Carbon dating reveals a seasonal progression in the source of particulate organic carbon exported from the Greenland Ice Sheet

T. J. Kohler; J. D. Žárský; J. C. Yde; G. Lamarche-Gagnon; J. R. Hawkings; A. J. Tedstone; J. L. Wadham; J. E. Box; Alex D Beaton; Marek Stibal

doi:10.1002/2017GL073219

Carbon dating reveals a seasonal progression in the source of particulate organic carbon exported from the Greenland Ice Sheet

T. J. Kohler^*, J. D. Žárský, J. C. Yde, G. Lamarche-Gagnon, J. R. Hawkings, A. J. Tedstone, J. L. Wadham, J. E. Box, Alex D Beaton, Marek Stibal

^*Corresponding author for this work

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Abstract

Surface melt from the Greenland Ice Sheet (GrIS) collects particulate organic carbon (POC) as it drains into subglacial environments and transports it downstream where it serves as a microbial substrate. We hypothesized that older POC is entrained by meltwaters as the subglacial drainage network expands upglacier over the summer. To test this, POC samples were collected from a meltwater river exiting the GrIS over an ablation season and ¹⁴C dated. Resulting values were compared with meltwater hydrochemistry and satellite observations of the catchment area. We found that POC ages increased from ~5000 to ~9000 years B.P. until peak discharge and catchment size. Afterward, significant fluctuations in POC age were observed, interpreted to result from periods of high and low subglacial hydrological pressure and sediment supply and subsequent exhaustion. These observations suggest a seasonal progression in the source of POC exported from the GrIS and provide evidence for a seasonally evolving subglacial drainage system.

Original language	English
Pages (from-to)	6209-6217
Number of pages	9
Journal	Geophysical Research Letters
Volume	44
Issue number	12
Early online date	22 Jun 2017
DOIs	https://doi.org/10.1002/2017GL073219
Publication status	Published - 28 Jun 2017

Keywords

glacial hydrology
Kangerlussuaq
Leverett Glacier
meltwater export
particulate organic carbon
subglacial drainage system

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Kohler, T. J., Žárský, J. D., Yde, J. C., Lamarche-Gagnon, G., Hawkings, J. R., Tedstone, A. J., Wadham, J. L., Box, J. E., Beaton, A. D., & Stibal, M. (2017). Carbon dating reveals a seasonal progression in the source of particulate organic carbon exported from the Greenland Ice Sheet. Geophysical Research Letters, 44(12), 6209-6217. https://doi.org/10.1002/2017GL073219

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abstract = "Surface melt from the Greenland Ice Sheet (GrIS) collects particulate organic carbon (POC) as it drains into subglacial environments and transports it downstream where it serves as a microbial substrate. We hypothesized that older POC is entrained by meltwaters as the subglacial drainage network expands upglacier over the summer. To test this, POC samples were collected from a meltwater river exiting the GrIS over an ablation season and 14C dated. Resulting values were compared with meltwater hydrochemistry and satellite observations of the catchment area. We found that POC ages increased from ~5000 to ~9000 years B.P. until peak discharge and catchment size. Afterward, significant fluctuations in POC age were observed, interpreted to result from periods of high and low subglacial hydrological pressure and sediment supply and subsequent exhaustion. These observations suggest a seasonal progression in the source of POC exported from the GrIS and provide evidence for a seasonally evolving subglacial drainage system.",

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author = "Kohler, {T. J.} and {\v Z}{\'a}rsk{\'y}, {J. D.} and Yde, {J. C.} and G. Lamarche-Gagnon and Hawkings, {J. R.} and Tedstone, {A. J.} and Wadham, {J. L.} and Box, {J. E.} and Beaton, {Alex D} and Marek Stibal",

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doi = "10.1002/2017GL073219",

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AU - Kohler, T. J.

AU - Žárský, J. D.

AU - Yde, J. C.

AU - Lamarche-Gagnon, G.

AU - Hawkings, J. R.

AU - Tedstone, A. J.

AU - Wadham, J. L.

AU - Box, J. E.

AU - Beaton, Alex D

AU - Stibal, Marek

PY - 2017/6/28

Y1 - 2017/6/28

N2 - Surface melt from the Greenland Ice Sheet (GrIS) collects particulate organic carbon (POC) as it drains into subglacial environments and transports it downstream where it serves as a microbial substrate. We hypothesized that older POC is entrained by meltwaters as the subglacial drainage network expands upglacier over the summer. To test this, POC samples were collected from a meltwater river exiting the GrIS over an ablation season and 14C dated. Resulting values were compared with meltwater hydrochemistry and satellite observations of the catchment area. We found that POC ages increased from ~5000 to ~9000 years B.P. until peak discharge and catchment size. Afterward, significant fluctuations in POC age were observed, interpreted to result from periods of high and low subglacial hydrological pressure and sediment supply and subsequent exhaustion. These observations suggest a seasonal progression in the source of POC exported from the GrIS and provide evidence for a seasonally evolving subglacial drainage system.

AB - Surface melt from the Greenland Ice Sheet (GrIS) collects particulate organic carbon (POC) as it drains into subglacial environments and transports it downstream where it serves as a microbial substrate. We hypothesized that older POC is entrained by meltwaters as the subglacial drainage network expands upglacier over the summer. To test this, POC samples were collected from a meltwater river exiting the GrIS over an ablation season and 14C dated. Resulting values were compared with meltwater hydrochemistry and satellite observations of the catchment area. We found that POC ages increased from ~5000 to ~9000 years B.P. until peak discharge and catchment size. Afterward, significant fluctuations in POC age were observed, interpreted to result from periods of high and low subglacial hydrological pressure and sediment supply and subsequent exhaustion. These observations suggest a seasonal progression in the source of POC exported from the GrIS and provide evidence for a seasonally evolving subglacial drainage system.

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KW - Leverett Glacier

KW - meltwater export

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Carbon dating reveals a seasonal progression in the source of particulate organic carbon exported from the Greenland Ice Sheet

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DELVE: Development and validation of first generation chemical sensors for icy ecosystems

BIOGENIC PRODUCTION OF CLIMATIC AMPLIFIERS UNDER ICE

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Carbon dating reveals a seasonal progression in the source of particulate organic carbon exported from the Greenland Ice Sheet

Abstract

Keywords

Access to Document

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Projects

DELVE: Development and validation of first generation chemical sensors for icy ecosystems

BIOGENIC PRODUCTION OF CLIMATIC AMPLIFIERS UNDER ICE

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