COMPREHENSIVE CALIBRATION OF CRITICAL PALEOCEANOGRAPHIC PROXIES

人类直接记录的气候信息范围很窄。关于更大范围可能的地球气候以及气候系统内阈值的证据，来自于从冰和沉积物岩心等档案中获得的古气候记录。如果我们要准确预测未来的气候，评估这些气候的范围和导致它们的机制是至关重要的。这种古气候工作完全依赖于代用物的应用。我们不能直接测量过去的环境变量，如海洋环流，但我们可以在古档案中找到这些变量的化学代用物。这些代用品的开发和校准对古气候至关重要。但这种校准有时会滞后于它们的应用，导致对过去的不确定重建。这里提出的工作旨在解决这一问题，明确关注古海洋学关键代理的校准。该提案汇集了各种化学专业的研究人员，但他们都在代理校准工作方面有着良好的记录。尽管这些研究人员也将代用物应用于古气候问题，但这并不是一个古气候建议，而是专注于理解作为古代用物的化学物种的现代水柱和上层沉积物行为。我们将了解将最终沉积物组成与气候变量联系起来的地球化学，并评估这些联系的局限性，从而避免不恰当地应用代用指标。我们将把重点放在数量有限的代理上，每个代理都有明确的（在大多数情况下，已经证明）提供有关过去的重要信息的潜力。这些代用物如果经过精确校准，将提供关于过去海洋环流的模式和速率的信息，以及关于过去生物生产力的组成、通量和养分利用的信息（这决定了海洋中碳的清除）。因此，它们具有巨大的潜力，可以告诉我们海洋在过去气候中的作用，包括通过热量和碳的运输。这里提出的代理校准工作将使这种潜力得到更好和更准确的实现。该提案的地球化学重点也是调查微量元素和同位素海洋循环的一项重要的新国际研究计划/ GEOTRACES的核心。建议在南大西洋进行一次研究巡航，以便收集水柱和沉积物样本进行代理校准工作。该邮轮将成为GEOTRACES项目的英国组成部分。虽然在这项提议中，资金只用于校准关键的古代用物，但研究巡航将成为一个广泛的其他生物地球化学研究的平台。这类工作可能包括评估海洋边缘具有重要生物学意义的金属通量、深水团块的化学运输，以及控制向低沙尘的南大西洋地表水提供微量营养素。我们将确保，尽管我们现有的GEOTRACES计划，在邮轮上实现尽可能广泛的此类研究，使其成为国际上广泛的地球化学家的重要研究邮轮。

Humans have directly recorded information about only a narrow range of climate. Evidence for a much larger range of possible Earth climate, and for thresholds within the climate system, come from paleoclimate records derived from archives such as ice and sediment cores. Assessing the range of such climates and the mechanisms that caused them is of fundamental importance if we are to accurately predict future climate. Such paleoclimate work relies absolutely on the application of proxies. We cannot measure environmental variables such as ocean circulation directly for past times, but we can find chemical proxies for these variables in paleo-archives. Development and calibration of these proxies is critical to paleoclimate. But such calibration can sometimes lag behind their application, leading to uncertain reconstructions of the past. The work proposed here seeks to address this issue with an explicit focus on calibration of critical proxies for paleoceanography. The proposal brings together researchers with a variety of chemical specialities, but all with a strong track record for proxy calibration work. Although each of these researcher also applies proxies to paleoclimate questions, this is not a paleoclimate proposal, but is focused on understanding the modern water-column and upper-sediment behaviour of chemical-species used as paleoproxies. We will understand the geochemistry that links the final sediment composition to climate variables, and assess the limitations on these links so that proxies are not applied inappropriately. We will focus on a limited number of proxies, each of which has clear (and, in most cases, demonstrated) potential to provide important information about the past. These proxies, if accurately calibrated, will provide information about the pattern and rate of past ocean circulation, and about the composition, flux and nutrient utilisation of past biological productivity (which sets the removal of carbon from the ocean). They therefore have tremendous potential to inform us about the role of the oceans in past climate, both through the transport of heat and carbon. The proxy calibration work proposed here will allow that potential to be better and more accurately realized. The geochemical focus of this proposal is also central to a major new international research programme investigating the marine cycling of trace elements and isotopes / GEOTRACES. A research cruise in the South Atlantic is proposed here to allow collection of water-column and sediment samples for the proxy calibration work. This cruise will form a UK component of the GEOTRACES programme. Although funds are only sought for the calibration of critical paleoproxies in this proposal, the research cruise will be a platform for a wide range of other biogeochemical research. Such work might include assessment of biologically significant metal fluxes at ocean margins, chemical transport in deep-water masses, and the controls on micronutrient supply to the surface waters of the low-dust South Atlantic. We will ensure, though our existing involvement in the GEOTRACES programme, that the widest possible range of such research is achieved on the cruise, making this an important research cruise to a wide range of geochemists internationally.