Rapid sea-level rise and reef back-stepping at the close of the last interglacial highstand
Rapid sea-level rise and reef back-stepping at the close of the last interglacial highstand
复制标题
DOI：
10.1038/nature07933
复制
发表时间：
2009-04-16
期刊：
影响因子：
64.8
通讯作者：
Liebetrau, Volker
中科院分区：
文献类型：
--
作者：
Blanchon, Paul;Eisenhauer, Anton;Liebetrau, Volker
广泛存在的证据表明，在末次间冰期（海洋同位素阶段5e），海平面高度为+4-6米，这导致了现代冰盖将因全球变暖而恶化的警告，并在公元2100年前开始类似幅度的上升（参考文献1）。这一预计的上升速度是基于冰盖融化模拟和淡化发现更快的冰损失（2，3）。了解最后一次间冰期海平面达到最高点的速度对于评估这种快速的冰损失过程是否会导致未来灾难性的海平面上升至关重要。在这一高水位期，海平面的最佳直接记录来自稳定地区（4-6）的年代久远的化石礁。然而，这一记录既缺乏从+6米处广泛的潮间带指标推断（7）的最高海拔的礁顶发育，也缺乏详细的年代学，因为很难在亚千年的时间尺度上复制U系列年龄（8）。在这里，我们提出了一个完整的礁顶序列的最后一个间冰期高位和它的U系列年代学从稳定的东北尤卡坦半岛，墨西哥。我们发现，在高位期间的珊瑚礁的发展是由+3米的礁顶消亡和后退到+6米打断。突然消亡的较低的礁顶，但不断增生之间的较低的泻湖单元和较高的礁顶，使我们能够推断，这种倒退发生在一个生态时间尺度上，并引发了海平面上升2-3米。使用严格可靠的Th-230年龄的珊瑚从上礁顶，和改进的地层筛选珊瑚年龄从其他稳定的网站，我们限制这种跳跃已经发生类似于121 kyr前，并得出结论，它支持一个插曲的冰盖不稳定在末次间冰期的末期。
Widespread evidence of a +4-6-m sea-level highstand during the last interglacial period (Marine Isotope Stage 5e) has led to warnings that modern ice sheets will deteriorate owing to global warming and initiate a rise of similar magnitude by AD 2100 (ref. 1). The rate of this projected rise is based on ice-sheet melting simulations and downplays discoveries of more rapid ice loss(2,3). Knowing the rate at which sea level reached its highstand during the last interglacial period is fundamental in assessing if such rapid ice-loss processes could lead to future catastrophic sea-level rise. The best direct record of sea level during this highstand comes from well-dated fossil reefs in stable areas(4-6). However, this record lacks both reef-crest development up to the full highstand elevation, as inferred(7) from widespread intertidal indicators at +6m, and a detailed chronology, owing to the difficulty of replicating U-series ages on submillennial timescales(8). Here we present a complete reef-crest sequence for the last interglacial highstand and its U-series chronology from the stable northeast Yucatan peninsula, Mexico. We find that reef development during the highstand was punctuated by reef-crest demise at +3m and back-stepping to +6m. The abrupt demise of the lower-reef crest, but continuous accretion between the lower-lagoonal unit and the upper-reef crest, allows us to infer that this back-stepping occurred on an ecological timescale and was triggered by a 2-3-m jump in sea level. Using strictly reliable Th-230 ages of corals from the upper-reef crest, and improved stratigraphic screening of coral ages from other stable sites, we constrain this jump to have occurred similar to 121 kyr ago and conclude that it supports an episode of ice-sheet instability during the terminal phase of the last interglacial period.