Surface ocean‐lower atmosphere interactions in the Northeast Pacific Ocean Gyre: Aerosols, iron, and the ecosystem response

Johnson, Kenneth S.; Elrod, Virginia A.; Fitzwater, Steve E.; Plant, Joshua N.; Chávez, Francisco P.; Tanner, Sara J.; Gordon, R. Michael; Westphal, Douglas L.; Perry, K. D.; Wu, Jingfeng; Karl, David M.

doi:10.1029/2002gb002004

Cited by 114 publications

(114 citation statements)

References 54 publications

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“…Johnson et al [2003] also found the inconsistency between the surface water aluminum and iron and the expected aerosol concentrations. They suggested a combined effect of higher solubility and higher aerosol scavenging rates (higher dust deposition rate) than generally assumed.…”

Section: Time Seriesmentioning

confidence: 97%

Constraining oceanic dust deposition using surface ocean dissolved Al

Qin

Moore

Zender

et al. 2008

Global Biogeochemical Cycles

101

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[1] We use measurements of ocean surface dissolved Al, a global Biogeochemical Elemental Cycling (BEC) ocean model, and the global Dust Entrainment and Deposition (DEAD) model to constrain dust deposition to the oceans. Our Al database contains all available measurements with best coverage in the Atlantic. Vertical profiles and seasonal data exist in limited regions. Observations show that surface dissolved Al is distributed similarly to the dust deposition predicted by DEAD and other models. There is an equatorial Atlantic Al maximum that decreases toward higher latitudes. There are high Al concentrations in the Mediterranean Sea and the Arabian Sea and low concentrations in the Pacific and the Southern Ocean. The ocean basins maintain more distinct Al profiles than Fe profiles in the upper ocean, consistent with a weaker biological influence on Al than Fe. The BEC-predicted surface dissolved Al compares relatively well with observations. The Al distribution reflects the combined effects of Al input from dust and Al removal by particle scavenging and biological uptake by diatoms. Model-observed biases suggest a southward shift of maximum dust deposition compared to current dust model predictions. DEAD appears to overestimate deposition north of 30°N in the Pacific and to underestimate deposition south of 30°N. Observed Al concentrations and the ocean model-predicted surface Al lifetime provide a semi-independent method to estimate oceanic dust deposition. This technique indicates that DEAD may overestimate dust deposition to the north equatorial Atlantic but underestimate in other Atlantic regions, the Southern Ocean, and the Arabian Sea. However, spatial variations in aerosol Al solubility may also contribute to the model-observation mismatch. Our results have implications for all dust-borne ocean nutrients including Fe and demonstrate the potential of marine geochemical data to constrain atmospheric aerosol deposition fields.

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Section: Time Seriesmentioning

confidence: 97%

Constraining oceanic dust deposition using surface ocean dissolved Al

Qin

Moore

Zender

et al. 2008

Global Biogeochemical Cycles

101

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“…The control run is forced with monthly mean [Mahowald et al, 2003] dust fluxes ( Figure 3). We assume a solubility of this iron of 2.5%, which is within the range (1-10%) suggested by recent studies [Jickells and Spokes, 2001;Duce and Tindale, 1991], but less than suggested by Johnson et al [2003] and Gao et al [2003].…”

Section: Gb1021 Dutkiewicz Et Al: Interactions Of the Iron And Phospmentioning

confidence: 99%

Interactions of the iron and phosphorus cycles: A three‐dimensional model study

Dutkiewicz

Follows

Parekh

2005

Global Biogeochemical Cycles

168

212

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[1] We use an ocean circulation, biogeochemistry, and ecosystem model to explore the interactions between ocean circulation, macro-and micro-nutrient supply to the euphotic layer, and biological productivity. The model suggests a tight coupling between the degree of iron limitation in the upwelling subpolar and tropical oceans and the productivity of the adjacent subtropical gyres. This coupling is facilitated by lateral Ekman transfer of macro-nutrients in the surface ocean. We describe a coarse resolution configuration of the MIT ocean circulation and biogeochemistry model in which there are fully prognostic representations of the oceanic cycles of phosphorus, iron, and silicon. The pelagic ecosystem is represented using two functional groups of phytoplankton and a single grazer. Using present-day forcing, the model qualitatively captures the observed basin and gyre scale patterns of nutrient distributions and productivity. In a suite of sensitivity studies we find significant regional variations in response to changes in the aeolian iron supply. In a dustier (model) world, the Southern Ocean and Indo-Pacific upwelling regions are more productive, but there is a decrease in productivity in the subtropical gyres and throughout the Atlantic basin. These results can be described most easily by a simple conceptual classification of the Southern and Indo-Pacific oceans into two regimes: (1) upwelling, iron limited regions and (2) macro-nutrient limited, oligotrophic subtropical gyres. Enhancing the aeolian iron supply to the upwelling regions relieves iron limitation and increases local primary and export production, but reduces the Ekman transfer of phosphate to the neighboring subtropical gyres. Consequently, over time, the gyres become further depleted in macro-nutrients and productivity decreases in response to global scale iron fertilization. In a large-scale analogy, the macro-nutrient budget of the Atlantic is maintained by lateral transfer of nutrients in the upper ocean. Enhanced aeolian supply of iron leads to increased productivity in the Southern Ocean and Indo-Pacific upwelling regions, reducing the lateral transfer of macro-nutrients to the Atlantic basin, which becomes increasingly macro-nutrient limited throughout.Citation: Dutkiewicz, S., M. J. Follows, and P. Parekh (2005), Interactions of the iron and phosphorus cycles: A three-dimensional model study, Global Biogeochem. Cycles, 19, GB1021,

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“…This phenomenon has been documented through decadal time-series measurements of aerosol-Al (Parrington et al, 1983) and Fe (Johnson et al, 2003) in Hawaii, and aerosol-232 Th in Japan (Hirose et al, 2012). Variability in dissolved Fe in surface waters at ALOHA station ( Fig.…”

Section: Seasonalitymentioning

confidence: 99%

Quantifying lithogenic inputs to the North Pacific Ocean using the long-lived thorium isotopes

Hayes

Anderson

Fleisher

et al. 2013

Earth and Planetary Science Letters

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Dissolved 232 Th is added to the ocean though the partial dissolution of lithogenic materials such as aerosol dust in the same way as other lithogenically sourced and more biologically important trace metals such as Fe. Oceanic 230 Th, on the other hand, is sourced primarily from the highly predictable decay of dissolved 234 U. The rate at which dissolved 232 Th is released by mineral dissolution can be constrained by a Th removal rate derived from 230 Th: 234 U disequilibria, assuming steady-state. Calculated fluxes of dissolved 232 Th can in turn be used to estimate fluxes of other lithogenically sourced dissolved metals as well as the original lithogenic supplies, such as aerosol dust deposition, given the concentration and fractional solubility of Th (or other metals) in the lithogenic material. This method is applied to 7 water column profiles from the Innovative North Pacific Experiment (INOPEX) cruise of 2009 and 2 sites from the subtropical North Pacific. The structure of shallow depth profiles suggests rapid scavenging at the surface and at least partial regeneration of dissolved 232 Th at 100-200 m depth. This rapid cycling could involve colloidal Th generated during mineral dissolution, which may not be subject to the same removal rates as the more truly dissolved 230 Th. An additional deep source of 232 Th was revealed in deep waters, most likely dissolution of seafloor sediments, and offers a constraint on dissolved trace element supply due to boundary exchange.

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Surface ocean‐lower atmosphere interactions in the Northeast Pacific Ocean Gyre: Aerosols, iron, and the ecosystem response

Cited by 114 publications

References 54 publications

Constraining oceanic dust deposition using surface ocean dissolved Al

Constraining oceanic dust deposition using surface ocean dissolved Al

Interactions of the iron and phosphorus cycles: A three‐dimensional model study

Quantifying lithogenic inputs to the North Pacific Ocean using the long-lived thorium isotopes

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