Deglacial history of the West Antarctic Ice Sheet in the western Amundsen Sea Embayment
Deglacial history of the West Antarctic Ice Sheet in the western Amundsen Sea Embayment
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阿蒙森海湾西部南极洲冰盖的消冰历史
DOI：
10.1016/j.quascirev.2010.11.020
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发表时间：
2011
影响因子：
4
通讯作者：
Smith J
中科院分区：
文献类型：
--
作者：
Smith J
阿蒙森海湾(ASE)排出了大约35%的西南极冰盖(WAIS)，是冰冻圈变化最快的部分之一。为了预测未来的冰盖行为，建模人员需要冰盖融化的长期记录，以约束和建立对他们的模拟的信心。在这里，我们提供了沿着ASE西部的三个古冰川支流槽的详细海洋地质和放射性碳数据，以建立自上一次冰盛期(LGM)以来WAIS冰川消融的重要信息。我们对岩心进行了多指标分析(岩心描述、剪切强度、X射线照片、磁化率、湿容重、总有机碳/氮、碳酸盐含量和粘土矿物分析)，目的是：(1)表征沉积相和沉积环境；(2)确定每个岩芯中能够产生最可靠的冰川消融年龄的层位(S)。根据以前的研究，我们确定了三个关键的相，它们通过记录从地面冰盖到开阔的海洋环境的转变，提供了最可靠的地层学来确定冰川消退的年代。这些相是：i)冰下相，ii)近岸接地线，以及iii)季节性开阔海相。此外，我们还将其他相的年龄(例如，在离基准线一定距离处沉积的冰川岩直径，如冰川成因的泥石流和冰山漂浮的直径和涡流)纳入我们的去冰川模型。我们总共测定了78个样品的年代(主要是酸不溶有机(AIO)组分，但也有钙质有孔虫)，其中包括63个下部样品和15个地表样品。通过在测年前仔细选择样品，我们已经为WAIS的这一部分建立了可靠的冰川消融年代学。我们的数据表明，西部陆架的冰川消融可能早在22,351年前就开始了(称为冰年BP)，在12,618到10,072年BP之间到达中陆架13,837年前，内陆架到现在冰架前缘约10-12公里范围内。尽管考虑到潜在的测年不确定性，在这些发现得到充分证实之前，还需要更多、更准确的年龄，但西部海平面的消融步骤与全球融水脉冲1a和1b相关的海平面快速上升大致上是一致的。最后，我们发现冰盖退缩的速度在内陆架的深盆地(高达1600米)上增加了，这突出了在冰川消融的加速阶段中反向坡度和钉扎点的重要性。
The Amundsen Sea Embayment (ASE) drains approximately 35% of the West Antarctic Ice Sheet (WAIS) and is one of the most rapidly changing parts of the cryosphere. In order to predict future ice sheet behaviour, modellers require long-term records of ice-sheet melting to constrain and build confidence in their simulations. Here, we present detailed marine geological and radiocarbon data along three palaeo-ice stream tributary troughs in the western ASE to establish vital information on the timing of deglaciation of the WAIS since the Last Glacial Maximum (LGM). We have undertaken multi-proxy analyses of the cores (core description, shear strength, x-radiographs, magnetic susceptibility, wet bulk density, total organic carbon/nitrogen, carbonate content and clay mineral analyses) in order to: (1) characterise the sedimentological facies and depositional environments; and (2) identify the horizon(s) in each core that would yield the most reliable age for deglaciation. In accordance with previous studies we identify three key facies, which offer the most reliable stratigraphies for dating deglaciation by recording the transition from a grounded ice sheet to open marine environments. These facies are: i) subglacial, ii) proximal grounding line, and iii) seasonal open marine. In addition, we incorporate ages from other facies (e.g., glaciomarine diamictons deposited at some distance from the grounding line, such as glaciogenic debris flows and iceberg-rafted diamictons and turbates) into our deglacial model. In total, we have dated 78 samples (mainly the acid insoluble organic (AIO) fraction, but also calcareous foraminifers), which include 63 downcore and 15 surface samples. Through careful sample selection prior to dating, we have established a robust deglacial chronology for this sector of the WAIS. Our data show that deglaciation of the western ASE was probably underway as early as 22,351 calibrated years before present (cal yr BP), reaching the mid-shelf by 13,837 cal yr BP and the inner shelf to within c.10–12 km of the present ice shelf front between 12,618 and 10,072 cal yr BP. The deglacial steps in the western ASE broadly coincide with the rapid rises in sea-level associated with global meltwater pulses 1a and 1b, although given the potential dating uncertainty, additional, more precise ages are required before these findings can be fully substantiated. Finally, we show that the rate of ice-sheet retreat increased across the deep (up to1600 m) basins of the inner shelf, highlighting the importance of reverse slope and pinning points in accelerated phases of deglaciation.