Origins of Carbon Isotope Signals in Tropical and Polar Oceans: 0-25,000 Years B.P.

南洋近极锋表层水体碳同位素信号以δ C-13的富集量为1.0 / mil，而南洋近极锋区浮游有孔虫的碳同位素变化较大，这与南极中间水（AAIW）碳同位素组成的变化有关。在热带地区，δ C-13信号很小，其来源尚有争议。提出的研究目标是分离热带和极地地表水同位素记录的全球、瞬态、热力学和“红场”变化。资金用于对过去250千万年从局部水域到极地水域的岩心进行为期两年的稳定同位素研究。破译碳同位素信号的来源。这项研究将有助于解决极锋位置和强度的变化。有孔虫Cibicides sp.的Cd/Ca比值分析及其碳同位素分析可能有助于确定两个体系的解耦是否可以用于识别AAIW的存在。

The carbon-isotopic signal of the Southern Ocean surface waters near the polar front is enriched in delta C-13 by 1.0 per mil. However, downcore the planktonic forams in the polar front region show a greater variation in C-13 because of the migrations of the front through time, linked to changes in carbon-isotopic composition of the Antarctic Intermediate Water (AAIW). In the tropics the delta C-13 signal is small and its origin is debated. The objective of the proposed research is to isolate global, transient, thermodynamic, and "Redfield" changes in the tropical and polar surface water isotopic records. Funds are provided for a two years' stable-isotopic study of cores from the topical to polar waters spanning the past 250 k.yrs. to decipher the origin of the carbon-isotopic signal. The study will help resolve the changes in the position and intensity of the polar front. The analyses of Cd/Ca ratios of forams Cibicides sp. along with their carbon-isotopic analyses may help determine if the decoupling of the two systems can be used to identify the presence of AAIW.