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Holocene centennial to millennial shifts in North-Atlantic storminess and ocean dynamics

机译:北大西洋风暴和海洋动力学的全新世百年至千年变化

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摘要

The forcing mechanisms responsible for centennial to millennial variability of mid-latitude storminess are still poorly understood. On decadal scales, the present-day geographic variability of North-Atlantic storminess responds to latitudinal shifts of the North-Atlantic westerly wind-belt under the prime control of the North-Atlantic Oscillation (NAO). An equivalent mechanism operating at centennial to millennial time scales during the Holocene is still to be ascertained, especially owing to the lack of high-resolution and continuous records of past-storminess extending far enough in time. Here we present a reconstruction of past storminess activity based on a high-resolution record of wind-blown sand retrieved from a near-coastal wetland. Our record extends back to ca. 10,000 B.P. and allows to continuously document fluctuations in the frequency of Holocene storm-force winds at our study-site at a mean high temporal resolution of 40 years. Large similarities between our record and palaeo-oceanographic records of Holocene climate changes in the North-Atlantic suggest that our past-storminess record reproduces a signal of significance for the North-Eastern Atlantic realm. We find that Holocene North-Atlantic storminess is dominated by robust millennial (≈2,500-year) to centennial (≈400 and 200-year) periodicities. These changes in storminess were accompanied by changes in the precipitation regimes over northern Europe, evidencing large-scale shifts in the latitudinal positions of the Atlantic westerlies akin to present-day NAO patterns. We propose that these shifts originate from changes in the position and extent of the Azores high-pressure system and Polar vortex, as supported by climate model simulations. Finally, we demonstrate that enhanced zonal storminess activity over the North-Atlantic was the driver of centennial-scale changes in North-Atlantic oceanic circulation, while ocean dynamics most likely influenced back the atmospheric circulation at millennial time-scales. This may vouch for the instrumental role played by North-Atlantic storminess in triggering abrupt climate change at centennial scales during the Holocene.
机译:对于中纬度暴风雨百年至千年变化的强迫机制仍然知之甚少。在十年尺度上,北大西洋风暴的当今地理变异性是在北大西洋涛动(NAO)的主要控制下响应北大西洋西风带的纬度变化的。尚待确定在全新世期间百年至千禧年尺度上运行的等效机制,特别是由于缺乏高分辨率和连续的暴风雨记录在时间上延伸得足够远。在这里,我们基于从近沿海湿地中回收的风沙的高分辨率记录,提出了过去暴风雨活动的重建。我们的记录可以追溯到大约公元前10,000年并能够以40年的平均高时间分辨率在我们的研究地点连续记录全新世暴风的频率波动。我们的记录与北大西洋全新世气候变化的记录和古海洋学记录之间的巨大相似之处表明,我们过去的暴风雨记录再现了对东北大西洋领域的重要信号。我们发现,全新世北大西洋的暴风雨主要由健壮的千年期(约2500年)到百年期(约400和200年)周期性决定。暴风雨的这些变化伴随着北欧降水方式的变化,证明了大西洋西风纬度位置的大规模变化类似于当今的NAO模式。我们认为,这些变化源自气候模型模拟所支持的亚速尔群岛高压系统和极地涡旋的位置和范围的变化。最后,我们证明了北大西洋地区纬向风暴活动的增强是北大西洋海洋环流百年尺度变化的驱动力,而海洋动力学最有可能在千禧年尺度上影响了大气环流。这也许可以证明北大西洋风暴在全新世以百年尺度引发突变的气候变化中所发挥的作用。

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