Abstract
Abstract. The aim of the GEOVIDE cruise (May–June 2014, R/V Pourquoi Pas?) was to provide a better understanding of trace metal biogeochemical cycles in the North Atlantic Ocean. As marine particles play a key role in the global biogeochemical cycle of trace elements in the ocean, we discuss the distribution of particulate iron (PFe), in relation to the distribution of particulate aluminium (PAl), manganese (PMn), and phosphorus (PP). Overall, 32 full vertical profiles were collected for trace metal analyses, representing more than 500 samples. This resolution provides a solid basis for assessing concentration distributions, elemental ratios, size fractionation, and adsorptive scavenging processes in key areas of the thermohaline overturning circulation. Total particulate iron concentrations ranged from as low as 9 pmol L−1 in surface waters of the Labrador Sea to 304 nmol L−1 near the Iberian margin, while median PFe concentrations of 1.15 nmol L−1 were measured over the sub-euphotic ocean interior. Within the Iberian Abyssal Plain, the ratio of PFe to PAl was identical to the continental crust molar ratio (0.21 mol mol−1), indicating the important influence of crustal particles in the water column. Overall, the lithogenic component explained more than 87% of PFe variance along the section. Within the Irminger and Labrador basins, the formation of biogenic particles led to an increase in the PFe∕PAl ratio (up to 0.64 mol mol−1) compared to the continental crust ratio. Continental margins induce high concentrations of particulate trace elements within the surrounding water masses (up to 10 nmol L−1 of PFe). For example, horizontal advection of PFe was visible more than 250 km away from the Iberian margin. Additionally, several benthic nepheloid layers were observed more than 200 m above the seafloor along the transect, especially in the Icelandic, Irminger, and Labrador basins, suspending particles with high PFe content of up to 89 nmol L−1.
Highlights
Particles play a key role in the ocean, where they drive the residence time of most elements (Jeandel and Oelkers, 2015) and strongly influence the global biogeochemistry of macroand micro-nutrients including iron (Milne et al, 2017)
As marine particles play a key role in the global biogeochemical cycle of trace elements in the ocean, we discuss the distribution of particulate iron (PFe), in relation to the distribution of particulate aluminium (PAl), manganese (PMn), and phosphorus (PP)
MW resulted from the mixing between the Mediterranean Overflow Water (MOW) plume coming from the Mediterranean Sea and local waters
Summary
Particles play a key role in the ocean, where they drive the residence time of most elements (Jeandel and Oelkers, 2015) and strongly influence the global biogeochemistry of macroand micro-nutrients including iron (Milne et al, 2017). Biological activity produces biogenic suspended matter through planktonic organisms, while atmospheric deposition (Jickells et al, 2005; Baker et al, 2013), riverine discharge (Ussher et al, 2004; Berger et al, 2008; Aguilar-Islas et al, 2013), or ice melting (Lannuzel et al, 2011, 2014; Hawkings et al, 2014) deliver mostly lithogenicderived particles to surface waters. Oceanic particles result from a complex combination of these different sources and processes (Lam et al, 2015)
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