The Community Earth System Model version 2.1 (CESM2.1) is used to investigate the evolution of the Greenland ice sheet (GrIS) surface mass balance (SMB) under an idealized CO₂ forcing scenario of 1% increase until stabilization at 4× pre‐industrial at model year 140. In this simulation, the SMB calculation is coupled with the atmospheric model, using a physically based surface energy balance scheme for melt, explicit calculation of snow albedo, and a realistic treatment of polar snow and firn compaction. By the end of the simulation (years 131–150), the SMB decreases with 994 Gt yr⁻¹ with respect to the pre‐industrial SMB, which represents a sea‐level rise contribution of 2.8 mm yr⁻¹. For a threshold of 2.7‐K global temperature increase with respect to pre‐industrial, the rate of expansion of the ablation area increases, the mass loss accelerates due to loss of refreezing capacity and accelerated melt, and the SMB becomes negative 6 years later. Before acceleration, longwave radiation is the most important contributor to increasing energy for melt. After acceleration, the large expansion of the ablation area strongly reduces surface albedo. This and much increased turbulent heat fluxes as the GrIS‐integrated summer surface temperature approaches melt point become the major sources of energy for melt.

中文翻译：

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全球变暖阈值和加速格陵兰冰盖表面质量损失的机制

社区地球系统模型版本2.1（CESM2.1）用于研究在1％的理想CO ₂强迫情景下格陵兰冰盖（GrIS）表面质量平衡（SMB）的演变，直到稳定在4 × pre-工业在模型年140。在此模拟中，SMB计算与大气模型相结合，使用基于物理的地表能量平衡方案进行融化，明确计算雪反照率，并实际处理极地积雪和杉木压实。到模拟结束时（131-150年），SMB相对于工业化之前的SMB以994 Gt yr ^-1减少，这表示海平面上升贡献为2.8 mm yr ^-1。对于相对于工业化前的温度升高2.7-K的阈值，消融区域的膨胀率增加，由于再冻能力的丧失和加速的熔化，质量损失加速，SMB在6年后变为负值。在加速之前，长波辐射是增加熔体能量的最重要因素。加速后，消融区域的大扩展会大大降低表面反照率。随着GrIS整合的夏季表面温度接近熔点，湍流通量随之增加，并成为湍流的主要能量来源。