50 year means of oxygen isotope data from ice core NGRIP

Two deep ice cores from central Greenland, drilled in the 1990s, have played a key role in climate reconstructions of the Northern Hemisphere, but the oldest sections of the cores were disturbed in chronology owing to ice folding near the bedrock. Here we present an undisturbed climate record from a North Greenland ice core, which extends back to 123,000 years before the present, within the last interglacial period. The oxygen isotopes in the ice imply that climate was stable during the last interglacial period, with temperatures 5 °C warmer than today. We find unexpectedly large temperature differences between our new record from northern Greenland and the undisturbed sections of the cores from central Greenland, suggesting that the extent of ice in the Northern Hemisphere modulated the latitudinal temperature gradients in Greenland. This record shows a slow decline in temperatures that marked the initiation of the last glacial period. Our record reveals a hitherto unrecognized warm period initiated by an abrupt climate warming about 115,000 years ago, before glacial conditions were fully developed. This event does not appear to have an immediate Antarctic counterpart, suggesting that the climate see-saw between the hemispheres (which dominated the last glacial period) was not operating at this time.

两支于1990年代钻取的格陵兰中部深层冰芯，在北半球气候重建研究中发挥了关键作用，但受基岩附近冰体褶皱影响，该批冰芯的最老层段的年代学信息遭到扰动。本研究报道了一支格陵兰北部冰芯的未受扰动气候记录，其时间跨度可追溯至距今12.3万年前，覆盖末次间冰期时段。冰体中的氧同位素（oxygen isotopes）数据显示，末次间冰期的气候处于稳定状态，当时气温较现代偏高5℃。我们发现，格陵兰北部的新记录与格陵兰中部冰芯未受扰动层段之间存在出乎意料的显著温差，这表明北半球冰盖规模调控了格陵兰地区的纬向温度梯度。该记录呈现出缓慢的气温下降过程，这一变化标志着末次冰期的起始。本研究的记录还揭示了一个此前未被认知的暖期：该暖期由约11.5万年前的突发性气候变暖所启动，发生在冰期条件完全形成之前。该事件似乎并未在南极地区出现对应的同期信号，这表明在该时段，主导末次冰期的南北半球气候跷跷板（climate see-saw）效应并未运作。