The oxygen isotopic composition and temperature of Southern Ocean bottom waters during the last glacial maximum

We provide two new determinations of the oxygen isotopic composition of seawater during the last glacial maximum (LGM). High-resolution oxygen isotopic measurements were made on interstitial waters from Ocean Drilling Program (ODP) Sites 1168 and 1170 in the southeast Indian Ocean sector of the Southern Ocean. We use a diffusion-advection numerical model to calculate the glacial-interglacial change in bottom-water δ¹⁸O_sw from the pore water δ¹⁸O profiles; the first such determinations from this part of the oceans. Statistical analyses of the model runs indicate that Circumpolar Deep Water (CDW) δ¹⁸O_sw changed by 1.0-1.1±0.15‰ since the last glacial maximum (LGM). Our results are consistent with a previous calculation from a South Atlantic Southern Ocean location (ODP Site 1093) also situated within CDW. The new values determined in this study, together with previous estimates, are converging on a global average Δδ¹⁸O_sw of 1.0-1.1‰.Using the calculated bottom-water δ¹⁸O_sw, we have extracted the temperature component from the benthic foraminiferal δ¹⁸O record at Sites 1168 and 1170. Since the LGM, bottom waters at these two sites warmed by 2.6 and 1.9°C, respectively. The absolute temperature estimates for the LGM (−0.5°C [Θ=−0.6°C] at Site 1168 and −0.2°C [Θ=−0.4°C] at Site 1170) are slightly warmer than those reported from previous studies using the same technique, but are consistent with more homogenous deep-ocean temperatures during the LGM relative to the modern.     

新疆北部花岗岩─水~18O/~16O交换反应动力学──对于造山带岩浆熔融与流体循环的意义

对新疆北部花岗岩的两个典型岩体-阿拉尔和二台北岩体进行了系统的氧同位素组成测定,以探讨造山带的流体循环以及岩浆源区的熔融两个岩体的岩浆源区相对亏损18OZ它们在上部地壳侵位的次团相冷凝过程中共生矿物向富集18O的方向不平衡偏转推覆到阿尔泰山区热板片之下的晚古生代沉积物冷板片,通过进变质过程中的脱水反应提供了大量的含水流体．在倒转地温梯度驱动下,含水流体从下伏冷板片释放到上覆热板片,与富18O的早古生代变质沉积物发生18O／16O交换反应,并且最终导致造山花岗岩源区的熔融,产生相对亏损18O的过铝质花岗岩浆．对于以二台北岩体为代表的非造山花岗岩而言,幔源岩浆的下垫诱导的进变质反应造成流体对流,促进了幔源岩浆与花岗岩源区岩石的18O／16O交换反应,从而降低了后者的δ18O值．流体循环是深熔作用的先驱事件．与两个岩体侵位相联系的流体具有围绕岩体分布的外封皮性质．当岩浆温度下降到某一数值时,它们迅速进入岩体,瞬间流动速率较大．随着18O／16O交换反应的进行,流体来源迅速枯竭.     

Holocene Climate Inferred from Oxygen Isotope Ratios in Lake Sediments, Central Brooks Range, Alaska

Analyses of sediment cores from two lakes in the central Brooks Range provide temperature and moisture balance information for the past 8500 cal yr at century-scale resolution. Two methods of oxygen isotope analysis are used to reconstruct past changes in the effective moisture (precipitation minus evaporation) and temperature. Effective moisture is inferred from oxygen isotope ratios in sediment cellulose from Meli Lake (area 0.13 km², depth 19.4 m). The lake has a low watershed-to-lake-area ratio (7) and significant evaporation relative to input. Summer temperature shifts are based on oxygen isotope analyses of endogenic calcite from Tangled Up Lake (area 0.25 km², depth 3.5 m). This basin has a larger watershed-to-lake-area ratio (91) and less evaporation relative to input. Sediment oxygen isotope analyses from the two sites indicate generally more arid conditions than present prior to 6000 cal yr B.P. Subsequently, the region became increasingly wet. Temperature variability is recorded minimally at centennial scale resolution with values that are generally cool for the past 6700 cal yr. The timing and direction of climate variability indicated by the oxygen isotope time series from Meli and Tangled Up lakes are consistent with previously established late Holocene glacier advances at 5000 cal yr B.P. in the central Brooks Range, and high lake-levels at Birch Lake since 5500 cal yr B.P. This unique use of oxygen isotopes reveals both moisture balance and temperature histories at previously undetected high-resolution temporal scales for northern Alaska during the middle to late Holocene.     

基于水化学和物理方法的井水位异常分析

针对2008年汶川M_S 8.0地震后江苏地区的地震观测井水位上升现象,选取了苏18井和井周边地表水进行了水化学和物理分析,研究了井水位异常与地表水和大气降水的补给关系,讨论了井水补给来源及其与高邮-宝应M_S 4.9地震的关系。离子含量和氢氧同位素结果表明,苏18井水主要为大气降水成因,存在一定的水岩作用。应用氯离子分析降水对地下水的补给,其结果显示大气降水在井水补给源中占了重要份额,井水位的突然上升与同期降水量增加有一定关系。水库水与苏18井水之间存在水力联系,大气降水增多致使水库水位升高,对该井水位变化有一定的影响。综合分析认为,大气降水的增多致使水库蓄水增加,水库水通过侧向渗透补给造成了2011年苏18井的水位显著升高。苏18井异常不是由构造活动引起的,作为高邮-宝应M_S 4.9地震的前兆依据不充分。水化学和物理结合的方法为今后判别地下水位异常干扰提供了依据。     

Climatic significance of δ <Superscript>18</Superscript>O records from an 80.36 m ice core in the East Rongbuk Glacier,Mount Qomolangma (Everest)

The δ ¹⁸O variations in an 80.36 m ice core retrieved in the accumulation zone of the East Rongbuk Glacier, Mount Qomolangma (Everest), is not consistent with changes of air temperature from both southern and northern slopes of Himalayas, as well as these of the temperature anomalies over the Northern Hemisphere. The negative relationship between the δ ¹⁸O and the net accumulation records of the ice core suggests the “amount effect” of summer precipitation on the δ ¹⁸O values in the region. Therefore, the δ ¹⁸O records of the East Rongbuk ice core should be a proxy of Indian Summer Monsoon intensity, which shows lower δ ¹⁸O values during strong monsoon phases and higher values during weak phases.     

Catchment transit times and landscape controls—does scale matter?

Mean transit times (MTTs) can give useful insights into the internal processes of hydrological systems. However, our understanding of how they vary and scale remains unclear. We used MTT estimates obtained from δ¹⁸O data from 20, mostly nested, contrasting catchments in North East Scotland, ranging from 1 to 1700 km². The estimated MTTs ranged between 270 and 1170 days and were used to test a previously developed multiple linear regression (MLR) model for MTT prediction based on metrics of soil cover, landscape organization and climate. We show that the controls on MTT identified by the MLR model hold with the independent data from these 20 sites and that the MLR can be used to predict MTT in ungauged montane catchments. The dominant controls also remain unchanged over four orders of magnitude of catchment size, suggesting no major change of dominant flow paths and mixing processes at larger scales. This is consistent with the fact that only the variance of MTT, rather than MTT, showed a scaling relationship. MTTs appeared to converge with increasing catchment scale, apparently due to the integration of heterogeneous headwater responses in larger downstream catchments. Copyright © 2009 John Wiley & Sons, Ltd.     

雷州半岛造礁珊瑚Porites lutea月分辨率的δ18O温度计研究

对雷州半岛西南部珊瑚岸礁区1995～1997年生长的造礁珊瑚Poriteslutea的骨骼密度、生长速度和δ¹⁸O分析表明：1)造礁珊瑚骨骼的密度、生长速度和δ¹⁸O与其生存环境的表层海水温度之间存在很好的相关性,高密度、低生长速率和高δ¹⁸O值对应于冬季;2)δ¹⁸O具有明显的年际和季节性变化。根据δ¹⁸O估计的表层海水温度变化范围与实测基本一致,进一步揭示了珊瑚骨骼δ¹⁸O可作为定量研究高分辨率表层海水温度变化的温度计。     

Controls, variation, and a record of climate change in detailed stable isotope record in a single bryozoan skeleton

The long-lived (about 20 yr) bryozoan Adeonellopsis sp. from Doubtful Sound, New Zealand, precipitates aragonite in isotopic equilibrium with seawater, exerting no metabolic or kinetic effects. Oxygen isotope ratios (δ¹⁸O) in 61 subsamples (along three branches of a single unaltered colony) range from −0.09 to +0.68‰ PDB (mean = +0.36‰ PDB). Carbon isotope ratios (δ¹³C) range from +0.84 to +2.18‰ PDB (mean = +1.69‰ PDB). Typical of cool-water carbonates, δ¹⁸O-derived water temperatures range from 14.2 to 17.5 °C. Adeonellopsis has a minimum temperature growth threshold of 14 °C, recording only a partial record of environmental variation. By correlating seawater temperatures derived from δ¹⁸O with the Southern Oscillation Index, however, we were able to detect major events such as the 1983 El Niño. Interannual climatic variation can be recorded in skeletal carbonate isotopes. The range of within-colony isotopic variability found in this study (0.77‰ in δ¹⁸O and 1.34 in δ¹³C) means that among-colony variation must be treated cautiously. Temperate bryozoan isotopes have been tested in less than 2% of described extant species — this highly variable phylum is not yet fully understood.     

环境同位素在邢台煤矿放水试验中的应用

根据氧－１８、氘、氚同位素在邢台煤矿放水试验中的变化规律，分析了奥灰水对大青水的影响程度、大青水的可能来源等，得出井田的３个水文地质单元富水地段以及补给源和补给强度。特别是用环境同位素方法进一步证实了该井田是一个３面阻水、北面进水的断块岩溶水区。为煤矿防治水提供了依据。     

低18O碱性花岗岩成因讨论——以内蒙巴尔哲碱性花岗岩为例

巴尔哲花岗岩是一个罕见的亏损^18O的碱性花岗岩体，其中的石英、长石、钠闪石、锆石以及全岩的氧同位素含量都是国内碱性花岗岩中最低的。根据其氧同位素资料，结合岩体地质地球化学特征，讨论了该岩体以及我国东部低^18O碱性花岗岩的成因，认为用岩石与大气降水间同位素交换和开放体系下的岩浆去气作用解释该类岩石成因较为合理，但也有缺陷，有待进一步研究。