Conroy Jessica L, Thompson Diane M, Cobb Kim M, Noone David, Rea Solanda, LeGrande Allegra N
Department of Geology, University of Illinois at Urbana-Champaign, Champaign, IL 61820, USA.
Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Paleoceanography. 2017 May 13;Volume 32(Iss 5):484-497. doi: 10.1002/2016PA003073.
The relationship between salinity and the stable oxygen isotope ratio of seawater (δO) is of utmost importance to the quantitative reconstruction of past changes in salinity from δO values of marine carbonates. This relationship is often considered to be uniform across water masses, but the constancy of the δO-salinity relationship across space and time remains uncertain, as δO responds to varying atmospheric vapor sources and pathways, while salinity does not. Here we present new δO-salinity data from sites spanning the tropical Pacific Ocean. New data from Palau, Papua New Guinea, Kiritimati, and Galápagos show slopes ranging from 0.09 ‰/psu in the Galápagos to 0.32‰/psu in Palau. The slope of the δO-salinity relationship is higher in the western tropical Pacific versus the eastern tropical Pacific in observations and in two isotope-enabled climate models. A comparison of δO-salinity relationships derived from short-term spatial surveys and multi-year time series at Papua New Guinea and Galápagos suggests spatial relationships can be substituted for temporal relationships at these sites, at least within the time period of the investigation. However, the δO-salinity relationship varied temporally at Palau, likely in response to water mass changes associated with interannual El Niño-Southern Oscillation (ENSO) variability, suggesting nonstationarity in this local δO-salinity relationship. Applying local δO-salinity relationships in a coral δO forward model shows that using a constant, basin-wide δO-salinity slope can both overestimate and underestimate the contribution of δO to carbonate δO variance at individual sites in the western tropical Pacific.
盐度与海水稳定氧同位素比值（δO）之间的关系对于根据海洋碳酸盐的δO值定量重建过去的盐度变化至关重要。这种关系通常被认为在不同水体中是一致的，但由于δO对不同的大气水汽源和路径有响应，而盐度则不然，所以δO - 盐度关系在空间和时间上的稳定性仍不确定。在此，我们展示了来自热带太平洋不同站点的新的δO - 盐度数据。来自帕劳、巴布亚新几内亚、基里巴斯的圣诞岛和加拉帕戈斯群岛的新数据显示，斜率范围从加拉帕戈斯群岛的0.09‰/psu到帕劳的0.32‰/psu。在观测数据以及两个启用同位素的气候模型中，热带西太平洋的δO - 盐度关系斜率高于热带东太平洋。对巴布亚新几内亚和加拉帕戈斯群岛短期空间调查和多年时间序列得出的δO - 盐度关系进行比较表明，在这些站点，至少在调查时间段内，空间关系可以替代时间关系。然而，帕劳的δO - 盐度关系随时间变化，可能是对与厄尔尼诺 - 南方涛动（ENSO）年际变化相关的水体变化的响应，这表明该局部δO - 盐度关系存在非平稳性。在珊瑚δO正向模型中应用局部δO - 盐度关系表明，使用恒定的、全盆地范围的δO - 盐度斜率可能会高估和低估热带西太平洋个别站点δO对碳酸盐δO方差的贡献。
