Climate variability over the circum-Caribbean region during the past 1200 years from oxygen-isotope analyses of lake sediments

可用水的变化，特别是干旱，在几年到几十年的时间尺度上是社会的一个主要关切。在这样的时间尺度上干旱的频率和程度的变化可能是未来气候变化的结果，特别是在亚热带地区。包括中美洲东部、墨西哥湾和加勒比地区(下称环加勒比地区)的地区未来可能对气候变化特别敏感，特别是在干旱的发生率和严重程度方面：正是这一地区是我们拟议研究的主题。关于降雨的气象记录太短，不能涵盖过去几年至几十年时间尺度上的所有降雨变化，也不能表明地理模式是否随时间和在不同条件下发生了变化。过去气候的自然“档案”，包括湖泊和海洋沉积物、洞穴沉积和树木年轮，为进一步追溯到过去的气象记录提供了机会，并阐明了降雨变异性的模式和原因。在这项研究中，我们将使用保存在湖泊沉积物中的介形类方解石壳的氧同位素分析来研究过去1200年的降雨变化。我们计划分析从墨西哥东部尤卡坦半岛、牙买加、海地和巴布达等地采集的湖泊沉积岩芯。这些地点位于从西向东的横断面上，已知近几十年来降雨量发生了变化。我们的重建将得到环加勒比地区从北向南横断面的现有研究的补充，从而使我们能够调查过去降雨地理模式的变化。过去1200年是一个值得研究的重要时间段，因为它涵盖了气候显著变化的时段，包括以潮湿气候为主的中世纪气候异常(MCA)、较干燥的小冰期(LIA)和MCA末期的明显干旱末期，这被认为对尤卡坦半岛的重大社会变化做出了贡献。气候在这段时间内的广泛变化是众所周知的，但该地区地理格局的变化，尽管现有数据暗示了这一点，但很难受到限制。此外，与潜在原因的联系，如海洋环流和海面温度的变化、太阳活动的变化和火山喷发，还没有得到很好的理解。通过生成过去1200年降雨量变化的新重建图，我们将对这段时间内变化的性质和原因提供进一步的见解。通过将记录的时间跨度延长到气象数据之外，我们将能够显示降雨变异性的地理模式在最近的过去是保持不变，还是(看起来可能)发生了变化。除了为环加勒比地区提供重要的古气候数据外，我们的研究还将为考古学家提供急需的气候重建，特别是那些研究墨西哥和巴布达气候与社会之间的联系的考古学家。

Variations in water availability, especially drought, on timescales of years to decades are a major concern for society. Changes in the frequency and magnitude of drought on such timescales are a likely outcome of future climate change, especially in subtropical regions. The area that encompasses the eastern part of Central America, the Gulf of Mexico and the Caribbean (hereafter the circum-Caribbean region) is likely to be especially sensitive to climate change in the future, especially in terms of the incidence and severity of drought: it is this region that is the subject of our proposed research. Meteorological records of rainfall are too short to encompass the full range of variations in past rainfall on timescales of years to decades or to indicate whether geographical patterns have changed through time and under different conditions. Natural 'archives' of past climate, including lake and marine sediments, speleothems (cave deposits) and tree rings, provide an opportunity to extend the meteorological records further back into the past and to shed light on the modes and causes of rainfall variability. In this research, we will investigate changes in rainfall over the past 1200 years using oxygen-isotope analyses of the calcite shells of ostracods preserved in lake sediments. We plan to analyse lake sediment cores that have already been collected from sites in the Yucatan Peninsula of eastern Mexico, Jamaica, Haiti and Barbuda. These sites are located on a west to east transect, along which changes in rainfall are known to have occurred over recent decades. Our reconstructions will be complemented by existing studies along a north to south transect within the circum-Caribbean region, thus allowing us to investigate changes in the geographical patterns of past rainfall. The past 1200 years is an important time period to study as it covers intervals of marked change in climate including the Medieval Climate Anomaly (MCA) of predominantly wet climate, the drier little ice age (LIA) and the terminal classic period of marked drought at the end of the MCA, which is thought to have contributed to major societal change in the Yucatan Peninsula. The broad variations in climate over this interval are quite well known, but changes in the geographical patterns in the region, despite being implied by existing data, are poorly constrained. Furthermore, links to potential causes, such as variations in ocean circulation and sea-surface temperatures, changes in solar activity and volcanic eruptions, are not well understood. By generating new reconstructions of variability in rainfall over the past 1200 years, we will provide further insights in to the nature and causes of change during this period. By extending the timespan of records beyond that of meteorological data, we will be able to show whether geographical patterns of rainfall variability have remained constant over the recent past or, as seems likely, have changed. In addition to providing important palaeoclimatic data for the circum-Caribbean region, our research will generate much-needed reconstructions of climate for archaeologists, especially those working on links between climate and society in Mexico and Barbuda.