An Investigation of Basin-Scale Controls on Upper Ocean Export and Remineralization

Erin Black, Ph.D., 2018
Ken Buesseler, Advisor

The biological carbon pump (BCP) helps to moderate atmospheric carbon dioxide levels by bringing carbon to the deep ocean, where it can be sequestered on timescales of centuries to millennia. Climate change is predicted to decrease the efficiency of the global BCP and therefore, it is imperative that we (1) accurately quantify the magnitude of surface export and remineralization of particulate organic carbon (POC) via the BCP over large regions of the global ocean, (2) examine the factors controlling these magnitudes and their variability, which includes the cycling of biologically-relevant trace metals, and (3) establish if and how the BCP is changing over time. This thesis focuses on addressing various aspects of these objectives using the ²³⁴Th-²³⁸U method across basin-scale GEOTRACES transects. First, the export and remineralization of POC were examined across large gradients in productivity, upwelling, community structure, and dissolved oxygen in the southeastern tropical Pacific Ocean. Second, trace metal export and remineralization was quantified across this Pacific transect and the controls on the cycling of these metals in the upper ocean were examined. Lastly, POC export was determined across two transect in the Western Arctic Ocean, where light and nutrient availability drive the biological pump.