Project: Sources of Iron to the EasterN tropical Atlantic

Acronym/Short Name:SIRENA
Project Duration:2007-07 - 2010-08
Geolocation:Tropical North Atlantic, focusing on a Cape Verde to Mauritanian Coast transect

Description

We will test the hypothesis that the continental margin of northwest Africa provides a significant subsurface supply of iron to the open eastern tropical Atlantic that supplements dust.

We will test our continental margin hypothesis with a wintertime visit to the new Tropical Eastern North Atlantic Time-Series Observatory (TENATSO) near Cape Verde, located in the eastern tropical Atlantic about 850 km downstream of Mauritanian coastal upwelling, and a summertime cross-shelf transect from the Mauritanian coast to TENATSO with Ed Boyle, who is already funded to study iron in the tropical Atlantic. Our cross-shelf transect will closely examine the potential lateral source of Fe, and evaluate it against an atmospheric source of Fe. Our proposal takes advantage of a novel combination of measurements to uniquely determine the importance of lateral transport vs. dust inputs and subsurface remineralization as Fe sources to the surface ocean. These measurements include:

1) synchrotron x-ray analysis of particulate iron "hotspots": micron-size particles of iron detected with a synchrotron x-ray fluorescence microprobe have been previously shown to exhibit maxima at depths of continental margin input in two ocean basins. Further, the Ti:Fe ratios and the mineralogy of these particles of iron can distinguish dust-derived vs. continental margin iron. This is a qualitative tracer for a dust vs continental margin source of Fe.

2) radium isotopes: the major source of 228Ra into the study area is by diffusion from 232Th-bearing near shore and continental shelf sediments. An open-ocean to coastal transect of 228Ra activities will allow us to determine horizontal mass transfer. 228Ra will be used to quantify the lateral flux of iron from the shelf.

3) 234Th profiles: high vertical resolution 234Th profiles can be used to determine the depth of particle remineralization. This will be used to determine whether or not putative subsurface Fe maxima are from remineralization of Fe-bearing particles.

TENATSO (Tropical Eastern North Atlantic Time-Series Observatory) time series station
16°N, 24°W, North-east of Mindelo, Sao Vicente, Cape Verde

TENATSO Home

TENATSO/SIRENA at Cafe Thorium/WHOI


DatasetLatest Version DateCurrent State
Averaged bottle measurements from CTD casts on R/V Oceanus cruise OC449-03 in the Coastal transect between Cape Verde and Mauritanian coast in 2008 (SIRENA project)2011-10-13Preliminary and in progress
McLane pumps summary from R/V Oceanus cruises OC449-02 and OC449-03 in the Eastern North Atlantic and Indian oceans in 2008 (SIRENA project)2011-05-23Preliminary and in progress
CTD profiles R/V Islandia cruise ISL0109 near the TENATSO (Tropical Eastern North Atlantic Time-Series Observatory) time series station Cape Verde. from 2009 to 2009 (SIRENA project)2011-05-20Preliminary and in progress
CTD profiles for OC449-03 from R/V Oceanus cruise OC449-03 in the Coastal transect between Cape Verde and Mauritanian coast from 2008 to 2008 (SIRENA project)2011-05-18Preliminary and in progress
MIT vane measurements from R/V Oceanus cruise OC449-03 in the Coastal transect between Cape Verde and Mauritanian coast in 2008 (SIRENA project)2011-05-11Preliminary and in progress
Upcast profiles from Seacat CTD on MacLane pump from R/V Oceanus cruises OC449-02, and OC449-03 in the Eastern Atlantic and Indian Oceans in 2008 (SIRENA project)2011-05-09Preliminary and in progress
Downcast profiles from Seacat CTD on MacLane pump from R/V Oceanus OC449-02 and OC449-03 in the Eastern North Atlantic and Indian oceans in 2008 (SIRENA project)2011-05-09Preliminary and in progress
Cruise Tracks from R/V Oceanus, R/V Islandia OC449-03, OC449-02,and ISL0109 in the Eastern Atlantic and Indian Oceans and TENATSO (Tropical Eastern North Atlantic Time-Series Observatory) station from 2008 to 2009 (SIRENA project)2011-05-04Preliminary and in progress
Station log from R/V Islandia, R/V Oceanus ISL0109, OC449-02, OC449-03 in the Eastern Atlantic and Indian oceans and TENATSO (Tropical Eastern North Atlantic Time-Series Observatory) time series station from 2008 to 2009 (SIRENA project)2011-05-03Preliminary and in progress

Project Home Page


People

Lead Principal Investigator: Phoebe J. Lam
Woods Hole Oceanographic Institution (WHOI)

Co-Principal Investigator: Kenneth O. Buesseler
Woods Hole Oceanographic Institution (WHOI)

Co-Principal Investigator: Dr Henrieta Dulaiova
University of Hawai'i (UH)


Programs

Ocean Carbon and Biogeochemistry [OCB]