Climate change decreases the cooling effect from postfire albedo in boreal North America
Climate change decreases the cooling effect from postfire albedo in boreal North America
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DOI：
10.1111/gcb.14888
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发表时间：
2019-11
影响因子：
11.6
通讯作者：
S. Potter;Kylen Solvik;A. Erb;S. Goetz;J. Johnstone;M. Mack;J. Randerson;M. Roman;C. Schaaf;M. Turetsky;S. Veraverbeke;X. Walker;Zhuosen Wang;R. Massey;B. Rogers
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文献类型：
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作者：
S. Potter;Kylen Solvik;A. Erb;S. Goetz;J. Johnstone;M. Mack;J. Randerson;M. Roman;C. Schaaf;M. Turetsky;S. Veraverbeke;X. Walker;Zhuosen Wang;R. Massey;B. Rogers
火是北方森林的主要干扰，产生正和负的气候强迫。火对地表温度的影响在北方森林中主要是负强迫，并且是整体上最强的影响之一，这是由于冬季和春季的积雪增加。反照率强迫是空间和时间上的异质性，并取决于各种因素相关的土壤，地形，气候，土地覆盖/植被类型，演替动态，火灾以来的时间，季节和火灾的严重程度。然而，这些变量如何相互作用，影响火灾还没有得到很好的理解，量化这些关系和预测火灾后的火灾变得越来越重要的气候变化和管理框架的演变，考虑气候影响。在这里，我们开发了一个MODIS衍生的“蓝天”产品和一个新的机器学习建模框架，以预测北美北部历史和未来气候情景下的火灾驱动的变化。转换为辐射强迫（RF），我们估计，在历史气候条件下（1971-2000年），火灾产生的年平均冷却量为−1.77 ± 1.35 W/m2。随着南北气候梯度的增加，火灾后的降雨量沿着增加，但太阳辐射几乎相反的梯度抵消了这一影响，因此RF的大尺度空间模式是最小的。我们的模型表明，气候变化将导致平均每年的火灾后降雨量减少，因此负RF的强度下降，这一趋势主要是春季积雪减少。考虑到未来气候情景的范围和模型的不确定性，我们估计，对于当前时代（2016年）的火灾，由于气候变化，火灾后长期的冷却效应将减少15%-28%。
Fire is a primary disturbance in boreal forests and generates both positive and negative climate forcings. The influence of fire on surface albedo is a predominantly negative forcing in boreal forests, and one of the strongest overall, due to increased snow exposure in the winter and spring months. Albedo forcings are spatially and temporally heterogeneous and depend on a variety of factors related to soils, topography, climate, land cover/vegetation type, successional dynamics, time since fire, season, and fire severity. However, how these variables interact to influence albedo is not well understood, and quantifying these relationships and predicting postfire albedo becomes increasingly important as the climate changes and management frameworks evolve to consider climate impacts. Here we developed a MODIS‐derived ‘blue sky’ albedo product and a novel machine learning modeling framework to predict fire‐driven changes in albedo under historical and future climate scenarios across boreal North America. Converted to radiative forcing (RF), we estimated that fires generate an annual mean cooling of −1.77 ± 1.35 W/m2 from albedo under historical climate conditions (1971–2000) integrated over 70 years postfire. Increasing postfire albedo along a south–north climatic gradient was offset by a nearly opposite gradient in solar insolation, such that large‐scale spatial patterns in RF were minimal. Our models suggest that climate change will lead to decreases in mean annual postfire albedo, and hence a decreasing strength of the negative RF, a trend dominated by decreased snow cover in spring months. Considering the range of future climate scenarios and model uncertainties, we estimate that for fires burning in the current era (2016) the cooling effect from long‐term postfire albedo will be reduced by 15%–28% due to climate change.