We reconstruct deep water-mass salinities and spatial distributions in the western North Atlantic during the Last Glacial Maximum (LGM, 19–26 ka), a period when atmospheric CO₂ was significantly lower than it is today. A reversal in the LGM Atlantic meridional bottom water salinity gradient has been hypothesized for several LGM water-mass reconstructions. Such a reversal has the potential to influence climate, ocean circulation, and atmospheric CO₂ by increasing the thermal energy and carbon storage capacity of the deep ocean. To test this hypothesis, we reconstructed LGM bottom water salinity based on sedimentary porewater chloride profiles in a north-south transect of piston cores collected from the deep western North Atlantic. LGM bottom water salinity in the deep western North Atlantic determined by the density-based method is 3.41–3.99 ± 0.15% higher than modern values at these sites. This increase is consistent with: (a) the 3.6% global average salinity change expected from eustatic sea level rise, (b) a northward expansion of southern sourced deep water, (c) shoaling of northern sourced deep water, and (d) a reversal of the Atlantic's north-south deep water salinity gradient during the LGM.

中文翻译：

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北大西洋深海末次冰期最大盐度重建

我们重建了末次盛冰期（LGM，19-26 ka）期间北大西洋西部的深水质量盐度和空间分布，当时大气 CO ₂明显低于今天。一些 LGM 水团重建假设 LGM 大西洋经向底水盐度梯度发生逆转。这种逆转有可能影响气候、海洋环流和大气 CO ₂通过增加深海的热能和碳储存能力。为了验证这一假设，我们根据从北大西洋西部深处收集的活塞岩心南北横断面中的沉积孔隙水氯化物剖面重建了 LGM 底部水盐度。通过基于密度的方法确定的北大西洋西部深部 LGM 底部水盐度比这些地点的现代值高 3.41–3.99 ± 0.15%。这种增加与：(a) 海平面上升导致的 3.6% 全球平均盐度变化一致，(b) 南部源深水向北扩张，(c) 北部源深水浅滩，以及 (d) a LGM期间大西洋南北深水盐度梯度的逆转。