Investigating Iceberg Calving from Antarctic Ice Sheets Through Isotope Stage 11

9615060该奖项支持更好地确定从南极冰盖到氧同位素第11阶段(距今364-423000年)的冰山崩解年代学的研究。对过去100ka期间公布的沉积物沉积数据的重新评估表明，在17ka、22ka、63ka和84ka之间，大西洋以及南大洋的印度部分的冰筏碎片(IRD)沉积急剧增加。将测试这些IRD事件的区域范围，并将通过检查在经过精选的岩心中恢复的沉积物记录来确定过去500 ka的其他事件。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，关键岩心也将获得碳-14年龄(使用加速器质谱仪)。将对非生物沉积(63m-1 mm)的堆积速率进行评估，并确定其岩性，以求出IRD堆积速率。初步的矿物学和地球化学分析将试图追踪IRD的源头地区。这些发现将产生对南极冰盖冰山崩解的高分辨率评估，并使人们能够深入了解诸如西南极冰盖的第四纪晚期历史等事情。这项研究还将评估南半球冰帽是否经历了2-3ka的时间尺度的融化事件，这可以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Heinrich事件进行比较。初步结果表明，南大洋和北半球的IRD沉积与海因里希事件1、2、6和84ka的一次数不清的事件之间存在近时间的相关性。在最近的两次事件中，南大洋IRD事件似乎比北半球的事件早3ka。北半球和南半球冰山崩解之间强烈的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不是内部冰盖动力驱动的。另一方面，如果南大洋IRD事件先于北半球事件，那么北大西洋盐度振荡器以外的因素一定在米兰科维奇以下的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.