Ice rafted debris distribution in 16 sediment cores from the South Atlantic

Terrigenous sediment parameters in modern sea-bottom samples and sediment cores of the South Atlantic are used to infer variations in detrital sources and modes of terrigenous sediment supply in response to environmental changes through the late Quaternary climate cycles. Massaccumulation rates of terrigenous sediment and fluxes of ice-rafted detritus are discussed in terms of temporal variations in detrital sediment input from land to sea. Grain-size parameters ofterrigenous mud document the intensity of bottom-water circulation, whereas clay-mineral assemblages constrain the sources and marine transport routes of suspended fine-grained particulates, controlled by the modes of sediment input and patterns of ocean circulation. The results suggest low-frequency East Antarctic ice dynamics with dominant 100-kyr cycles and high rates of Antarctic Bottom Water formation and iceberg discharge during interglacial times. In contrast, the more subpolar ice masses of the Antarctic Peninsula also respond to short-term climate variability with maximum iceberg discharges during glacial terminations related to the rapid disintegration of advanced ice masses. In the northern Scotia Sea, increased sediment supply from southern South America points to extended ice masses in Patagonia during glacial times. In the southeastern South Atlantic, changes in regional ocean circulation are linked to global thermohaline ocean circulation and are in phase with northern-hemispheric processes of ice build-up and associated formation of North Atlantic Deep Water, which decreased during glacial times and permitted a wider extension of southern-source water masses in the study area.

本数据集以南大西洋现代海底样品及沉积岩芯中的陆源沉积物参数为研究基础，用以反演晚第四纪气候旋回背景下，响应环境变化的陆源碎屑物源与陆源沉积物供给模式的演化特征。研究通过分析陆源碎屑入海输入的时间序列变化，探讨了陆源沉积物质量堆积速率与冰筏碎屑（ice-rafted detritus）通量的变化规律。陆源泥质沉积物的粒度参数可指示底层环流强度；而黏土矿物组合则可限定悬浮细颗粒物质的物源与海洋搬运路径，其分布受控于沉积物供给模式与大洋环流格局。

研究结果表明，东南极冰盖动力学过程以低频变化为主，主导周期为10万年；间冰期阶段，南极底层水（Antarctic Bottom Water）形成速率与冰山崩解强度均处于较高水平。与之相对，南极半岛周边的亚极地冰体亦响应短期气候波动，在冰消期达到冰山崩解峰值，该过程与成熟冰体的快速崩解存在紧密关联。在斯科舍海（Scotia Sea）北部，来自南美南部的沉积物供给量显著增加，指示冰期时期巴塔哥尼亚地区发育大规模扩张的冰体。

在南大西洋东南部区域，局地大洋环流变化与全球温盐环流（thermohaline ocean circulation）紧密耦合，且与北半球冰体堆积及伴随的北大西洋深层水（North Atlantic Deep Water）形成过程同步；冰期时期北大西洋深层水形成强度减弱，使得本研究区域内南源水团的分布范围进一步扩张。