Seasonal climate variability is an important component of Earth's climate system, and has a significant impact on ecosystems and social systems. However, the temporal resolution of most proxy-based paleoclimate records is limiting to fully understand the past seasonal changes. Here, we used high-precision monthly resolution Sr/Ca records of three Tridacna squamosa specimens from the northern South China Sea (SCS) to reconstruct the sea surface temperature (SST) seasonality during three time periods from the middle Holocene. The results suggested that SST seasonality in the northern SCS during the middle Holocene (3.21 ± 0.98°C) was smaller than that for recent decades (AD 1994–2004, 4.32 ± 0.59°C). Analysis of modern instrumental data showed that the SST seasonality in the northern SCS was dominated by the winter SST, which was deeply influenced by the intensity of East Asian winter monsoon (EAWM). A strong EAWM usually resulted in cooler winter SST and a larger SST seasonality in the northern SCS. The reconstructed Holocene EAWM records showed that the EAWM strengthened from the middle to late Holocene, which was seen in our reconstruction of less SST seasonality changes during the middle Holocene in the northern SCS. This study highlighted that the Sr/Ca ratios from Tridacna shells can be used as a potential high-resolution indicator of past seasonal climate changes.

中文翻译：

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全新世中期南海北部海表温度季节性从砗磲贝壳的高分辨率Sr/Ca比值得到

季节性气候变率是地球气候系统的重要组成部分，对生态系统和社会系统具有重要影响。然而，大多数基于代理的古气候记录的时间分辨率限制了充分了解过去的季节性变化。在这里，我们使用了三个高精度月分辨率 Sr/Ca 记录鳞砗磲来自南海北部（SCS）的标本，以重建中全新世三个时期的海表温度（SST）季节性。结果表明，中全新世南海北部海温季节性（3.21±0.98°C）小于近几十年（公元1994-2004，4.32±0.59°C）。现代仪器资料分析表明，南海北部海温季节性以冬季海温为主，受东亚冬季风（EAWM）强度影响较大。强东亚冬季风通常导致南海北部冬季海温较冷和海温季节性较大。重建的全新世 EAWM 记录表明，EAWM 在全新世中晚期增强，这在我们重建南海北部中期全新世期间较少的 SST 季节性变化中可以看出。本研究强调 Sr/Ca 比值砗磲贝壳可用作过去季节性气候变化的潜在高分辨率指标。