deletions | additions       diff --git a/discussion.tex b/discussion.tex  index fa76377..eb457ae 100644  --- a/discussion.tex  +++ b/discussion.tex 
...
By using the bimodal phase peaks as a means to define PSA pattern activity, it was possible to identify a trend towards the negative phase of the pattern over the period 1979-2014 on an annual basis and also during summer, autumn and winter. This autumn trend (and the high latitude temperature and sea ice anomalies associated with the negative phase of the PSA pattern) is consistent with the work of \citet{Ding2013}, who found that autumn warming over the Antarctic Peninsula and associated sea ice declines over the Bellingshausen Sea are associated with an atmospheric circulation resembling the negative phase of the PSA pattern. While this explanation makes sense on the eastern flank of the central circulation anomaly associated with that pattern, the negative phase of the PSA pattern is also associated with strong cooling over West Antarctica. Autumn temperature declines have not been observed in that region, and thus our results suggest that the PSA-related cooling must have been offset by other factors.   In contrast to the autumn warming over the Antarctic Peninsula, winter warming over West Antarctica has been associated with an atmospheric circulation resembling the positive phase of the PSA pattern \citep{Ding2011}. Our climatology revealed a (albeit non-significant) trend towards the negative phase of the PSA pattern during winter, which raises the question: how is it that winter temperature trends over West Antarctica are associated with an atmospheric circulation resembling the positive phase of the PSA pattern, but a climatology of PSA pattern activity does not reveal trends consistent with that finding? One possible answer to this question comes from \citet{Li2015a}. They analyzed Rossby wave trains associated with observed SST trends in the tropical Atlantic, tropical Indian, west Pacific and east Pacific regions and found that all four have a center of action over the Amundsen Sea. While none of these individual wave trains resembled the PSA pattern, a linear combination of the four of them did (with the tropical Atlantic and west Pacific identified as most influential). In other words, the integrated influence of tropical SST trends on the atmospheric circulation resembles the positive phase of the PSA pattern, but the waves underpinning that teleconnection do not. This result is consistent with earlier studies that identified the tropical Atlantic as a driver of recent trends in West Antarctica \citep{Li2014,Simpkins2014}. Another possible answer comes from \citet{Fogt2015}, who suggest that radiative forcing has played a role in ASL Amundsen Sea Low  trends that are consistent with warming in West Antarctica.These alternative explanations go to the heart of the reversibility argument made at the beginning of this paper. For a proposed teleconnection to be robust, it must be evident when looking through the lens of both the variable and mechanism of interest.  While This idea that wave trains from the tropical Atlantic and/or radiatively forced Amundsen Sea Low variability might be responsible for a teleconnection pattern resembling the PSA pattern (i.e. as opposed to changes in actual PSA pattern activity) goes to the heart of the reversibility argument made at the beginning of this paper. For a proposed teleconnection to be robust, it must be evident when looking through the lens of both the variable and mechanism of interest. However, even if  these alternative explanations appear to do  reconcile the discrepancy between our climatology and winter warming over West Antarcitca, the associated circulation anomaly would bring cooler conditions and wind-driven increases in sea ice along the western Antarctic Peninsula, contrary to the observed warming and sea ice declines \citep{Clem2015}. One possible explanation is that the negative autumn sea ice anomalies persist into winter \citep{Ding2013}, however it is clear that there is still work to be done to fully understand recent temperature and sea ice changes in the region. One topic not addressed by our climatology is variability in the east/west location of the PSA pattern. In response to the emergence of central Pacific ENSO events in recent years \citep[e.g.][]{Ashok2007}, some authors have suggested that the PSA pattern moves east/west depending on the precise location of the associated tropical SST anomalies \citep[e.g.][]{Sun2013,Wilson2014,Ciasto2015}. Others suggest that the pattern is relatively stationary \citep[e.g.][]{Liu2007,Ding2012}, however either way the broad region (10$^{\circ}$N to 10$^{\circ}$S in the rotated coordinate system) used by our identification algorithm renders it insensitive to subtle east/west movements. Given that the PSA pattern did not show a strong association with the Ni\~{n}o 3.4 index (an index that is sensitive to both central and eastern Pacific ENSO events), it would be fair to say that even if the location of tropical SSTs does cause the pattern to move slightly, this would represent only a small fraction of all PSA pattern activity.