Glacier retreat in New Zealand during the Younger Dryas stadial
Glacier retreat in New Zealand during the Younger Dryas stadial
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DOI：
10.1038/nature09313
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发表时间：
2010-09-09
期刊：
影响因子：
64.8
通讯作者：
Doughty, Alice M.
中科院分区：
文献类型：
--
作者：
Kaplan, Michael R.;Schaefer, Joerg M.;Doughty, Alice M.
两个半球高纬度地区千年尺度的冷逆转中断了从完整冰期到间冰期气候条件的最后一次转变。在北方半球的大部分地区都已经确定了新仙女木事件的存在（类似于12.9万年前到11.7万年前），但是全球的时间、事件的性质和范围还没有很好的确定。特别是南半球中低纬度地区的证据仍然令人困惑（1-6）。这场辩论部分集中在新西兰山区冰川的行为上，以前的研究发现了关于冰范围增加或减少的确切时间的模棱两可的证据（1-3）。因此，新仙女木期气候系统的半球间行为仍然是一个悬而未决的问题，从根本上限制了我们制定这一时期全球气候动力学现实模型的能力。在这里，我们表明，新西兰的冰川退缩后，类似于13 kyr BP，在新仙女木的开始，并在随后的1.5 kyr期间。我们的证据是基于详细的地形测绘、高精度Be-10年代学（7）以及从保存完好的冰斗冰碛中重建的以前的冰范围和雪线。我们的晚冰期冰川年表与南极洲的气候趋势、南大洋的行为和大气中二氧化碳的变化相匹配。证据表明，在新仙女木时期，南部中纬度大气明显变暖，新西兰冰冻圈与南部高纬度气候密切相关。这些发现支持了这样一种假设，即北大西洋冬季海冰的扩展和北半球海洋翻转的减少导致了晚冰期期间强的半球间温度梯度（8），进而导致南大洋上升流和CO2释放的增加（9），从而引发了新仙女木北方期间南半球的变暖。
Millennial-scale cold reversals in the high latitudes of both hemispheres interrupted the last transition from full glacial to interglacial climate conditions. The presence of the Younger Dryas stadial (similar to 12.9 to similar to 11.7 kyr ago) is established throughout much of the Northern Hemisphere, but the global timing, nature and extent of the event are not well established. Evidence in mid to low latitudes of the Southern Hemisphere, in particular, has remained perplexing(1-6). The debate has in part focused on the behaviour of mountain glaciers in New Zealand, where previous research has found equivocal evidence for the precise timing of increased or reduced ice extent(1-3). The interhemispheric behaviour of the climate system during the Younger Dryas thus remains an open question, fundamentally limiting our ability to formulate realistic models of global climate dynamics for this time period. Here we show that New Zealand's glaciers retreated after similar to 13 kyr BP, at the onset of the Younger Dryas, and in general over the subsequent similar to 1.5-kyr period. Our evidence is based on detailed landform mapping, a high-precision Be-10 chronology(7) and reconstruction of former ice extents and snow lines from well-preserved cirque moraines. Our late-glacial glacier chronology matches climatic trends in Antarctica, Southern Ocean behaviour and variations in atmospheric CO2. The evidence points to a distinct warming of the southern mid-latitude atmosphere during the Younger Dryas and a close coupling between New Zealand's cryosphere and southern high-latitude climate. These findings support the hypothesis that extensive winter sea ice and curtailed meridional ocean overturning in the North Atlantic led to a strong interhemispheric thermal gradient(8) during late-glacial times, in turn leading to increased upwelling and CO2 release from the Southern Ocean(9), thereby triggering Southern Hemisphere warming during the northern Younger Dryas.