The Heat and Water Budgets in the Active Layer of the Arctic Tundra at Barrow, Alaska
The Heat and Water Budgets in the Active Layer of the Arctic Tundra at Barrow, Alaska
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阿拉斯加巴罗北极苔原活跃层的热量和水预算
DOI：
10.2480/agrmet.52.293
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发表时间：
1996
影响因子：
1.3
通讯作者：
W. Oechel
中科院分区：
文献类型：
--
作者：
M. Yoshimoto;Y. Harazono;G. Vourlitis;W. Oechel
1993年夏季对阿拉斯加州巴罗附近的北极沿海冻土带生态系统进行了微气象观测，考察了活动层的热量和水分收支特征。IBP现场解冻层深度的直接测量结果表明，从6月中旬到8月中旬，解冻层加深了10~22 cm。利用给出的水分平衡模型，分析了解冻对解冻层土壤水分的影响。1993年夏季蒸散量远大于降水量，过剩的蒸散量由冻土融化水补给。融化潜热与土壤表面热通量G的比值直到8月中旬开始复冻时才发生显著变化，Qthaw/G值在15-20%之间。融化层的储热量可以忽略不计，地表约80%的热量被转移到孔隙度小、导热系数大的多年冻土中。通过模型分析，得到了以下结论。全球变暖加速了北极冻土带的蒸发蒸散，使冻土深层和活动层表面干燥，导致冻土表层和深层干燥，导致多年冻土层下降，从而导致冻土层热量减少，Qthaw/G增大，从而加速了冻土的融化。
The micrometeorology of the Arctic coastal tundra ecosystem near Barrow, Alaska was observed during the summer of 1993, and the characteristics of the heat and water budgets in the active layer were examined.Direct measurement results of the thawed layer depth at the IBP site indicated that the thawed layer deepened from 10 to 22cm between mid June and mid-August. The effect of the thawing on the soil water content of the thawed layer was analyzed using the water budget model provided. The evapotranspiration (ET) was much larger than the precipitation during the summer of 1993, and the excess ET was supplied by the thawed water from the frost soil. Therefore, the excess ET makes dry the active layer.The ratio of the latent heat of the thawing, Qthaw to the soil surface heat flux, G did not change remarkably until mid-August when it started refreezing and the value Qthaw/G ranged within 15-20%. The heat storage in the thawed layer was negligible and about 80% of the heat from the ground surface was transfered to the permafrost which had little porosity and large thermal conductivity. From model analyses the followings were obtained. The drying of the active layer caused by the excess ET decreases the ice content of the frost soil, which causes the decrease in the heat transfer to the permafrost and the increase of Qthaw/G, which might accelerate the thawing.Global warming accelerate evapotranspiration at the Arctic tundra which makes the soil dry at the deeper part as well as at the surface of the active layer, thus leads the descent of the permafrost table.