Firn data compilation reveals widespread decrease of firn air content in western Greenland
Firn data compilation reveals widespread decrease of firn air content in western Greenland
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DOI：
10.5194/tc-13-845-2019
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发表时间：
2019-03
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通讯作者：
B. Vandecrux;M. Macferrin;H. Machguth;W. Colgan;D. van As;A. Heilig;C. M. Stevens;Charalampos Charalampidis;R. Fausto;Elizabeth M. Morris;E. Mosley‐Thompson;Lora S. Koenig;L. Montgomery;C. Miège;S. Simonsen;T. Ingeman‐Nielsen;J. Box
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作者：
B. Vandecrux;M. Macferrin;H. Machguth;W. Colgan;D. van As;A. Heilig;C. M. Stevens;Charalampos Charalampidis;R. Fausto;Elizabeth M. Morris;E. Mosley‐Thompson;Lora S. Koenig;L. Montgomery;C. Miège;S. Simonsen;T. Ingeman‐Nielsen;J. Box
抽象。一层多孔的多年积雪覆盖着格陵兰冰盖的内部。积雪层通过保留一部分夏季融化的液态水和再冻结的冰来缓冲冰盖对海平面上升的贡献。在这项研究中，我们量化格陵兰冰盖积雪空气含量（FAC），一个指标的融水保留能力，基于360点的观测。我们量化的FAC在最高的10米和整个雪列插值前FAC在整个冰盖积雪面积作为长期平均气温（Ta）和净积雪（C stechte）的经验函数。我们估计，2010-2017年期间，冰盖宽度的FAC总面积为26800 ±1840 km 3，其中6500±450 km 3位于积雪的最高10 m范围内。在干雪区（Ta ≤-19 ° C），FAC自1953年以来变化不明显。在低堆积渗流区（Ta>-19 ° C，c <600 mm w.e.）yr-1），FAC在1998-2008年和2010-2017年之间下降了23± 16%。这反映了从顶部10 m和整个雪柱分别损失150±100 Gt和540±440 Gt的雪保持能力。三个区域气候模式（HIRHAM 5、RACMO2.3p2和MARv3.9）模拟的前10 m FAC与观测值的一致性在12%以内。然而，模型偏差的总FAC和显着的区域差异突出需要谨慎使用模型时，量化当前和未来的FAC和积雪保持能力。
Abstract. A porous layer of multi-year snow known as firn covers the Greenland-ice-sheet interior. The firn layer buffers the ice-sheet contribution to sea-level rise by retaining a fraction of summer melt as liquid water and refrozen ice. In this study we quantify the Greenland ice-sheet firn air content (FAC), an indicator of meltwater retention capacity, based on 360 point observations. We quantify FAC in both the uppermost 10 m and the entire firn column before interpolating FAC over the entire ice-sheet firn area as an empirical function of long-term mean air temperature (Ta‾) and net snow accumulation (c˙‾). We estimate a total ice-sheet-wide FAC of 26 800±1840 km3, of which 6500±450 km3 resides within the uppermost 10 m of firn, for the 2010–2017 period. In the dry snow area (Ta‾≤-19 ∘C), FAC has not changed significantly since 1953. In the low-accumulation percolation area (Ta‾>-19 ∘C and c˙‾≤600 mm w.e. yr−1), FAC has decreased by 23±16 % between 1998–2008 and 2010–2017. This reflects a loss of firn retention capacity of between 150±100 Gt and 540±440 Gt, respectively, from the top 10 m and entire firn column. The top 10 m FACs simulated by three regional climate models (HIRHAM5, RACMO2.3p2, and MARv3.9) agree within 12 % with observations. However, model biases in the total FAC and marked regional differences highlight the need for caution when using models to quantify the current and future FAC and firn retention capacity.