挪威北极大学Bochow, Nils课题组在研究格陵兰冰盖的临界阈值中取得新进展，他们认为格陵兰冰盖的临界阈值正在被超过。相关论文于2023年10月18日发表于国际顶尖学术期刊《自然》杂志上。

课题组的研究人员设计了两个独立的冰盖模型，以研究具有不同峰值温度和汇聚温度的不同超额情景、对大范围变暖和随后的变冷速率的影响。研究结果表明，最大全球平均温度和超过给定全球平均温度目标的时间跨度是决定格陵兰冰盖稳定性的关键。研究人员发现，全球平均温度的临界阈值高于工业化水平之上 1.7°C 和 2.3°C 之间时，冰盖就会突然消融。

如果全球平均温度，在随后在几个世纪内降低到比工业化前水平高不到 1.5℃ 时，即使全球平均温度比工业化前水平高6°C或更多，格陵兰冰盖的损失也可以大大减少。然而，研究结果也表明，即使暂时超过温度阈值，没有过渡到一个新的冰盖状态，仍然会引起高达几米的海平面上升峰值。

据介绍，人类活动造成全球变暖引发的格陵兰冰盖(GrIS)的融化，对全球海平面上升(SLR)构成了严重威胁。模拟和古气候证据表明，北极迅速上升的温度会触发格陵兰冰盖的正反馈机制，导致其自持融化，并且格陵兰冰盖已被证明可能存在几种稳定状态。当全球平均温度(GMT)超过特定阈值时，在稳定状态之间存在相当大的滞后，并预计会出现临界转变。

附：英文原文

Title: Overshooting the critical threshold for the Greenland ice sheet

Author: Bochow, Nils, Poltronieri, Anna, Robinson, Alexander, Montoya, Marisa, Rypdal, Martin, Boers, Niklas

Issue&Volume: 2023-10-18

Abstract: Melting of the Greenland ice sheet (GrIS) in response to anthropogenic global warming poses a severe threat in terms of global sea-level rise (SLR). Modelling and palaeoclimate evidence suggest that rapidly increasing temperatures in the Arctic can trigger positive feedback mechanisms for the GrIS, leading to self-sustained melting, and the GrIS has been shown to permit several stable states. Critical transitions are expected when the global mean temperature (GMT) crosses specific thresholds, with substantial hysteresis between the stable states. Here we use two independent ice-sheet models to investigate the impact of different overshoot scenarios with varying peak and convergence temperatures for a broad range of warming and subsequent cooling rates. Our results show that the maximum GMT and the time span of overshooting given GMT targets are critical in determining GrIS stability. We find a threshold GMT between 1.7°C and 2.3°C above preindustrial levels for an abrupt ice-sheet loss. GrIS loss can be substantially mitigated, even for maximum GMTs of 6°C or more above preindustrial levels, if the GMT is subsequently reduced to less than 1.5°C above preindustrial levels within a few centuries. However, our results also show that even temporarily overshooting the temperature threshold, without a transition to a new ice-sheet state, still leads to a peak in SLR of up to several metres.

DOI: 10.1038/s41586-023-06503-9

Source: https://www.nature.com/articles/s41586-023-06503-9