Seasonal variability of organic matter composition in an Alaskan glacier outflow: insights into glacier carbon sources
Glacier ecosystems are a significant source of bioavailable, yet ancient dissolved organic carbon (DOC). Characterizing DOC in Mendenhall Glacier outflow (southeast Alaska) we document a seasonal persistence to the radiocarbon-depleted signature of DOC, highlighting ancient DOC as a ubiquitous featu...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2014-01-01
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| Series: | Environmental Research Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.1088/1748-9326/9/5/055005 |
| _version_ | 1797747915451531264 |
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| author | Robert G M Spencer Andrew Vermilyea Jason Fellman Peter Raymond Aron Stubbins Durelle Scott Eran Hood |
| author_facet | Robert G M Spencer Andrew Vermilyea Jason Fellman Peter Raymond Aron Stubbins Durelle Scott Eran Hood |
| author_sort | Robert G M Spencer |
| collection | DOAJ |
| description | Glacier ecosystems are a significant source of bioavailable, yet ancient dissolved organic carbon (DOC). Characterizing DOC in Mendenhall Glacier outflow (southeast Alaska) we document a seasonal persistence to the radiocarbon-depleted signature of DOC, highlighting ancient DOC as a ubiquitous feature of glacier outflow. We observed no systematic depletion in Δ ^14 C-DOC with increasing discharge during the melt season that would suggest mobilization of an aged subglacial carbon store. However, DOC concentration, δ ^13 C-DOC, Δ ^14 C-DOC and fluorescence signatures appear to have been influenced by runoff from vegetated hillslopes above the glacier during onset and senescence of melt. In the peak glacier melt period, the Δ ^14 C-DOC of stream samples at the outflow (−181.7 to −355.3‰) was comparable to the Δ ^14 C-DOC for snow samples from the accumulation zone (−207.2 to −390.9‰), suggesting that ancient DOC from the glacier surface is exported in glacier runoff. The pre-aged DOC in glacier snow and runoff is consistent with contributions from fossil fuel combustion sources similar to those documented previously in ice cores and thus provides evidence for anthropogenic perturbation of the carbon cycle. Overall, our results emphasize the need to further characterize DOC inputs to glacier ecosystems, particularly in light of predicted changes in glacier mass and runoff in the coming century. |
| first_indexed | 2024-03-12T15:57:28Z |
| format | Article |
| id | doaj.art-354423b2ecab478285e477b3af8a0634 |
| institution | Directory Open Access Journal |
| issn | 1748-9326 |
| language | English |
| last_indexed | 2024-03-12T15:57:28Z |
| publishDate | 2014-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | Environmental Research Letters |
| spelling | doaj.art-354423b2ecab478285e477b3af8a06342023-08-09T14:46:02ZengIOP PublishingEnvironmental Research Letters1748-93262014-01-019505500510.1088/1748-9326/9/5/055005Seasonal variability of organic matter composition in an Alaskan glacier outflow: insights into glacier carbon sourcesRobert G M Spencer0Andrew Vermilyea1Jason Fellman2Peter Raymond3Aron Stubbins4Durelle Scott5Eran Hood6Woods Hole Research Center, 149 Woods Hole Road, Falmouth, Massachusetts 02540, USANatural Sciences Department, Jeffords Science Center, Castleton State College, Vermont 05735, USAEnvironmental Science and Geography Program, University of Alaska Southeast , Juneau, Alaska 99801, USAYale School of Forestry and Environmental Studies, Yale University , New Haven, Connecticut 06405, USASkidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, Georgia 31411, USADepartment of Biological Systems Engineering, Virginia Tech, Blacksburg, Virginia 24061, USAEnvironmental Science and Geography Program, University of Alaska Southeast , Juneau, Alaska 99801, USAGlacier ecosystems are a significant source of bioavailable, yet ancient dissolved organic carbon (DOC). Characterizing DOC in Mendenhall Glacier outflow (southeast Alaska) we document a seasonal persistence to the radiocarbon-depleted signature of DOC, highlighting ancient DOC as a ubiquitous feature of glacier outflow. We observed no systematic depletion in Δ ^14 C-DOC with increasing discharge during the melt season that would suggest mobilization of an aged subglacial carbon store. However, DOC concentration, δ ^13 C-DOC, Δ ^14 C-DOC and fluorescence signatures appear to have been influenced by runoff from vegetated hillslopes above the glacier during onset and senescence of melt. In the peak glacier melt period, the Δ ^14 C-DOC of stream samples at the outflow (−181.7 to −355.3‰) was comparable to the Δ ^14 C-DOC for snow samples from the accumulation zone (−207.2 to −390.9‰), suggesting that ancient DOC from the glacier surface is exported in glacier runoff. The pre-aged DOC in glacier snow and runoff is consistent with contributions from fossil fuel combustion sources similar to those documented previously in ice cores and thus provides evidence for anthropogenic perturbation of the carbon cycle. Overall, our results emphasize the need to further characterize DOC inputs to glacier ecosystems, particularly in light of predicted changes in glacier mass and runoff in the coming century.https://doi.org/10.1088/1748-9326/9/5/055005glacierorganic matterdissolved organic carbonradiocarbonAlaska |
| spellingShingle | Robert G M Spencer Andrew Vermilyea Jason Fellman Peter Raymond Aron Stubbins Durelle Scott Eran Hood Seasonal variability of organic matter composition in an Alaskan glacier outflow: insights into glacier carbon sources Environmental Research Letters glacier organic matter dissolved organic carbon radiocarbon Alaska |
| title | Seasonal variability of organic matter composition in an Alaskan glacier outflow: insights into glacier carbon sources |
| title_full | Seasonal variability of organic matter composition in an Alaskan glacier outflow: insights into glacier carbon sources |
| title_fullStr | Seasonal variability of organic matter composition in an Alaskan glacier outflow: insights into glacier carbon sources |
| title_full_unstemmed | Seasonal variability of organic matter composition in an Alaskan glacier outflow: insights into glacier carbon sources |
| title_short | Seasonal variability of organic matter composition in an Alaskan glacier outflow: insights into glacier carbon sources |
| title_sort | seasonal variability of organic matter composition in an alaskan glacier outflow insights into glacier carbon sources |
| topic | glacier organic matter dissolved organic carbon radiocarbon Alaska |
| url | https://doi.org/10.1088/1748-9326/9/5/055005 |
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