The iron isotopic composition of subglacial streams draining the Greenland ice sheet
In this study, we present the first measurements of iron (Fe) stable isotopic composition (δ56Fe) of subglacial streams draining the Greenland Ice Sheet (GIS). We measure the δ56Fe values [(δ56Fe, ‰ = (56Fe/54Fe)sample/(56Fe/54Fe)standard − 1) × 103] of both dissolved and suspended sediment Fe in su...
Published in: | Geochimica et Cosmochimica Acta |
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Elsevier
2017
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ftucambridgeesc:oai:eprints.esc.cam.ac.uk:4006 2023-05-15T16:21:25+02:00 The iron isotopic composition of subglacial streams draining the Greenland ice sheet Stevenson, E. I. Fantle, M. S. Das, S. B. Williams, H. M. Aciego, S. M. 2017 text http://eprints.esc.cam.ac.uk/4006/ http://eprints.esc.cam.ac.uk/4006/1/1-s2.0-S0016703717303502-main.pdf http://eprints.esc.cam.ac.uk/4006/2/1-s2.0-S0016703717303502-mmc2.pdf http://eprints.esc.cam.ac.uk/4006/3/1-s2.0-S0016703717303502-mmc1.xlsx https://doi.org/10.1016/j.gca.2017.06.002 en eng Elsevier http://eprints.esc.cam.ac.uk/4006/1/1-s2.0-S0016703717303502-main.pdf http://eprints.esc.cam.ac.uk/4006/2/1-s2.0-S0016703717303502-mmc2.pdf http://eprints.esc.cam.ac.uk/4006/3/1-s2.0-S0016703717303502-mmc1.xlsx Stevenson, E. I. and Fantle, M. S. and Das, S. B. and Williams, H. M. and Aciego, S. M. (2017) The iron isotopic composition of subglacial streams draining the Greenland ice sheet. Geochimica Et Cosmochimica Acta, 213. pp. 237-254. ISSN 0016-7037 DOI https://doi.org/10.1016/j.gca.2017.06.002 <https://doi.org/10.1016/j.gca.2017.06.002> cc_by CC-BY 01 - Climate Change and Earth-Ocean Atmosphere Systems Article PeerReviewed 2017 ftucambridgeesc https://doi.org/10.1016/j.gca.2017.06.002 2020-08-27T18:09:52Z In this study, we present the first measurements of iron (Fe) stable isotopic composition (δ56Fe) of subglacial streams draining the Greenland Ice Sheet (GIS). We measure the δ56Fe values [(δ56Fe, ‰ = (56Fe/54Fe)sample/(56Fe/54Fe)standard − 1) × 103] of both dissolved and suspended sediment Fe in subglacial outflows from five distinct land-terminating glaciers. Suspended sediments have δ56Fe values that lie within the crustal array (δ56Fe ∼ 0‰). In contrast, the δ56Fe values of dissolved Fe in subglacial outflows are consistently less than 0‰, reaching a minimum of −2.1‰ in the outflow from the Russell Glacier. The δ56Fe values of dissolved Fe vary geographically and on daily time scales. Major element chemistry and mineral saturation state modeling suggest that incongruent silicate weathering and sulfide oxidation are the likely drivers of subglacial stream Fe chemistry, and that the extent of chemical weathering influences the δ56Fe of dissolved Fe. The largest difference in δ56Fe between dissolved and suspended load is −2.1‰, and occurs in the subglacial system from the Russell glacier (southwest GIS). Major element chemistry indicates this outflow to be the least chemically weathered, while more mature subglacial systems (i.e., that exhibit greater extents of subglacial weathering) have dissolved loads with δ56Fe that are indistinguishable from suspended sediments (Δ56Fesuspended-dissolved ∼ 0‰). Ultimately, the dissolved Fe generated in some subglacial systems from the GIS is a previously unrecognized source of isotopically light Fe into the hydrosphere. The data illustrate that the dissolved Fe supplied by subglacial weathering can have variable δ56Fe values depending on the degree of chemical weathering. Thus, Fe isotopes have potential as a proxy for subglacial chemical weathering intensity or mode. Finally, based on our regional Fe concentration measurements from each glacial outflow, we estimate a flux weighted continental scale dissolved iron export of 2.1 Gg Fe yr−1 to the coastal ocean, which is within the range of previous estimates. Article in Journal/Newspaper glacier Greenland Ice Sheet University of Cambridge, Department of Earth Sciences: ESC Publications Greenland Geochimica et Cosmochimica Acta 213 237 254 |
institution |
Open Polar |
collection |
University of Cambridge, Department of Earth Sciences: ESC Publications |
op_collection_id |
ftucambridgeesc |
language |
English |
topic |
01 - Climate Change and Earth-Ocean Atmosphere Systems |
spellingShingle |
01 - Climate Change and Earth-Ocean Atmosphere Systems Stevenson, E. I. Fantle, M. S. Das, S. B. Williams, H. M. Aciego, S. M. The iron isotopic composition of subglacial streams draining the Greenland ice sheet |
topic_facet |
01 - Climate Change and Earth-Ocean Atmosphere Systems |
description |
In this study, we present the first measurements of iron (Fe) stable isotopic composition (δ56Fe) of subglacial streams draining the Greenland Ice Sheet (GIS). We measure the δ56Fe values [(δ56Fe, ‰ = (56Fe/54Fe)sample/(56Fe/54Fe)standard − 1) × 103] of both dissolved and suspended sediment Fe in subglacial outflows from five distinct land-terminating glaciers. Suspended sediments have δ56Fe values that lie within the crustal array (δ56Fe ∼ 0‰). In contrast, the δ56Fe values of dissolved Fe in subglacial outflows are consistently less than 0‰, reaching a minimum of −2.1‰ in the outflow from the Russell Glacier. The δ56Fe values of dissolved Fe vary geographically and on daily time scales. Major element chemistry and mineral saturation state modeling suggest that incongruent silicate weathering and sulfide oxidation are the likely drivers of subglacial stream Fe chemistry, and that the extent of chemical weathering influences the δ56Fe of dissolved Fe. The largest difference in δ56Fe between dissolved and suspended load is −2.1‰, and occurs in the subglacial system from the Russell glacier (southwest GIS). Major element chemistry indicates this outflow to be the least chemically weathered, while more mature subglacial systems (i.e., that exhibit greater extents of subglacial weathering) have dissolved loads with δ56Fe that are indistinguishable from suspended sediments (Δ56Fesuspended-dissolved ∼ 0‰). Ultimately, the dissolved Fe generated in some subglacial systems from the GIS is a previously unrecognized source of isotopically light Fe into the hydrosphere. The data illustrate that the dissolved Fe supplied by subglacial weathering can have variable δ56Fe values depending on the degree of chemical weathering. Thus, Fe isotopes have potential as a proxy for subglacial chemical weathering intensity or mode. Finally, based on our regional Fe concentration measurements from each glacial outflow, we estimate a flux weighted continental scale dissolved iron export of 2.1 Gg Fe yr−1 to the coastal ocean, which is within the range of previous estimates. |
format |
Article in Journal/Newspaper |
author |
Stevenson, E. I. Fantle, M. S. Das, S. B. Williams, H. M. Aciego, S. M. |
author_facet |
Stevenson, E. I. Fantle, M. S. Das, S. B. Williams, H. M. Aciego, S. M. |
author_sort |
Stevenson, E. I. |
title |
The iron isotopic composition of subglacial streams draining the Greenland ice sheet |
title_short |
The iron isotopic composition of subglacial streams draining the Greenland ice sheet |
title_full |
The iron isotopic composition of subglacial streams draining the Greenland ice sheet |
title_fullStr |
The iron isotopic composition of subglacial streams draining the Greenland ice sheet |
title_full_unstemmed |
The iron isotopic composition of subglacial streams draining the Greenland ice sheet |
title_sort |
iron isotopic composition of subglacial streams draining the greenland ice sheet |
publisher |
Elsevier |
publishDate |
2017 |
url |
http://eprints.esc.cam.ac.uk/4006/ http://eprints.esc.cam.ac.uk/4006/1/1-s2.0-S0016703717303502-main.pdf http://eprints.esc.cam.ac.uk/4006/2/1-s2.0-S0016703717303502-mmc2.pdf http://eprints.esc.cam.ac.uk/4006/3/1-s2.0-S0016703717303502-mmc1.xlsx https://doi.org/10.1016/j.gca.2017.06.002 |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
glacier Greenland Ice Sheet |
genre_facet |
glacier Greenland Ice Sheet |
op_relation |
http://eprints.esc.cam.ac.uk/4006/1/1-s2.0-S0016703717303502-main.pdf http://eprints.esc.cam.ac.uk/4006/2/1-s2.0-S0016703717303502-mmc2.pdf http://eprints.esc.cam.ac.uk/4006/3/1-s2.0-S0016703717303502-mmc1.xlsx Stevenson, E. I. and Fantle, M. S. and Das, S. B. and Williams, H. M. and Aciego, S. M. (2017) The iron isotopic composition of subglacial streams draining the Greenland ice sheet. Geochimica Et Cosmochimica Acta, 213. pp. 237-254. ISSN 0016-7037 DOI https://doi.org/10.1016/j.gca.2017.06.002 <https://doi.org/10.1016/j.gca.2017.06.002> |
op_rights |
cc_by |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1016/j.gca.2017.06.002 |
container_title |
Geochimica et Cosmochimica Acta |
container_volume |
213 |
container_start_page |
237 |
op_container_end_page |
254 |
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1766009416113455104 |