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Xiaofang Feng, Qinghua Ding, Liguang Wu, Charles Jones, Ian Baxter, Robert Tardif, Samantha Stevenson, Julien Emile-Geay, Jonathan Mitchell, Leila M. V. Carvalho, Huijun Wang, and Eric J. Steig

similar teleconnection pattern as that derived from LMR2, so our discussion focuses on results from LMR2. b. CMIP5 and five model large ensembles To examine the effects of increasing anthropogenic forcing on global climate, we use two sets of multimodel ensemble means to reduce uncertainties in each model ( Deser et al. 2020 ). One is the ensemble mean of all 40 climate models provided in CMIP5 ( Taylor et al. 2012 ; Table 1 ) over the 1979–2017 period, combining model outputs from the 1979

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Lee J. Welhouse, Matthew A. Lazzara, Linda M. Keller, Gregory J. Tripoli, and Matthew H. Hitchman

1. Introduction This research focuses on the El Niño–Southern Oscillation (ENSO) signal found throughout Antarctic surface observations and reanalysis data. [For a more complete review of prior literature on interactions between ENSO and Antarctica see Turner (2004) .] Understanding of ENSO, and its effects, has expanded substantially since it was initially investigated in depth. ENSO is now understood to be among the dominant modes of variability of both the atmosphere and ocean on decadal

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David P. Schneider, Clara Deser, and Tingting Fan

radiative forcings [including greenhouse gasses (GHGs), natural and anthropogenic aerosols, solar variability, etc.] into a single category of “other” forcing. This is motivated by the fact that the direct impacts of these other radiative forcings (i.e., the components of the response not mediated by SSTs) have been previously found to be very small relative to the effects of ozone and SSTs (e.g., Deser and Phillips 2009 ; Polvani et al. 2011 ; Staten et al. 2012 ; Grise and Polvani 2014 ). Our

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Kyle R. Clem, James A. Renwick, and James McGregor

similarities in the ENSO and SAM-related circulation anomalies over the South Pacific during DJF ( Karoly 1989 ; L’Heureux and Thompson 2006 ). Possible reasons for the relatively weak PC1 correlations with ENSO and SAM compared to other seasons, including the role of lagged sea ice effects, are discussed in the next section. Table 1. Seasonal detrended correlations, 1979–2015, of PC1 and PC2 with the SOI, SST anomalies in the Niño-4, -3.4, and -3 regions, and SAM index. Correlations significant at the

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Ryan L. Fogt and Alex J. Wovrosh

topography, specifically the nonsymmetric orientation of the continent, such as the high plateau of East Antarctica (which reaches an elevation of over 3000 m) and the western Antarctic Peninsula ( Baines and Fraedrich 1989 ; Lachlan-Cope et al. 2001 ). The ASL has a seasonal movement due to the location of the Rossby long waves in the Southern Hemisphere ( Turner et al. 2013 ), being farther east toward the Antarctic Peninsula in austral summer and farther west toward the Ross Sea in austral winter

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Xiaojun Yuan, Michael R. Kaplan, and Mark A. Cane

CP El Niño propagates west of the wave emanated by EP El Niño and produces a less significant positive center in the Amundsen Sea ( Sun et al. 2013 ). The responses of southern high latitudes to ENSO events are not only sensitive to different flavors of El Niño, but also sensitive to seasons when the teleconnection occurs. The seasonally changing background circulation affects the energy propagation of atmospheric Rossby waves, as well as their interactions with transient eddies. Based on

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Robert A. Tomas, Clara Deser, and Lantao Sun

; Sun et al. 2015 ) and an increase in warm extremes ( Screen et al. 2015b ) as a result of Arctic sea ice loss. In addition to local thermodynamic effects, diminished Arctic sea ice cover will weaken the tropospheric westerly winds along the poleward flank of the jet stream in association with a reduced north–south temperature gradient due to enhanced lower-tropospheric warming in the Arctic ( Deser et al. 2010 ; Peings and Magnusdottir 2014 ; Deser et al. 2015 , hereafter D15 ; Harvey et al

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Kyle R. Clem and James A. Renwick

Peninsula. The warming observed in temperature reconstructions across West Antarctica is supported by warming trends in the recently patched temperature record at Byrd station ( Bromwich et al. 2013 ) located in central West Antarctica and also by nearby observations across the Antarctic Peninsula ( Turner et al. 2005 ), although the peninsula and West Antarctic warming are likely linked to different mechanisms. A strong seasonality to the warming is seen across West Antarctica, being strongest in

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Aaron B. Wilson, David H. Bromwich, and Keith M. Hines

-century trends toward a high-polarity SAM have been linked to decreases in stratospheric ozone over Antarctica with propagating effects into the troposphere during austral summer (e.g., Thompson and Solomon 2002 ; Gillett and Thompson 2003 ; Thompson et al. 2011 ), as well as increasing greenhouse gases ( Fyfe et al. 1999 ; Kushner et al. 2001 ; Marshall et al. 2004 ; Simpkins and Karpechko 2012 ; Zheng et al. 2013 ). Low-frequency forcing of the atmospheric circulation in the SH is also tied to the

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Bradley P. Goodwin, Ellen Mosley-Thompson, Aaron B. Wilson, Stacy E. Porter, and M. Roxana Sierra-Hernandez

; Hosking et al. 2013 ; Clem and Fogt 2013 ). All of these factors have demonstrated highly regional and seasonal impacts on the climate of the AP and West Antarctica. These processes are linked to large-scale atmospheric oscillations, which are important determinants of both weather and climate in this region. One of the primary controls on southern high-latitude climate is the southern annular mode (SAM) (e.g., Thompson and Wallace 2000 ), defined by Gong and Wang (1999) as the difference in zonal

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