Oxygen and carbon stable isotope tracers of Weddell Sea water masses: new data and some paleoceanographic implications
Oxygen and carbon stable isotope tracers of Weddell Sea water masses: new data and some paleoceanographic implications
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DOI：
10.1016/s0967-0637(00)00093-5
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发表时间：
2001-06-01
影响因子：
2.4
通讯作者：
Mackensen, A
中科院分区：
文献类型：
--
作者：
Mackensen, A
本文报道了威德尔海南部陆架海水的稳定氧同位素组成和溶解无机碳（DIC）的稳定碳同位素组成。利用1995年夏季取样的观测站，可以建立两个剖面，一个与冰架边缘密切平行，另一个与上大陆坡垂直。一般来说，三角洲O-18值明显分开不同的陆架水质量取决于在冰川冰融化过程中加入的大气融水的含量。外推高盐度陆架水（HSSW）和过冷冰架水（ISW）岩心之间的混合线显示，冰川冰的δ O-18值为-27 ‰，而外推最高盐度HSSW和最低温度ISW的δ O-18值之间的混合线，冰川冰的δ O-18值为-34 ‰。这些数值表明融水来自冰架下方，那里的冰O-18消耗较少，因为在冰架下方靠近接地线的深处，数值可能达到千分之-40。如果将-34至-27 ‰之间的值用作冰川冰的δ O-18端元值，则冰架的融水量增加了Filchner-Ronne冰架外ISW形成的范围为0.2%至0.8%，与先前基于δ O-18和He-4的研究一致。由于在低温下大气和海洋之间的气体交换而导致的碳同位素分馏导致威德尔海深水的Delta Delta C-13（DIC）值为0.20 +/- 0.17千分之一，威德尔海深水是为全球深海通风的水体，通常被定义为南极底层水（AABW）。这证实了先前估计的范围下限（千分之0.2-0.4），从而证实了生物在形成深水和底层水三角洲C-13信号方面的主导地位。据推测，不同模式的冰川/间冰期南极底层水的形成可能是由不同的深海有孔虫方解石的稳定同位素组成。在这里，我表明，三角洲三角洲C-13和三角洲O-18值的HSSW和ISW，这两者都有助于今天的底层水形成之间的差异太小，无法解决在深水和底层水团。因此，南极深海和底层水中这些水体的相对比例的冰期/间冰期变化不能通过化石底栖有孔虫方解石的稳定同位素来区分。(C)2001爱思唯尔科技有限公司版权所有。
Stable oxygen isotopic composition of sea water and stable carbon isotopes of dissolved inorganic carbon (DIC) on the continental shelf in the southern Weddell Sea are presented. Using the stations sampled during the summer 1995 two sections can be constructed, one closely parallel to the ice shelf edge and the other perpendicular to the upper continental slope. Generally, delta O-18 values clearly separate between different shelf water masses depending on the content of meteoric meltwater added during melting of glacial ice. Extrapolation of the mixing line between the cores of High Salinity Shelf Water (HSSW) and supercooled Ice shelf Water (ISW) reveals delta O-18 values of the glacial ice of -27 parts per thousand, whereas extrapolation of the mixing line between the delta O-18 Values of the most-saline HSSW and lowest temperature ISW results in delta O-18 values of -34 parts per thousand for glacial ice. These values point to an origin of meltwater from below the ice shelf, where ice is less depleted in O-18, since deep beneath the ice shelf close to the grounding line, values may reach -40 parts per thousand. If values between -34 and -27 parts per thousand are used as delta O-18 end member values for glacial ice, the amount of meltwater from the ice shelf that adds to the formation of ISW off the Filchner-Ronne Ice Shelf ranges from 0.2 to 0.8%, in agreement with previous studies based on delta O-18 and He-4. Carbon isotopic fractionation due to gas exchange between the atmosphere and the ocean at cold temperatures results in Delta delta C-13(DIC) values of 0.20 +/- 0.17 parts per thousand for Weddell Sea Deep Water, the water mass that ventilates the global abyssal ocean, typically defined as Antarctic Bottom Water (AABW). This confirms the low end of the range estimated previously (0.2-0.4 parts per thousand), and thus corroborates the dominance of biology in shaping the deep and bottom water delta C-13 signal. It has been hypothesized that different modes of glacial/interglacial Antarctic bottom water formation may be separated by different stable isotopic compositions of deep-sea foraminiferal calcite. Here I show that differences between Delta delta C-13 and delta O-18 values of HSSW and ISW, both of which contribute to bottom water formation today, are too small to be resolved in deep and bottom water masses. Therefore, glacial/interglacial changes in relative proportions of these water masses in Antarctic deep and bottom water cannot be separated by stable isotopes of fossil benthic foraminiferal calcite. (C) 2001 Elsevier Science Ltd. All rights reserved.