Global ice volume (sea level) and deep-sea temperature are key measures of Earth's climatic state. We synthesize evidence for multi-centennial to millennial ice-volume and deep-sea temperature variations over the past 40 million years, which encompass the early glaciation of Antarctica at ∼34 million years ago (Ma), the end of the Middle Miocene Climate Optimum, and the descent into bipolar glaciation from ∼3.4 Ma. We compare different sea-level and deep-water temperature reconstructions to build a resource for validating long-term numerical model-based approaches. We present: (a) a new template synthesis of ice-volume and deep-sea temperature variations for the past 5.3 million years; (b) an extended template for the interval between 5.3 and 40 Ma; and (c) a discussion of uncertainties and limitations. We highlight key issues associated with glacial state changes in the geological record from 40 Ma to present that require attention in further research. These include offsets between calibration-sensitive versus thermodynamically guided deep-sea paleothermometry proxy measurements; a conundrum related to the magnitudes of sea-level and deep-sea temperature change at the Eocene-Oligocene transition at 34 Ma; a discrepancy in deep-sea temperature levels during the Middle Miocene; and a hitherto unquantified non-linear reduction of glacial deep-sea temperatures through the past 3.4 million years toward a near-freezing deep-sea temperature asymptote, while sea level stepped down in a more uniform manner. Uncertainties in proxy-based reconstructions hinder further distinction of “reality” among reconstructions. It seems more promising to further narrow this using three-dimensional ice-sheet models with realistic ice-climate-ocean-topography-lithosphere coupling, as computational capacities improve.

中文翻译：

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近4000万年海平面和深海温度变化的比较与综合

全球冰量（海平面）和深海温度是衡量地球气候状况的关键指标。我们综合了过去 4000 万年数百年到千年的冰量和深海温度变化的证据，其中包括约 3400 万年前（Ma）的南极洲早期冰川作用，中中新世气候最佳期结束，以及从 ~3.4 Ma 下降到双极冰川。我们比较了不同的海平面和深水温度重建，以构建用于验证基于长期数值模型的方法的资源。我们提出：(a) 过去 530 万年冰量和深海温度变化的新模板合成；(b) 5.3 至 40 Ma 区间的扩展模板；(c) 对不确定性和限制的讨论。我们强调了与地质记录中从 40 Ma 到现在的冰川状态变化相关的关键问题，这些问题需要在进一步研究中引起注意。这些包括校准敏感与热力学引导的深海古温度测量代理测量之间的偏移；与 34 Ma 始新世-渐新世过渡时海平面和深海温度变化幅度有关的难题；中新世深海温度水平的差异；在过去的 340 万年里，冰川深海温度向接近冰点的深海温度渐近线的非线性下降迄今尚未量化，同时海平面以更均匀的方式下降。基于代理的重建中的不确定性阻碍了重建之间“现实”的进一步区分。