A Westward-Intensified Decadal Change in the North Pacific Thermocline and Gyre-Scale Circulation
A Westward-Intensified Decadal Change in the North Pacific Thermocline and Gyre-Scale Circulation
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北太平洋温跃层和环流环流向西加剧的年代际变化
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W. A. B. W. Hite
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作者：
A. R. J. M. Iller;And D ANIEL R. C AYAN;W. A. B. W. Hite
从20世纪70年代初到80年代中期，北太平洋fic洋次北极环流的主要温跃层在该区域上空变浅，温度在200-400米深，降温1(CID：56)-4(CID：56)℃。浅滩的环流尺度结构是准静止的，在30(CID：56)N以北的盆地西部强烈，表明环流尺度输送的同步变化。在25(CID：56)N以南的副热带环流中也观察到了类似的准静止冷却，但比亚极变化晚了几年。为了探索这些变化的物理机制，作者检验了1970年至1988年观测到的风应力和热flUX异常强迫的海洋模式，在该模式中，它们fi和环流尺度温跃层结构的类似变化。模式Currentfi场显示，从20世纪70年代到80年代，北太平洋fic副极地和副热带涡旋加强了大约10%。模式黑潮-Oyashio延伸的大部分向东的flow通过副极涡旋环流向西返回，而副热带涡旋沿20(CID：56)N返回的flow滞后于亚极变化数年。作者证明，模式温跃层的冷却和输送的增加是对盆地尺度风应力旋度的年代际变化的响应，而准静态海洋响应在日期线以东的盆地大部分地区处于随时间变化的准Sverdrup平衡中。这种由风应力旋度驱动的响应是准平稳的，但它与与北太平洋中部俯冲有关的传播温度异常一起发生，该异常连接着副极地和副热带涡旋的平稳变化，并给出了旋转传播的外观。不同的物理特征明显控制着温带北太平洋fic.不同区域的次表层温度信号。
From the early 1970s to the mid-1980s, the main thermocline of the subarctic gyre of the North Pacific Ocean shoaled with temperatures at 200–400-m depth cooling by 1 (cid:56) –4 (cid:56) C over the region. The gyre-scale structure of the shoaling is quasi-stationary and intensified in the western part of the basin north of 30 (cid:56) N, suggestingconcurrent changes in gyre-scale transport. A similar quasi-stationary cooling in the subtropical gyre south of 25 (cid:56) N is also observed but lags the subpolar change by several years. To explore the physics of these changes, the authors examine an ocean model forced by observed wind stress and heat flux anomalies from 1970–88 in which they find similar changes in gyre-scale thermocline structure. The model current fields reveal that the North Pacific subpolar and subtropical gyres strengthened by roughly 10% from the 1970s to the 1980s. The bulk of the eastward flow of the model Kuroshio–Oyashio Extension returned westward via the subpolar gyre circuit, while the subtropical gyre return flow along 20 (cid:56) N lags the subpolar changes by several years. The authors demonstrate that the model thermocline cooling and increased transport occurred in response to decadal-scale changes in basin-scale wind stress curl with the quasi-stationary oceanic response being in a time-dependent quasi-Sverdrup balance over much of the basin east of the date line. This wind stress curl driven response is quasi-stationary but occurs in conjunction with a propagating temperature anomaly associated with subduction in the central North Pacific that links the subpolar and subtropical gyre stationary changes and gives the appearance of circumgyre propagation. Different physics evidently controls the decadal subsurface temperature signal in different parts of the extratropical North Pacific.
T.Yamagata：“西太平洋年代际自然气候变率及其对全球变暖的影响”J.Met.Soc.Japan。
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