Collaborative Research: Refining a 500-kyr Climate Record from the Moulton Blue Ice Field in West Antarctica

山顶陨石坑。在南极洲西部的莫尔顿，有一段600米厚的水平裸露的冰层，中间夹杂着来自附近柏林山的火山灰层。Ar-40/Ar-39测年表明，水平冰段的年龄在15,000到492,000年之间。因此，莫尔顿山遗址提供了一个无与伦比的西南极古代积雪和滞留空气的储存库，可以用来研究过去50万年来西南极的气候。冰盖的平面性和一致的倾斜度表明，尽管冰层已经变薄，但它在其他方面没有变形。这座山。在1999/2000年实地考察期间访问了莫尔顿遗址，当时收集了一个水平冰芯，代表大约400米厚的冰，年龄从15,000年到48万年以上不等。除了这个水平岩心，还采集了一定深度的冰样，以测试冰层中气候记录的质量。还收集了40个夹在冰层中的Tephra层，以提供冰段的年代学。这第一次努力的结果是非常令人鼓舞的。例如，根据冰的d？18O，显然有一份关于芒特山过去气候的有用记录。莫尔顿的历史可以追溯到14万年前。然而，要实现这个水平冰芯的全部潜力，还有很多工作要做。例如，被困气体的元素和同位素组成表明，现代空气受到了某种污染。由于冰芯气体交叉测年是目前比较气候记录的标准，在将莫尔顿添加到我们的冰芯古气候记录之前，我们需要了解气体记录被破坏的原因和方式。该奖项支持三个机构之间的合作努力，目标如下：1)通过浅层钻探蓝色冰区以及蓝色冰层上坡的雪场，更彻底地评估气候记录的完整性；2)改进特定特弗拉层的放射性同位素测年；3)获得有关现代降雪沉积、年平均温度和山顶附近的风泵的基线信息。4)研究地表堆积由净堆积变为净剥蚀时，积雪致密化的差异。

The summit crater of Mt. Moulton, in West Antarctica, contains a 600-m thick horizontally-exposed section of ice with intercalated tephra layers from nearby Mt Berlin. Argon-40/Argon-39 dating of the thick, near-source tephra indicates that the age of the horizontal ice section ranges between 15,000 and 492,000 years. Thus, the Mt Moulton site offers an unparalleled repository of ancient West Antarctic snow and trapped air that can be used to investigate West Antarctic climate over much of the past 500,000 years. The planar nature and consistent dips of the tephra layers suggests that, although the ice section has thinned, it is otherwise undeformed. The Mt. Moulton site was visited during the 1999/2000 field season, at which time a horizontal ice core representing approximately 400 meters of ice was collected, ranging in age from 15,000 to older than 480,000 years. In addition to this horizontal core, samples of ice at a range of depths were collected in order to test the quality of the climate record in the ice. Forty tephra layers intercalated in the ice were also collected in order to provide chronology for the ice section. The results of this first effort are extremely encouraging. Based on the d?18 O of ice, for example, there is clearly a useable record of past climate at Mt. Moulton extending back beyond 140,000 years. There is work to do, however, to realize the full potential of this horizontal ice core. The elemental and isotopic composition of trapped gases suggest some contamination with modern air, for example. As gas cross-dating of ice cores is the current standard by which climate records are intercompared, we need to understand why and how the gas record is compromised before adding Moulton to our arsenal of ice core paleoclimate records. This award supports a collaborative effort between three institutions with following objectives: 1) to evaluate more thoroughly the integrity of the climatic record through shallow drilling of the blue ice area, as well as the snow field upslope from the blue ice; 2) to improve the radioisotopic dating of specific tephra layers; 3) to obtain baseline information about modern snowfall deposition, mean annual temperature, and wind pumping around the summit of Mt. Moulton; and 4) to study how firn densification differs when surface accumulation changes from net accumulation to net ablation.