| MU Longjiang,ZHAO Jinping,ZHONG Wenli. 2017. Regime shift of the dominant factor for halocline depth in the Canada Basin during 1990-2008. Acta Oceanologica Sinica, 36(1):35－43 |
| Regime shift of the dominant factor for halocline depth in the Canada Basin during 1990-2008 |
| 1990~2008年间加拿大海盆盐跃层深度控制机制的转变 |
| Received:January 06, 2016 Revised:March 02, 2016 |
| DOI：10.1007/s13131-016-0883-0 |
| Key words:Canada Basin Beaufort high Transpolar Drift circumpolar boundary current halocline depth freshwater |
| 中文关键词: 加拿大海盆 波弗特高压 穿极流 环极边界流 盐跃层深度 淡水 |
| 基金项目:The National Basic Research Program (973 Program) of China under contract No. 2015CB953900; the National Natural Science Foundation of China under contract No. 41330960. |
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| Abstract: |
| The World Ocean Database (WOD) is used to evaluate the halocline depth simulated by an ice-ocean coupled model in the Canada Basin during 1990-2008. Statistical results show that the simulated halocline is reliable. Comparing of the September sea ice extent between simulation and SSM/I dataset, a consistent interannual variability is found between them. Moreover, both the simulated and observed September sea ice extent show staircase declines in 2000-2008 compared to 1990-1999. That supports that the abrupt variations of the ocean surface stress curl anomaly in 2000-2008 are caused by rapid sea ice melting and also in favor of the realistic existence of the simulated variations. Responses to these changes can be found in the upper ocean circulation and the intermediate current variations in these two phases as well. The analysis shows that seasonal variations of the halocline are regulated by the seasonal variations of the Ekman pumping. On interannual time scale, the variations of the halocline have an inverse relationship with the ocean surface stress curl anomaly after 2000, while this relationship no longer applies in the 1990s. It is pointed out that the regime shift in the Canada Basin can be derived to illustrate this phenomenon. Specifically, the halocline variations are dominated by advection in the 1990s and Ekman pumping in the 2000s respectively. Furthermore, the regime shift is caused by changing Transpolar Drift pathway and Ekman pumping area due to spatial deformation of the center Beaufort high (BH) relative to climatology. |
| 中文摘要: |
| 本文利用World Ocean Database (WOD)数据验证了冰海耦合模式模拟的加拿大海盆盐跃层在1990-2008年间的时空变化，统计结果显示模拟结果具有可信性。将模拟的九月份的海冰覆盖范围与卫星观测数据进行比较，发现二者具有一致的年际变化。相比1990-1999年，2000-2008年模式和观测得到的九月份海冰覆盖范围均出现阶梯式下降。这表明模式中因海冰减少导致的海表面应力旋度异常的变化幅度在后段时间显著增大是事实存在的。淡水含量、上层和中层流场在2000年之前和之后也出现了相应显著的改变。通过分析海表面应力旋度异常与盐跃层深度之间的关系发现，盐跃层对季节性尺度上的Ekman Pumping有快速的响应；而在年际变化尺度上，2000年之后盐跃层的变化与海表面应力旋度异常呈反相关，在之前却呈正相关。我们指出该现象的出现是由于控制盐跃层变化的机制出现转变，即平流输运和Ekman抽吸相继控制了盐跃层的变化。而该转变出现的原因是因波弗特高压中心区空间分布的形变影响了穿极流的摆动以及Ekman抽吸的范围和强度。 |
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