Global and Zonal‐Mean Hydrological Response to Early Eocene Warmth-猫眼课题宝

DOI：

10.1029/2022pa004542

发表时间：

2023-06

期刊：

Paleoceanography and Paleoclimatology

影响因子：

3.5

通讯作者：

中科院分区：

地球科学2区

文献类型：

作者：

M. Cramwinckel;N. Burls;A. A. Fahad-A.;Scott Knapp;C. K. West;T. Reichgelt;D. Greenwood;W. Chan;Y. Donnadieu;D. Hutchinson;A. D. de Boer;J. Ladant;P. Morozova;I. Niezgodzki;G. Knorr;S. Steinig;Zhongshi Zhang;Jiang Zhu;R. Feng;D. Lunt;A. Abe‐Ouchi;G. Inglis

地球的水文循环预计将加强，以应对全球变暖，与“湿越来越湿，干越来越干”的反应预计在海洋上。亚热带地区（北纬15°-30 ° N/S）预计会变得更干燥，但过去温暖气候的替代证据表明，这些地区可能以更潮湿的条件为特征。在这里，我们使用一种集成的数据建模方法来重建始新世早期（2.56 - 4800万年前）的全球和纬向平均降雨模式。DeepMIP（DeepTime Model Intercomparison Project）模式集合表明，中纬度（30°-60 ° N/S）和高纬度（>60°N/S）地区的特点是对变暖和总体湿润条件的水文响应以季节性为主。热带天气带（0°-15 ° N/S）的特征也是较为湿润，有多个DeepMIP模式模拟了热带辐合带的收窄。然而，从代理数据来看，后者并不明显。亚热带地区的特点是降水蒸发负异常（即，在DeepMIP模式中，干旱条件下），但平均年降水量（MAP）的模式间变异性令人惊讶地大。有趣的是，我们发现，具有较弱温度梯度的模型（例如，CESM，GFDL）的特点是减少副热带水分散度，导致MAP增加。这些模型模拟与我们新的代理衍生降水重建和其他关键气候指标更接近，并意味着始新世早期的特征是亚热带水分分歧减少。如果赤道温度梯度甚至比DeepMIP模型所建议的还要弱，那么环流引起的变化可能会超过热力学变化，导致亚热带更加潮湿。这凸显了在重建过去的降雨模式时准确重建纬向温度梯度的重要性。

Earth's hydrological cycle is expected to intensify in response to global warming, with a “wet‐gets‐wetter, dry‐gets‐drier” response anticipated over the ocean. Subtropical regions (∼15°–30°N/S) are predicted to become drier, yet proxy evidence from past warm climates suggests these regions may be characterized by wetter conditions. Here we use an integrated data‐modeling approach to reconstruct global and zonal‐mean rainfall patterns during the early Eocene (∼56–48 million years ago). The Deep‐Time Model Intercomparison Project (DeepMIP) model ensemble indicates that the mid‐ (30°–60°N/S) and high‐latitudes (>60°N/S) are characterized by a thermodynamically dominated hydrological response to warming and overall wetter conditions. The tropical band (0°–15°N/S) is also characterized by wetter conditions, with several DeepMIP models simulating narrowing of the Inter‐Tropical Convergence Zone. However, the latter is not evident from the proxy data. The subtropics are characterized by negative precipitation‐evaporation anomalies (i.e., drier conditions) in the DeepMIP models, but there is surprisingly large inter‐model variability in mean annual precipitation (MAP). Intriguingly, we find that models with weaker meridional temperature gradients (e.g., CESM, GFDL) are characterized by a reduction in subtropical moisture divergence, leading to an increase in MAP. These model simulations agree more closely with our new proxy‐derived precipitation reconstructions and other key climate metrics and imply that the early Eocene was characterized by reduced subtropical moisture divergence. If the meridional temperature gradient was even weaker than suggested by those DeepMIP models, circulation‐induced changes may have outcompeted thermodynamic changes, leading to wetter subtropics. This highlights the importance of accurately reconstructing zonal temperature gradients when reconstructing past rainfall patterns.

Global and Zonal‐Mean Hydrological Response to Early Eocene Warmth

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