Cyclic ice sheet collapses, meltwater events and proxies for a reduction of bottom water circulation along the West Antarctic Peninsula margin

循环冰盖崩塌、融水事件以及南极西部半岛边缘底部水循环减少的替代因素

• 批准号: 49148206
• 负责人: Dr. Daniel A. Hepp
• 金额: --
• 依托单位: Niedersächsisches Institut für historische Küstenforschung (NIhK)
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2009-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/49148206?language=en
• 关键词: Cyclic; ice; sheet; collapses; meltwater

The melting of continental ice sheets during deglaciations provides freshwater to the oceans that affect the global sea level and the strength of the thermohaline circulation (THC). This is well documented in the Northern Hemisphere but less understood for the Southern Ocean. Recent climate models indicate that sea ice reduction, meltwater and deepwater formation in Antarctica is equally important for the meridional overturning circulation. Cores from drifts along the West Antarctic Peninsula offer the chance to study more than eighty deglaciation cycles with ice sheet collapses. During those collapses intriguing occurrences of iron diagenesis in conjunction with well-preserved diatom plume deposits suggest episodes of anaerobic sediment conditions and reduced bottom water dynamics. We propose to use U/Th as additional evidence for the suggested anoxic conditions. 34S-isotopes and diffusion reaction models will constrain the duration and vertical extend of anaerobic episodes in the sediment column. Those episodes documented from Sites of active Antarctic bottom water formation likely represent the peak in meltwater production and at the same time the onset of increased THC, initiating a gradual Antarctic cooling that preludes the next glaciation. Better constrains on Antarctic bottom water circulation will ultimately improve our understanding of South-North climate feedbacks.

冰川消退期间大陆冰盖的融化为海洋提供了淡水，影响了全球海平面和温盐环流的强度。这在北方半球有很好的记录，但对南大洋的了解较少。最近的气候模式表明，海冰减少，融水和深水形成在南极洲是同样重要的纬向翻转环流。从西南极半岛沿着的漂流物中获得的岩芯，为研究80多个冰盖崩塌的冰川消退周期提供了机会。在这些崩塌期间，有趣的铁成岩作用与保存完好的硅藻羽状沉积物一起发生，表明厌氧沉积条件和底层水动力学降低。我们建议使用U/Th作为建议的缺氧条件的额外证据。34 S同位素和扩散反应模型将制约沉积柱中厌氧事件的持续时间和垂直延伸。从活跃的南极底层水形成的地点记录的这些事件可能代表了融水生产的高峰，同时也是THC增加的开始，开始了下一次冰川作用的逐渐南极冷却。更好地限制南极底层水循环将最终提高我们对南北气候反馈的理解。