An improved estimate of microbially mediated carbon fluxes from the Greenland ice sheet
An improved estimate of microbially mediated carbon fluxes from the Greenland ice sheet
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DOI：
10.3189/2012jog12j001
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发表时间：
2012-01-01
影响因子：
3.4
通讯作者：
Huybrechts, P.
中科院分区：
文献类型：
--
作者：
Cook, J. M.;Hodson, A. J.;Huybrechts, P.
Hodson 等人 (2010) 最近通过测量碎片（冰石）表面覆盖度以及与冰盖边缘附近碎片相关的生物生产速率，对格陵兰冰盖 (GrIS) 表面微生物介导的碳通量进行了量化。我们提出的更新模型不假设 Hodson 等人 (2010) 使用的关键参数具有相同的空间均匀性，因为它们利用了来自 GrIS 79 公里横断面的生物量分布和生物生产数据。此外，这里提出的模型还首次包括与冰石孔和表面藻类相关的生物量。田间横断面周围一小部分冰（1600 km(2)）的预测年碳通量约为该地区使用空间均匀生物量和产量估计的四倍。当包括表层藻类时，该模型预测每年通过光合作用的碳固定量比仅使用冰晶石的模型多约 11 倍。因此，我们认为，GrIS 的冰上碳通量之前被低估了一个数量级以上，而迄今为止被忽视的地表藻类生态系统可能是最关键的贡献者。根据我们的模型，GrIS 显示处于相对稳定的净自养状态，因此裸冰面积和总碳通量之间的紧密联系是显而易见的。这意味着生物量反馈到地表反照率并因此增强了烧蚀。 2100 年的气候预测表明，气候变暖也可能导致更大的碳固定。
Microbially mediated carbon fluxes on the surface of the Greenland ice sheet (GrIS) were recently quantified by Hodson and others (2010) using measurements of the surface coverage of debris (cryoconite) and rates of biological production associated with debris near the ice-sheet margin. We present updated models that do not assume the same spatial uniformity in key parameters employed by Hodson and others (2010) because they make use of biomass distribution and biological production data from a 79 km transect of the GrIS. Further, the models presented here also include for the first time biomass associated with both cryoconite holes and surficial algae. The predicted annual carbon flux for a small (1600 km(2)) section of ice surrounding the field transect is about four times that estimated using spatially uniform biomass and production in this area. When surficial algae are included, the model predicts about 11 times more carbon fixation via photosynthesis per year than the cryoconite-only models. We therefore suggest that supraglacial carbon fluxes from the GrIS have previously been underestimated by more than an order of magnitude and that the hitherto overlooked surficial algal ecosystem can be the most crucial contributor. The GrIS is shown to be in a relatively stable state of net autotrophy according to our model and so a strong link between bare-ice area and total carbon fluxes is evident. The implication is a biomass feedback to surface albedo and enhanced ablation as a result. Climate predictions for the year 2100 show that greater carbon fixation could also result from climate warming.