Project: Dissolved Th/Pa from GEOTRACES transect GA13: tracers of hydrothermal scavenging

Hydrothermal activity alters the chemistry of the deep ocean and is important in many different global geochemical budgets. This imprint can be surprisingly long-lived and potentially serves as a source or sink of elements up to 1000s of km from its source. While there is much research about the effects of hydrothermal particles on scavenging, or the adsorption and sinking of elements by marine particles, close to vent sites, much less is known about the regional impact of hydrothermal scavenging. Here, we present dissolved seawater concentrations of 230Th and 231Pa, two elements that help indicate scavenging intensity, for 7 hydrothermal sites in the North Mid-Atlantic Ridge as part of GEOTRACES section GA13. Changes in the distribution of 230Th and 231Pa due to hydrothermal activity were estimated by comparison to historical profiles with similar organic particle flux, dust deposition, and water mass aging, then attributing deviation in concentration profile to hydrothermal influence. We find that hydrothermal depletions of 230Th and 231Pa at our site can be explained by simple dispersal of hydrothermal particles from areas with active venting and dilution of this depleted water as it mixes with seawater. Open questions remain, however, about how the precise timing and scale of vent water dispersal impact concentrations of 230Th and 231Pa off the ridge system. We recommend that future modeling parameterize hydrothermal scavenging by predicting 230Th and 231Pa distributions, and potentially other radiotracers, at sub-degree resolution over the MAR. This would allow basin-scale hydrothermal features to be incorporated into global budgets.

 

This description is from the following dissertation:
Redmond, Neil, "THE MOBILITY OF LONG-LIVED RADIOISOTOPES AND THEIR BURIAL IN THE MARINE ENVIRONMENT" (2023). Dissertations. 2161. https://aquila.usm.edu/dissertations/2161