Carbon dating reveals a seasonal progression in the source of particulate organic carbon exported from the Greenland Ice Sheet
Carbon dating reveals a seasonal progression in the source of particulate organic carbon exported from the Greenland Ice Sheet
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DOI：
10.1002/2017gl073219
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发表时间：
2017-06
影响因子：
5.2
通讯作者：
T. Kohler;J. Žárský;J. Yde;G. Lamarche-Gagnon;J. Hawkings;A. Tedstone;J. Wadham;J. Box;A. Beaton;M. Stibal
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文献类型：
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作者：
T. Kohler;J. Žárský;J. Yde;G. Lamarche-Gagnon;J. Hawkings;A. Tedstone;J. Wadham;J. Box;A. Beaton;M. Stibal
格陵兰冰盖（GrIS）的表面融化收集了颗粒有机碳（POC），因为它排入冰下环境并将其运输到下游，在那里它作为微生物基质。我们假设，随着夏季冰下排水网络向冰川上游扩展，较老的POC被融水带走。为了验证这一点，在消融季节从GrIS流出的融水河流中收集了POC样本，并测定了14C。结果与融水水化学和集水区的卫星观测值进行了比较。发现POC年龄从~5000年B.P.增加到~9000年B.P.，直到峰值流量和流域规模。随后，观测到POC年龄的显著波动，这被解释为冰川下水文压力和沉积物供应以及随后的枯竭期的高低。这些观测结果表明，从GrIS输出的POC来源存在季节性变化，并为冰下排水系统的季节性演变提供了证据。
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.