Greenland Ice Sheet Surface Mass Balance Variability (1988–2004) from Calibrated Polar MM5 Output*
Greenland Ice Sheet Surface Mass Balance Variability (1988–2004) from Calibrated Polar MM5 Output*
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来自校准的 Polar MM5 输出的格陵兰冰盖表面质量平衡变化（1988-2004）*
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
Sheng‐Hung Wang
中科院分区：
文献类型：
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作者：
J. Box;D. Bromwich;Bruce A. Veenhuis;L. Bai;J. Stroeve;J. Rogers;K. Steffen;T. Haran;Sheng‐Hung Wang
区域气候模式运行采用宾夕法尼亚州立大学-国家大气研究中心第五代极地中尺度模式（polar MM5），经独立的原位观测校准，显示了格陵兰冰盖表面物质平衡（SMB）在以变暖为特征的17年期间（1988-2004）变化的一致性区域模式。累积速率和融化速率都增加了，在一定程度上相互抵消，使得SMB趋势总体上可以忽略不计。然而，在此期间融水径流增加了30%，这表明，考虑到观测到的融水引起的流动加速，整个冰盖的质量平衡已经越来越负。整个冰盖的SMB时间变异性最好地表示为消融带变异性，这表明在变暖情景中，增加的融化比增加的积累占主导地位。融化季节的持续时间几乎在整个消融区增加了40天，平均10天。堆积面积比降低3%。在中分辨率成像光谱辐射计（MODIS）衍生数据的五年中（2000 - 2004年），反照率明显降低。先进甚高分辨率辐射计（AVHRR）衍生的反照率变化（1988 - 1999）在空间上不太一致。关于冰川流量和基底融化的保守假设表明，这一时期冰盖的质量损失超过100公里/年，这将格陵兰冰盖视为近期全球海平面上升的最大单一冰川贡献者。地表质量平衡的不确定性，由模型和独立观测之间的剩余随机误差量化，表明两件事：1)小于约200 km³年1的变化将不满足保守的统计显著性阈值（即两个标准差）；2)尽管在本分析中分离了自然变率和模式不确定性，但它们的大小大致相等。因此，对于确定的质量平衡变化评估，需要改进模型的准确性和分析更长的周期（假设更大的变化）。
Regional climate model runs using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesocale Model modified for use in polar regions (Polar MM5), calibrated by independent in situ observations, demonstrate coherent regional patterns of Greenland ice sheet surface mass balance (SMB) change over a 17-yr period characterized by warming (1988–2004). Both accumulation and melt rates increased, partly counteracting each other for an overall negligible SMB trend. However, a 30% increase in meltwater runoff over this period suggests that the overall ice sheet mass balance has been increasingly negative, given observed meltwater-induced flow acceleration. SMB temporal variability of the whole ice sheet is best represented by ablation zone variability, suggesting that increased melting dominates over increased accumulation in a warming scenario. The melt season grew in duration over nearly the entire ablation zone by up to 40 days, 10 days on average. Accumulation area ratio decreased by 3%. Albedo reductions are apparent in five years of the Moderate Resolution Imaging Spectroradiometer (MODIS) derived data (2000–04). The Advanced Very High Resolution Radiometer (AVHRR)-derived albedo changes (1988–99) were less consistent spatially. A conservative assumption as to glacier discharge and basal melting suggests an ice sheet mass loss over this period greater than 100 km 3 yr 1 , framing the Greenland ice sheet as the largest single glacial contributor to recent global sea level rise. Surface mass balance uncertainty, quantified from residual random error between model and independent observations, suggests two things: 1) changes smaller than approximately 200 km 3 yr 1 would not satisfy conservative statistical significance thresholds (i.e., two standard deviations) and 2) although natural variability and model uncertainty were separated in this analysis, the magnitude of each were roughly equivalent. Therefore, improvements in model accuracy and analysis of longer periods (assuming larger changes) are both needed for definitive mass balance change assessments.