Disentangling seasonal signals in Holocene climate trends by satellite-model-proxy integration
Disentangling seasonal signals in Holocene climate trends by satellite-model-proxy integration
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DOI：
10.1029/2009pa001893
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发表时间：
2010-12
期刊：
影响因子：
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通讯作者：
B. Schneider;G. Leduc;W. Park
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文献类型：
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作者：
B. Schneider;G. Leduc;W. Park
过去的海表温度（SST）通常是根据从海底沉积物中回收的浮游植物或浮游动物生物化石的有机和无机残留物来估计的。潜在的季节性偏差的古代理进行了深入的研究，在过去，然而，即使是最常用的两个古代理SST，UK 0 37和Mg/Ca比，一个清晰的全球图片还不存在。在本研究中，我们结合联合收割机全新世SST的趋势来自UK 0 37和Mg/Ca比的结果，从理想化的气候模式模拟被迫在轨道曲率的变化，这代表了主要的气候驱动器在过去的10 kyrs。这种变化造成入射太阳辐射的时空重新分布，导致季节周期的幅度和相位的调制。考虑到气候信号所记录的一个以南极洲为基础的古代理可能会受到各自生物的季节性生产力周期的影响，我们使用SST和海洋净初级生产力（NPP）之间的现代关系，两者都从卫星观测，计算季节性指数（SI）作为一个独立的约束，以链接模拟SST趋势与代理数据。虽然气候模型系统地低估了全新世SST的趋势，我们发现，季节性生产力峰值的phytocarpton-based UK 0 37结果在高（低）纬度地区的暖（冷）季的优先登记，因为它是预期的SI分布。从动物园衍生的Mg/Ca-SST的整体平滑趋势表明，在较长的时间平均值，这也可能带有季节性偏差，但空间模式不太清楚更集成的信号。根据我们的研究结果，仔细的多代理方法实际上可以超越平均气候趋势的重建，特别是允许解决季节性的演变。
Past sea surface temperatures (SSTs) are routinely estimated from organic and inorganic remains of fossil phytoplankton or zooplankton organisms, recovered from sea floor sediments. Potential seasonal biases of paleo proxies were intensely studied in the past, however, even for the two most commonly used paleo proxies for SST, UK0 37 and Mg/Ca ratios, a clear global picture does not yet exist. In the present study we combine Holocene SST trends derived from UK0 37 and Mg/Ca ratios with results from idealized climate model simulations forced by changes in the orbital conguration, which represents the major climate driver over the last 10 kyrs. Such changes cause a spatio-temporal redistribution of incoming solar radiation resulting in a modulation of amplitude and phasing of the seasonal cycle. Considering that the climate signal recorded by a plankton-based paleo proxy may be aected by the seasonal productivity cycle of the respective organism, we use the modern relationship between SST and marine net primary production (NPP), both obtained from satellite observations, to calculate a seasonality index (SI) as an independent constraint to link modeled SST trends with proxy data. Although the climate model systematically underestimates Holocene SST trends, we find that seasonal productivity peaks of the phytoplankton-based UK0 37 result in a preferential registering of the warm (cold) season in high (low) latitudes, as it was expected from the SI distribution. The overall smoother trends from the zooplankton-derived Mg/Ca-SSTs suggest a more integrated signal over longer time averages, which may also carry a seasonal bias, but the spatial pattern is less clear. Based on our ndings, careful multi-proxy approaches can actually go beyond the reconstruction of average climate trends, specifically allowing to resolve the evolution of seasonality.