The distribution of reactive iron in northern Gulf of Alaska coastal waters

Lippiatt, Sherry M.; Lohan, Maeve C.; Bruland, Kenneth W.

doi:10.1016/j.marchem.2010.04.007

Cited by 61 publications

(69 citation statements)

References 45 publications

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“…Fe distribution in Godthåbsfjord surface waters (Figures 6, 7) is typical in this respect and similar to observations made previously downstream of Alaskan glacial catchments (Lippiatt et al, 2010;Schroth et al, 2014). Whilst the surface freshwater layer in Godthåbsfjord is exported toward the fjord mouth in the summer circulation mode , the sheer length of the fjord (the closest glacial inputs are >100 km from the fjord mouth) is a mitigating factor in considering both dissolved and particulate Fe export to coastal waters (Figure 6).…”

Section: Fe Input and Potential Export To Coastal Seassupporting

confidence: 89%

“…As normally observed in both glacial discharge (Hawkings et al, 2014) and estuarine environments (Buck et al, 2007;Lippiatt et al, 2010), TdFe concentrations were much higher than DFe concentrations at every station. DFe was equivalent to a mean of 3% TdFe at GFx stations in May, 1% in August and 1% of TdFe at LTx stations.…”

Section: Particles and Fesupporting

confidence: 72%

“…Fjords are however a key influence on the physical dynamics and biogeochemistry of coastal waters around Greenland and yet their influence on Fe export from glaciers to coastal seawater has not previously been characterized. Here we demonstrate that due to a combination of the summer circulation mode in Godthåbsfjord, rapid iceberg melting, scavenging and the likely saturation of Fe ligands in fjord waters (Lippiatt et al, 2010;Thuroczy et al, 2012), almost all of the new Fe (dissolved and particulate) entering the fjord from glacial outflows in summer appears to be trapped within this fjord. There is thus no clear mechanism, other than possibly an increase in ligand concentration, via which increasing supply of meltwater could directly lead to increasing dissolved or particulate Fe concentrations in coastal or offshore waters.…”

Section: Discussionmentioning

confidence: 73%

“…The magnitude and speciation of Fe passing through estuaries may however vary seasonally (Mayer, 1982;Ozturk et al, 2002;Hopwood et al, 2014a), so it is not entirely clear whether it is generally correct to assume that river water DFe concentration is always proportional to DFe concentration in high salinity estuarine water. Whilst, to our knowledge, no measurements of trace metal ligand concentrations are available for a high latitude fjord environment, if ligands can limit DFe in estuaries (Buck et al, 2007) then the DFe capacity of high Fe, low DOC meltwater is always likely to be constrained by a low ligand concentration (Lippiatt et al, 2010). A major question beyond the scope of this manuscript is therefore how ligand concentrations will change within this environment as glaciers retreat and fresh water fluxes increase.…”

Section: Fe Input and Potential Export To Coastal Seasmentioning

confidence: 97%

“…As DFe is present at similar concentrations in May and August, despite very different water column properties, we can speculate that the concentration of DFe observed at stations GF2-9 may be at, or close to, a maximum value that cannot increase further without an increase in ligand concentration. Ligands within the vicinity of Fe-rich glacial outflows are likely to be saturated (Lippiatt et al, 2010;Thuroczy et al, 2012), so DFe export away from such Fe inputs may be "ligand limited." For rivers the fraction of DFe removed from the dissolved phase during transport through an estuary is normally estimated as a fixed percentage (typically 90-98%) of the freshwater Fe concentration (Boyle et al, 1977;Sholkovitz et al, 1978;Mayer, 1982).…”

Section: Fe Input and Potential Export To Coastal Seasmentioning

confidence: 99%

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Seasonal Changes in Fe along a Glaciated Greenlandic Fjord

et al. 2016

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Greenland's ice sheet is the second largest on Earth, and is under threat from a warming Arctic climate. An increase in freshwater discharge from Greenland has the potential to strongly influence the composition of adjacent water masses with the largest impact on marine ecosystems likely to be found within the glaciated fjords. Here we demonstrate that physical and chemical estuarine processes within a large Greenlandic fjord are critical factors in determining the fate of meltwater derived nutrients and particles, especially for non-conservative elements such as Fe. Concentrations of Fe and macronutrients in surface waters along Godthåbsfjord, a southwest Greenlandic fjord with freshwater input from six glaciers, changed markedly between the onset and peak of the meltwater season due to the development of a thin (<10 m), outflowing, low-salinity surface layer. Dissolved (<0.2 µm) Fe concentrations in meltwater entering Godthåbsfjord (200 nM), in freshly melted glacial ice (mean 38 nM) and in surface waters close to a land terminating glacial system (80 nM) all indicated high Fe inputs into the fjord in summer. Total dissolvable (unfiltered at pH <2.0) Fe was similarly high with concentrations always in excess of 100 nM throughout the fjord and reaching up to 5.0 µM close to glacial outflows in summer. Yet, despite the large seasonal freshwater influx into the fjord, Fe concentrations near the fjord mouth in the out-flowing surface layer were similar in summer to those measured before the meltwater season. Furthermore, turbidity profiles indicated that sub-glacial particulate Fe inputs may not actually mix into the outflowing surface layer of this fjord. Emphasis has previously been placed on the possibility of increased Fe export from Greenland as meltwater fluxes increase. Here we suggest that in-fjord processes may be effective at removing Fe from surface waters before it can be exported to coastal seas.

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Section: Fe Input and Potential Export To Coastal Seassupporting

confidence: 89%

Section: Particles and Fesupporting

confidence: 72%

Section: Discussionmentioning

confidence: 73%

Section: Fe Input and Potential Export To Coastal Seasmentioning

confidence: 97%

Section: Fe Input and Potential Export To Coastal Seasmentioning

confidence: 99%

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Seasonal Changes in Fe along a Glaciated Greenlandic Fjord

et al. 2016

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Seasonal and spatial variabilities in northern Gulf of Alaska surface water iron concentrations driven by shelf sediment resuspension, glacial meltwater, a Yakutat eddy, and dust

Crusius¹,

Schroth

Cullen

et al. 2017

Global Biogeochemical Cycles

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Phytoplankton growth in the Gulf of Alaska (GoA) is limited by iron (Fe), yet Fe sources are poorly constrained. We examine the temporal and spatial distributions of Fe, and its sources in the GoA, based on data from three cruises carried out in 2010 from the Copper River (AK) mouth to beyond the shelf break. April data are the first to describe late winter Fe behavior before surface water nitrate depletion began. Sediment resuspension during winter and spring storms generated high “total dissolvable Fe” (TDFe) concentrations of ~1000 nmol kg−1 along the entire continental shelf, which decreased beyond the shelf break. In July, high TDFe concentrations were similar on the shelf, but more spatially variable, and driven by low‐salinity glacial meltwater. Conversely, dissolved Fe (DFe) concentrations in surface waters were far lower and more seasonally consistent, ranging from ~4 nmol kg−1 in nearshore waters to ~0.6–1.5 nmol kg−1 seaward of the shelf break during April and July, despite dramatic depletion of nitrate over that period. The reasonably constant DFe concentrations are likely maintained during the year across the shelf by complexation by strong organic ligands, coupled with ample supply of labile particulate Fe. The April DFe data can be simulated using a simple numerical model that assumes a DFe flux from shelf sediments, horizontal transport by eddy diffusion, and removal by scavenging. Given how global change is altering many processes impacting the Fe cycle, additional studies are needed to examine controls on DFe in the Gulf of Alaska.

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Atmospheric deposition of glacial iron in the Gulf of Alaska impacted by the position of the Aleutian Low

Schroth

Crusius

Gassó

et al. 2017

Geophysical Research Letters

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Our understanding of glacial flour dust storm delivery of iron to the Gulf of Alaska (GoA) is limited. Here we interpret concurrent time series satellite, meteorological, and aerosol geochemical data from the GoA to examine how interannual variability in regional weather patterns impacts offshore aerosol glacial Fe deposition. In 2011, when a northerly Aleutian Low (AL) was persistent during fall, dust emission was suppressed and highly intermittent due to prevalent wet conditions, low winds, and a deep early season snowpack. Conversely, in 2012, frequent and prolonged fall dust storms and high offshore glacial Fe transport were driven by dry conditions and strong offshore winds generated by persistent strong high pressure over the Alaskan interior and Bering Sea and a southerly AL. Twenty‐five‐fold interannual variability in regional offshore glacial aerosol Fe deposition indicates that glacial dust's impact on GoA nutrient budgets is highly dynamic and particularly sensitive to regional climate forcing.

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The distribution of reactive iron in northern Gulf of Alaska coastal waters

Cited by 61 publications

References 45 publications

Seasonal Changes in Fe along a Glaciated Greenlandic Fjord

Seasonal Changes in Fe along a Glaciated Greenlandic Fjord

Seasonal and spatial variabilities in northern Gulf of Alaska surface water iron concentrations driven by shelf sediment resuspension, glacial meltwater, a Yakutat eddy, and dust

Atmospheric deposition of glacial iron in the Gulf of Alaska impacted by the position of the Aleutian Low

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