Centennial-scale climate change from decadally-paced explosive volcanism: a coupled sea ice-ocean mechanism
Centennial-scale climate change from decadally-paced explosive volcanism: a coupled sea ice-ocean mechanism
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DOI：
10.1007/s00382-010-0967-z
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发表时间：
2011-12
期刊：
影响因子：
4.6
通讯作者：
Y. Zhong;G. Miller;B. Otto‐Bliesner;M. Holland;D. Bailey;D. Schneider;D. Schneider;Á. Geirsdóttir
中科院分区：
文献类型：
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作者：
Y. Zhong;G. Miller;B. Otto‐Bliesner;M. Holland;D. Bailey;D. Schneider;D. Schneider;Á. Geirsdóttir
北方半球夏季的冷却在很大程度上是由夏季日照的稳定减少所驱动的，这种减少与分点的岁差有关。然而，百年尺度的气候偏离，如小冰期，必须由其他强迫引起，最有可能是爆发性火山活动和太阳辐照度的变化。平流层火山气溶胶具有更强的强迫作用，但它们的停留时间很短，可能会排除一次喷发对气候的持久影响。十年一次的火山爆发可能会对气候产生更大的影响，因为海洋表面沃茨的反应时间很长，使海洋表面温度的累积下降超过任何一次火山爆发。在这里，我们使用一个全球气候模型来评估潜在的长期气候影响，从四个十年节奏的大型热带火山爆发。直接强迫导致北冰洋海冰迅速扩张，并在整个喷发期间持续存在。扩展的海冰增加了输出到北大西洋北方的海冰通量，足够长的时间，它减少了副极地北大西洋表面沃茨的对流变暖。在我们的四个模拟中的两个中，较冷的表面沃茨被平流输送到北冰洋，降低了北冰洋大西洋部分基底海冰融化的速度，使海冰在火山气溶胶从平流层中去除后保持在扩张状态超过100个模型年。在这些模拟中，海冰-海洋耦合机制保持了北冰洋海冰覆盖面积扩大的强烈正反馈，使与火山气溶胶直接影响有关的初始冷却得以延续，可能导致北极气候百年尺度或更长时间的状态变化。在我们的四次模拟中，有两次没有建立海冰-海洋机制，这一事实表明，海冰对火山强迫的长期反应对爆发期间北大西洋海水柱、风和洋流的稳定性很敏感。
Northern Hemisphere summer cooling through the Holocene is largely driven by the steady decrease in summer insolation tied to the precession of the equinoxes. However, centennial-scale climate departures, such as the Little Ice Age, must be caused by other forcings, most likely explosive volcanism and changes in solar irradiance. Stratospheric volcanic aerosols have the stronger forcing, but their short residence time likely precludes a lasting climate impact from a single eruption. Decadally paced explosive volcanism may produce a greater climate impact because the long response time of ocean surface waters allows for a cumulative decrease in sea-surface temperatures that exceeds that of any single eruption. Here we use a global climate model to evaluate the potential long-term climate impacts from four decadally paced large tropical eruptions. Direct forcing results in a rapid expansion of Arctic Ocean sea ice that persists throughout the eruption period. The expanded sea ice increases the flux of sea ice exported to the northern North Atlantic long enough that it reduces the convective warming of surface waters in the subpolar North Atlantic. In two of our four simulations the cooler surface waters being advected into the Arctic Ocean reduced the rate of basal sea-ice melt in the Atlantic sector of the Arctic Ocean, allowing sea ice to remain in an expanded state for > 100 model years after volcanic aerosols were removed from the stratosphere. In these simulations the coupled sea ice-ocean mechanism maintains the strong positive feedbacks of an expanded Arctic Ocean sea ice cover, allowing the initial cooling related to the direct effect of volcanic aerosols to be perpetuated, potentially resulting in a centennial-scale or longer change of state in Arctic climate. The fact that the sea ice-ocean mechanism was not established in two of our four simulations suggests that a long-term sea ice response to volcanic forcing is sensitive to the stability of the seawater column, wind, and ocean currents in the North Atlantic during the eruptions.