A multimillion-year-old record of Greenland vegetation and glacial history preserved in sediment beneath 1.4 km of ice at Camp Century
A multimillion-year-old record of Greenland vegetation and glacial history preserved in sediment beneath 1.4 km of ice at Camp Century
复制标题
DOI：
10.1073/pnas.2021442118
复制
发表时间：
2021-03-30
影响因子：
11.1
通讯作者：
Southon, John
中科院分区：
文献类型：
--
作者：
Christ, Andrew J.;Bierman, Paul R.;Southon, John
了解格陵兰冰盖（GrIS）的历史对于确定其对变暖的敏感性和对海平面的贡献至关重要;然而，在最后一次间冰期之前，人们对这一历史知之甚少。大多数知识来自对海洋沉积物的解释，这是对过去冰盖范围和行为的间接记录。冰芯底部的冰下沉积物和岩石为更新世期间GrIS的行为提供了陆地证据。在这里，我们使用多种方法来确定GrIS的历史，从冰下沉积物在1966年收集的营地世纪冰芯的基础。这些资料包含了格陵兰西北部更新世以来冰川作用和植被的地层记录。丰富的稳定同位素的孔隙冰表明降水在低海拔地区，这意味着冰盖的情况下。沉积物中的植物宏体化石和生物标志物表明，前间冰期的古生态系统保存在GrIS之下。宇宙成因的Al-26/Be-10和发光数据将最低层沉积物的埋藏时间确定在< 3.2 +/- 0.4 Ma和>0.7 - 1.4 Ma之间。在最上层的沉积物中，宇宙成因的Al-26/Be-10数据需要在最后1.0 +/- 0.1 My内暴露。世纪营地独特的冰下沉积物记录至少记录了两次无冰的植被条件，每次之后都是冰川作用。下部沉积物来自早更新世GrIS推进。Al-26/Be-10的比例在最上层的沉积物中匹配的冰下基岩从格陵兰岛中部，这表明类似的冰盖历史在整个GrIS。我们的结论是，GrIS坚持通过更新世的大部分时间，但熔化和改造至少一次，因为1.1马。
Understanding the history of the Greenland Ice Sheet (GrIS) is critical for determining its sensitivity to warming and contribution to sea level; however, that history is poorly known before the last interglacial. Most knowledge comes from interpretation of marine sediment, an indirect record of past ice-sheet extent and behavior. Subglacial sediment and rock, retrieved at the base of ice cores, provide terrestrial evidence for GrIS behavior during the Pleistocene. Here, we use multiple methods to determine GrIS history from subglacial sediment at the base of the Camp Century ice core collected in 1966. This material contains a stratigraphic record of glaciation and vegetation in northwestern Greenland spanning the Pleistocene. Enriched stable isotopes of pore-ice suggest precipitation at lower elevations implying ice-sheet absence. Plant macrofossils and biomarkers in the sediment indicate that paleo-ecosystems from previous interglacial periods are preserved beneath the GrIS. Cosmogenic Al-26/Be-10 and luminescence data bracket the burial of the lower-most sediment between < 3.2 +/- 0.4 Ma and >0.7 to 1.4 Ma. In the upper-most sediment, cosmogenic Al-26/Be-10 data require exposure within the last 1.0 +/- 0.1 My. The unique subglacial sedimentary record from Camp Century documents at least two episodes of ice-free, vegetated conditions, each followed by glaciation. The lower sediment derives from an Early Pleistocene GrIS advance. Al-26/Be-10 ratios in the upper-most sediment match those in subglacial bedrock from central Greenland, suggesting similar ice-cover histories across the GrIS. We conclude that the GrIS persisted through much of the Pleistocene but melted and reformed at least once since 1.1 Ma.