The effects of dilution and mixed layer depth on deliberate ocean iron fertilization: 1-D simulations of the southern ocean iron experiment (SOFeX)

Krishnamurthy, Aparna; Moore, J. Keith; Doney, Scott C.

doi:10.1016/j.jmarsys.2007.07.002

Cited by 11 publications

(12 citation statements)

References 39 publications

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“…ic dust input is realistic compared to field experiments [Moore et al, 2004[Moore et al, , 2006Krishnamurthy et al, 2008]. This indicates that this model is appropriate for studying the relationship between atmospheric dust input and ocean Al concentration.…”

Section: Global Biogeochemical Modelmentioning

confidence: 73%

“…The BEC model realistically simulates the biogenic silica production as well as the ocean circulation (e.g., mixed layer depth, element transport) which helps us estimate dust deposition from dissolved Al. Sensitivity tests indicate that the model response to variations in atmospher- ic dust input is realistic compared to field experiments [Moore et al, 2004[Moore et al, , 2006Krishnamurthy et al, 2008]. This indicates that this model is appropriate for studying the relationship between atmospheric dust input and ocean Al concentration.…”

Section: Global Biogeochemical Modelmentioning

confidence: 81%

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Constraining oceanic dust deposition using surface ocean dissolved Al

Qin

Moore

Zender

et al. 2008

Global Biogeochemical Cycles

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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: Global Biogeochemical Modelmentioning

confidence: 73%

Section: Global Biogeochemical Modelmentioning

confidence: 81%

Constraining oceanic dust deposition using surface ocean dissolved Al

Qin

Moore

Zender

et al. 2008

Global Biogeochemical Cycles

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101

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“…Variability in primary production and sinking POC is tightly linked to variations in nutrient availability and the light regime. Around islands and plateaus, trends in phytoplankton production were mainly driven by light availability, because light often limits phytoplankton growth more in these iron‐enriched waters, in part due to self‐shading at higher chlorophyll concentrations [ de Baar et al , 2005; Krishnamurthy et al , 2008]. Iron concentration change was the major driver for production trends in the open ocean, which depends on local mixing processes, atmospheric deposition, and lateral transport.…”

Section: Resultsmentioning

confidence: 99%

“…Our results suggest that SO phytoplankton productivity is sensitive to climate change and has significant impacts on the SO carbon cycle, especially in high‐productivity regions. A number of previous studies have suggested that iron‐light co‐limitation is common in the Southern Ocean [ Boyd et al , 1999, 2001; Boyd , 2002; de Baar et al , 2005; Krishnamurthy et al , 2008]. However, coarse resolution circulation models tend to underestimate mixed layer depths in this region, potentially missing a key control on biological productivity.…”

Section: Discussionmentioning

confidence: 99%

Variability of primary production and air‐sea CO₂ flux in the Southern Ocean

Wang¹,

Moore²

2012

Global Biogeochemical Cycles

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[1] Biogeochemical cycling in the Southern Ocean (SO) plays a key role in the global sea-air CO 2 balance and in the ocean anthropogenic carbon inventory (Ito et al., 2010;Khatiwala et al., 2009;Sarmiento et al., 2004). Some previous studies suggest a decreasing trend in the Southern Ocean carbon sink (Le Quéré et al., 2007;Lovenduski et al., 2007;Wetzel et al., 2005). We investigate the interannual and decadal variations in sea-air CO 2 flux and phytoplankton production in the SO with hindcast simulations by an ocean biogeochemical model. Decreasing trends in sinking POC and primary production are found from 1979 to 2003, concurrent with a decreasing trend in carbon uptake from the atmosphere. Simulations show substantial interannual and decadal variability in productivity. The sea-air CO 2 flux is significantly correlated with sinking POC, especially in high productivity regions of the Southern Ocean. Both mixed layer depths and iron concentrations are important to the long-term trends in production and phytoplankton community structure. Sea ice cover also plays an important role at high latitudes. Variability in dust deposition in recent decades has little influence on total SO productivity and carbon uptake, however, there are regional impacts near dust source regions. Accurately representing mixed layer depths and their impacts on phytoplankton light stress are critical for understanding how climate change impacts SO ecosystems and biogeochemistry.

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“…They suggested that as mixed layer depth increases, light‐limitation of phytoplankton becomes increasingly important in restraining the bloom due to self‐shading (light absorption by phytoplankton) within the mixed layer. Krishnamurthy et al [2007] conducted 1D simulations of the Southern Ocean Iron Experiment (SOFeX) to examine the relative roles of light and nutrients with iron additions and with ambient nutrients. At the South Patch location (within the SIZ) there was a strong impact of wind speed and corresponding changes in mixed layer depth under iron‐fertilized conditions.…”

Section: Introductionmentioning

confidence: 99%

Wind speed influence on phytoplankton bloom dynamics in the Southern Ocean Marginal Ice Zone

Fitch¹,

Moore²

2007

J. Geophys. Res.

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[1] Analysis of satellite ocean color and wind speed data within the seasonal ice zone (SIZ) of the Southern Ocean sheds light on the physical processes that influence phytoplankton biomass distributions. A compilation of monthly averaged chlorophyll and percent sea ice cover data within the SIZ from 1997 to 2005 has been compared with monthly average wind speed data from 1999 to 2005. The size of the marginal ice zone (MIZ, areas of recent ice retreat) was fairly consistent from year to year, always peaking in December, with a mean area of 6.0 million km 2 . The mean area within the MIZ with phytoplankton blooms (chlorophyll exceeding 0.8 mg/m 3 ) was 0.36 million km 2 . While the bloom areal extent seems small compared to the MIZ, in reality, because of gaps in the chlorophyll data, blooming regions comprise a much larger fraction of the MIZ. Considering only areas with valid chlorophyll data, the percentage of the MIZ with blooms was 17%, 21%, and 24% for the months of December, January, and February, respectively. December always has the largest MIZ area, but MIZ mean chlorophyll concentrations sometimes do not peak until February. Wind speed strongly impacts phytoplankton bloom dynamics within the MIZ. There is an inverse relation between wind speed and bloom occurrence, with blooms largely suppressed at high wind speeds. At low wind speeds ($5 m/s), blooms are observed over about one third of the MIZ. Blooms are also much more frequent near the continent than in offshore waters, likely due to increased iron availability. Open ocean phytoplankton blooms in the Southern Ocean are likely to become iron-light co-limited except in regions where the mixed layer depth is relatively shallow.

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The effects of dilution and mixed layer depth on deliberate ocean iron fertilization: 1-D simulations of the southern ocean iron experiment (SOFeX)

Cited by 11 publications

References 39 publications

Constraining oceanic dust deposition using surface ocean dissolved Al

Constraining oceanic dust deposition using surface ocean dissolved Al

Variability of primary production and air‐sea CO₂ flux in the Southern Ocean

Wind speed influence on phytoplankton bloom dynamics in the Southern Ocean Marginal Ice Zone

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The effects of dilution and mixed layer depth on deliberate ocean iron fertilization: 1-D simulations of the southern ocean iron experiment (SOFeX)

Cited by 11 publications

References 39 publications

Constraining oceanic dust deposition using surface ocean dissolved Al

Constraining oceanic dust deposition using surface ocean dissolved Al

Variability of primary production and air‐sea CO2 flux in the Southern Ocean

Wind speed influence on phytoplankton bloom dynamics in the Southern Ocean Marginal Ice Zone

Contact Info

Product

Resources

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Variability of primary production and air‐sea CO₂ flux in the Southern Ocean