Neodymium isotopic compositions (Nd-143/Nd-144 or epsilon(Nd)) have been used as a tracer of water masses and lithogenic inputs to the ocean. To further evaluate the faithfulness of this tracer, we have updated a global seawater epsilon(Nd) database and combined it with hydrography parameters (temperature, salinity, nutrients and oxygen concentrations), carbon isotopic ratio and radiocarbon of dissolved inorganic carbon. Archive epsilon(Nd) data are also compiled for leachates, foraminiferal tests, deep-sea corals and fish teeth/debris from the Holocene period (< 10,000 years). At water depths >= 1500m, property-property plots show clear correlations between seawater epsilon(Nd) and the other variables, suggesting that large-scale water mass mixing is a primary control of deepwater epsilon(Nd) distribution. At >= 200m, basin-scale seawater T-S-epsilon(Nd) diagrams demonstrate the isotopic evolution of different water masses. Seawater and archive epsilon(Nd) values are compared using property-property plots and T-S-epsilon(Nd) diagrams. Archive values generally agree with corresponding seawater values although they tend to be at the upper limit in the Pacific. Both positive and negative offsets exist in the northern North Atlantic. Applying multiple regression analysis to deep (>= 1500m) seawater data, we established empirical equations that predict the main, large-scale, deepwater epsilon(Nd) trends from hydrography parameters. Large offsets from the predicted values are interpreted as a sign of significant local/regional influence. Dominant continental influence on seawater and archive epsilon(Nd) is observed mainly within 1000 km from the continents. Generally, seawater and archive epsilon(Nd) values form gradual latitudinal trend in the Atlantic and Pacific at depths >= 600m, consistent with the idea that Nd isotopes help distinguish between northern/southern sourced water contributions at intermediate and deep water depths.
The large-scale evolution of neodymium isotopic composition in the global modern and Holocene ocean revealed from seawater and archive data
Montagna P;
2017
Abstract
Neodymium isotopic compositions (Nd-143/Nd-144 or epsilon(Nd)) have been used as a tracer of water masses and lithogenic inputs to the ocean. To further evaluate the faithfulness of this tracer, we have updated a global seawater epsilon(Nd) database and combined it with hydrography parameters (temperature, salinity, nutrients and oxygen concentrations), carbon isotopic ratio and radiocarbon of dissolved inorganic carbon. Archive epsilon(Nd) data are also compiled for leachates, foraminiferal tests, deep-sea corals and fish teeth/debris from the Holocene period (< 10,000 years). At water depths >= 1500m, property-property plots show clear correlations between seawater epsilon(Nd) and the other variables, suggesting that large-scale water mass mixing is a primary control of deepwater epsilon(Nd) distribution. At >= 200m, basin-scale seawater T-S-epsilon(Nd) diagrams demonstrate the isotopic evolution of different water masses. Seawater and archive epsilon(Nd) values are compared using property-property plots and T-S-epsilon(Nd) diagrams. Archive values generally agree with corresponding seawater values although they tend to be at the upper limit in the Pacific. Both positive and negative offsets exist in the northern North Atlantic. Applying multiple regression analysis to deep (>= 1500m) seawater data, we established empirical equations that predict the main, large-scale, deepwater epsilon(Nd) trends from hydrography parameters. Large offsets from the predicted values are interpreted as a sign of significant local/regional influence. Dominant continental influence on seawater and archive epsilon(Nd) is observed mainly within 1000 km from the continents. Generally, seawater and archive epsilon(Nd) values form gradual latitudinal trend in the Atlantic and Pacific at depths >= 600m, consistent with the idea that Nd isotopes help distinguish between northern/southern sourced water contributions at intermediate and deep water depths.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
