Future projections of the Greenland ice sheet energy balance driving the surface melt
Future projections of the Greenland ice sheet energy balance driving the surface melt
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DOI：
10.5194/tc-7-1-2013
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发表时间：
2013-01-01
期刊：
影响因子：
5.2
通讯作者：
Erpicum, M.
中科院分区：
文献类型：
--
作者：
Franco, B.;Fettweis, X.;Erpicum, M.
在这项研究中，在25公里分辨率的模拟在格陵兰冰盖（GrIS）在整个20世纪和21世纪，使用区域气候模式MAR迫使四个RCP情景从三个CMIP 5全球环流模式（GCM），以调查预计的变化的表面能量平衡（SEB）组件驱动的表面融化。与1980-1999年融化结果相比，对2000-2100年融化异常的分析揭示了MAR模拟的GrIS表面融化速率与近地面气温（TAS）异常之间的指数关系，这主要是由于与地表反射率相关的正反馈。夏季裸冰区的扩展。在GrIS边缘，未来的融化异常优先驱动较强的感热通量，引起的增强暖空气平流在冰盖。在中央干雪区，夏季融化量增加引起的地面反作用正反馈超过了TAS异常高于4摄氏度时较重降雪的负反馈。除了与大气变暖相关的入射长波通量增加外，GCM强迫MAR模拟还预测了云量的增加，从而降低了入射短波与长波辐射的比率，并抑制了短波反馈。然而，应该指出的是，云量的这一趋势与ERA-中期-强迫MAR对最近气候条件的模拟相反，在最近的气候条件下，自20世纪90年代以来观察到的融化增加似乎主要是反气旋大气条件的结果。最后，预计在融化季节的长度没有显着的变化，这突出了太阳辐射的冰盖表面吸收的融化SEB的重要性。
In this study, simulations at 25 km resolution are performed over the Greenland ice sheet (GrIS) throughout the 20th and 21st centuries, using the regional climate model MAR forced by four RCP scenarios from three CMIP5 global circulation models (GCMs), in order to investigate the projected changes of the surface energy balance (SEB) components driving the surface melt. Analysis of 2000-2100 melt anomalies compared to melt results over 1980-1999 reveals an exponential relationship of the GrIS surface melt rate simulated by MAR to the near-surface air temperature (TAS) anomalies, mainly due to the surface albedo positive feedback associated with the extension of bare ice areas in summer. On the GrIS margins, the future melt anomalies are preferentially driven by stronger sensible heat fluxes, induced by enhanced warm air advection over the ice sheet. Over the central dry snow zone, the surface albedo positive feedback induced by the increase in summer melt exceeds the negative feedback of heavier snowfall for TAS anomalies higher than 4 degrees C. In addition to the incoming longwave flux increase associated with the atmosphere warming, GCM-forced MAR simulations project an increase of the cloud cover decreasing the ratio of the incoming shortwave versus longwave radiation and dampening the albedo feedback. However, it should be noted that this trend in the cloud cover is contrary to that simulated by ERA-Interim-forced MAR for recent climate conditions, where the observed melt increase since the 1990s seems mainly to be a consequence of more anticyclonic atmospheric conditions. Finally, no significant change is projected in the length of the melt season, which highlights the importance of solar radiation absorbed by the ice sheet surface in the melt SEB.