Investigation of subglacial weathering under the Greenland Ice Sheet using silicon isotopes

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11310%2F19%3A10407804" target="_blank" >RIV/00216208:11310/19:10407804 - isvavai.cz</a>

Výsledek na webu

<a href="https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=-Zu5lhbH35" target="_blank" >https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=-Zu5lhbH35</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.gca.2018.12.033" target="_blank" >10.1016/j.gca.2018.12.033</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Investigation of subglacial weathering under the Greenland Ice Sheet using silicon isotopes

Popis výsledku v původním jazyce

Subglacial chemical weathering plays a key role in global silicate weathering budgets, contributing to the cycling of silicon (Si) in terrestrial and marine systems and the potential drawdown of carbon dioxide from the atmosphere. Here, we use data from two Greenland Ice Sheet (GrIS) catchments to demonstrate how Si isotopes from dissolved and amorphous particulate fractions (delta30DSi and delta30 ASi respectively) can be used together with major ion data to assess the degree of secondary silicate weathering product formation and redissolution in subglacial environments. We compare a time-series of summer melt seasons from the two study sites, which differ in catchment size (similar to 600 km2 for Leverett Glacier (LG) and similar to 36 km2 for Kiattuut Sermiat (KS)). Subglacial waters from LG have elevated Na+ and K+ ions in relation to Ca (2+) and Mg2+ ions, indicating a predominance of silicate weathering, whilst meltwaters from KS are characterised by carbonate weathering (hydrolysis and carbonation) throughout the melt season. Both catchments have mean delta30DSi values substantially lower than average riverine values (KS 0.41 parts per thousand, LG -0.25 parts per thousand, versus a global riverine mean of 1.25 parts per thousand) and display a seasonal decline, which is more pronounced at LG. The delta30 ASi values (discharge weighted mean values KS -0.44 per mille parts per thousand, LG -0.22 per mille parts per thousand) are lighter than the bedrock (mean values KS -0.18 +/- 0.12 per mille parts per thousand, LG 0.00 +/- 0.07 per mille parts per thousand) in both catchments, indicating a secondary weathering product origin or leaching of lighter isotopes during initial weathering of crushed rock. When used in combination, the major ion and silicon isotope data reveal that the extent of silicate weathering and secondary phase redissolution are more pronounced at LG compared to KS. Contrasting weathering regimes and subglacial hydrology between catchments need to be considered when estimating the delta Si-30 composition of silica exported into polar oceans from the GrIS, with larger catchments likely to produce fluxes of lighter delta Si-30. As larger catchments dominate freshwater export to the ocean, GrIS meltwater is likely to be very light in isotopic composition, and the flux is likely to increase with ice melt as the climate warms.

Název v anglickém jazyce

Investigation of subglacial weathering under the Greenland Ice Sheet using silicon isotopes

Popis výsledku anglicky

Subglacial chemical weathering plays a key role in global silicate weathering budgets, contributing to the cycling of silicon (Si) in terrestrial and marine systems and the potential drawdown of carbon dioxide from the atmosphere. Here, we use data from two Greenland Ice Sheet (GrIS) catchments to demonstrate how Si isotopes from dissolved and amorphous particulate fractions (delta30DSi and delta30 ASi respectively) can be used together with major ion data to assess the degree of secondary silicate weathering product formation and redissolution in subglacial environments. We compare a time-series of summer melt seasons from the two study sites, which differ in catchment size (similar to 600 km2 for Leverett Glacier (LG) and similar to 36 km2 for Kiattuut Sermiat (KS)). Subglacial waters from LG have elevated Na+ and K+ ions in relation to Ca (2+) and Mg2+ ions, indicating a predominance of silicate weathering, whilst meltwaters from KS are characterised by carbonate weathering (hydrolysis and carbonation) throughout the melt season. Both catchments have mean delta30DSi values substantially lower than average riverine values (KS 0.41 parts per thousand, LG -0.25 parts per thousand, versus a global riverine mean of 1.25 parts per thousand) and display a seasonal decline, which is more pronounced at LG. The delta30 ASi values (discharge weighted mean values KS -0.44 per mille parts per thousand, LG -0.22 per mille parts per thousand) are lighter than the bedrock (mean values KS -0.18 +/- 0.12 per mille parts per thousand, LG 0.00 +/- 0.07 per mille parts per thousand) in both catchments, indicating a secondary weathering product origin or leaching of lighter isotopes during initial weathering of crushed rock. When used in combination, the major ion and silicon isotope data reveal that the extent of silicate weathering and secondary phase redissolution are more pronounced at LG compared to KS. Contrasting weathering regimes and subglacial hydrology between catchments need to be considered when estimating the delta Si-30 composition of silica exported into polar oceans from the GrIS, with larger catchments likely to produce fluxes of lighter delta Si-30. As larger catchments dominate freshwater export to the ocean, GrIS meltwater is likely to be very light in isotopic composition, and the flux is likely to increase with ice melt as the climate warms.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10511 - Environmental sciences (social aspects to be 5.7)

Projekt

<a href="/cs/project/GJ15-17346Y" target="_blank" >GJ15-17346Y: Světlé zítřky subglaciálních ekosystémů: Dopady odledňování na mikrobiální aktivitu a koloběh uhlíku pod ledovci</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2019

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Geochimica et Cosmochimica Acta

ISSN

0016-7037

e-ISSN

—

Svazek periodika

247

Číslo periodika v rámci svazku

January

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

16

Strana od-do

191-206

Kód UT WoS článku

000456159500012

EID výsledku v databázi Scopus

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