GRGC: High Resolution Stable Isotopic Fluctuations in Tropical Marine Waters

9419176 Grammer该项目的重点是使用巴哈马和伯利兹的海洋文石水泥，以提高热带海洋最近一次冰川消融期间稳定同位素骨骼记录的分辨率。具体地说，我们将讨论：1)与年轻仙女木事件之前的“融水脉冲”有关的明显变暖趋势的时间和幅度，以及迄今为止仅从冰芯记录中已知的较早的明显高频冷却事件：2)大约10-14ka(放射性碳年龄)期间近地表热带海洋水域的绝对温度；以及3)在这些热带海洋胶结中记录到的甚高频(2，5，11，22和83年)气候信号的程度。利用无机碳酸盐胶结物确定古海洋学和古气候变化提供了一个机会，既可以提高从海洋骨架材料得出的同位素记录的准确性，也可以提高热带海洋高频变化的分辨率。这些胶结物在几百年的时间周期内，提供了十年甚至更高频率范围内的同位素变化的连续记录。目前现有的海洋骨架记录不可能达到这种分辨率，这为比较热带海洋的高频气候事件与最近记录在冰芯数据中的气候事件提供了独特的机会，并可能相互关联。初步工作表明，我们目前的样本集包含的水泥年龄范围为10.9-13.6ka(AMS14C)，水泥的平均生长速度约为1毫米/10年，水泥的生长周期约为50-500年。由于水泥的长寿性质，许多样品在时间上重叠。在同位素上，胶结物在这段时间内表现出强烈的18O亏损趋势，这与海洋骨骼记录的值有很好的相关性。此外，由于单个胶结物的十年到世纪尺度的记录，有强有力的证据表明，这些胶结物在热带海洋记录了高频的同位素波动。我们目前的数据集显示，同位素漂移的时间和幅度都有很强的相关性，就像在较年轻的仙女木冷却事件之前报道的“融水脉冲”，以及其他高频漂移到更冷的条件的证据，到目前为止只在冰芯中报道过。这项提案要求资金对我们的初步发现进行扩展，通过对这些单独的水泥进行高密度AMS 14C采样横断面结合微量采样(100微米尺度)同位素分析来评估热带海洋中的这些高频同位素变化。由于单个水泥的连续和重叠记录，我们预计能够记录至少十年尺度的变化，并可能以更高的分辨率记录。这些数据将提高热带海洋同位素记录的准确性和分辨率，并直接影响我们对快速气候变化和高纬度转移到热带地区的可能性的理解。

9419176 Grammer This project focuses on the use of marine aragonite cements from the Bahamas and Belize to increase the resolution of the stable isotopic skeletal record during the latest deglaciation for tropical oceans. Specifically we will address: 1) the timing and magnitude of the apparent warming trend associated with the "melt water pulse" immediately preceding the Younger Dryas event, as well as apparent earlier higher frequency cooling events, to date only known from ice core records: 2) the absolute temperature of near surface tropical ocean waters during the period from about 10-14ka (radiocarbon age); and 3) to what degree the very high frequency (2,5,11,22 and 83yr) climate signals may be recorded in these tropical marine cements. The use of inorganic carbonate cements to determine paleo- oceanographic and paleoclimatic changes provides an opportunity to increase both the accuracy of the isotopic record derived from marine skeletal material, as well as to increase the resolution of high-frequency changes in the tropical oceans. These cements provide a continuous record of isotopic changes on a decadal and possibly higher frequency scale, over time periods of several hundreds of years. This degree of resolution has not been possible with the currently available marine skeletal records, and provides a unique opportunity to compare and possibly correlate the high- frequency climatic events in the tropical oceans with those recently documented in the ice core data. Preliminary work has established that our present sample set contains cements that range in age from 10.9-13.6ka (AMS 14C), that the cements grew at average rates of approximately 1mm/10yr, and that the cements grew for periods of approximately 50-500 years. Because of the long-lived nature of the cements, many of the samples overlap in time. Isotopically the cements exhibit a strong depletion trend in 18O over this time interval that correlates well with those values reported fo r the marine skeletal records. In addition, because of the decadal to century scale record within individual cements, there is strong evidence that the cements are recording high-frequency isotopic fluctuations in the tropical oceans. Our present data set shows a strong correlation in both the timing and magnitude of the isotopic shift as reported for the "melt-water pulse" immediately preceding the Younger Dryas cooling event as well as evidence for other higher frequency shifts to cooler conditions that to date has only been reported in ice cores. This proposal requests funds to expand upon our preliminary findings by doing high density AMS 14C sampling transects combined with microsampled (100 um scale) isotopic analysis on these individual cements to evaluate these high-frequency isotopic shifts in the tropical oceans. We anticipate being able to document changes on at least a decadal scale, and possibly at a higher resolution, due to the continuous and overlapping record of the individual cements. This data should increase both the accuracy and resolution of the isotopic records in tropical oceans, and have direct impact on our understanding of rapid climate change and the potential for high latitude shift to be carried over into the tropics