Poleward amplification, seasonal rainfall and forest heterogeneity in the Miocene of the eastern USA
Poleward amplification, seasonal rainfall and forest heterogeneity in the Miocene of the eastern USA
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DOI：
10.1016/j.gloplacha.2023.104073
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发表时间：
2023-02
影响因子：
3.9
通讯作者：
T. Reichgelt;A. Baumgartner;R. Feng;D. Willard
中科院分区：
文献类型：
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作者：
T. Reichgelt;A. Baumgartner;R. Feng;D. Willard
古气候重建可以为了解地球历史上大气二氧化碳浓度高于今天的环境条件提供一个窗口。在美国东部，古气候重建是稀疏的，因为陆地沉积物是罕见的。尽管如此，美国东部拥有北美最大的人口和人口密度，了解当前和未来气候变化的影响至关重要。在这里，我们提供了美国东部的陆地古气候重建中新世化石植物群。此外，我们比较代理古气候重建从最温暖的时期在中新世，中新世气候最佳（MCO），MCO地球系统模型。重建的中新世温度和35°N以北的降水量高于现代。相比之下，北纬35°以南的气温和降水与今天相似，这表明北美东部存在向极放大效应。重建的中新世降雨季节性主要是高于现代，无论纬度，表明更大的变化在一年内的水分输送。重建的气候在温带季节性森林生物群落中几乎是一致的，但特定森林类型的异质性是显而易见的。重建的美国东部中新世陆地温度低于模拟温度和同时代大西洋海面温度。然而，重建的降雨量是一致的模拟降雨。我们的研究结果表明，在中新世，气候是最不同的现代在东北部各州，并可能表明急剧减少的纬向温度梯度沿着北美东海岸相比，今天。
Paleoclimate reconstructions can provide a window into the environmental conditions in Earth history when atmospheric carbon dioxide concentrations were higher than today. In the eastern USA, paleoclimate reconstructions are sparse, because terrestrial sedimentary deposits are rare. Despite this, the eastern USA has the largest population and population density in North America, and understanding the effects of current and future climate change is of vital importance. Here, we provide terrestrial paleoclimate reconstructions of the eastern USA from Miocene fossil floras. Additionally, we compare proxy paleoclimate reconstructions from the warmest period in the Miocene, the Miocene Climatic Optimum (MCO), to those of an MCO Earth System Model. Reconstructed Miocene temperatures and precipitation north of 35°N are higher than modern. In contrast, south of 35°N, temperatures and precipitation are similar to today, suggesting a poleward amplification effect in eastern North America. Reconstructed Miocene rainfall seasonality was predominantly higher than modern, regardless of latitude, indicating greater variability in intra-annual moisture transport. Reconstructed climates are almost uniformly in the temperate seasonal forest biome, but heterogeneity of specific forest types is evident. Reconstructed Miocene terrestrial temperatures from the eastern USA are lower than modeled temperatures and coeval Atlantic sea surface temperatures. However, reconstructed rainfall is consistent with modeled rainfall. Our results show that during the Miocene, climate was most different from modern in the northeastern states, and may suggest a drastic reduction in the meridional temperature gradient along the North American east coast compared to today.