Holocene climate trend, variability, and shift documented by lacustrine stable-isotope record in the northeastern United States
Holocene climate trend, variability, and shift documented by lacustrine stable-isotope record in the northeastern United States
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DOI：
10.1016/j.quascirev.2010.03.018
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发表时间：
2010-07
影响因子：
4
通讯作者：
Cheng Zhao;Zicheng Yu;E. Ito;Yan Zhao
中科院分区：
文献类型：
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作者：
Cheng Zhao;Zicheng Yu;E. Ito;Yan Zhao
早期研究表明，美国东北部全新世气候总体格局由寒干（11.6 ~ 8.2ka; 1ka=1000 cal yr BP）→暖湿（8.2 ~ 5.4ka）→暖干（5.4 ~ 3ka）→凉湿（3ka以后）。来自新泽西州北部格林内尔湖沉积物岩心的内生方解石的新的~ 35年分辨率稳定同位素记录提供了一个更详细地研究该地区全新世气候变化的机会。新仙女木期冷气候逆转后，δ18O在−7.4‰附近波动至5.8ka，此后δ18O逐渐减小，最近值为−8.2‰。作为对这一转变的回应，在美国东北部广泛观察到的铁杉数量下降发生在大约350-500（±143.5）年后。δ18O和δ13C的趋势记录在910年的周期内显示出明显的协方差。4.7ka后，百年际δ18O变化幅度减小。与此同时，这些变化的主要频率从330年到500年发生变化。从δ18O值的减小可以看出，5.8ka气候趋势的变化是由大气环流对日晒逐渐减少的非线性响应引起的。太阳强迫的主导性频移和日照季节对比的减弱可能通过调节海洋和大气环流导致4.7ka气候变率的变化。
Earlier studies indicated that the general pattern of the Holocene climate in the northeastern United States changed from cool and dry (11.6–8.2ka; 1ka=1000 cal yr BP) to warm and wet (8.2–5.4ka) to warm and dry (5.4–3ka) to cool and wet (after 3ka). A new ∼35-year resolution stable isotope record of endogenic calcite from a sediment core for Lake Grinnell in northern New Jersey provided a chance to examine the Holocene climate variations of the region in a finer detail. After the Younger Dryas cold climate reversal, the δ18O fluctuated around a constant value of −7.4‰ until 5.8ka, thereafter shifted to a steadily decreasing trend to the most recent value of −8.2‰. Responding to this shift, the widely observed hemlock decline in the northeastern USA occurred about ∼350–500 (±143.5) years later. Detrended δ18O and δ13C records show a clear covariance at 910-year periodicity. The amplitudes of centennial-scale δ18O variations became much smaller after 4.7ka. At the same time, the dominant frequency of these variations changed from 330 to 500 years. We suggest that a non-linear response of atmospheric circulation to the gradual decrease in insolation is responsible for the shift in the climate trend at 5.8ka as indicated by the deceasing δ18O values. A dominant frequency shift in solar forcing and the decreased seasonal contrast of insolation might have caused the change in climate variability at 4.7ka through modulating ocean and atmosphere circulations.