Interdecadal variations of the Western Subarctic Gyre (WSAG) in the North Pacific were examined mainly by analysis of absolute dynamic topography (ADT) during 1993–2017. The ADT was based on altimetry-derived sea level anomalies superimposed on state-of-the-art mean dynamic topography. We specified geostrophic surface streamlines of the WSAG associated with closed isolines of the ADT. The WSAG intensity was the strongest in the late 1990s, when the WSAG was zonally contracted, and it decreased to the mid-2010s in a linear manner with time. The WSAG expanded abruptly toward the east around 2001 in a step function–like manner. After this abrupt shift, the WSAG was connected most strongly to the Alaskan Gyre. This condition persisted even into the late 2010s. The shift to the very elongated pattern was also accompanied by a drastic lowering of the ADT around 170°W, 50°N, where the WSAG and Alaskan Gyre had been distinctly separated by a peak of the ADT during the previous period when the shape of the gyre was less elongated. A reduced-gravity model of wind-induced, long, baroclinic Rossby waves with weak dissipation could account for both the interdecadal weakening of the WSAG and the step function–like lowering of the ADT peak at the time of the shift of the WSAG to the very elongated pattern. In addition to the baroclinic response of the subarctic ocean to basin-scale wind stress, mesoscale clockwise eddies contributed to sea level rise around the center of the WSAG. In particular, there was an interdecadal increase in the frequency of appearance of strong, mesoscale, clockwise eddies that were generated south of the Aleutian Islands at longitudes of 170°E−180°. Those eddies propagated approximately to the west-southwest, and they disappeared around the center of the WSAG.

主要通过分析1993-2017年期间的绝对动态地形（ADT）来研究北太平洋西部亚北极回转（WSAG）的年代际变化。ADT基于叠加了最先进的平均动态地形的高程异常海平面异常。我们指定了与ADT的封闭等高线相关的WSAG的地转表面流线。WSAG强度在1990年代末期最强，当时WSAG呈区域性收缩，并随时间线性下降到2010年代中期。WSAG在2001年左右以类似阶梯函数的方式突然向东方扩张。经过这种突然的转变，WSAG与阿拉斯加的涡流之间的联系最为牢固。这种情况一直持续到2010年代后期。转向非常细长的模式还伴随着ADT急剧下降，大约在170°W，50°N时，在上一个时期，当WSAG和Alaskan Gyre的形状呈ADT峰形时，WSAG和Alaskan Gyre明显分开回旋不那么拉长。具有弱耗散的风致，长斜斜Rossby波的重力减小模型可以解释WSAG年代际减弱和阶跃函数，例如WSAG转变为WSAG时ADT峰值的降低。非常细长的图案。除了南极洋对盆地规模的风应力的斜压响应外，中尺度顺时针涡旋还导致了WSAG中心附近海平面的上升。特别是，中尺度，强尺度，在阿留申群岛以南经度为170°E-180°的地方产生的顺时针漩涡。这些漩涡大致向西南偏西传播，并在WSAG中心附近消失。