Oceanography Seminar

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

Chris Measures
Department of Oceanography

"Dissolved Al during the N Atlantic US GEOTRACES cruises; subsurface surprises and how a little data can ruin a theory"

Abstract: The 2010 and 2011 US GEOTRACES cruises provided an opportunity to produce a highly detailed full depth section of the concentrations of dissolved Al across the N Atlantic between 22 and 70ËšW and 17-37ËšN, providing an opportunity to produce a semi-synoptic section across the basins of the N Atlantic.

Along this transect, surface water dissolved Al concentrations, reflect the deposition and partial dissolution of aluminosilicate mineral dust into the surface ocean. The subsequent inclusion of this signal into the seasonally formed, classical, 18Ëš sub-tropical mode water indicates the susceptibility of the upper ocean to imprinting by atmospherically borne materials. Similarly in the eastern basin, the Mediterranean outflow water at ~ 1300m is clearly delineated by its elevated Al signal again a result of the intense deposition of eolian materials to the surface waters of the Mediterranean. The biggest surprise though is an entirely different source of dissolved Al which is seen entering the deeper waters of the Atlantic at the station occupied in the axial valley of the Mid Atlantic Ridge (MAR) near the TAG hydrothermal site. Here, elevated dissolved Al values of over 40 nM, are seen in the buoyant hydrothermal plume and the effect of this input is visible in the elevated deep water concentrations of the nearby stations. This previously unrecognised input has important consequences for recently resurrected theories of Al cycling in the ocean.

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Oceanography, Mānoa Campus

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