Paleosols comprise an important archive of continental paleoclimate information throughout geologic history, but resolving temperature seasonality poses a challenge to the application of paleosol-derived temperature proxies. Not only does seasonality exert a strong control on the biosphere, but it can also obfuscate accurate interpretation of proxy records of paleotemperature. In order to examine the effect temperature seasonality has on paleosol temperature proxies, soil temperature data were compiled from over 200 stations that comprise the NRCS Soil Climate Analysis Network. Observed and modeled seasonal soil temperature variations were then compared to quantify system behavior. Greater than predicted soil temperature seasonality is observed at nearly half of the sites, driven primarily by direct heating of the soil surface by solar radiation. The ground-heating effect becomes more pronounced at sites receiving less than 600 mm of annual precipitation, with an average effect > 4 °C when mean annual precipitation falls below 300 mm. Large ground heating effects cannot be presumed for all carbonate-bearing paleosols, but the effect can be approximated when combined with paleo-precipitation estimates. Approximately two-fifths of sites record less temperature variation than predicted. This reduction in soil temperature seasonality is a result of warmer cold-season soil temperatures, driven by processes such as snow cover insulation and explains why pedotransfer functions break down below mean annual air temperatures (MAAT) of 6 to 8 °C. Clumped isotope measurements of pedogenic carbonate from a stacked series of late Eocene paleosols from Northeastern Spain are also examined to demonstrate how the documented seasonal trends in modern soils can inform paleo-applications, by considering carbonate formation depth and predicted ground heating effect. These paleosol results are best explained by a MAAT of ∼27 °C with annual temperature seasonality of 25 °C.

中文翻译：

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土壤温度季节性对古土壤气候重建的影响

古土壤是整个地质历史中大陆古气候信息的重要档案，但解决温度季节性对古土壤衍生温度代理的应用提出了挑战。季节性不仅对生物圈有很强的控制作用，而且还会混淆对古温度代用记录的准确解释。为了检查温度季节性对古土壤温度代理的影响，从 200 多个站点收集了土壤温度数据，这些站点包括 NRCS 土壤气候分析网络。然后比较观察和模拟的季节性土壤温度变化以量化系统行为。在近一半的地点观察到大于预测的土壤温度季节性，主要是由太阳辐射直接加热土壤表面造成的。在年降水量低于 600 毫米的地点，地热效应变得更加明显，当年平均降水量低于 300 毫米时，平均效应 > 4 °C。不能假设所有含碳酸盐的古土壤都有大的地热效应，但是当结合古降水估计值时可以近似估计这种效应。大约五分之二的站点记录的温度变化比预测的要小。土壤温度季节性的降低是寒冷季节土壤温度升高的结果，由积雪绝缘等过程驱动，并解释了为什么土壤传递函数在低于 6 至 8 °C 的年平均气温 (MAAT) 时分解。还检查了来自西班牙东北部一系列堆积的始新世晚期古土壤的成土碳酸盐的成簇同位素测量，以通过考虑碳酸盐形成深度和预测的地面加热效应来证明现代土壤中记录的季节性趋势如何为古应用提供信息。这些古土壤结果最好用约 27 °C 的 MAAT 来解释，年温度季节性为 25 °C。