Oceanography Seminar

December 5, 3:00pm - 4:15pm
Mānoa Campus, MSB 100 Add to Calendar

Mariko Hatta
Postdoctoral Researcher
Dept. of Oceanography

“Dissolved Fe and Mn concentrations in the North Atlantic Ocean during GEOTRACES 2010/2011 cruises”

Abstract: High-resolution dissolved Fe and dissolved Mn distributions were obtained using a trace metal clean rosette during the U.S. GEOTRACES zonal expeditions (USGT10 & USGT11) across the North Atlantic Ocean. This presentation provides a general overview of those distributions which reveal several inputs of Fe at varying depths across the region. Elevated dissolved Fe (dFe) values correspond to elevated dissolved Al values in the surface waters of the subtropical gyre, suggesting a significant atmospheric source of Fe. In the subsurface water, dFe maxima are a result of the remineralization process, as indicated by their coincidence with the oxygen minima. In this region, the ratio of dFe to apparent oxygen utilization (AOU), when combined with the measured values of Fe in surface water biological materials, suggests a significant amount of dFe remineralised from this material (~63-90%) is scavenged from the water column. This remineralization rate, which is based on the slope of dFe:AOU plots, is similar across a wide area of the North Atlantic. In addition to the remineralization process, sedimentary inputs are seen in the eastern basin, particularly near the African coast. In the western basin, sedimentary input is also occurring along the advective flow path of the Upper Labrador Sea Water as it transits the North American shelf region. The largest dFe anomaly (~68nM) is seen in the neutrally buoyant hydrothermal plume sampled near the Mid-Atlantic Ridge, and that signal is visible for ~500 km to the west of the ridge.

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Oceanography, Mānoa Campus

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