GRGC: High Resolution Stable Isotopic Fluctuations in Tropical Marine Waters

这个项目的重点是使用来自巴哈马和伯利兹的海洋文石胶结物，以提高热带海洋最近一次冰川消退期间稳定同位素骨骼记录的分辨率。具体来说，我们将讨论：1)与新仙女木事件之前的“融水脉冲”相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得知的明显更早的高频冷却事件；2)大约10-14ka（放射性碳年龄）期间近地表热带海水的绝对温度；3)这些热带海洋胶结物在多大程度上可能记录到高频（2、5、11、22和83年）气候信号。使用无机碳酸盐胶结物来确定古海洋学和古气候变化提供了一个机会，既可以提高来自海洋骨骼材料的同位素记录的准确性，又可以提高热带海洋高频变化的分辨率。这些胶结物提供了一个连续的同位素变化记录，以年代际为单位，可能频率更高，时间跨度为几百年。这种程度的解析度是目前可用的海洋骨骼记录无法做到的，它提供了一个独特的机会来比较热带海洋的高频气候事件，并可能将其与最近记录在冰芯数据中的气候事件联系起来。初步工作已经确定，我们目前的样品集包含的胶结物的年龄范围为10.9-13.6ka (AMS 14C)，胶结物的平均生长速度约为1毫米/10年，胶结物的生长周期约为50-500年。由于胶结物的寿命长，许多样品在时间上重叠。在这段时间内，胶结物在18O年表现出强烈的衰竭趋势，这与海洋骨骼记录中报告的值有很好的相关性。此外，由于单个胶结物的年代际到世纪尺度记录，有强有力的证据表明，胶结物记录了热带海洋中的高频同位素波动。我们目前的数据集显示，在“新仙女木”冷却事件之前的“融水脉冲”中报道的同位素转移的时间和幅度，以及迄今为止仅在冰芯中报道的其他更高频率转移到更冷条件的证据，都具有很强的相关性。该提案要求资金来扩展我们的初步发现，通过对这些单个胶结物进行高密度AMS 14C采样样带结合微采样（100微米尺度）同位素分析，以评估热带海洋中这些高频同位素变化。我们预计至少能够在十年尺度上记录变化，并且可能具有更高的分辨率，因为单个胶结物的连续和重叠记录。这些数据将提高热带海洋中同位素记录的准确性和分辨率，并对我们对快速气候变化和高纬度转移转移到热带地区的可能性的理解产生直接影响

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