Tropical Pacific Modulation of the Asian Summer Monsoon Over the Last Millennium in Paleoclimate Data Assimilation Reconstructions
Tropical Pacific Modulation of the Asian Summer Monsoon Over the Last Millennium in Paleoclimate Data Assimilation Reconstructions
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DOI：
10.1029/2023jd039207
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发表时间：
2023-09
期刊：
影响因子：
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通讯作者：
Jun Hu;S. Dee;Grant Parajuli;K. Thirumalai
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作者：
Jun Hu;S. Dee;Grant Parajuli;K. Thirumalai
亚洲夏季风（ASM）的气候模式预测存在很大的不确定性。厄尔尼诺-南方涛动（ENSO）是夏季风的重要调制因子，但ENSO-夏季风遥相关不是平稳的。此外，ENSO与东亚和南亚亚分量的ASM之间的遥相关表现出不同的特征。因此，了解ENSO-ASM遥相关的变化对于预测ASM强度的未来变化至关重要。为此，我们在这里使用古气候记录，以延长时间的覆盖范围超过仪器时代的千年。最近，数据同化技术已被应用于上个千年，这有助于物理上一致的，全球网格气候重建古气候观测资料。我们使用这些新的数据同化产品来研究过去1,000年来ENSO-ASM关系的变化。我们发现，ENSO和ASM指数之间的相关性大多是负的，在过去的千年，这表明强ASM年往往与拉尼娜事件。在ENSO和东亚夏季风之间的弱相关期间，我们在太平洋观察到类似厄尔尼诺的海表温度（SST）模式。此外，与ENSO和南亚夏季风降水之间的弱相关性的时期相关的SST模式是不一致的数据同化产品。这强调了在过去的一千年中，在印度次大陆领域开发更多降水敏感的古气候代理的重要性。我们的研究为未来评估古气候同化产品提供了一个基线，并为我们使用古气候数据集了解十年尺度ENSO-ASM遥相关变率提供了一个例子。
Large uncertainties exist in climate model projections of the Asian summer monsoon (ASM). The El Niño‐Southern Oscillation (ENSO) is an important modulator of the ASM, but the ENSO‐ASM teleconnection is not stationary. Furthermore, teleconnections between ENSO and the East Asian versus South Asian subcomponents of the ASM exhibit distinct characteristics. Therefore, understanding the variability of the ENSO‐ASM teleconnection is critical for anticipating future variations in ASM intensity. To this end, we here use paleoclimate records to extend temporal coverage beyond the instrumental era by millennia. Recently, data assimilation techniques have been applied for the last millennium, which facilitates physically consistent, globally gridded climate reconstructions informed by paleoclimate observations. We use these novel data assimilation products to investigate variations in the ENSO‐ASM relationship over the last 1,000 years. We find that correlations between ENSO and ASM indices are mostly negative in the last millennium, suggesting that strong ASM years are often associated with La Niña events. During periods of weak correlations between ENSO and the East Asian summer monsoon, we observe an El Niño‐like sea surface temperature (SST) pattern in the Pacific. Additionally, SST patterns associated with periods of weak correlations between ENSO and South Asian summer monsoon rainfall are not consistent among data assimilation products. This underscores the importance of developing more precipitation‐sensitive paleoclimate proxies in the Indian subcontinental realm over the last millennium. Our study serves as a baseline for future appraisals of paleoclimate assimilation products and an example of informing our understanding of decadal‐scale ENSO‐ASM teleconnection variability using paleoclimate data sets.