A complete review of published and new water column profiles of thorium-230 (230Th) and protactinium-231 (231Pa) concentrations and neodymium (Nd) isotopic compositions collected in the Amerasian Basin of the Arctic Ocean between 1983 and 2015 was performed by Grenier and co-workers (2019, see reference below). This review allowed them to identify regional and temporal variability […]
Mar / 27 / 2020
Joint Science Highlight with US-Ocean Carbon & Biogeochemistry (OCB). Carbon storage in the ocean is sensitive to the depths at which particulate organic carbon (POC) is respired back to CO2 within the twilight zone (100-1000m). For decades, it has been an oceanographic priority to determine the depth scale of this regeneration process. To investigate this, […]
May / 16 / 2019
The insoluble radiogenic isotopes of thorium (Th) are produced at a known rate in the water column via the decay of soluble uranium (234Th, 230Th) and radium (228Th) isotopes. These three isotopes are radioactive and their half-lives vary from days (234Th) to years (228Th) to tens of thousands of years (230Th). Combining their known production […]
Feb / 07 / 2019
Thorium-230 (230Th) and protactinium-231 (231Pa) are two geochemical tracers extensively used for investigating particle transport in the ocean and reconstructing past ocean circulation. A key feature in reproducing their distributions by modelling is to understand and constrain as good as possible the scavenging processes, which means: 1) having the good adsorption-desorption kinetic rates and 2) describing […]
Dec / 10 / 2018
This timeframe, sometimes called a residence time, ranges from decades for the most reactive trace elements to millions of years for the most unreactive elements such as the major components of sea salt. The residence time is often difficult to constrain and involves estimating how much of an element is presently in the ocean (i.e., […]
Nov / 15 / 2018
Chemical species are constantly exchanged between seawater (solution, D) and particles (solid material, P). This continuous D-P exchange is a key process determining the chemical composition of the ocean. Particles are heterogeneous materials, made of (i) biological material from the surface ocean, (ii) lithogenic material from external inputs to the ocean, and (iii) authigenic (oxyhydr)oxides […]
Sep / 04 / 2018
Dissolved thorium (Th) isotopes and iron (Fe) are used to document the transfer of lithogenic material to the ocean. Two contrasting areas are compared: the Atlantic Ocean around Barbados Islands, under the influence of the Amazon plume and dust of Saharan origin, and the remote North East Pacific Ocean, far from dust inputs. The Amazon […]
Mar / 23 / 2017
Insoluble thorium (Th) isotopes are particle reactive while their radioactive parents are fairly soluble. This difference of behaviour has allowed chemical oceanographers to use Th isotopes to develop understanding about the scavenging of particle reactive elements and the cycling of particles in the water column. However, many prior models rely on numerous assumptions. Among these […]
Aug / 30 / 2016
Phoebe Lam and Olivier Marchal (2015, see reference below) propose to describe, with the same model, the dynamics of particles in the oceanic water column and its effects –on four different tracers characterized by very distinct sources and sinks. The considered tracers are: Particulate Organic Carbon (POC) (a biogenic compound), barium (Ba) (an authigenic mineral), […]
May / 21 / 2015