Sea level and climate change from geochemical analysis of corals from the Great Barrier Reef: IODP Expedition 325

环境变化预估中最大的不确定性之一涉及格陵兰和南极冰盖对“温室变暖”的反应。这些冰盖通过影响风型、通过将阳光反射回太空以及通过提供可影响海洋环流的淡水来源，在确定气候方面发挥着重要作用。随着地球变暖，我们预计这些冰盖会做出反应，但我们不确定具体是什么方式。格陵兰冰盖很可能开始融化，事实上已经有证据表明这可能正在发生。南极冰盖最初可能会略微增长（因为它太冷了，轻微的变暖只会让那里更容易下雪）。然而，来自过去的证据与现代观测相结合表明，这些冰盖能够通过大片的灾难性崩塌而极其迅速地衰减，从而导致海平面大幅而迅速地上升。这里提出的工作重点是澳大利亚的大堡礁，尽管远离冰盖，但它的位置很好，可以揭示过去冰盖生长和崩塌的证据。我们将通过分析从岩心中采集的珊瑚的化学成分来重建1.1万至2万年前的水深变化，从而重建海平面的变化。这一间隔与冰盖从上一个冰河时期的最大范围到现在的大小的衰减相吻合。在最后一个冰河时代的高峰时期，由于大量的水以冰的形式结合，全球海平面比现在的水平低约120米，因此随着冰盖的融化，海平面上升。我们的珊瑚记录将与岩心中珊瑚和藻类种类的其他证据一起使用，以确定这些海平面变化的速度、时间和幅度，并重建当地温度的变化。这些数据将有助于我们了解冰盖崩塌和海平面上升的触发因素。

One of the largest uncertainties in projections of environmental change involves the response of the Greenland and Antarctic ice sheets to 'greenhouse warming'. These ice sheets play an important role in defining climate through affecting wind patterns, through reflecting sunlight back to space and through providing sources of fresh water the can influence ocean circulation. As the planet warms, we expect these ice sheets to respond, but we are not sure in exactly what ways. The Greenland ice sheet is likely to start melting, and indeed there is already evidence to suggest that this might be happening. The Antarctic ice sheet may initially grow slightly (since it is so cold that a slight warming simply makes it easier to snow there). However, evidence from the past combined with modern observations suggests that these ice sheets are capable of extremely rapid decay through catastrophic collapse of large segments, resulting in large and rapid sea level rises. The work proposed here is focussed on the Great Barrier Reef of Australia, which, although far from the ice sheets, is well placed to reveal evidence for past ice sheet growth and collapse. We will use analysis of the chemistry of corals collected in drill cores down through the reef to reconstruct changes in water depth, and hence sea level, in the interval 11,000- 20,000 years ago. This interval coincides with the decay of the ice sheets from their maximum extent during the last ice age, to their present size. At the peak of the last ice age, global sea level was about 120m below its present level, due to the amount of water bound up as ice, so as the ice sheets melted, sea level rose. Our coral records will be used with other evidence from the types of corals and algae in the cores, to identify the rate, timing and magnitude of these sea level changes, as well as to reconstruct changes in local temperature. These data will contribute to our understanding of the triggers of ice sheet collapse and sea level rise.