Ice retreat in Wilkes Basin of East Antarctica during a warm interglacial
Ice retreat in Wilkes Basin of East Antarctica during a warm interglacial
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DOI：
10.1038/s41586-020-2484-5
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发表时间：
2020-07-23
期刊：
影响因子：
64.8
通讯作者：
Babbe, J. T.
中科院分区：
文献类型：
--
作者：
Blackburn, T.;Edwards, G. H.;Babbe, J. T.
东南极冰盖威尔克斯盆地冰下沉积物中的铀同位素揭示了大约40万年前更新世间冰期温暖时期的冰川消退。为了提高对变暖地球的海平面预测，人们将重点放在确定地球过去间冰期暖期(1-3)期间的温度、海平面和极地冰盖范围。大约40万年前，在被称为海洋同位素第11阶段(MIS11)的间冰期，全球气温高出1至2摄氏度(2)，海平面高出6至13米(1，3)。然而，估计超过10米的海平面已经打折，因为这需要南极东部冰盖(3)的贡献，该冰盖被认为在数百万年前一直保持稳定，包括MIS11(4，5)。在这里，我们展示了南极东部冰下水域中(234)U丰度的演变记录了冰盖对MIS11变暖的反应。在Wilkes盆地内，蛋白石和方解石的冰下化学沉淀物记录的(234)U(冰下孤立水库内岩石-水接触的产物)的积累量比在海水中发现的高出20倍。~(234)U浓缩的时间尺度将该储集层的形成时间定为MIS11。根据在Laurentide冰盖中观察到的(234)U循环，其中(234)U在冰稳定时期积累(6)，并因冰川消融而被冲到全球海洋(7)，我们将东南极数据集解释为代表MIS11的Wilkes盆地内的冰丢失。在威尔克斯盆地内的McMurdo干河谷卤水(8-10)中也观察到了(234)U的聚集，表明(11)卤水起源于邻近的东南极冰盖之下。卤水盐(10)和细菌(12)的海洋来源意味着MIS11冰的丧失与海洋洪水相结合。总体而言，这些数据表明，在最温暖的更新世间冰期之一，威尔克斯盆地的冰盖边缘后退到距离冰缘目前位置内陆约700公里的降水位置附近，假设目前的冰量，这将对全球海平面造成约3至4米(13)的影响。
Uranium isotopes in subglacial precipitates from the Wilkes Basin of the East Antarctic Ice Sheet reveal ice retreat during a warm Pleistocene interglacial period about 400,000 years ago.Efforts to improve sea level forecasting on a warming planet have focused on determining the temperature, sea level and extent of polar ice sheets during Earth's past interglacial warm periods(1-3). About 400,000 years ago, during the interglacial period known as Marine Isotopic Stage 11 (MIS11), the global temperature was 1 to 2 degrees Celsius greater(2)and sea level was 6 to 13 metres higher(1,3). Sea level estimates in excess of about 10 metres, however, have been discounted because these require a contribution from the East Antarctic Ice Sheet(3), which has been argued to have remained stable for millions of years before and includes MIS11(4,5). Here we show how the evolution of(234)U enrichment within the subglacial waters of East Antarctica recorded the ice sheet's response to MIS11 warming. Within the Wilkes Basin, subglacial chemical precipitates of opal and calcite record accumulation of(234)U (the product of rock-water contact within an isolated subglacial reservoir) up to 20 times higher than that found in marine waters. The timescales of(234)U enrichment place the inception of this reservoir at MIS11. Informed by the(234)U cycling observed in the Laurentide Ice Sheet, where(234)U accumulated during periods of ice stability(6)and was flushed to global oceans in response to deglaciation(7), we interpret our East Antarctic dataset to represent ice loss within the Wilkes Basin at MIS11. The(234)U accumulation within the Wilkes Basin is also observed in the McMurdo Dry Valleys brines(8-10), indicating(11)that the brine originated beneath the adjacent East Antarctic Ice Sheet. The marine origin of brine salts(10)and bacteria(12)implies that MIS11 ice loss was coupled with marine flooding. Collectively, these data indicate that during one of the warmest Pleistocene interglacials, the ice sheet margin at the Wilkes Basin retreated to near the precipitate location, about 700 kilometres inland from the current position of the ice margin, which-assuming current ice volumes-would have contributed about 3 to 4 metres(13)to global sea levels.