GEOTRACES GP15 Meridional Section: Preliminary Results for REEs, Ba, V, methane, and Other Dissolved Trace Elements

The GEOTRACES GP15 section from the Aleutians to Tahiti during fall 2018 afforded the opportunity to collect dissolved trace element samples along 152 W in the Pacific Ocean. This section passed through a variety of ocean environments including the equatorial upwelling, the oldest deep ocean waters, ultra-oligotrophic waters in the South Pacific, gradients in atmospheric input and productivity, margin influences, and the Loihi hydrothermal plume. We analyzed samples for dissolved rare earth elements (REEs), Ba, V, Ga, Cu, Ni, and Mn as well as methane and present preliminary results and interpretations here. Interesting initial observations include the following. Near surface, in a region near 10 N where the nutricline was very shallow, depletions in some elements such as Ba and V were observed. In the Loihi plume, a slight increase in Ce along with methane was observed. Near the Aleutian margin, Ce and the Ce anomaly increased, probably reflecting margin input. In the strong oxygen minimum of the North Pacific, there also appear to be low values of Ba* (the Ba anomaly relative to Si) but a small increase in the Nd/Yb ratio. In general, dissolved trace elements show highest values in the old Pacific Deep Water, but some distributions (e.g., Nd, Cu) show a greater increase near the bottom than others (e.g., Ba, Ni) , suggesting difference in relative inputs from the bottom.