Chifflard Peter, Boodoo Kyle S, Ditzel Lukas, Reiss Martin, Fasching Christina
Department of Geography, Philipps-University Marburg, Germany.
Department of Geography and Regional Research, Geoecology, University of Vienna, Austria; Environment and Climate Research Hub, University of Vienna, Austria.
Sci Total Environ. 2024 Dec 20;957:177366. doi: 10.1016/j.scitotenv.2024.177366. Epub 2024 Nov 13.
Despite their relatively large size, Icelandic glaciers, and their organic carbon (OC) fluxes, have not been explicitly considered in current global glacial OC flux calculations. Most global glacial OC estimates are based on limited individual flux estimates, often determined during the melt season, rarely accounting for the seasonal and diurnal variability of glacial dissolved organic matter (DOM). Using an annual dataset of 25 Icelandic glaciers (and their glacial streams) we investigate DOM concentration and composition, calculating an estimate for downstream OC fluxes from Icelandic glaciers, considering diurnal and seasonal variability. DOM source and composition distinctly changed from a terrestrial character toward a more proteinaceous character as melt increased, both on a seasonal and diurnal basis, likely reflecting the flow path of the meltwater. While DOC concentration did not change on a diurnal basis, DOM composition was more labile in the afternoons, possibly indicating photochemical or biological transformation processes. Overall, the glacial streams predominantly acted as CO sinks. However, higher DOC concentrations, along with contributions of more proteinaceous DOM in proglacial streams, led to a decrease in the uptake potential for CO. Finally, we estimated an export flux of 0.0026 ± 0.0029 Gg C yr km of DOC, and 0.011 ± 0.007 Tg C yr km of POC, from Icelandic glaciers. We reveal larger than previously assumed DOC and POC fluxes from Icelandic glaciers, with higher-than-global-average areal fluxes (~3 % and 9 % of global glacial C flux respectively). Our findings underscore the importance of revising current global estimates to include the not-fully-accounted-for contribution of Icelandic, and other glaciers. This is particularly important considering ongoing climatic changes will likely affect glacial meltwater discharge and sources, leading to altered DOM composition and DOC concentration, having potentially considerable consequences for glacial OC export and CO uptake potentials of glacial streams.
尽管冰岛的冰川规模相对较大，且有有机碳（OC）通量，但目前的全球冰川OC通量计算中并未明确考虑它们。大多数全球冰川OC估算基于有限的个别通量估算，这些估算通常在融化季节确定，很少考虑冰川溶解有机物质（DOM）的季节和昼夜变化。利用25条冰岛冰川（及其冰川溪流）的年度数据集，我们研究了DOM的浓度和组成，计算了冰岛冰川下游OC通量的估算值，同时考虑了昼夜和季节变化。随着融化量增加，无论是在季节还是昼夜尺度上，DOM的来源和组成都从陆地特征明显转变为更具蛋白质特征，这可能反映了融水的流动路径。虽然DOC浓度在昼夜尺度上没有变化，但DOM组成在下午更不稳定，这可能表明存在光化学或生物转化过程。总体而言，冰川溪流主要充当CO汇。然而，较高的DOC浓度，以及冰前溪流中更多蛋白质类DOM的贡献，导致了CO吸收潜力的下降。最后，我们估计冰岛冰川的DOC输出通量为0.0026±0.0029 Gg C yr km，POC输出通量为0.011±0.007 Tg C yr km。我们发现冰岛冰川的DOC和POC通量比之前假设的要大，其面积通量高于全球平均水平（分别约占全球冰川碳通量的3%和9%）。我们的研究结果强调了修订当前全球估算以纳入冰岛及其他冰川未被充分考虑的贡献的重要性。考虑到持续的气候变化可能会影响冰川融水排放和来源，导致DOM组成和DOC浓度改变，这对冰川OC输出和冰川溪流的CO吸收潜力可能产生重大影响，这一点尤为重要。
