Investigating Iceberg Calving from Antarctic Ice Sheets Through Isotope Stage 11

Hays，Burckle，Isley 9615060该奖项支持更好地定义南极冰盖的冰山崩解年代学的研究，追溯到氧同位素阶段11（距今364-423万年）。 对最近100 ka沉积物的已发表数据的重新评估表明，在17、22、63和84 ka，大西洋的冰筏碎片（IRD）沉积急剧增加，可能还有南大洋的印度洋部分。 这些IRD事件的区域范围将进行测试，和其他人将被确定为最后500万年通过检查的沉积物记录在策划的核心恢复。 生物地层学、化学地层学（蛋白石和碳酸盐记录）和氧同位素地层学将提供年龄限制。然而，还将在关键岩心中获取碳-14年代（使用加速器质谱法）。 将评估非生物成因沉积物（63 m - 1 mm）的累积率，并确定其岩性，以得出IRD累积率。 初步的矿物学和地球化学分析将试图追踪IRD的来源地区。 研究结果将产生一个高分辨率的评估从南极冰盖的冰山崩解，并允许洞察力，以了解这样的事情，如晚第四纪的历史，南极西部冰盖。 这项研究还将评估南半球冰盖是否经历了2-3万年的时间尺度融化事件，这可能是从南极冰芯的大气温度记录中推断出来的。 此外，这些南大洋IRD事件的时间将与北方半球的海因里希事件进行比较。 初步结果表明，IRD沉积在南大洋和北方半球海因里希事件1，2，6和一个未编号的事件在84 ka之间的近时相关。 对于最近的两个事件，南大洋IRD事件出现之前的北方半球的3 ka。 在北方和南方半球的冰山崩解之间存在强烈的时间相关性，这一发现表明，外部强迫而不是内部冰盖动力学驱动了至少一些海因里希事件。 另一方面，如果南大洋IRD事件先于北方半球的IRD事件，则北大西洋盐度振荡器以外的因素必须在次米兰科维奇时间尺度上影响全球气候。

Hays, Burckle, & Isley 9615060 This award supports research to better define the chronology of iceberg calving from Antarctic ice sheets back to oxygen isotope stage 11 (364-423 thousand-years before present (ka)). Re- assessment of published data for sediments deposited during the last 100 ka suggests deposition of ice-rafted debris (IRD) increased dramatically at 17, 22, 63 and 84 ka in the Atlantic and possibly the Indian sectors of the Southern Ocean. The regional extent of these IRD events will be tested, and others will be identified for the last 500 ka by examining the sediment record recovered in curated cores. Age constraints will be provided by biostratigraphy, chemostratigraphy (opal and carbonate records) and oxygen isotope stratigraphy. However, carbon-14 dates (using accelerator mass-spectrometry) will also be acquired in critical cores. The accumulation rate of abiogenic sediment (63 m - 1 mm) will be assessed and its lithology determined to derive IRD accumulation rates. Preliminary mineralogical and geochemical analyses will attempt to trace IRD to their source areas. Findings will yield a high resolution assessment of iceberg calving from Antarctic ice sheets and allow insights to understanding such things as the late Quaternary history of the West Antarctic Ice Sheet. This study will also assess whether Southern Hemisphere ice caps experienced melting episodes at timescales of 2-3 ka, as might be inferred from records of atmospheric temperatures in Antarctic Ice cores. Furthermore, the timing of these Southern Ocean IRD events will be compared with Heinrich Events in the Northern Hemisphere. Preliminary results suggest near-temporal correlations between IRD deposition in the Southern Ocean and Northern Hemisphere Heinrich Events 1, 2, 6 and an un-numbered event at 84 ka. For the two most recent events, Southern Ocean IRD events appear to precede those of the Northern Hemisphere by 3 ka. A finding of strong temporal correlation bet ween iceberg calving in the Northern and Southern Hemispheres would suggest that external forcing rather than internal ice sheet dynamics drove at least some of the Heinrich events. On the other hand, if Southern ocean IRD events preceded those of the Northern Hemisphere, factors other than the North Atlantic salinity oscillator must have impacted global climate at sub-Milankovich timescales.