The ocean plays a vital role in global climate through the vertical transfer of biogenic carbon from the ocean surface to depth where respired carbon dioxide is then isolated from the atmosphere. While critically important for ecosystem function and future climate projections, the annual magnitude of (and variability in) global carbon export remains poorly constrained, with estimates ranging from ~5 to >12 Pg C yr-1. These estimates are often derived from regional empirical relationships between field and satellite observations that are then applied globally. However, discrepancies between in situ geochemical and satellite-based estimates of carbon export at time series sites and across ocean basins reveal a fundamental research need. Thus, a central goal in chemical oceanography is to advance our mechanistic understanding of carbon export in order to achieve quantitative and predictive assessments of the biological pump at a global scale.
The work proposed herein addresses this need through the development of a scalable, in situ method for quantifying the export of distinct biogenic carbon pools using biogeochemical profiling floats. Specifically, particulate and dissolved organic carbon and particulate inorganic carbon cycling can be differentiated using biogeochemical tracer budgets over the ~5-year float life cycles. Application of this method at a global scale could resolve the biological pump on a ~weekly timescale. Still, remote sensing will continue to be a powerful tool for filling in unavoidable oceanographic observational gaps. Using biogeochemical profiling floats to develop a carbon export database with a spatiotemporal scale that is complementary to satellite observations is a pragmatic way to improve the validation and training of algorithms necessary for global carbon export determinations. Thus, the proposed project is a first step toward improved, real-time, global quantification of the biological pump from remote-sensing that may ultimately inform the mechanistic studies needed to achieve the predictive capabilities sought.