analyze impacts of specific methodological choices on pCO₂ trends, with a focus on regional binning, time series length, and spatial biases. We find the most robust approach to include binning based on geographic areas, the removal of spatial gradients in climatological pCO₂, the utilization of annual data, and the consideration of trends across multiple combinations of start and end years. Previously results showed Southern Ocean carbon uptake slowing from about 1990 to 2006 followed by a subsequently strengthening. Utilizing newly released, expanded datasets, we will present trend results providing updates for this highly dynamic region. Such work is essential to increase our ability to diagnose change in the Southern ocean carbon sink.