Overview

The aerosol deposition of continental material and its partial dissolution in the surface ocean exerts an important control on the distribution of iron and other potentially limiting trace metal (TM) micronutrients in the open ocean. This dust deposition has implications for the regulation of global climate through the coupling of biolimiting TM cycles, marine productivity, and the global carbon cycle. Thus, it is important to determine the locations of dust deposition in the open ocean and to quantify the magnitude and subsequent dissolution of the dust. At present, there are too few dust deposition estimates and solubility measurements in the open ocean to adequately constrain this key source term in global biogeochemical models.

While early sampling efforts were invaluable in highlighting the importance of TMs in regulating nutrient cycling and phytoplankton productivity in vast ocean regions, they lacked the spatial resolution and global coverage required to constrain model simulations and identify features that illuminate the processes controlling TM distributions. Starting in 2003, the US Climate Variability and Predictability (CLIVAR)-CO₂ Repeat Hydrography Program provided an hour of ship time for dedicated TM sampling at every degree of latitude or longitude along selected cruise tracks. The principal goals for CLIVAR TM sampling were to produce a high-resolution dissolved iron (Fe) and aluminum (Al) data set with global coverage to better understand upper-ocean Fe biogeochemistry, determine patterns of atmospheric dust deposition based on surface dissolved Al levels, and improve our estimates of the fractional solubility of aerosol TMs using a dedicated shipboard aerosol sampling program. This paper describes recent advances in our understanding of dust deposition and the solubility of aerosol material resulting from 10 years of collaborative work under the US CLIVAR-CO₂ Repeat Hydrography Program.

Grand, M.M., C.S. Buck, W.M. Landing, C.I. Measures, M. Hatta, W.T. Hiscock, M. Brown, and J.A. Resing. 2014. Quantifying the impact of atmospheric deposition on the biogeochemistry of Fe and Al in the upper ocean: A decade of collaboration with the US CLIVAR-CO2 Repeat Hydrography Program. Oceanography 27(1):62–65, https://doi.org/10.5670/oceanog.2014.08.

Baker, A.R., and P.L. Croot. 2010. Atmospheric and marine controls on aerosol iron solubility in seawater. Marine Chemistry 120:4–13, https://doi.org/10.1016/j.marchem.2008.09.003.

Barrett, P.M., J.A. Resing, N.J. Buck, C.S. Buck, W.M. Landing, and C.I. Measures. 2012. The trace element composition of suspended particulate matter in the upper 1000 m of the eastern North Atlantic Ocean: A16N. Marine Chemistry 142–144:41–53, https://doi.org/10.1016/j.marchem.2012.07.006.

Buck, C.S., W.M. Landing, and J.A. Resing. 2013. Pacific Ocean aerosols: Deposition and solubility of iron, aluminum, and other trace elements. Marine Chemistry 157:117–130, https://doi.org/10.1016/j.marchem.2013.09.005.

Buck, C.S., W.M. Landing, J.A. Resing, and G.T. Lebon. 2006. Aerosol iron and aluminum solubility in the Northwest Pacific Ocean: Results from the 2002 IOC cruise. Geochemistry, Geophysics, Geosystems 7, Q04M07, https://doi.org/10.1029/2005GC000977.

Buck, C.S., W.M. Landing, J.A. Resing, and C.I. Measures. 2010. The solubility and deposition of aerosol Fe and other trace elements in the North Atlantic Ocean: Observations from the A16N CLIVAR/CO
repeat hydrography section. Marine Chemistry 120:57–70, https://doi.org/10.1016/j.marchem.2008.08.003.

Cutter, G.A., and K.W. Bruland. 2012. Rapid and noncontaminating sampling system for trace elements in global ocean surveys. Limnology and Oceanography Methods 10:425–436, https://doi.org/10.4319/lom.2012.10.425.

Dammshäuser, A., T. Wagener, and P.L. Croot. 2011. Surface water dissolved aluminum and titanium: Tracers for specific time scales of dust deposition to the Atlantic? Geophysical Research Letters 38, L24601, https://doi.org/10.1029/2011GL049847.

Duce, R.A., P.S. Liss, J.T. Merrill, E.L. Atlas, P. Buat-Menard, B.B. Hicks, J.M. Miller, J.M. Prospero, R. Arimoto, T.M. Church, and others. 1991. The atmospheric input of trace species to the world ocean. Global Biogeochemical Cycles 5(3):193–259, https://doi.org/10.1029/91GB01778.

Han, Q., J.K. Moore, C. Zender, C.I. Measures, and D. Hydes. 2008. Constraining oceanic dust deposition using surface ocean dissolved Al. Global Biogeochemical Cycles 22, GB2003, https://doi.org/10.1029/2007GB002975.

Measures, C.I., and E.T. Brown. 1996. Estimating dust input to the Atlantic Ocean using surface Al concentrations. Pp. 301–311 in The Impact of African Dust Across the Mediterranean. Environmental Science and Technology Library, vol. 11, S. Guerzoni and R. Chester, eds, Springer.

Measures, C.I., W.M. Landing, M.T. Brown, and C.S. Buck. 2008a. A commercially available rosette system for trace metal-clean sampling. Limnology and Oceanography Methods 6:384–394, https://doi.org/10.4319/lom.2008.6.384.

Measures, C.I., W.M. Landing, M.T. Brown, and C.S. Buck. 2008b. High-resolution Al and Fe from the Atlantic Ocean CLIVAR-CO2 Repeat Hydrography A16N transect: Extensive linkages between atmospheric dust and upper ocean geochemistry. Global Biogeochemical Cycles 22, GB1005, https://doi.org/10.1029/2007GB003042.

Measures, C.I., and S. Vink. 2000. On the use of dissolved aluminum in surface waters to estimate dust deposition to the ocean. Global Biogeochemical Cycles 14(1):317–327, https://doi.org/10.1029/1999GB001188.

SCOR Working Group. 2006. GEOTRACES: An International Study of the Biogeochemical Cycles of Trace Elements and Their Isotopes. Science Plan. Scientific Committee on Ocean Research, 79 pp. Available online at: http://www.ldeo.columbia.edu/res/pi/geotraces/documents/indexDOC/GEOTRACESSciencePlan.pdf (accessed November 15, 2013).

Sholkovitz, E.R., P.N. Sedwick, T.M. Church, A.R. Baker, and C.F. Powell. 2012. Fractional solubility of aerosol iron: Synthesis of a global-scale data set. Geochimica et Cosmochimica Acta 89:173–189, https://doi.org/10.1016/j.gca.2012.04.022.

Srinivas, B., and M.M. Sarin. 2013. Atmospheric dry-deposition of mineral dust and anthropogenic trace metals to the Bay of Bengal. Journal of Marine Systems 126:56–68, https://doi.org/10.1016/j.jmarsys.2012.11.004.

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