The marine δ18O record overestimates continental ice volume during Marine Isotope Stage 3
The marine δ18O record overestimates continental ice volume during Marine Isotope Stage 3
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DOI：
10.1016/j.gloplacha.2022.103814
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发表时间：
2022-04-22
影响因子：
3.9
通讯作者：
Helmens, Karin F.
中科院分区：
文献类型：
--
作者：
Dalton, April S.;Pico, Tamara;Helmens, Karin F.
第四纪研究界对海洋818 O信号有多少是由冰量变化驱动的存在分歧。在这里，我们研究这一主题，汇集了海洋同位素阶段3（MIS 3; 57 ka至29 ka）的经验和建模工作，海洋818 O记录表明中度大陆冰川作用和全球平均海平面在-60米和-90米之间。我们编译和解释地质数据追溯到MIS 3，以限制主要的北方半球冰盖（欧亚，劳伦蒂德，科迪勒支）的范围。许多关键数据，特别是在过去15年中发表的数据，认为以前的冰川地区的无冰核心与海洋818 O记录的推论不一致。我们编译的结果，从以前的研究冰川均衡调整显示冰量推断海洋818 O记录无法适应合理的足迹北方冰盖在MIS 3。相反，全球平均海平面在-30米和-50米之间是从地质约束和冰川均衡模型推断出来的。此外，有限的北美冰量在MIS 3是一致的，大多数海平面边界通过该间隔。我们没有发现MIS 3期间大规模冰川作用的具体证据，可以解释在此期间海平面当量的-30米缺失，这表明海洋818 O记录的变化是由其他变量驱动的，包括水温。这项工作敦促人们在几乎没有地质限制的情况下，对依赖海洋818 O记录作为大陆冰事实上的指标持谨慎态度，这是许多第四纪研究的基础。
There is disagreement in the Quaternary research community in how much of the marine 818O signal is driven by change in ice volume. Here, we examine this topic by bringing together empirical and modelling work for Marine Isotope Stage 3 (MIS 3; 57 ka to 29 ka), a time when the marine 818O record indicates moderate continental glaciation and a global mean sea level between -60 m and -90 m. We compile and interpret geological data dating to MIS 3 to constrain the extent of major Northern Hemisphere ice sheets (Eurasian, Laurentide, Cordilleran). Many key data, especially published in the past -15 years, argue for an ice-free core of the formerly glaciated regions that is inconsistent with inferences from the marine 818O record. We compile results from prior studies of glacial isostatic adjustment to show the volume of ice inferred from the marine 818O record is unable to fit within the plausible footprint of Northern Hemisphere ice sheets during MIS 3. Instead, a global mean sea level between -30 m and - 50 m is inferred from geological constraints and glacial isostatic modelling. Furthermore, limited North American ice volumes during MIS 3 are consistent with most sea-level bounds through that interval. We can find no concrete evidence of large-scale glaciation during MIS 3 that could account for the missing -30 m of sea-level equivalent during that time, which suggests that changes in the marine 818O record are driven by other variables, including water temperature. This work urges caution regarding the reliance of the marine 818O record as a de facto indicator of continental ice when few geological constraints are available, which underpins many Quaternary studies.