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Guoqi Han and Weigen Huang

1. Introduction The Bohai, Yellow, and East China Seas ( Fig. 1 ) are shallow marginal seas enclosed by East China, the Korean Peninsula, and Japan with open connections to the northwest Pacific, the South China Sea, and the Sea of Japan ( Su 1998 ). In addition to local atmospheric forcing and freshwater runoff, the large-scale atmospheric and oceanic variability, such as the Pacific decadal oscillation (PDO) may impact the seasonal and longer-term hydrography and circulation variability in

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Jie Zhang, Zhiheng Chen, Haishan Chen, Qianrong Ma, and Asaminew Teshome

North Atlantic (NA) jet ( Trouet et al. 2018 ), the North Pacific jet ( Strong and Davis 2008 ; Belmecheri et al. 2017 ), and the Afro-Asian jet ( Branstator 2002 ); however, all of them show inconsistent variability at interannual to decadal time scales. Therefore, considering their different impacts, the jet effects on summer extremes should be discussed separately. The NA jet has been identified to result in extratropical extremes such as heatwaves and droughts in Europe ( Trouet et al. 2018

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Dongxia Yang, Julie M. Arblaster, Gerald A. Meehl, Matthew H. England, Eun-Pa Lim, Susan Bates, and Nan Rosenbloom

waves of a broad range of phase speeds. Despite the well-established interannual ENSO–SAM relationship, less is known about the influence of internal decadal variability on the midlatitude jet. Some research has related the interdecadal Pacific oscillation (IPO) transition in the late 1990s to Antarctic climate variability. For example, the negative phase of the IPO has been linked to Antarctic sea ice expansion via a positive phase of the SAM combined with a deepened Amundsen Sea low (ASL), which

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Hanna Na, Kwang-Yul Kim, Shoshiro Minobe, and Yoshi N. Sasaki

variability in the NP, partly because of its better availability in both time and space. The most dominant mode of the NP variability [i.e., the Pacific decadal oscillation (PDO); Mantua et al. (1997) ] is derived from empirical orthogonal function (EOF) analysis of SST in the NP (north of 20°N) and has been widely used to understand the long-term changes in the physical and biological conditions in the NP. However, the different vertical structures of the KE and SAFZ have raised the importance of

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Yang Yang, X. San Liang, Bo Qiu, and Shuiming Chen

figure are Izu–Ogasawara Ridge (IO), Shatsky Rise (SR), and Emperor Seamounts (ES). (b) Long-term mean eddy kinetic energy (colored shading; J m −3 ). The black line shows the jet axis (100-cm isobath of the sea surface height). Significant decadal variability has been observed in the Kuroshio Extension, reflected by multiple indices such as the regional sea surface height (SSH) anomalies, jet strength, latitudinal position, and pathlength, to name a few ( Qiu and Chen 2005 ). During the past decade

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Yong-Jhih Chen, Yen-Ting Hwang, Mark D. Zelinka, and Chen Zhou

the absence of forcing are described in section 3 . The estimated contributions of the decadal variability to the observed cloud cover trends, along with the estimated contributions of GHG forcing, are described in section 4 . In section 5 we summarize our findings. 2. Data and methodology a. Data The SST data used in this study were obtained from the Hadley Centre Global Sea Ice and Sea Surface Temperature dataset (HadISST; Rayner et al. 2003 ) and the Extended Reconstructed Sea Surface

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Marius Årthun, Robert C. J. Wills, Helen L. Johnson, Léon Chafik, and Helene R. Langehaug

1. Introduction The North Atlantic Ocean displays pronounced decadal variability ( Fig. 1 ; Deser and Blackmon 1993 ; Czaja and Marshall 2001 ). Decadal variations in North Atlantic sea surface temperature (SST) influence climate over adjacent continents and are a major source of skill in climate predictions ( Hermanson et al. 2014 ; Msadek et al. 2014 ; Årthun et al. 2017 ; Yeager and Robson 2017 ). Understanding the physical mechanisms responsible is thus important for attributing

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Bo Qiu, Shuiming Chen, Niklas Schneider, Eitarou Oka, and Shusaku Sugimoto

during 1995–2001, 2006–09, and 2016–17. This decadal modulation of the KE system has persisted after the 1976–77 “climate shift” in the North Pacific ( Qiu et al. 2014 ) and the basinwide wind stress curl variability associated with the Pacific decadal oscillations (PDOs; Mantua et al. 1997 ), or the North Pacific gyre oscillations (NPGOs; Di Lorenzo et al. 2008 ), has been identified as the external forcing that controls the phase change between the stable/unstable dynamic states. Fig . 2. Yearly

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Julien Emile-Geay and Mark A. Cane

1. Introduction The existence of decadal-scale variability in the Pacific Ocean is now well documented, and it affects the climate and fisheries of the neighboring regions to a significant extent (e.g., Trenberth and Hurrell 1994 ; Zhang et al. 1997 ; Mantua et al. 1997 ). This Pacific decadal variability (PDV) in the North Pacific is usually described by the Pacific decadal oscillation (PDO) index ( Mantua and Hare 2002 ), which is quite energetic in the interdecadal spectral range. There

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Richard Kleeman

spectrum of ENSO variability (e.g., Kleeman 2008b ) and another that is proposed as a mechanism for midlatitude decadal variability (see Saravanan and McWilliams 1998 ). In both these cases one can show that the basic behavior of the stochastic model is explicable using a two-dimensional OU process (see Kleeman 2002 , 2008a ). Qualitatively such a system is a white noise–forced damped oscillation with the period of oscillation determined by a natural physical time scale. In the ENSO case this is

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