Stone Hally B, Banas Neil S, MacCready Parker
School of Oceanography University of Washington Seattle Washington USA.
Department of Mathematics and Statistics University of Strathclyde Glasgow UK.
J Geophys Res Oceans. 2018 Jan;123(1):265-286. doi: 10.1002/2017JC013174. Epub 2018 Jan 15.
The Northern California Current System experiences highly variable seasonal upwelling in addition to larger basin-scale variability, both of which can significantly affect its water chemistry. Salinity and temperature fields from a 7 year ROMS hindcast model of this region (43°N-50°N), along with extensive particle tracking, were used to study interannual variability in water properties over both the upper slope and the midshelf bottom. Variation in slope water properties was an order of magnitude smaller than on the shelf. Furthermore, the primary relationship between temperature and salinity anomalies in midshelf bottom water consisted of variation in density (cold/salty versus warm/fresh), nearly orthogonal to the anomalies along density levels (cold/fresh versus warm/salty) observed on the upper slope. These midshelf anomalies were well-explained ( = 0.6) by the combination of interannual variability in local and remote alongshore wind stress, and depth of the California Undercurrent (CUC) core. Lagrangian analysis of upper slope and midshelf bottom water shows that both are affected simultaneously by large-scale alongcoast advection of water through the northern and southern boundaries. The amplitude of anomalies in bottom oxygen and dissolved inorganic carbon (DIC) on the shelf associated with upwelling variability are larger than those associated with typical variation in alongcoast advection, and are comparable to observed anomalies in this region. However, a large northern intrusion event in 2004 illustrates that particular, large-scale alongcoast advection anomalies can be just as effective as upwelling variability in changing shelf water properties on the interannual scale.
北加利福尼亚洋流系统除了具有较大的盆地尺度变化外，还经历高度可变的季节性上升流，这两者都会显著影响其水化学性质。利用该区域（北纬43°-50°）一个7年的ROMS后报模型的盐度和温度场，以及广泛的粒子追踪，研究了上斜坡和陆架中部底部水体性质的年际变化。斜坡水体性质的变化比陆架上的变化小一个数量级。此外，陆架中部底部水体温度和盐度异常之间的主要关系是密度变化（冷/咸与暖/淡），几乎与在上斜坡观测到的沿密度层的异常（冷/淡与暖/咸）正交。当地和远程沿岸风应力的年际变化以及加利福尼亚潜流（CUC）核心深度的组合很好地解释了这些陆架中部异常（ = 0.6）。对上斜坡和陆架中部底部水体的拉格朗日分析表明，两者同时受到通过北部和南部边界的大规模沿岸平流水的影响。陆架上与上升流变化相关的底部氧气和溶解无机碳（DIC）异常幅度大于与典型沿岸平流变化相关的异常幅度，并且与该区域观测到的异常相当。然而，2004年的一次大型北部入侵事件表明，在年际尺度上，特定的大规模沿岸平流异常在改变陆架水体性质方面与上升流变化同样有效。
