Long term records and impacts of glacially-fed river systems in Patagonia

这项研究的重点是在Chubut河（阿根廷）的河流地貌和沉积动力学的长期变化。其目的是发展地貌历史，并测试负责地貌发展的时间变化的环境驱动因素。第四纪科学家研究巴塔哥尼亚冰盖的过去行为，以帮助理解和预测当代气候变化的环境影响（Darvill等人，2017; Boex等人，2013; Glasser等人，2008）。冰盖及其冰川的扩张和退缩会导致与之相关的环境系统的地貌变化。这包括冰前湖，已对其高分辨率纹层记录进行了研究（Bendle等人，2017）。然而，广泛的网络的河流系统，排水冰盖融化的水取决于冰的程度，是在该地区的研究不足，尽管是高度敏感的冰动力学和环境changes.Research方法，这项研究开始与地形图使用遥感数据，如航空图像的里约丘布特识别地貌单位，表明过去的环境条件。小规模的度量数据，如通道宽度和曲折波长已被收集到废弃的河道，以推断历史供水和系统中的能量水平。实地工作已于二零一九年十月/十一月完成，当中进行了地球物理调查、沉积物描述及发光测年取样，以分别收集更多有关河道特征、沉积物供应的数据及界定变化的年代。野外收集的数据最终将为基于发光的地貌年表提供信息（将于第2年完成）和水文地貌建模（将于第3年完成），可检验有关河流变化的幅度、频率和时间尺度的假设。鉴于冰川消退与冰块的脱钩以及与南部西风带的相互作用，和其他水文气候参数，如厄尔尼诺/南方涛动（ENSO），冰川沃茨水从河流系统的损失是一个日益关注的巴塔哥尼亚形成一个关键的供水来源。描述过去河流系统在冰期、冰消期和冰后期的动力学和长期演变，为理解未来变化提供了有价值的类比。总之，本项目将深入了解以前由冰川沉积物补给的河流在第四纪晚期主要冰期期间和之后对气候变化的反应方式。帕尔默，AP，Thorndycraft，V.R.和马修斯，IP，2017.通过纹藻年代学和贝叶斯年龄模型揭示的布宜诺斯艾利斯湖巴塔哥尼亚冰盖（46.5 S）冰川消退的高分辨率年代学。Quaternary Science Reviews，177，pp.314-339.Boex，J.，Fogwill，C.，哈里森，S.，Glasser，N.F.，Hein，A.，施纳贝尔角和Xu，S.，2013.更新世晚期巴塔哥尼亚冰盖的迅速变薄伴随着南西风带的迁移。科学报告，3，第2118页，Darvill，C.M.，C.R.斯托克斯本特利，M. J.，Evans，D.J.和Lovell，H.，2017.基于冰川陆地系统方法的最南端巴塔哥尼亚冰盖前冰瓣的动力学。《第四纪科学杂志》，32（6），第857 - 876页。Jansson，K.N.，Harrison，S.和Kleman，J.，2008.南美38 ~ 56年的冰川地貌和更新世历史。Quaternary Science Reviews，27（3-4），pp.365-390.

This research focuses on the long-term changes in fluvial geomorphology and sediment dynamics at the Rio Chubut (Argentina). The aim is to develop a geomorphological history and test the environmental drivers responsible for the temporal changes in geomorphic development. Quaternary scientists study the past behaviour of the Patagonian ice sheet to aid understanding and projections of the environmental impact of contemporary climate change (Darvill et al, 2017; Boex et al, 2013; Glasser et al, 2008). Expansion and recession of the ice sheet and its glaciers cause geomorphic change in the environmental systems that it is coupled to. This includes proglacial lakes which have been studied for their high resolution varve records (Bendle et al, 2017). However, the extensive network of river systems that drain the ice sheet melt water depending on the extent of the ice, are understudied in the region despite being highly sensitive to ice dynamics and environmental change.Research methods for this study begin with the mapping of geomorphology using remotely sensed data e.g. aerial imagery of the Rio Chubut to identify geomorphic units that indicate past environmental conditions. Small scale metric data such as channel width and meander wavelength has been collected from abandoned river channels to infer historic water supply and energy levels in the system. Fieldwork has been completed in Oct/Nov 2019 where geophysical survey, sediment description and sampling for luminescence dating was carried out to collect more data on channel characteristic, sediment supply and to constrain a chronology of change respectively. The data collected in the field will ultimately inform a luminescence-based landform chronology (to be completed in year 2) and hydrogeomorphological modelling (to be completed in year 3) which can test hypotheses on the magnitude, frequency and time scale of fluvial change.Fluvial change in this region has wider significance given the deglacial decoupling from ice masses and the interaction with the Southern Westerlies, and other hydroclimate parameters e.g. El Nñio Southern Oscillation (ENSO), the loss of glacial waters from fluvial systems is a growing concern in Patagonia forming a key water supply sources. Characterising the dynamics and long term evolution of past fluvial systems through glacial, deglacial and postglacial times forms a valuable analogue for understanding future changes,In summary, this project will develop insight into the way rivers formerly fed by glacial outwash have responded to climate shifts during and after the major glacial episodes of the late Quaternary.ReferencesBendle, J.M., Palmer, A.P., Thorndycraft, V.R. and Matthews, I.P., 2017. High-resolution chronology for deglaciation of the Patagonian Ice Sheet at Lago Buenos Aires (46.5 S) revealed through varve chronology and Bayesian age modelling. Quaternary Science Reviews, 177, pp.314-339.Boex, J., Fogwill, C., Harrison, S., Glasser, N.F., Hein, A., Schnabel, C. and Xu, S., 2013. Rapid thinning of the late Pleistocene Patagonian Ice Sheet followed migration of the Southern Westerlies. Scientific reports, 3, p.2118.Darvill, C.M., Stokes, C.R., Bentley, M.J., Evans, D.J. and Lovell, H., 2017. Dynamics of former ice lobes of the southernmost Patagonian Ice Sheet based on a glacial landsystems approach. Journal of Quaternary Science, 32(6), pp.857-876.Glasser, N.F., Jansson, K.N., Harrison, S. and Kleman, J., 2008. The glacial geomorphology and Pleistocene history of South America between 38 S and 56 S. Quaternary Science Reviews, 27(3-4), pp.365-390.