The silicon isotopic composition of surface waters in the Atlantic and Indian sectors of the Southern Ocean
The silicon isotopic composition of surface waters in the Atlantic and Indian sectors of the Southern Ocean
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DOI：
10.1016/j.gca.2011.06.028
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发表时间：
2011-09
影响因子：
5
通讯作者：
C. Rocha;Pierre Bescont;Alice Croguennoc;E. Ponzevera
中科院分区：
文献类型：
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作者：
C. Rocha;Pierre Bescont;Alice Croguennoc;E. Ponzevera
本文报道了2007年2月初至3月底采集的来自德雷克海峡、威德尔环流、南极绕极流南部边界以南的其他地区和凯尔盖朗高原附近的南极绕极流的42个表层水样品的溶解硅（DSi）的硅同位素组成（δ 30 Si）。从航行开始到结束（ANTXXIII/9），南极的DSi减少了50μmolL− 1，而硝酸盐+亚硝酸盐和磷酸盐的浓度没有净下降，这表明南大洋众所周知的高季节性Si/N去除率可能更多地与南大洋的硅酸盐泵的强度有关，而不是硅藻的瞬时Si/N吸收率。在含有大于20μM DSi的样品中，DSi的δ 30 Si与DSi浓度呈强负相关，支持使用δ 30 Si作为DSi去除的替代。观测到的“开放系统”分馏，ε=−1.2±0.11‰，与以前在其他地区的工作结果吻合得很好，DSi的初始δ 30 Si的估计值为+1.4‰，与该地区冬季水（WW）中DSi的δ 30 Si的观测值相差不远。结果被用来模拟过去从沉积物岩心的δ 30 Si中提取的DSi，尽管二氧化硅溶解过程中的同位素分馏似乎会影响某些地表水样品的δ 30 Si，但这一现象仍有待进一步研究。
We report here the silicon isotopic composition (δ30Si) of dissolved silicon (DSi) from 42 surface water samples from the Drake Passage, the Weddell Gyre, other areas south of the Southern Boundary of the Antarctic Circumpolar Current (ACC), and the ACC near the Kerguelen Plateau, taken between the beginning of February and the end of March 2007. From the beginning to end of the cruise (ANTXXIII/9), DSi diminished in the Antarctic by 50μmolL−1while concentrations of nitrate+nitrite and phosphate showed no net decline, indicating that the high seasonal Si/N removal ratios well known for the Southern Ocean may be more related to the strength of the silicate pump in the Southern Ocean than to the instantaneous Si/N uptake ratio of diatoms. The δ30Si of DSi in samples containing more than 20μM DSi were strongly negatively correlated to DSi concentrations, supporting the use of δ30Si as a proxy for DSi removal. The “open system” fractionation observed, ε=−1.2±0.11‰, agrees well with results from previous work in other areas, and the estimate of the initial δ30Si of DSi of +1.4‰ is not far off observations of the δ30Si of DSi in Winter Water (WW) in this area. Results were used to model DSi draw down in the past from the δ30Si of sediment cores, although isotopic fractionation during silica dissolution appeared to influence the δ30Si of some surface water samples, inviting further study of this phenomenon.