Collaborative Research: Quantifying the ocean's response to solar forcing:Multidecadal to century-scale variability of North Atlantic SSTs over recent millennia

该项目的目的是开发北大西洋海表温度（SST）变化的第一个详细的，年代测定的记录，以调查在过去的3000年中，在几十年到世纪的时间尺度上，海洋对自然太阳强迫的反应。尽管可靠的SST代理和采样点的必要的高沉积率的可用性，有没有重建北大西洋海盆规模的SST场在过去的千年直接或基本上基于海洋观测。这几乎完全是由于缺乏对海洋沉积物年代测定的适当控制。 这一合作项目由哥伦比亚大学拉蒙特-多尔蒂地球观测站和科罗拉多大学博尔德分校的一个小组进行，开发了一种新的海洋应用，即所谓的放射性碳“摆动匹配”测年法，在这种方法中，可以获得可靠的日历年龄估计值，而不需要对当地海洋水库年龄的大小和过去的变化作出假设，这是测年不确定性的主要来源。由于该方法客观地映射下芯海洋沉积物放射性碳的变化，晚全新世放射性碳校准的树木年轮，其中还包含一个记录的初始大气放射性碳活动控制（在感兴趣的时间尺度在这里）主要是由太阳的开放磁通量的变化，它提供了直接比较SST和太阳代理在相同的沉积物的变化。 研究人员利用八个高积累率的沉积物岩心，这些岩心在全流域范围内分布，以捕捉当今大西洋温度变化的主要模式（NAO和AMO）的空间表达。每个岩芯的年表都是基于AMS放射性碳测年（标称分辨率为40年），并使用为该项目开发的自动摆动匹配算法客观地指定日历年龄。SST重建将基于有孔虫氧同位素地层学和Mg/Ca，这提供了过去钙化温度的可靠估计。这些数据将提供必要的观测，以测试任何可能的全流域SST模式对太阳强迫的响应，以及这种响应是否与北大西洋涛动（NAO），大西洋年代际振荡（AMO）或其他先前模拟的响应具有共同特征。 更广泛的影响：这项工作直接涉及到需要根据需要确定自然气候变异性的特征，以便区分对自然和人为强迫因子的持续反应，并改进预测模型。虽然海洋区域在空间上，在许多情况下，在能量上占主导地位，但目前在海洋上缺乏这种特征。该项目还将支持哥伦比亚大学一名博士生的教育和研究培训。

The purpose of this project is to develop the first detailed, calendrically-dated records of North Atlantic Sea Surface Temperature (SST) variability in order to investigate the ocean's response to natural solar forcing at multi-decadal to century time scales over the last 3000 years. Despite the availability of reliable SST proxies and of sampling sites with the necessary high deposition rates, there exist no reconstructions of the North Atlantic basin-scale SST field over past millennia based directly or substantially on ocean observations. This is due almost entirely to the lack of adequate age-dating control in marine sediments. This collaborative project, undertaken by a team from both Columbia University's Lamont-Doherty Earth Observatory and the University of Colorado, Boulder, develops a new marine application of the so-called radiocarbon "wiggle-match" dating method in which reliable calendar age estimates are obtained free of assumptions regarding the size and past variability of the local marine reservoir age, which is the principle source of dating uncertainty. Because the method objectively maps down-core marine sediment radiocarbon variations to the late Holocene radiocarbon calibration in tree-rings, which also contains a record of initial atmospheric radiocarbon activity controlled (at the timescale of interest here) largely by variations in the Sun's open magnetic flux, it provides for direct comparison of SST and solar proxy variability in the same sediments. The researchers makes use of eight high-accumulation rate sediment cores with a basin-wide distribution selected to capture the spatial expression of the leading modes of Atlantic temperature variability today (the NAO and AMO). Chronologies for each core are based on AMS radiocarbon dating (at a nominal resolution of 40 years) with calendar ages assigned objectively using an automated wiggle-match algorithm developed for this project. SST reconstructions will be based on foraminiferal oxygen isotope stratigraphy and Mg/Ca, which provide a reliable estimate of past calcification temperature. Together these data will provide the observations necessary to test for any possible basin-wide SST pattern response to solar forcing and whether this response has features in common with the North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO) or with other previously simulated responses. Broader Impacts: This work directly addresses the need to characterize natural climate variability as needed in order to separate ongoing responses to natural and anthropogenic forcing agents and to improve predictive models. Such characterization is presently lacking over the oceans although ocean regions are spatially and, in many instances, energetically dominant. The project will also support education and research training for a PhD student at Columbia University.