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

Schroth, Andrew W.; Crusius, John; Gassó, Santiago; Moy, Christopher M.; Buck, Nathaniel J.; Campbell, Robert W.

doi:10.1002/2017gl073565

Cited by 18 publications

(50 citation statements)

References 34 publications

(52 reference statements)

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“…The FeA and FeD contents in Icelandic dust are similar to what were measured by Raiswell et al (2016) in ice-hosted sediments: 0.03 wt %-0.2 wt % for FeA and 0.04 wt %-0.7 wt % for FeD. Previous research investigated the initial fractional Fe solubility of dust from glacial sediments in the Copper River valley, an important source of Fe for the Gulf of Alaska, which is Fe limited (Crusius et al, 2011;Schroth et al, 2009Schroth et al, , 2017. Glacial dust and sediments showed high initial fractional Fe solubility, which was associated with a low degree of chemical weathering (Schroth et al, 2009(Schroth et al, , 2017.…”

Section: Factors Controlling Fe Solubility In Icelandic Dustsupporting

confidence: 67%

“…The imaginary part of the complex refractive index (k), responsible for absorption, was 0.01 (λ = 647 nm), which is around 1 order of magnitude higher than the average values for natural dust from the Sahel (0.002, λ = 660 nm) and northern-Africa-Sahara and eastern Asia (0.001, λ = 660 nm) (Di Biagio et al, 2019). In the shortwave spectrum, the k values reported in literature for volcanic ash from Iceland range from around 0.0001 to 0.02 (Ball et al, 2015;Bukowiecki et al, 2011;Derimian et al, 2012;Hervo et al, 2012;Reed et al, 2017;Rocha-Lima et al, 2014;Schumann et al, 2011;Toledano et al, 2012;Vogel et al, 2017;Weinzierl et al, 2012), which makes it difficult to evaluate the absorption properties of volcanic dust.…”

Section: Implications For the Soluble Fe Deposition To The Oceanmentioning

confidence: 69%

“…Previous research investigated the initial fractional Fe solubility of dust from glacial sediments in the Copper River valley, an important source of Fe for the Gulf of Alaska, which is Fe limited (Crusius et al, 2011;Schroth et al, 2009Schroth et al, , 2017. Glacial dust and sediments showed high initial fractional Fe solubility, which was associated with a low degree of chemical weathering (Schroth et al, 2009(Schroth et al, , 2017. The initial fractional Fe solubility reported for the glacial dust from the Copper River valley is 1.4 % (multiple leaches in Milli-Q water), 2-14 times higher than the initial Fe solubility observed for Icelandic dust.…”

Section: Factors Controlling Fe Solubility In Icelandic Dustmentioning

confidence: 99%

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Distinct chemical and mineralogical composition of Icelandic dust compared to northern African and Asian dust

Baldo

Formenti

Nowak³

et al. 2020

Atmos. Chem. Phys.

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Abstract. Iceland is a highly active source of natural dust. Icelandic dust has the potential to directly affect the climate via dust–radiation interaction and indirectly via dust–cloud interaction, the snow/ice albedo effect and impacts on biogeochemical cycles. The impacts of Icelandic dust depend on its mineralogical and chemical composition. However, a lack of data has prevented an accurate assessment of the role of Icelandic dust in the Earth system. Here, we collected surface sediment samples from five major Icelandic dust hotspots. Dust aerosols were generated and suspended in atmospheric chambers, and PM10 and PM20 fractions were collected for further analysis. We found that the dust samples primarily consist of amorphous basaltic materials ranging from 8 wt % (from the Hagavatn hotspot) to 60 wt %–90 wt % (other hotspots). Samples had relatively high total Fe content (10 wt %–13 wt %). Sequential extraction of Fe to determine its chemical form shows that dithionite Fe (Fe oxides such as hematite and goethite) and ascorbate Fe (amorphous Fe) contribute respectively 1 %–6 % and 0.3 %–1.4 % to the total Fe in Icelandic dust. The magnetite fraction is 7 %–15 % of total Fe and 1 %–2 wt % of PM10, which is orders of magnitude higher than in mineral dust from northern Africa. Nevertheless, about 80 %–90% of the Fe is contained in pyroxene and amorphous glass. The initial Fe solubility (ammonium acetate extraction at pH 4.7) is from 0.08 % to 0.6 %, which is comparable to low-latitude dust such as that from northern Africa. The Fe solubility at low pH (i.e. pH 2) is significantly higher than typical low-latitude dust (up to 30 % at pH 2 after 72 h). Our results revealed the fundamental differences in composition and mineralogy of Icelandic dust from low-latitude dust. We attribute these differences to the low degree of chemical weathering, the basaltic composition of the parent sediments and glacial processes. Icelandic dust contributes to the atmospheric deposition of soluble Fe and can impact primary productivity in the North Atlantic Ocean. The distinct chemical and mineralogical composition, particularly the high magnetite content (1 wt %–2 wt %), indicates a potentially significant impact of Icelandic dust on the radiation balance in the subpolar and polar regions.

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Section: Factors Controlling Fe Solubility In Icelandic Dustsupporting

confidence: 67%

Section: Implications For the Soluble Fe Deposition To The Oceanmentioning

confidence: 69%

Section: Factors Controlling Fe Solubility In Icelandic Dustmentioning

confidence: 99%

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Distinct chemical and mineralogical composition of Icelandic dust compared to northern African and Asian dust

Baldo

Formenti

Nowak³

et al. 2020

Atmos. Chem. Phys.

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“…Shoenfelt et al [116] recently proposed that nutrients contained in dust originating from glacigenic sources at high latitudes show higher levels of bioavailability and thus a stronger potential to influence on the oceans bioproductivity and thus the global carbon cycle. Strong interannual variability in dust storm occurrence and thus dust deposition fluxes lead to significant interannual variability in iron deposition fluxes as shown by Schroth et al [117] for the Gulf of Alaska.…”

Section: Blowing With the Wind: Atmospheric Transport Of Mineral Dustmentioning

confidence: 85%

Transport of Mineral Dust and Its Impact on Climate

Schepanski

2018

Geosciences

138

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Mineral dust plays a pivotal role in the Earth's system. Dust modulates the global energy budget directly via its interactions with radiation and indirectly via its influence on cloud and precipitation formation processes. Dust is a micro-nutrient and fertilizer for ecosystems due to its mineralogical composition and thus impacts on the global carbon cycle. Hence, dust aerosol is an essential part of weather and climate. Dust suspended in the air is determined by the atmospheric dust cycle: Dust sources and emission processes define the amount of dust entrained into the atmosphere. Atmospheric mixing and circulation carry plumes of dust to remote places. Ultimately, dust particles are removed from the atmosphere by deposition processes such as gravitational settling and rain wash out. During its residence time, dust interacts with and thus modulates the atmosphere resulting into changes such as in surface temperature, wind, clouds, and precipitation rates. There are still uncertainties regarding individual dust interactions and their relevance. Dust modulates key processes that are inevitably influencing the Earth energy budget. Dust transport allows for these interactions and at the same time, the intermittency of dust transport introduces additional fluctuations into a complex and challenging system.

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“…Fe-limited. Dust storms emanating from glacierized river valleys along the northern GoA coastline have been shown to transport dust hundreds of kilometers beyond the shelf break in the late autumn [e.g., Crusius et al, 2011;Schroth et al, 2017], while dust from the Gobi and other deserts have been reported in this region in the spring [Zdanowicz et al, 2006;Yasunari et al, 2007]. The annual dust flux to the eastern subarctic North Pacific ocean has been estimated by several different independent methods to be approximately 1 g m À2 a À1 (Table 2).…”

Section: 1002/2016gb005493mentioning

confidence: 99%

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

Cited by 18 publications

References 34 publications

Distinct chemical and mineralogical composition of Icelandic dust compared to northern African and Asian dust

Distinct chemical and mineralogical composition of Icelandic dust compared to northern African and Asian dust

Transport of Mineral Dust and Its Impact on Climate

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

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