A multi-element perspective on Pacific dissolved trace metal cycling from the GEOTRACES GP15 PMT cruise

Meridional studies of the Pacific Ocean are a particularly exciting way to study biogeochemical fluxes and processes, since many Pacific fluxes are zonally oriented, and thus Pacific meridional transects cross gradients and allow estimation of the meridional extent of different ocean influences. Here, we present an overview of the dissolved Fe, Mn, Zn, Cu, Cd, Ni, and Pb concentrations across the U.S. GEOTRACES GP15 section, which extends from Alaska to Tahiti along 152°W. Our goal here is to provide an overview of metal distributions and compare patterns across metals in order to highlight features that will be explored in more detail for individual metals. We will first interpret the metal distributions as a function of water mass, especially at the equator and in deep water masses where remineralization and scavenging modifications can be assessed over relevant advection timescales. Then, we will interpret features within the metal distributions as a function of source fluxes, including hydrothermal vents, dust inputs, and shelf and slope sediment inputs; these will be identified using metal:metal ratios and auxiliary data that trace these individual processes. Additionally, we will identify influences of oxygen gradients, especially in oxygen deficient zones, as well the effects of metals on biological production; these will both be evaluated using metal:macronutrient ratios. In summary, we hope to characterize trace metal cycling in the open Pacific Ocean, especially in the context of prior work at nearby individual stations and along zonal transects in the Pacific.