Ikaite: A palaeoenvironmental proxy

为了预测全球变暖的后果，必须了解温度和冰量（因此海平面）对大气二氧化碳的气候反应。过去气候波动的地质记录有能力揭示这三个地球系统参数之间的自然相互作用。古海洋学自成立以来面临的最大挑战之一是重建整个更新世冰期的海洋温度或海平面的独立记录，以了解冰川循环期间冰量和温度这两个关键气候组成部分的敏感性和阶段性。有孔虫d18 O，传统的代理，是冰量和温度的组合的影响，因此缺乏对海水d18 O的约束，防止任何海洋碳酸盐d18 O记录的完整和定量的解释。我们已经假设，在富含有机物的沉积物中沉淀的碳酸钙的亚稳水合形式-钙钛矿（CaCO 3·6 H2O），捕获环境沃茨的同位素组成作为晶体内的水合沃茨（Rickaby等人，20061），并提供了一个有前途的方法直接探测d18 Osw的时期以外的末次盛冰期（LGM）。我们提出了一个多学科的方法，将矿物学和地球化学实验室实验与实地观察相结合，以确定和了解自然环境中伊卡特及其同位素的存在和气候意义。我们的主要目的是奠定基础，并应用这种新的ikaite代理重建d18 Osw，因此冰量，并扩展应用代理不同的时间片和水团。

In order to predict the consequences of global warming, it is essential to understand the climate response in terms of temperature and ice volume (hence sea level) to atmospheric carbon dioxide. The geological record of past climatic fluctuations has the power to reveal the natural interplay between these three Earth system parameters. One of the great challenges in paleoceanography since its inception, has been to reconstruct an independent record of oceanic temperature, or sea level throughout the Pleistocene ice ages in order to obtain an idea of the sensitivity and phasing of two crucial climate components: ice volume and temperature, during the glacial cycles. Foraminiferal d18O, the traditional proxy, is influenced by a combination of both ice volume and temperature so lack of constraint on seawater d18O prevents complete and quantitative interpretation of any marine carbonate d18O record. We have hypothesised that ikaite (CaCO3.6H2O), a metastable hydrated form of calcium carbonate which precipitates in organic rich sediments, captures the isotopic composition of ambient waters as hydration waters within the crystal (Rickaby et al., 20061), and offers a promising method of probing directly the d18Osw for periods other than the Last Glacial Maximum (LGM). We propose a multi-disciplinary approach to integrate mineralogical and biogeochemical laboratory experiments with field observations to characterise and understand the presence and climatic significance of ikaite and its isotopes within the natural environment. Our primary aims are to lay the foundations for, and apply this novel ikaite proxy to the reconstruction of d18Osw, hence ice volume, and extend application of the proxy to different timeslices and water masses.