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

水供应的变化，特别是干旱，在几年到几十年的时间尺度上，是社会的一个主要问题。在这样的时间尺度上，干旱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、墨西哥湾和加勒比在内的地区（下称环加勒比地区）今后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：这一地区正是我们拟议研究的对象。降雨量的气象记录太短，无法涵盖过去几年至几十年时间尺度上降雨量的全部变化，也无法表明地理格局是否随着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，洞穴沉积物（洞穴沉积物）和树木年轮，提供了一个机会，将气象记录进一步追溯到过去，并阐明降雨变化的模式和原因。在这项研究中，我们将调查在过去1200年的降雨量变化，利用湖泊沉积物中保存的介形虫的方解石壳的氧同位素分析。我们计划分析已经从墨西哥东部尤卡坦半岛、牙买加、海地和巴布达收集的湖泊沉积物岩心。这些地点位于一条由西向东的样带上，沿着该样带，已知近几十年来降雨量发生了变化。我们的重建将补充现有的研究沿着北到南的横断面内环加勒比地区，从而使我们能够调查过去降雨的地理格局的变化。过去的1200年是一个重要的时间段研究，因为它涵盖了显着的气候变化的间隔，包括中世纪气候异常（MCA）的主要是潮湿的气候，干燥的小冰期（LIA）和终端的显着干旱的经典时期，在MCA的结束，这被认为是促成了重大的社会变化在尤卡坦半岛。在这段时间内气候的广泛变化是众所周知的，但该地区地理模式的变化，尽管是由现有的数据暗示，很难约束。此外，人们对海洋环流和海面温度变化、太阳活动变化和火山爆发等潜在原因之间的联系也不甚了解。通过对过去1200年降雨量变化的重建，我们将进一步了解这一时期变化的性质和原因。通过将记录的时间跨度扩展到气象数据的时间跨度之外，我们将能够显示降雨变化的地理模式在最近的过去是否保持不变，或者似乎已经发生了变化。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，特别是那些致力于墨西哥和巴布达气候与社会之间联系的考古学家，提供急需的气候重建。

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.