北极加拿大海盆中一个次表层涡旋的结构研究

STRUCTURE OF A SUBSURFACE EDDY IN CANADIAN BASIN OF ARCTIC OCEAN

利用2003年7—9月中国第二次北极科学考察期间,在北冰洋加拿大海盆的一个冰站上得到的温度、盐度和流速的连续剖面观测资料,对一个次表层的北冰洋涡旋进行了分析。在温度断面图中,该涡旋表现为一个核心位于60m深度、最低温度为-1.5°C的孤立冷水块,比周边水体的温度低约0.5°C。涡旋中的等密度面呈现凸透镜的结构,表明该涡旋是反气旋式的。虽然同步观测的流场中确实存在速度接近0.4ms-1的异常强流,但实测流场的结构却与一个典型的涡旋流场相去甚远。进一步分析发现,涡旋所在的次表层流场存在变化幅度与涡旋旋转速度相当的惯性频率振荡。在滤除惯性流和平均流之后,得到了轴对称的涡旋流场,涡旋的最大流速半径约为5km。对涡旋核心及其周边海域水体的温盐性质对比分析表明,该涡旋可能在楚科奇陆架上形成,然后向东北方向运动并进入了加拿大海盆。

An Arctic Ocean eddy in subsurface layer is analyzed in this paper with temperature, salinity and current profile data obtained at an ice camp in the Canada Basin during the second Chinese Arctic Expedition in summer of 2003. In the vertical temperature section, the eddy shows itself as an isolated cold water block at depth of 60 m with a minimum temperature of - 1.5℃ that is -0.5℃ colder than the ambient water. Isopycnals in the eddy form a pattern of convex, which indicates the eddy is anticyclonic. Although maximum velocity near 0.4 ms^-1 occurs in the current records observed synchronously, the current pattern is far away from a typical eddy. By further analysis, inertial frequency oscillations with amplitudes comparable with the eddy velocity are found in the subsurface layer currents. After removing the inertial current and mean current, an axisymmetric current pattern of an eddy with maximum velocity radius of 5 km is obtained. The analysis of the T-S characteristics of the eddy core water and its ambient waters supports the conclusion that the eddy was formed on the Chukchi Shelf and migrated northeastward into the northern Canada Basin.