A Pb (and Sr) isotopic return address for trans-Pacific transported aerosols

The degree that isotope ratios of trace elements vary geographically within the oceans to a large extent reflects their residence times. Nd isotope ratios are distinct in different oceans but nearly uniform within each ocean (Piepgras et aL, 1979; Goldstein and O'Nions, 1981) reflecting a residence time longer than the mixing time of individual oceans but shorter than the whole ocean (~1500yrs) (Elderfield and Greaves, 1982). Pb has a residence time about an order of magnitude shorter than Nd, about 80-100 yrs (Craig et al., 1973). Because of their short but different oceanic residence time, Pb and Nd are useful to study mixing processes involved in the oceans through water masses movement. Sr and Nd isotopic studies of Mn nodules have shown that these trace elements are primarily derived from ambient seawater and is likely also to hold for Pb. Since the pioneering studies of Chow and Patterson (1959; 1962), few Pb isotopic data have been reported on marine Mn nodules, although Pb is the most sensitive to variations in local inputs and changes through time. We report Pb isotope ratios of Mn nodules from the Circum-Antarctic ocean, which is the link between the Atlantic, Indian and Pacific through the Antarctic Circumpolar Current (AAC) which flows eastward around Antarctica.

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Circulation (fluid dynamics)

10.1180/minmag.1994.58a.1.04

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Anthropogenic Asian aerosols provide Fe to the North Pacific Ocean

Proceedings of the National Academy of Sciences (2020)

Paulina Pinedo‐González Nicholas J. Hawco Randelle M. Bundy E. Virginia Armbrust Michael J. Follows

Significance Mineral dust has long been considered an important source of Fe to the surface ocean, especially in remote areas away from continental margins. However, anthropogenic Fe derived from fossil-fuel burning may also contribute Fe to surface waters. Here we show in situ evidence of anthropogenic Fe in seawater, based on the concentrations and isotopic composition of Fe measured during a springtime cruise which transected the North Pacific Ocean. Our results suggest that anthropogenic Fe could play a globally important role in marine productivity and carbon cycling.

Carbon fibers

10.1073/pnas.2010315117

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