Holocene sediment transport from the glaciated margin of East/Northeast Greenland to the N Iceland shelves

We examine variations in the ice-rafted sources for sediments in the Iceland/East Greenland offshore marine archives by utilizing a sediment unmixing model and link the results to a coupled iceberg-ocean model. Surface samples from around Iceland and along the E/NE Greenland shelf are used to define potential sediment sources, and these are examined within the context of the down-core variations in mineralogy in the <2 mm sediment fraction from a transect of cores across Denmark Strait. A sediment unmixing model is used to estimate the fraction of sediment <2 mm off NW and N Iceland exported across Denmark Strait; this averaged between 10 and 20%. Both the sediment unmixing model and the coupled iceberg-ocean model are consistent in finding that the fraction of "far-travelled" sediments in the Denmark Strait environs is overwhelmingly of local, mid-East Greenland, provenance, and therefore with a significant cross-channel component to their travel. The Holocene record of ice-rafted sediments denotes a three-part division of the Holocene in terms of iceberg sediment transport with a notable increase in the process starting ca 4000 cal yr BP. This latter increase may represent the re-advance during the Neoglacial period of land-terminating glaciers on the Geikie Plateau to become marine-terminating. The contrast in spectral signals between these cores and the 1500-yr cycle at VM28-14, just south of the Denmark Strait, combined with the coupled iceberg-model results, leads us to speculate that the signal at VM28-14 reflects pulses in overflow waters, rather than an ice-rafted signal.本研究借助沉积物分解模型（sediment unmixing model），探究冰岛与东格陵兰近海海洋沉积记录中沉积物的冰筏物源变化，并将分析结果与耦合冰山-海洋模型（coupled iceberg-ocean model）进行关联。研究团队采集冰岛周边及东/东北格陵兰陆架的表层沉积物样品，以明确潜在沉积物物源；同时基于横穿丹麦海峡的岩芯断面中<2 mm粒级沉积物的矿物学垂向变化，对上述物源开展系统性分析。本研究利用沉积物分解模型，估算经冰岛西北及北部海域输出并跨越丹麦海峡的<2 mm粒级沉积物占比，其平均值介于10%至20%之间。沉积物分解模型与耦合冰山-海洋模型均得到一致结论：丹麦海峡周边海域的“长距离搬运”沉积物，其物源绝大多数为格陵兰中东部本土源区，因此其搬运过程存在显著的跨海峡分量。冰筏沉积（ice-rafted sediments）的全新世（Holocene）记录显示，全新世的冰山沉积物搬运过程可划分为三个阶段，且该过程在约4000个校准距今年（cal yr BP）左右出现显著增强。此次后期的增强可能对应于盖基高原（Geikie Plateau）的陆终止冰川在新冰期（Neoglacial）期间向海终止冰川的再度推进。上述岩芯与丹麦海峡以南的VM28-14岩芯的光谱信号差异，结合耦合冰山模型的结果，使我们推测：VM28-14岩芯的信号反映的是溢流水体的脉冲事件，而非冰筏沉积信号。