北冰洋入海径流变化状况及其与近岸海冰关系

VARIATION OF ARCTIC OCEAN RUNOFF AND ITS CORRELATION WITH COASTAL SEA ICE

北极入海径流是北冰洋最主要的淡水来源之一,也是影响北极变化的重要因素。利用Dai和Trenberth发布的1979-2010年全球河流流量和陆地径流数据集、全球径流数据中心(GRDC)数据集和美国国家冰雪中心数据集,以入海口位置划分研究区域为楚科奇海区、东西伯利亚海区、拉普捷夫海区和喀拉海区;以流量特征,选取注入北冰洋的前12条大河中的6条主要河流为代表,采用Mann-Kendall趋势分析方法,检测了不同海区入海径流在不同季节的变化特征及趋势,并对其与边缘海区海冰覆盖面积的关系进行分析。结果表明:所有河流的季节特征明显且一致,径流量集中在4-11月, 6月前后的洪峰流量远大于春季和秋季的径流量,且叶尼塞河和勒拿河洪峰时期的流量是其他河流的3-4倍。径流季节变化明显,在全球变暖的影响下,径流总体呈现显著增长趋势,春季径流量增加最为明显,其中东西伯利亚海域入海径流增长最快。楚科奇海春季径流量与融化开始时间显著相关,径流量每增加5.9 km^3·a^–1,海冰融化时间提前一天。东西伯利亚海夏季径流量与融化开始时间(8月)显著相关,径流量每增加30.7km^3·a^–1,海冰融化时间提前一天。东西伯利亚海8月最大日径流量与当月冰情显著相关,最大日径流量发生时间平均提前于海冰低谷发生时间8天。不考虑其他因素的情况下,最大日径流量每增加15.7km^3·a^–1,海冰低谷距平降低1%,表明其促进融冰期海冰的融化,导致冰情减轻。东西伯利亚海秋季径流的增大加速了结冰后期海冰的冻结。

Arctic runoff is one of the most important sources of freshwater to the Arctic Ocean and an important factor influencing changes in the Arctic. This study analyzes the relationship between sea ice extent and runoff using the National Snow and Ice Center dataset, the Global River Data Center(GRDC) dataset and the Dai and Trenberth global and river runoff datasets from 1979 to 2010. Based on the locations of Arctic estuaries, the study area is divided into the Chukchi Sea Area, the East-Siberian Sea Area, the Laptev Sea Area and the Kara Sea Area. Choosing six of the 12 largest rivers that flow into the Arctic Ocean based on flow characteristics, a Mann-Kendall trend analysis method was used to detect the variations in characteristics and trends of runoff in different sea areas during different seasons. Results show that the seasonal characteristics of all rivers are clear and consistent. Runoff is concentrated from April to November, and the peak flow around June is much larger than runoff in spring and autumn. The peak flow of the Yenisei and Lena rivers is 3–4 times that of the others. The seasonal variation in runoff is obvious. Under the influence of global warming, runoff exhibits a significant growth trend, and runoff increases most in the spring. Runoff to the East Siberian Sea increases the fastest. The spring runoff of the Chukchi Sea is significantly correlated with the start time of sea-ice melting. For every 5.9 km^3·a^-1 increase in runoff sea-ice melts one day earlier. In contrast, sea-ice melt in the Eastern Siberian Sea is significantly related to summer runoff(August). For every 30.7 km^3·a^-1 increase in runoff, sea ice melts one day earlier. The maximum daily runoff in August in the Eastern Siberian Sea is significantly correlated with the ice condition. The maximum daily runoff occurs 8 days before the minimum sea-ice extent. Regardless of other factors, for every 15.7 km^3·a^-1 increase in the maximum daily runoff, the sea ice anomaly decreases by 1%, indicating that runoff promotes the melting of sea ice during the melting ice period, resulting in a reduction in ice conditions. The increase in autumn runoff in the Eastern Siberian Sea accelerates freezing of sea ice during the late freezing period.