Milankovitch and Tidal Cycle History (MATCH)

1969年7月20日阿波罗11号登月，是人类文明史上的一项重大成就。带回来的岩石样本显示，月球有45亿年的历史，所以一定是在地球形成后大约2亿年才形成的。阿波罗任务期间留在月球表面的镜子使我们能够非常准确地测量地月分离，以及地球和月球相互远离或后退的速度。这一衰退速度估计为3.8厘米/年。然而，如果这个衰退率在时间上是恒定的，那么月球只有15亿年的历史，否则它就会被地球引力场撕裂。这里存在一个明显的悖论：月球的年龄和现在的衰退率并不相加！月球正在后退的原因是潮汐摩擦：潮汐能量进入海洋的损失正在逐渐减缓地球的自转速度，并将月球推离地球。如果潮汐摩擦力较弱，月球退去的速度会较慢，而如果潮汐耗散较大，则月球退去的速度会较快。然而，我们目前对地球历史上潮汐能量的耗散几乎没有可靠的估计。此外，这些数据仅限于最近地球历史(过去2.5亿年)的几个时间片段。这些估计表明，潮汐消散率不是随着时间的推移而恒定的。研究小组成员的工作预测了一个周期为4亿年的“超级潮汐周期”的存在，在这个周期中，潮汐消散的变化是大陆漂移的四倍。超级计算机的出现促进了高精度全球潮汐模型的发展，使我们能够模拟地球过去的潮汐消散率。根据模拟的耗散，我们可以计算出过去大量时间片的月球衰退率。该模型的衰退率将使用钻孔数据在几个时期内受到限制。在钻孔中，沉积物中有长期气候周期的信号，但要分析它们，你需要月球衰退率。使用该团队开发的一种新方法，我们将分析来自多个洞的数据，并提供工具来确认模型结果。我们方法的新奇之处在于，它不假设一个恒定的衰退率，因此使我们能够实现对全球潮汐演化的理解的一步改变，并量化地质时间尺度上地月分离的演化。实现这一目标将使我们能够通过提供对过去6亿年月球衰退率的详细估计，更好地预测地月系统的演化。这对地球系统中的海洋潮汐有影响，例如，潮汐如何为搅动海洋提供能量，从而维持生物生产并影响控制气候的全球海洋环流模式。该项目的结果对于任何需要月球退缩或潮汐消散率的调查也将是重要的，例如调查过去的气候周期、沉积物分层，以及对过去气候的模拟。

The Apollo 11 moon landing on July 20 1969, was a major achievement in the history of human civilization. The rock samples brought back showed that the moon was 4.5 billion years old, and so must have formed only 200 million years or so after Earth formed. The mirrors left on the surface of the moon during the Apollo missions allowed us to very accurately measure the Earth-moon separation, and the rate at which the Earth and the Moon are moving away from each other or receding. This recession rate is estimated to be 3.8 cm/year. However, if this recession rate was constant in time, the moon would only be 1.5 billion years old, otherwise it would have been torn apart by the Earth's gravitational field. Here lies an obvious paradox: the age of the moon and the present-day recession rate do not add up!The reason the moon is receding is tidal friction: the loss of tidal energy into the ocean is gradually slowing the Earth's rotation rate and pushing the moon away from the Earth. If tidal friction is weak, the moon will recede more slowly, whilst if tidal dissipation is large, the moon will recede more quickly. However, we currently have very few reliable estimates of the dissipation of tidal energy over the history of Earth. Furthermore, these are restricted to a few time slices over the more recent Earth history (the past 250 million years). These estimates indicate that the tidal dissipation rate has not been constant over time. Work by team members have predicted the existence of a "super tidal cycle" - with a period of 400 million years - in which the tidal dissipation varies by a factor of four and is associated with continental drift.The dawn of supercomputers has facilitated the development of high-accuracy global tidal models, which allow us to simulate the tidal dissipation rates in Earth's past. From the modelled dissipation, we can compute the past lunar recession rates for a large number of time slices. The recession rates from the model will be constrained for a few periods using data from bore holes. In bore holes there are signals of long-term climate cycles laid down in the sediments, but to analyse them you need the lunar recession rate. Using a new approach developed by the team, we will analyse data from a number of holes and provide a tool to confirm the model results. The novelty of our approach being that it does not assume a constant recession rate and so allows us to achieve a step change in our understanding of the evolution of the tides globally and quantify the evolution of Earth-Moon separation on geological time-scales.Achieving this aim will allow us to better predict the evolution of the Earth-moon system by providing detailed estimates of the lunar recession rate over the past 600 million years. This has implications for ocean tides in the Earth system, for example how the tide provides energy for stirring the ocean and thus sustaining biological production and influencing the climate-controlling global ocean circulation patterns. The project results will also be important for any investigation in need of lunar recession or tidal dissipation rates, for example investigations of past climate cycles, sediment laminations, and for simulations of past climates.