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The PSA pattern is most commonly analyzed with respect to a pair of Empirical Orthogonal Function (EOF) patterns (e.g. Figure \ref{fig:eof}). Known as PSA-1 and PSA-2, these patterns are in quadrature and depict a wave train extending along an approximate great circle path from the central Pacific Ocean to the Amundsen and Weddell Seas. Some authors interpret these patterns as a single eastward propagating wave \citep{Mo1998}, while others argue that variability in the PSA sector is better described as a set of geographically fixed regimes \citep{Robertson2003}. On a decadal time scale, PSA-1 has been related to sea surface temperature (SST) anomalies over the central and eastern Pacific, while on an interannual time scale it appears as a response to ENSO \citep{Mo2001}. The association of PSA-2 with tropical variability is less clear, with some authors relating it to the quasi-biennial component of ENSO variability \citep{Mo2000} and others to the Madden Julian Oscillation \citep{Renwick1999}. While most of the features of the PSA pattern are consistent with theory and/or modelling of Rossby wave dispersion from anomalous tropical heat sources \citep[e.g.][]{Liu2007,Li2015}, it is recognized that the pattern can also result from internal atmospheric fluctuations caused by instabilities of the basic state \citep[and that both mechanisms likely act in concert; e.g.][]{Grimm2009}.  It has been shown that the PSA pattern plays a role inSouth American rainfall variability \citep{Mo2001},  blocking events \citep{Sinclair1997,Renwick1999} and poleward heat transport (Christoph et al. 1998, Hall South American rainfall variability \citep{Mo2001}  andVisbeck, 2002). It  is also closely related to prominent regional features such as the Amundsen Sea Low \citep{Turner2013} and \citep{Turner2013},  Antartic Dipole \citep{Yuan2001} \citep{Yuan2001}, Antarctic Circumpolar Wave \citep{Christoph1998}  andprojects onto the  Southern Annular Mode \citep{Ding2012}. \citep[SAM; e.g.][]{Ding2012}.  While these are all important mid-to-high latitude impacts and relationships, in recent years the PSA pattern has been mentioned most frequently in the literature in relation to the rapid warming observed over West Antarctica and the Antarctic Peninsula \citep{Nicolas2014}. In particular, it has been suggested that seasonal trends in tropical Pacific SSTs may be responsible, via circulation trends resembling the PSA pattern, for winter (and to a lesser extent spring) surface warming in West Antarctica \citep{Ding2011} and autumn surface warming across the Antarctic Peninsula \citep{Ding2013}. The pattern has also been associated with declines in sea ice in the Amunden and Bellingshausen Seas \citep{Schneider2012} and glacier retreat in the Amundsen Sea Embayment \citep{Steig2012}. In identifying the PSA pattern as a possible contributor to these trends, the aforementioned studies looked through the lens of the variable/s of interest. For instance, \citet{Ding2011} performed a maximum covariance analysis to look at the relationship between central Pacific SSTs and the broader SH circulation (the 200hPa geopotential height). The second mode of that analysis revealed a circulation resembling the PSA pattern (and that brings warm air over West Antarctica), and atmospheric model runs forced with the associated central Pacific SSTs produced a PSA-like wave train. While this is certainly a valid research methodology, the result would be more robust if a climatology of PSA pattern activity also displayed trends consistent with warming in West Antarctica. This concept of teleconnection reversibility was recently invoked to question the relationship between Indian Ocean SSTs and heat waves in south-western Australia \citep{Boschat2016}.