The rapidly retreating Thwaites and Pine Island glaciers together dominate present-day ice loss from the West Antarctic Ice Sheet and are implicated in runaway deglaciation scenarios. Knowledge of whether these glaciers were substantially smaller in the mid-Holocene and subsequently recovered to their present extents is important for assessing whether current ice recession is irreversible. Here we reconstruct relative sea-level change from radiocarbon-dated raised beaches at sites immediately seawards of these glaciers, allowing us to examine the response of the earth to loading and unloading of ice in the Amundsen Sea region. We find that relative sea level fell steadily over the past 5.5 kyr without rate changes that would characterize large-scale ice re-expansion. Moreover, current bedrock uplift rates are an order of magnitude greater than the rate of long-term relative sea-level fall, suggesting a change in regional crustal unloading and implying that the present deglaciation may be unprecedented in the past ~5.5 kyr. While we cannot preclude minor grounding-line fluctuations, our data are explained most easily by early Holocene deglaciation followed by relatively stable ice positions until recent times and imply that Thwaites and Pine Island glaciers have not been substantially smaller than present during the past 5.5 kyr.

迅速消退的思韦茨冰川和松岛冰川共同主导了当今南极西部冰盖的冰层流失，并与失控的冰川消融情景有关。了解这些冰川在全新世中期是否明显变小并随后恢复到目前的程度对于评估当前的冰衰退是否不可逆转非常重要。在这里，我们重建了这些冰川紧靠海面地点的放射性碳测年凸起海滩的相对海平面变化，从而使我们能够检查地球对阿蒙森海地区冰的装载和卸载的响应。我们发现，在过去 5.5 kyr 中，相对海平面稳步下降，而没有发生大规模冰再膨胀的速率变化。而且，目前的基岩抬升速率比长期相对海平面下降的速率大一个数量级，这表明区域地壳卸载发生了变化，并暗示目前的冰消可能在过去约 5.5 kyr 中是前所未有的。虽然我们不能排除轻微的接地线波动，但我们的数据最容易解释为早期全新世冰川消融，然后是最近相对稳定的冰位，这意味着在过去 5.5 kyr 期间，Thwaites 和 Pine Island 冰川并没有比现在小很多。