Re-analysis of Bioactive Trace Element Atmospheric Deposition along the P16 CLIVAR Line

William M Landing, Florida State University, Earth, Ocean, and Atmospheric Science, Tallahassee, FL, United States, Clifton S Buck, Skidaway Institute of Oceanography, Savannah, GA, United States, David C Kadko, Florida International University, Applied Research Center, Miami, FL, United States and Angela Milne, University of Plymouth, Plymouth, United Kingdom
An earlier analysis (2011) of the sources of bioactive trace elements (focused on iron) needed to support new primary production along the P16 CLIVAR transect (Kodiak to Antarctica) suggested that atmospheric deposition was sufficient in the central North Pacific gyre, that upwelling was sufficient near the equator, and that significant horizontal transport was needed everywhere south of the equator. This earlier analysis used a constant aerosol dry deposition velocity of 1000 meter per day and relied on the standard VPGM primary productivity model to estimate new production rates. Recent data from US GEOTRACES cruises has demonstrated that the radioactive tracer Be-7 can be used to estimate more reliable bulk deposition velocities as a function of rainfall rate to calculate air-to-sea aerosol fluxes. New production estimates have also improved over time, as have estimates of phytoplankton trace element requirements. Rainfall estimates for the time and location of the P16 transect are available from the GPCP program. These new model data are combined with the P16 aerosol and water column trace element data to re-evaluate how important atmospheric deposition, upwelling, and horizontal transport of bioactive trace elements are for fueling new production along the P16 line.