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High‐resolution fjord sediment record of a receding glacier with growing intermediate proglacial lake (Steffen Fjord, Chilean Patagonia)
Earth Surface Processes and Landforms ( IF 2.8 ) Pub Date : 2020-10-10 , DOI: 10.1002/esp.5015 Loic Piret 1 , Sebastien Bertrand 1 , Jon Hawkings 2, 3 , Malin E. Kylander 4 , Fernando Torrejón 5 , Benjamin Amann 1 , Jemma Wadham 6
Earth Surface Processes and Landforms ( IF 2.8 ) Pub Date : 2020-10-10 , DOI: 10.1002/esp.5015 Loic Piret 1 , Sebastien Bertrand 1 , Jon Hawkings 2, 3 , Malin E. Kylander 4 , Fernando Torrejón 5 , Benjamin Amann 1 , Jemma Wadham 6
Affiliation
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Proglacial lakes are effective sediment traps but their impact on the reliability of downstream sediment records to reconstruct glacier variability remains unclear. Here, we investigate the sedimentary signature of the recent recession of Steffen Glacier (Chilean Patagonia, 47°S) in downstream fjord sediments, with a focus on identifying the trapping (decreased downstream sediment yield) and filtering (removal of coarse particles) effectiveness of a growing intermediate proglacial lake. Four sediment cores were collected along a 14 km longitudinal transect in Steffen Fjord and the sediment physical and chemical properties were compared with aerial imagery at high temporal resolution. The caesium‐137 (137Cs) chronology of the most distal core and sediment trap data suggest that sediment accumulation in the fjord remained relatively stable through time, despite the accelerating glacier recession and the growth of Steffen proglacial lake. This is in contrast with many studies that indicate a decrease in sediment yield during proglacial lake expansion. It implies that the increase in sediment export due to accelerating meltwater production may be balanced by the sediment trapping effect of the growing proglacial lake. The fjord sediments show a slight fining upward accompanied by a marked decrease in flood‐induced grain‐size peaks, most likely due to the increasing filtering and dampening effect of the expanding proglacial lake. Our findings show that the filtering effect of the proglacial lake reached a threshold in 1985, when the lake attained an area of 2.02 km2. The additional 5 km of glacier recession during the following 32 years did not have any significant impact on downstream sedimentation. This study confirms that proglacial lakes act as sediment traps but it indicates that (1) the trapping effect can be outpaced by accelerating glacier recession and (2) the filtering effect becomes stable once the lake attains a certain critical size. © 2020 John Wiley & Sons, Ltd.
中文翻译：
冰川消融的高分辨率峡湾沉积记录，中间冰川湖不断发育（智利巴塔哥尼亚，斯特芬峡湾）
冰川湖是有效的沉积物陷阱，但其对下游沉积物记录重建冰川变异性的可靠性的影响尚不清楚。在这里，我们研究了Steffen冰川（智利巴塔哥尼亚，47°S）最近衰退在下游峡湾沉积物中的沉积特征，重点是确定了捕集（降低下游沉积物产量）和过滤（去除粗颗粒）的有效性。一个正在生长的中游湖。在斯特芬峡湾沿14公里的纵向样带收集了四个沉积物岩心，并将沉积物的物理和化学性质与高空分辨率的航空影像进行了比较。铯137（137Cs）最远的岩心和沉积物陷阱数据的年代顺序表明，尽管冰川退缩加速，Steffen冰川湖的生长，峡湾中的沉积物随时间仍保持相对稳定。这与许多研究表明形成鲜明对比，这些研究表明，在冰川湖扩张期间，沉积物的产量会下降。这意味着由于熔融水生产加速而导致的泥沙出口增加可能与生长中的冰河湖的泥沙捕集作用所平衡。峡湾的沉积物显示出轻微的向上细化，并伴随着洪水诱发的粒度峰的显着减少，这很可能是由于扩张的冰河湖的增加的过滤和阻尼作用所致。我们的发现表明，1985年，冰川湖的过滤效果达到了一个阈值，2。在随后的32年中，另外5 km的冰川衰退对下游沉积没有任何重大影响。这项研究证实了冰川湖是沉积物的陷阱，但它表明（1）加速冰川退缩可以超过捕获作用；（2）一旦湖泊达到一定的临界尺寸，过滤作用就会变得稳定。分级为4 +©2020 John Wiley＆Sons，Ltd.
更新日期：2020-10-10
中文翻译：
冰川消融的高分辨率峡湾沉积记录，中间冰川湖不断发育（智利巴塔哥尼亚，斯特芬峡湾）
冰川湖是有效的沉积物陷阱，但其对下游沉积物记录重建冰川变异性的可靠性的影响尚不清楚。在这里，我们研究了Steffen冰川（智利巴塔哥尼亚，47°S）最近衰退在下游峡湾沉积物中的沉积特征，重点是确定了捕集（降低下游沉积物产量）和过滤（去除粗颗粒）的有效性。一个正在生长的中游湖。在斯特芬峡湾沿14公里的纵向样带收集了四个沉积物岩心，并将沉积物的物理和化学性质与高空分辨率的航空影像进行了比较。铯137（137Cs）最远的岩心和沉积物陷阱数据的年代顺序表明，尽管冰川退缩加速，Steffen冰川湖的生长，峡湾中的沉积物随时间仍保持相对稳定。这与许多研究表明形成鲜明对比，这些研究表明，在冰川湖扩张期间，沉积物的产量会下降。这意味着由于熔融水生产加速而导致的泥沙出口增加可能与生长中的冰河湖的泥沙捕集作用所平衡。峡湾的沉积物显示出轻微的向上细化，并伴随着洪水诱发的粒度峰的显着减少，这很可能是由于扩张的冰河湖的增加的过滤和阻尼作用所致。我们的发现表明，1985年，冰川湖的过滤效果达到了一个阈值，2。在随后的32年中，另外5 km的冰川衰退对下游沉积没有任何重大影响。这项研究证实了冰川湖是沉积物的陷阱，但它表明（1）加速冰川退缩可以超过捕获作用；（2）一旦湖泊达到一定的临界尺寸，过滤作用就会变得稳定。分级为4 +©2020 John Wiley＆Sons，Ltd.
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