Soluble iron inputs to the Southern Ocean through recent andesitic to rhyolitic volcanic ash eruptions from the Patagonian Andes

SIMONELLA, L.E.; PALOMEQUE, M.E.; CROOT, P.L.; STEIN, A.; KUPCEZEWWSKI, M.; ROSALES, A; MONTES, M.L.; COLOMBO, F.; GARCÍA, M.G.; VILLAROSA, G.; GAIERO, D.M.

GLOBAL BIOGEOCHEMICAL CYCLES

AMER GEOPHYSICAL UNION

Año: 2015 vol. 29 p. 1125 - 1144

0886-6236

Patagonia,due to its geographic position and the dominance of westerly winds, is a keyarea that contributes to the supply of nutrients to the Southern Ocean, boththrough mineral dust and through the periodic deposits of volcanic ash. Here weevaluate the characteristics of Fe dissolved (into soluble and colloidal species)from volcanic ash for three recent southern Andes volcanic eruptions havingcontrasting features and chemical compositions. Contact between cloud waters(wet deposition) and end-members of andesitic (Hudson volcano) and rhyolitic(Chaitén volcano) materials was simulated. Results indicate higher Fe releaseand faster liberation rates in the andesitic material. Fe release duringparticle-seawater interaction (dry deposition) has higher rates inrhyolitic-type ashes. Rhyolitic ashes under acidic conditions release Fe inhigher amounts and at a slower rate, while in those samples containing mostlyglass shards, Fe release was lower and faster. The 2011 Puyehue eruptionwas observedby a dustmonitoring station. Puyehue-type eruptions can contribute soluble Fe tothe ocean via dry or wet deposition, nearly reaching the limit required forphytoplankton growth. In contrast, the input of Fe after processing by anacidic eruption plume could raise the amount of dissolved Fe in surface oceanwaters several times, above the threshold required to initiate phytoplanktonblooms. A single eruption like the Puyehue one represents more than half of theyearly Fe flux contributed by dust