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Irrigation Raises Sea Levels
by Sid Perkins 胡德良 译
| Melting glaciers and icecaps aren't the only things raising sea levels—so is watering your lawn. According to a study published in Geophysical Research Letters, irrigation and other ground water extractions pull immense volumes of water from deep underground and dump it into the oceans via runoff into streams, rivers, and other waterways. Using information gathered worldwide and then extrapolating known trends to regions where data is sparse or missing altogether, one researcher estimates that, over the last century, humans pumped more than 4500 cubic kilometers of water from the ground—enough to boost sea level by 12.6 millimeters, or more than 6% of the overall increase measured during that period. In recent years, when ground water extractions have skyrocketed, the contribution was even larger: From 2000 to 2008, humans pumped on average about 145 cubic kilometers of ground water from aquifers each year—enough to raise sea levels by about 0.4 millimeters annually, or about 13% of the measured amount during that interval. Of the remaining 87% of sea level rise, some studies suggest that about half results from the melting and runoff of land-based ice, with the other half stemming from the thermal expansion of the oceans due to an increase in their temperature, particularly in their surface waters. |
融化的冰川和冰盖不是仅有的促使海平面上升的因素，浇灌草坪也会使海平面上升。根据《地球物理学研究快报》上发表的研究论文，灌溉和其他的地面用水抽取了大量的深层地下水，这些地下水又通过小溪、河流和其他的水沟泻入海洋中。利用全球范围搜集起来的信息，然后对于资料很少或没有的所有地区，推测了已经为人所知的倾向，据此，一位研究人员估计：在上个世纪期间，人类从地下抽取了4500立方千米的水，足以使海平面上升12.6毫米，或者说相当于那个时期所测得的总上升幅度的6%还要多。近年来，在地下水抽取量猛增的同时，海平面的上升幅度也更大了：自从2000年至2008年，人类平均每年从地下蓄水层抽取大约145立方千米的地下水，足以每年使海平面上升0.4毫米，或者说相当于同期总上升幅度的大约13%。一些研究表明：在海平面的上升幅度中，剩下的87%有一半来自于融化并流失的陆地冰；随着海洋温度的上升，尤其是表层水温的上升，另一半来自于海洋的热膨胀。 |
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