Assessing bare-ice albedo simulated by MAR over the Greenland ice sheet (2000–2021) and implications for meltwater production estimates
Assessing bare-ice albedo simulated by MAR over the Greenland ice sheet (2000–2021) and implications for meltwater production estimates
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DOI：
10.5194/tc-16-4185-2022
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发表时间：
2022-10
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影响因子：
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通讯作者：
R. Antwerpen;M. Tedesco;X. Fettweis;P. Alexander;W. J. van de Berg
中科院分区：
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作者：
R. Antwerpen;M. Tedesco;X. Fettweis;P. Alexander;W. J. van de Berg
抽象的。格陵兰冰盖(GRIS)的表面质量损失在过去几十年中加速，主要是由于大气变暖导致的表面融化和液态水径流增加。GRIS的很大一部分径流来自于当上面的雪融化时，消融区较暗的裸露冰的暴露，那里的表面反照率在调节可用于融化的能量方面起着关键作用。在这方面，必须了解控制反照率变化的过程，以便准确预测全球资源监测系统未来的质量损失。裸冰反照率在空间和时间上是可变的，取决于非线性反馈和光吸收成分的存在。评估旨在模拟反照率变化及其对融水生产的相关影响的模型，对于提高我们对控制这些反馈的过程以及反过来管理格陵兰岛表面质量损失的过程的理解至关重要。在这里，我们报告了区域气候模式MAR模拟的裸冰范围和反照率与来自中分辨率成像光谱仪(MODIS)的卫星图像在70∘N以下的比较结果。我们的结果表明，在2000年至2021年期间，MAR平均高估了该地区裸冰反照率的22.8%。使用能量平衡模式来参数化融水生产，我们发现这种裸冰反照率偏差会导致对2000年至2021年夏季裸冰地区70∘N以下的总融水生产的低估为42.8%。
Abstract. Surface mass loss from the Greenland ice sheet (GrIS) has accelerated over the past decades, mainly due to enhanced surface melting and liquid water runoff in response to atmospheric warming. A large portion of runoff from the GrIS originates from exposure of the darker bare ice in the ablation zone when the overlying snow melts, where surface albedo plays a critical role in modulating the energy available for melting. In this regard, it is imperative to understand the processes governing albedo variability to accurately project future mass loss from the GrIS. Bare-ice albedo is spatially and temporally variable and contingent on non-linear feedbacks and the presence of light-absorbing constituents. An assessment of models aiming at simulating albedo variability and associated impacts on meltwater production is crucial for improving our understanding of the processes governing these feedbacks and, in turn, surface mass loss from Greenland. Here, we report the results of a comparison of the bare-ice extent and albedo simulated by the regional climate model Modèle Atmosphérique Régional (MAR) with satellite imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) for the GrIS below 70∘ N. Our findings suggest that MAR overestimates bare-ice albedo by 22.8 % on average in this area during the 2000–2021 period with respect to the estimates obtained from MODIS. Using an energy balance model to parameterize meltwater production, we find this bare-ice albedo bias can lead to an underestimation of total meltwater production from the bare-ice zone below 70∘ N of 42.8 % during the summers of 2000–2021.