2012年夏季挪威海和格陵兰海水文特征分析

利用2012年夏季在北欧海(挪威海和格陵兰海)的水文考察数据,对调查区域内海洋水团性质和分布进行了分析,并对北欧海冷却对流的发展加深过程进行了研究。在上层,从东侧暖而咸的大西洋水跨越锋区至西侧低温低盐的格陵兰海盆上层水体,温度和盐度的变化分别可以达到8℃和0.4 psu。中层与深层水体的性质则相对均匀和稳定,3个海盆内从浅至深依次分布着北极中层水、海盆深层水、北极深层水以及海盆底层水。格陵兰海盆中深层水体在3 500 m深度上位温约为-0.97℃,相比较1970s观测到的-1.30℃,升温幅度超过了0.3℃,表明海盆深层存储的热量显著增加。在只考虑局地表面冷却的简化条件下,当前格陵兰海内部通过冷却对流混合至季节性跃层下界需要向大气释放0.9×109~1.2×109J的热量,这一过程至少需要2个月的时间而不利于对流向深层的发展。大量的热量被存储于北欧海深海盆中使得北欧海已经成为北半球高纬海域的热量存储器,对当前北极气候变化的影响有待深入研究。

Hydrographic Features of the Norwegian Sea and the Greenland Sea in Summer 2012

Based on observations during the 5th Chinese Arctic expedition in 2012, the property and distribution of water masses were identified and the evolution of cooling convection was studied. In the upper layer, from the warm and salty Atlantic waters, which mainly lie on the east, westerly to the cold and fresh Greenland upper waters, the temperature and the salinity decreases were about 8 ℃ and 0.4 psu respectively. As for the intermediate and deep waters, water properties were more homogeneous and stable. Along with the depth deepening, there existed the Arctic Intermediate Water, the Basin Deep Water, the Arctic Deep Water and the Basin Bottom Water in all the three deep basins. In the center of the Greenland Basin, the potential temperature was about -0.97 ℃ at depth 3 500 m, which was nearly 0.3 ℃ warmer compared to the value -1.30 ℃ observed in 1970s, implying a heat increase in the deep layer. Under a simplified hypothesis only concerning the surface cooling to erode the seasonal pycnocline, now a total heat loss of about 0.9×10⁹~1.2×10⁹ J/m² was needed for the upper ocean of the Greenland Sea. This process may take at least two months and thus leaves less time for the following deep reaching convection. At present, the Nordic seas are becoming a heat reservoir on the northern hemisphere and impacts of such change on the Arctic climate are worthy of further study.