國家地理:不再凍人的五大湖(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.

五大湖約占地球淡水資源的20%。湖泊的地理分布也很難徹底理清。它們的流域總面積超過94000平方英里，大約相當(dāng)于英國的面積。而這五個(gè)湖泊的海岸線的測(cè)量長度，要比美國的太平洋或大西洋海岸線長數(shù)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.

所有這些水資源的存在，都是由于地球氣候隨時(shí)間的自然變化而形成的。但是現(xiàn)在五大湖面臨著前所未有的變化，而這一次，人類是幕后黑手。

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.

從19世紀(jì)80年代開始到今天，地球平均變暖了近2華氏度（1攝氏度）。五大湖地區(qū)與全球趨勢(shì)相當(dāng)：盆地內(nèi)的空氣溫度與20世紀(jì)前60年相比平均上升了1.6華氏度。而這種變暖主要集中在冬天的幾個(gè)月里，冰層越來越接近它的臨界點(diǎn)。

"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."

多倫多約克大學(xué)的湖泊生態(tài)學(xué)家薩佩納·沙瑪表示：“湖冰是一個(gè)關(guān)于氣候的神奇的指標(biāo)。這是氣候變化的一個(gè)明顯跡象，人們?cè)谀承┣闆r下已經(jīng)記錄了幾個(gè)世紀(jì)。”