Total Fe Flux. Al (derived from Ti) Flux. Al Flux. Figure 2. LWCC set up for the analysis of labile Fe species using the ferrozine method. Figure 3 . Particle dry deposition velocity data for deposition on a water surface in a wind tunnel (Slinn et al., 1978). R/V Kilo Moana. Fe (II) Flux.
Al (derived from Ti) Flux
Figure 2. LWCC set up for the analysis of labile Fe species using the ferrozine method.
Figure 3. Particle dry deposition velocity data for deposition on a water surface in a wind tunnel (Slinn et al., 1978)
R/V Kilo Moana
Fe (II) Flux
Figure 5. Al fluxes based on measured Al (left) and Ti concentrations (right). Assumes a crustal average Ti/Al ratio of ~0.063 [Taylor and McLennan, 1985]
Easily reducible Fe(III) Flux
Figure 1: From left: high volume cascade impactor, R/V Kilo Moana, EUCFe 2006 Cruise track.
Total Labile Fe Flux
Figure 6. NO3- fluxes versus Sample ID.
Figure 4. Fe fluxes to the three distinct regions of the cruise vs. Sample ID. Top: total Fe; middle left Fe(II); middle right: Fe(III)hydrox, and bottom: total labile Fe.
Atmospheric trace metal and labile iron deposition fluxes to the equatorial Pacific during EUCFe2006
In the equatorial Pacific Ocean iron limitation persists despite the existence of the equatorial undercurrent which carries high loads of nutrients. Deposition of atmospheric particles may constitute another important pathway for which iron is delivered to this remote ocean, where only sparse atmospheric data exists. We collected aerosols over the Equatorial Pacific Ocean between Hawaii and Papua New Guinea during the EUCFe cruise (R/V Kilo Moana in Aug-Oct 2006) as part of the larger campaign to characterize the various iron sources to this region. Ahigh-volume cascade impactor operating at 760 L min-1 was used to resolve aerosols in four size fractions. Samples were digested and analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and long pathlength absorbance spectroscopy for trace metals and iron speciation respectively. The high-flow rate and particle size fractionation enabled greater temporal and spatial resolution that allows us to estimate fluxes with unprecedented precision.
Iron (Fe) is an essential micronutrient necessary for the metabolic processes (e.g., photosynthesis and cellular respiration) of marine phytoplankton in remote ocean regions considered High-Nutrient-Low-Chlorophyll (HNLC). The equatorial Pacific Ocean (EPO) is unique in that it contains the world’s most expansive HNLC region. [Chavez and Barber, 1987] suggested that because of its vastness and large proportion, the equatorial Pacific could account for up to 50% of global new production.
The equatorial Pacific is characterized as an upwelling zone where the supply of major nutrients from below leads to some enhancement of biological production [Turner and Hunter, 2001]. Yet iron limitation persists despite the existence of the equatorial undercurrent, and it is thought that the main delivery pathway for iron to this region is the atmosphere. Measurements of iron flux to this particular part of the world’s ocean remains limited, and therefore atmospheric influence on phytoplankton productivity is unknown in this region with high global production potential. Although assumed to be small [Gao et al., 2001; Raemdonck et al., 1986] this atmospheric contribution of Fe may control productivity in this vast oceanic region, analogous to results of a Southern Ocean study by [Cassar et al., 2007]. Therefore, the present study addresses the delivery and deposition of nutrients, with a particular focus on iron and its speciation, to this unique ocean basin, providing a much needed data set to the oceanography and atmospheric scientific communities.
This research was supported by National Science Foundation Grant ATM-0137891 and Central Washington University.
People: Dr. Jim Murray, CWU Atmospheric Chemistry Group
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