Abstract
Radiogenic Neodymium (Nd) isotopes in the central North Pacific deep water have been generally interpreted as reflecting Pacific arcs input according to previous studies, while little is known about the specific path and mode of radiogenic Nd from these arcs to deep water. In this study, Nd isotopic data from surface scrapings of 17 Fe-Mn crusts from the central North Pacific deep water (around 20°N) have been reported. Based on these data together with recently published data on dissolved Nd isotopes in seawater for this region, we propose that radiogenic Nd isotopes in North Pacific Intermediate Water (NPIW 300–800 m) from the western Pacific margin is an important source for the central North Pacific deep water, while the surface water of this area has little influence on dominating deep water Nd isotopes. Such a view emphasizes the role of vertical mixing and advection of the marginal ocean currents in balancing Nd isotopes in central North Pacific deep water, and helps to understand oceanic Nd cycling. Moreover, the values of e Nd from surface scrapings of Fe-Mn crusts are relatively homogenous, with an average value of about −3.4, which is higher than that of modern seawater (∼−3.9). This difference over short time scales reflects the quick evolution of Nd isotopes in central North Pacific deep water.
Highlights
Radiogenic Neodymium (Nd) isotopes in the central North Pacific deep water have been generally interpreted as reflecting Pacific arcs input according to previous studies, while little is known about the specific path and mode of radiogenic Nd from these arcs to deep water
Nd isotopic data from surface scrapings of 17 Fe-Mn crusts from the central North Pacific deep water have been reported. Based on these data together with recently published data on dissolved Nd isotopes in seawater for this region, we propose that radiogenic Nd isotopes in North Pacific Intermediate Water (NPIW 300–800 m) from the western Pacific margin is an important source for the central North Pacific deep water, while the surface water of this area has little influence on dominating deep water Nd isotopes
The shelf sediment-seawater Nd isotope exchange can transfer Nd to the deep ocean [15,16,17]. Based on these and the modern ocean current studies and data of this study, we demonstrate that the advective transport of Nd by North Pacific Intermediate Water is an important source of radiogenic Nd
Summary
Radiogenic Neodymium (Nd) isotopes in the central North Pacific deep water have been generally interpreted as reflecting Pacific arcs input according to previous studies, while little is known about the specific path and mode of radiogenic Nd from these arcs to deep water. The values of Nd from surface scrapings of Fe-Mn crusts are relatively homogenous, with an average value of about 3.4, which is higher than that of modern seawater (~ 3.9) This difference over short time scales reflects the quick evolution of Nd isotopes in central North Pacific deep water. The shelf sediment-seawater Nd isotope exchange can transfer Nd to the deep ocean [15,16,17] Based on these and the modern ocean current studies and data of this study, we demonstrate that the advective transport of Nd by North Pacific Intermediate Water is an important source of radiogenic Nd. we find the quick evolution of Nd isotope composition of the North Pacific deep water in a short time scale. More details about present-day North Pacific circulation can be found in [24]
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