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

这项研究集中在里奥楚布特河(阿根廷)河流地貌和沉积物动力学的长期变化。其目的是绘制地貌历史，并测试地貌发展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年；Boex等人，2013年；Glasser等人，2008年)。冰盖及其冰川的扩张和退缩导致了与其相关的环境系统的地貌变化。这包括因其高分辨率变化记录而被研究的冰川湖泊(Bendle等人，2017年)。然而，尽管该区域对冰的动态和环境变化高度敏感，但该地区对冰盖融水的广泛河系网络研究不足。这项研究的研究方法始于使用遥感数据绘制地貌图，例如里约热内卢的航空图像，以确定表明过去环境状况的地貌单元。从废弃的河道中收集了小尺度的测量数据，如河道宽度和曲折波长，以推断系统中的历史供水量和能量水平。野外工作已于2019年10月/11月完成，其中进行了地球物理调查、沉积物描述和发光测年采样，以分别收集更多关于河道特征、沉积物供应和约束变化年表的数据。野外收集的数据最终将为基于发光的地貌年代学(将于第二年完成)和水文地貌模拟(将于第三年完成)提供信息，这可以检验关于河流变化的规模、频率和时间尺度的假设。由于该地区的河流变化具有更广泛的意义鉴于冰川与冰块的脱钩以及与南部西风带的相互作用，以及其他水文气候参数，如厄尔尼诺-南方涛动(ENSO)，河流系统中冰川水的流失是巴塔哥尼亚一个日益令人担忧的问题，形成了一个关键的供水来源。描述过去河流系统在冰期、非冰期和冰后期的动态和长期演变特征对于理解未来的变化是一个有价值的类比，总而言之，该项目将深入了解在第四纪末的主要冰期期间和之后，以前由冰川冲出的河流对气候变化的反应方式。布宜诺斯艾利斯湖巴塔哥尼亚冰盖的高分辨率年代学研究(S 46.5.)《第四纪科学评论》，177，第314-339页。Boex，J.，Fogwill，C.，Harison，S.，Glasser，N.F.，Hein，A.，Schnabel，C.和Xu，S.，2013。随着南部西风带的迁移，晚更新世巴塔哥尼亚冰盖迅速变薄。科学报告，3，第218页。Darvill，C.M.，Stokes，C.R.，Bentley，M.J.，Evans，D.J.和Lovell，H.基于冰川陆地系统方法的巴塔哥尼亚最南端冰盖前冰叶的动力学。《第四纪科学杂志》，32(6)，第857-876页，Glasser，N.F.，Jansson，K.N.，Harison，S.和Kleman，J.S 38-56年间的南美洲冰川地貌和更新世历史。第四纪科学评论，第27期(3-4)，第365-390页。

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.