Preston Cosslett Kemeny, Gen K. Li, Madison Douglas, William Berelson, Austin J. Chadwick, Nathan F. Dalleska, Michael P. Lamb, William Larsen, John S. Magyar, Nick E. Rollins, Joel Rowland, M. Isabel Smith, Mark A. Torres, Samuel M. Webb, Woodward W. Fischer, A. Joshua West
{"title":"Arctic Permafrost Thawing Enhances Sulfide Oxidation","authors":"Preston Cosslett Kemeny, Gen K. Li, Madison Douglas, William Berelson, Austin J. Chadwick, Nathan F. Dalleska, Michael P. Lamb, William Larsen, John S. Magyar, Nick E. Rollins, Joel Rowland, M. Isabel Smith, Mark A. Torres, Samuel M. Webb, Woodward W. Fischer, A. Joshua West","doi":"10.1029/2022GB007644","DOIUrl":null,"url":null,"abstract":"<p>Permafrost degradation is altering biogeochemical processes throughout the Arctic. Thaw-induced changes in organic matter transformations and mineral weathering reactions are impacting fluxes of inorganic carbon (IC) and alkalinity (ALK) in Arctic rivers. However, the net impact of these changing fluxes on the concentration of carbon dioxide in the atmosphere (<i>p</i>CO<sub>2</sub>) is relatively unconstrained. Resolving this uncertainty is important as thaw-driven changes in the fluxes of IC and ALK could produce feedbacks in the global carbon cycle. Enhanced production of sulfuric acid through sulfide oxidation is particularly poorly quantified despite its potential to remove ALK from the ocean-atmosphere system and increase <i>p</i>CO<sub>2</sub>, producing a positive feedback leading to more warming and permafrost degradation. In this work, we quantified weathering in the Koyukuk River, a major tributary of the Yukon River draining discontinuous permafrost in central Alaska, based on water and sediment samples collected near the village of Huslia in summer 2018. Using measurements of major ion abundances and sulfate (<math>\n <semantics>\n <mrow>\n <msup>\n <mrow>\n <msub>\n <mtext>SO</mtext>\n <mn>4</mn>\n </msub>\n </mrow>\n <mrow>\n <mn>2</mn>\n <mo>−</mo>\n </mrow>\n </msup>\n </mrow>\n <annotation> ${{\\text{SO}}_{4}}^{2-}$</annotation>\n </semantics></math>) sulfur (<sup>34</sup>S/<sup>32</sup>S) and oxygen (<sup>18</sup>O/<sup>16</sup>O) isotope ratios, we employed the MEANDIR inversion model to quantify the relative importance of a suite of weathering processes and their net impact on <i>p</i>CO<sub>2</sub>. Calculations found that approximately 80% of <math>\n <semantics>\n <mrow>\n <msup>\n <mrow>\n <msub>\n <mtext>SO</mtext>\n <mn>4</mn>\n </msub>\n </mrow>\n <mrow>\n <mn>2</mn>\n <mo>−</mo>\n </mrow>\n </msup>\n </mrow>\n <annotation> ${{\\text{SO}}_{4}}^{2-}$</annotation>\n </semantics></math> in mainstem samples derived from sulfide oxidation with the remainder from evaporite dissolution. Moreover, <sup>34</sup>S/<sup>32</sup>S ratios, <sup>13</sup>C/<sup>12</sup>C ratios of dissolved IC, and sulfur X-ray absorption spectra of mainstem, secondary channel, and floodplain pore fluid and sediment samples revealed modest degrees of microbial sulfate reduction within the floodplain. Weathering fluxes of ALK and IC result in lower values of <i>p</i>CO<sub>2</sub> over timescales shorter than carbonate compensation (∼10<sup>4</sup> yr) and, for mainstem samples, higher values of <i>p</i>CO<sub>2</sub> over timescales longer than carbonate compensation but shorter than the residence time of marine <math>\n <semantics>\n <mrow>\n <msup>\n <mrow>\n <msub>\n <mtext>SO</mtext>\n <mn>4</mn>\n </msub>\n </mrow>\n <mrow>\n <mn>2</mn>\n <mo>−</mo>\n </mrow>\n </msup>\n </mrow>\n <annotation> ${{\\text{SO}}_{4}}^{2-}$</annotation>\n </semantics></math> (∼10<sup>7</sup> yr). Furthermore, the absolute concentrations of <math>\n <semantics>\n <mrow>\n <msup>\n <mrow>\n <msub>\n <mtext>SO</mtext>\n <mn>4</mn>\n </msub>\n </mrow>\n <mrow>\n <mn>2</mn>\n <mo>−</mo>\n </mrow>\n </msup>\n </mrow>\n <annotation> ${{\\text{SO}}_{4}}^{2-}$</annotation>\n </semantics></math> and Mg<sup>2+</sup> in the Koyukuk River, as well as the ratios of <math>\n <semantics>\n <mrow>\n <msup>\n <mrow>\n <msub>\n <mtext>SO</mtext>\n <mn>4</mn>\n </msub>\n </mrow>\n <mrow>\n <mn>2</mn>\n <mo>−</mo>\n </mrow>\n </msup>\n </mrow>\n <annotation> ${{\\text{SO}}_{4}}^{2-}$</annotation>\n </semantics></math> and Mg<sup>2+</sup> to other dissolved weathering products, have increased over the past 50 years. Through analogy to similar trends in the Yukon River, we interpret these changes as reflecting enhanced sulfide oxidation due to ongoing exposure of previously frozen sediment and changes in the contributions of shallow and deep flow paths to the active channel. Overall, these findings confirm that sulfide oxidation is a substantial outcome of permafrost degradation and that the sulfur cycle responds to permafrost thaw with a timescale-dependent feedback on warming.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":null,"pages":null},"PeriodicalIF":5.4000,"publicationDate":"2023-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2022GB007644","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Global Biogeochemical Cycles","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1029/2022GB007644","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENVIRONMENTAL SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
Permafrost degradation is altering biogeochemical processes throughout the Arctic. Thaw-induced changes in organic matter transformations and mineral weathering reactions are impacting fluxes of inorganic carbon (IC) and alkalinity (ALK) in Arctic rivers. However, the net impact of these changing fluxes on the concentration of carbon dioxide in the atmosphere (pCO2) is relatively unconstrained. Resolving this uncertainty is important as thaw-driven changes in the fluxes of IC and ALK could produce feedbacks in the global carbon cycle. Enhanced production of sulfuric acid through sulfide oxidation is particularly poorly quantified despite its potential to remove ALK from the ocean-atmosphere system and increase pCO2, producing a positive feedback leading to more warming and permafrost degradation. In this work, we quantified weathering in the Koyukuk River, a major tributary of the Yukon River draining discontinuous permafrost in central Alaska, based on water and sediment samples collected near the village of Huslia in summer 2018. Using measurements of major ion abundances and sulfate () sulfur (34S/32S) and oxygen (18O/16O) isotope ratios, we employed the MEANDIR inversion model to quantify the relative importance of a suite of weathering processes and their net impact on pCO2. Calculations found that approximately 80% of in mainstem samples derived from sulfide oxidation with the remainder from evaporite dissolution. Moreover, 34S/32S ratios, 13C/12C ratios of dissolved IC, and sulfur X-ray absorption spectra of mainstem, secondary channel, and floodplain pore fluid and sediment samples revealed modest degrees of microbial sulfate reduction within the floodplain. Weathering fluxes of ALK and IC result in lower values of pCO2 over timescales shorter than carbonate compensation (∼104 yr) and, for mainstem samples, higher values of pCO2 over timescales longer than carbonate compensation but shorter than the residence time of marine (∼107 yr). Furthermore, the absolute concentrations of and Mg2+ in the Koyukuk River, as well as the ratios of and Mg2+ to other dissolved weathering products, have increased over the past 50 years. Through analogy to similar trends in the Yukon River, we interpret these changes as reflecting enhanced sulfide oxidation due to ongoing exposure of previously frozen sediment and changes in the contributions of shallow and deep flow paths to the active channel. Overall, these findings confirm that sulfide oxidation is a substantial outcome of permafrost degradation and that the sulfur cycle responds to permafrost thaw with a timescale-dependent feedback on warming.
期刊介绍:
Global Biogeochemical Cycles (GBC) features research on regional to global biogeochemical interactions, as well as more local studies that demonstrate fundamental implications for biogeochemical processing at regional or global scales. Published papers draw on a wide array of methods and knowledge and extend in time from the deep geologic past to recent historical and potential future interactions. This broad scope includes studies that elucidate human activities as interactive components of biogeochemical cycles and physical Earth Systems including climate. Authors are required to make their work accessible to a broad interdisciplinary range of scientists.