Glacial dust surpasses both volcanic ash and desert dust in its iron fertilization potential

Bess G. Koffman; Meg F. Yoder; Taylor Methven; Lena Hanschka; Helen B. Sears; Patrick L. Saylor; Kristi L. Wallace

doi:10.1029/2020gb006821

Home/Archive/USGS

USGS · 70260135

Glacial dust surpasses both volcanic ash and desert dust in its iron fertilization potential

Bess G. Koffman·Meg F. Yoder·Taylor Methven·Lena Hanschka·Helen B. Sears·Patrick L. Saylor·Kristi L. Wallace

View original source ↗Export metadata ↓

Abstract

The subarctic Pacific Ocean and Bering Sea comprise the second-largest high nitrate, low chlorophyll region in the world, where primary production is limited by the availability of iron (Fe). To estimate the potential impact of different terrestrial aerosol Fe sources on marine ecosystems, we performed a suite of laboratory assessments following established protocols, including: (1) leaching with Milli-Q water, (2) sequential extractions, (3) complete acid digestions, (4) X-ray diffraction, and (5) grain size analysis. Measurements were performed on 20 fine-grained (<5 μm) glacier-derived sediments from Alaska and the Yukon, two fresh, never-wetted volcanic ashes (Redoubt 2009 and Pavlof 2016), and six weathered ashes (Redoubt and Augustine) which span the past ~8,700 years. We compared results to published data on Asian desert-derived sediments, finding that the glacier-derived sediments have five times higher easily reducible Fe (median 2.3 ± 0.6 wt.%) than desert-derived samples (0.49 ± 0.1 wt.%) and fourteen times higher easily reducible Fe than fresh ash (0.16 ± 0.1 wt.%). In addition, fractional Fe solubility was higher in glacial sediment (median cumulative 0.31 ± 0.11% FeS) than volcanic ash (0.04 ± 0.02% FeS). Glacial sediments contained higher concentrations of other bioactive metals including Co, Ni, Cu, Zn, Mo, Cd, and Pb. Results suggest that glacier-derived dust may provide the subarctic Pacific with more bioavailable iron per unit mass than either volcanic ash or Asian desert-derived dust.

Explore related subjects

Global Biogeochemical Cycles Article

Source-reported bounding extent: 54.60514707536916° to 64.07015039411576° latitude; -162.65841833672906° to -141.37301895851397° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Bess G. Koffman, Meg F. Yoder, Taylor Methven, Lena Hanschka, Helen B. Sears, Patrick L. Saylor, Kristi L. Wallace. 2021-04-18. Glacial dust surpasses both volcanic ash and desert dust in its iron fertilization potential. https://doi.org/10.1029/2020gb006821

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Global carbon investment in terrestrial biological nitrogen fixation

Biological nitrogen (N) fixation (BNF) provides the N needed to produce proteins and other biological building blocks, helping feed humanity and mitigate climate change. Due to its high energetic cost compared to other forms of N acquisition, biotic investment in BNF indicates N limitation. Globally gridded BNF flux data provide an opportunity to determine the energetic investment in BNF across ecosystems, which would help reconcile conflicting indicators of N limitation. Here, we use a new BNF synthesis to quantify the relative importance of BNF in different N-fixing niches, in different biomes, and across the globe by calculating the fraction of net primary productivity (NPP) invested in BNF and the fraction of plant N acquisition provided by BNF. Larger fractions of non-agricultural NPP were invested in BNF in less-productive, higher-latitude biomes. This pattern was driven by biocrusts and mosses. Similarly, non-agricultural symbiotic N-fixing plants invested relatively more of their own NPP in BNF in less-productive, higher-latitude biomes. This symbiotic plant pattern was driven by shrubs and herbs, overriding the opposite pattern in trees. Symbiotic plants also acquired a higher fraction of their N from BNF at higher latitudes and in less productive biomes. Investments in symbiotic BNF were 10× higher in agricultural (2.9% of NPP) versus natural (0.29%) biomes, providing 26% versus 3.1% of ecosystem-scale plant N acquisition. These results support the paradigm of strong N limitation at higher latitudes, help understand the rarity of N-fixing trees at higher latitudes, underscore the dominance of human activity, and inform terrestrial biosphere models.

Global Biogeochemical Cycles↗

USGS2026

Erosional and hydrological controls on the age and thermochemical stability of particulate organic carbon in an Arctic river

Understanding the mechanisms that drive the mobilization and fate of organic carbon (OC) in Arctic landscapes is important for modeling the feedbacks among permafrost thaw, carbon cycling, and climate change. While significant progress has been made toward measuring in situ OC decomposition in permafrost soils and bulk particulate organic carbon (POC) export from Arctic rivers, few studies have distinguished the source and lability of POC across Arctic landscapes, limiting our ability to predict whether mobilized POC will be oxidized to CO 2 and CH 4 or buried in downstream depositional environments. This study uses ramped pyrolysis/oxidation radiocarbon (RPO- 14 C) analyses to investigate spatial and temporal variations in the thermochemical stability and radiocarbon content of fluvial POC during downstream transport from mountains to the coast in the Canning River (North Slope, Alaska). Fluvial POC in the headwaters is predominantly comprised of high activation energy, thermally recalcitrant petrogenic OC (OC petro ) derived from shale bedrock. Moving into the foothills and low-relief coastal plains, river bank erosion primarily drives mobilization of labile, low activation energy, soil-derived OC (OC soil ). Fluvial POC in mountainous upstream reaches consisted of ∼70% OC petro and just ∼30% OC soil , while POC in the downstream coastal plain reaches comprised ∼85% OC soil and ∼15% OC petro . The high relative lability of POC exported to the coast indicates high susceptibility to oxidation and microbial decomposition, which could enhance CO 2 release as the Arctic hydrologic cycle intensifies. However, the persistence of refractory OC petro in the suspended load indicates the potential for long-term burial of rock organic carbon in marine sediments.

Alaska↗

USGS2026

Net CO2 emissions from dry inland waters persist in the presence of vegetation

Many inland waters are shrinking due to shifts in climate and water diversion for human uses. As they dry out, their exposed sediments emit large amounts of carbon dioxide (CO 2 ) to the atmosphere. However, current global estimates of CO 2 emissions from dry inland waters are derived exclusively from bare sediment dark-chamber measurements that do not account for the colonization of desiccated areas by vegetation. To understand the impact of vegetation on CO 2 emissions from dry sediments, we analyzed 164 dry inland water bodies across five climatic regions and five inland water body types (lakes, ponds, reservoirs, streams and wetlands). On average, within vegetated zones, vegetation occupied 47 ± 35% in measured biomass quadrants. Light-induced decreases in instantaneous CO 2 emissions in vegetated dry sediments were lower (mean ± SD = −3.7 ± 12.9 mmol CO 2 m −2 hr −1 ) than increases during dark conditions (14.7 ± 20.1 mmol CO 2 m −2 hr −1 ). Diel (24-hr) CO 2 emissions from dry, vegetated sediments (mean ± SD = 100 ± 261 mmol CO 2 m −2 d −1 ) were 25% lower than in bare sediments (133 ± 245 mmol CO 2 m −2 d −1 ). These results indicate that vegetation can partially off-set sediment respiration, although the magnitude of this effect is insufficient to switch dry beds from net sources to net sinks of carbon.

Global Biogeochemical Cycles↗