国家地理:不再冻人的五大湖(3)

The Great Lakes account for about 20 percent of the freshwater on Earth's surface. The lakes' geographical footprint is also hard to fathom. Their combined surfaces span more than 94,000 square miles, about the size of the United Kingdom. The combined measurement of the coasts of the five lakes is thousands of miles longer than either the Pacific or Atlantic coastline of the contiguous U.S.

五大湖约占地球淡水资源的20%。湖泊的地理分布也很难彻底理清。它们的流域总面积超过94000平方英里，大约相当于英国的面积。而这五个湖泊的海岸线的测量长度，要比美国的太平洋或大西洋海岸线长数千英里。

The presence of all that water was shaped by natural changes in Earth's climate through time. But the lakes now face unprecedented change—and this time, humans are behind it.

所有这些水资源的存在，都是由于地球气候随时间的自然变化而形成的。但是现在五大湖面临着前所未有的变化，而这一次，人类是幕后黑手。

The planet has warmed by an average of nearly two degrees Fahrenheit (one degree Celsius) since the 1880s. The Great Lakes region is on a par with this global trend: Within the basin, air temperatures have risen by an average of 1.6 degrees Fahrenheit compared with the first 60 years of the 1900s. And much of that warming has been concentrated in the winter months, nudging the ice ever closer to its tipping point.

从19世纪80年代开始到今天，地球平均变暖了近2华氏度（1摄氏度）。五大湖地区与全球趋势相当：盆地内的空气温度与20世纪前60年相比平均上升了1.6华氏度。而这种变暖主要集中在冬天的几个月里，冰层越来越接近它的临界点。

"Lake ice is an amazing indicator of climate," says Sapna Sharma, a lake ecologist at York University in Toronto. "It's a clear indication of climate change, and people have recorded it, in some cases, for centuries."

多伦多约克大学的湖泊生态学家萨佩纳·沙玛表示：“湖冰是一个关于气候的神奇的指标。这是气候变化的一个明显迹象，人们在某些情况下已经记录了几个世纪。”