Investigating Iceberg Calving from Antarctic Ice Sheets Through Isotope Stage 11

该奖项支持更好地确定从南极冰盖到氧同位素阶段11（距今364- 42.3万年）的冰山崩解年表的研究。对最近100 ka沉积的已发表资料的重新评估表明，在17、22、63和84 ka，大西洋以及可能在南大洋的印度部分，冰筏碎屑（IRD）的沉积急剧增加。将测试这些IRD事件的区域范围，并通过检查在整理的岩心中恢复的沉积物记录来确定过去500 ka的其他IRD事件。年龄限制将由生物地层学、化学地层学（蛋白石和碳酸盐记录）和氧同位素地层学提供。然而，碳14日期（使用加速器质谱法）也将在关键岩心中获得。将评估非生物成因沉积物（63 m - 1 mm）的堆积速率，并确定其岩性，以得出IRD堆积速率。初步的矿物学和地球化学分析将试图追踪IRD的来源。这些发现将对南极冰原上的冰山崩解进行高分辨率评估，并有助于理解南极西部冰原的晚第四纪历史等问题。这项研究还将评估南半球冰盖是否在2-3 ka的时间尺度上经历了融化事件，这可能从南极冰芯的大气温度记录中推断出来。此外，这些南大洋IRD事件的时间将与北半球的海因里希事件进行比较。初步结果表明，南大洋和北半球海因里希事件1、2、6与84 ka的一次未计数事件之间存在近时间相关性。在最近的两次事件中，南大洋的IRD事件似乎比北半球的IRD事件早3 ka。一项关于南北半球冰山崩解的强时间相关性的发现表明，至少部分海因里希事件是由外部强迫而非内部冰盖动力学造成的。另一方面，如果南大洋IRD事件先于北半球，那么北大西洋盐度振荡器以外的因素一定在亚米兰科维奇时间尺度上影响了全球气候。

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.