Relative sea-level data preclude major late Holocene ice-mass change in Pine Island Bay
Relative sea-level data preclude major late Holocene ice-mass change in Pine Island Bay
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DOI：
10.1038/s41561-022-00961-y
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发表时间：
2022-06-09
影响因子：
18.3
通讯作者：
Woodward, John
中科院分区：
文献类型：
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作者：
Braddock, Scott;Hall, Brenda L.;Woodward, John
快速消退的Thwaites冰川和Pine Island冰川共同主导着西南极冰盖今天的冰川消融，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显著变小，并随后恢复到现在的程度，对于评估目前的冰川衰退是否不可逆转至关重要。在这里，我们重建了这些冰川附近海域的放射性碳年代测定的隆起海滩的相对海平面变化，使我们能够检查地球对阿蒙森海地区冰装载和卸载的反应。我们发现，相对海平面在过去5.5KYR期间稳步下降，没有表现出大规模冰层重新膨胀的速率变化。此外，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，这表明区域地壳卸荷发生了变化，并意味着目前的冰川消融可能是过去前所未有的，类似于5.5KYR。虽然我们不能排除较小的基准线波动，但我们的数据最容易解释为全新世早期冰川消融，随后是直到最近的相对稳定的冰层位置，这意味着在过去5.5KYR期间，Thwaites和Pine Island冰川并没有比现在小很多。
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 similar to 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.