Direct measurements of atmospheric iron, cobalt, and aluminum-derived dust deposition at Kerguelen Islands

• Published in: Global Biogeochemical Cycles
• Main Authors: Heimburger, A., Losno, Remi, Triquet, S., Dulac, F., Mahowald, Natalie
• Format: Text
• Language: English
• Published: Amer Geophysical Union
• Subjects: envir; geo; Kerguelen; Kerguelen Islands; Southern Ocean
• Online Access: https://doi.org/10.1029/2012GB004301; https://archimer.ifremer.fr/doc/00265/37585/36830.pdf; https://archimer.ifremer.fr/doc/00265/37585/36831.pdf; https://archimer.ifremer.fr/doc/00265/37585/

Atmospheric deposition is one of the major sources of nutrients bringing trace metals to remote marine biota. In this study, total atmospheric deposition and crustal aerosol concentrations were monitored at Kerguelen Islands (49 degrees 18'S; 70 degrees 07'E) in the Southern Ocean during a short campaign in early 2005 and then continuously for about 2 years (2009-2010). Results show very low levels of atmospheric dust and trace metals concentrations but higher deposition fluxes than expected. The averaged total dust deposition flux as derived from Al deposition measurements is 659 mu g m(-2) d(-1). Simultaneously measured Fe and Co deposition fluxes are respectively 29 mu g m(-2) d(-1) (520 nmol m(-2) d(-1)) and 0.014 mu g m(-2) d(-1) (0.24 nmol m(-2) d(-1)), giving typically crustal elemental ratios to Al of 0.54 and 2.6 10(-4). Measured dust deposition is in relatively good agreement with those simulated by current atmospheric models, but suggest that previous indirect calculations from field experiments are too low by a factor of 20. Observations and model results show that dust is transported above the marine atmospheric boundary layer to Kerguelen Islands, and thus that surface concentrations are not representative of the total dust column. Indeed, using surface concentrations leads to very large computed wet scavenging ratios, and to the conclusion that it is not appropriate to derive deposition fluxes from surface concentrations at remote ocean sites.