No abstract

[1] Recent studies have identified a significant warming trend across West Antarctica and the Antarctic Peninsula, which is likely linked to tropical forcing. Here we investigate temporal variations in El Niño-Southern Oscillation (ENSO)-related tropical forcing and Southern Annular Mode (SAM)-related forcing on the Amundsen-Bellingshausen Seas Low and the regional climate during austral spring. We find a spatial dependency regarding the impacts each of these climate modes have on the Antarctic Peninsula: relationships with ENSO and Antarctic Peninsula climate are persistent and significant across the western Peninsula, while relationships with the SAM are persistent and significant across the northeastern Peninsula. Other ENSO/SAM-Peninsula temperature correlations appear weak since 1957 as they vary temporally, fluctuating in response to changing correlations between the SAM index and the Southern Oscillation Index in austral spring. Changes in the ENSO-SAM correlations are due primarily to the 1988 La Niña/SAM negative event, which significantly altered the location of the ENSO teleconnection in the South Pacific Ocean and, therefore, its influence on the regional climate. Whether or not there is decadal variability in the ENSO-SAM relationship remains unclear; however, it is evident that the influence across the Peninsula varies in both space and time, related to the strength and spatial extent of the response in the Amundsen-Bellingshausen Seas. This suggests that in order to accurately attribute the warming to ENSO-related tropical forcing, it is necessary to consider the role of the regional circulation manifested by the phase of each climate mode together.

Variability and change in near-surface air temperature at 17 Antarctic stations is examined using data from the SCAR READER database. We consider the relationships between temperature, and atmospheric circulation, sea ice concentration and forcing by the tropical oceans. All 17 stations have their largest inter-annual temperature variability during the winter and the annual mean temperature anomalies are dominated by winter temperatures. The large interannual temperature variability on the western Antarctic Peninsula has decreased over the instrumental period as sea ice has declined. Variability in the phase of the SAM exerts the greatest control of temperatures, although tropical Pacific forcing has also played a large part, along with local atmospheric circulation variability at some locations. The relationship of positive (negative) SAM and high (low) Peninsula and low (high) East Antarctic temperatures was not present before the mid-1970s. Thirteen of the 17 stations have experienced a positive trend in their annual mean temperature over the full length of their record, with the largest being at Vernadsky (formerly Faraday) (0.46 ± 0.15 CÁdec −1 ) on the western side of the Antarctic Peninsula. The deepening of the Amundsen Sea low as a result of the more positive SAM and changes in the IPO and PDO have contributed to the warming of the Peninsula. Beyond the Antarctic Peninsula there has been little significant change in temperature.The two plateau stations had a small cooling from the late 1970s to the late 1990s consistent with the SAM becoming positive, but have subsequently warmed. During spring there has been an Antarctic-wide warming, with all but one station having experienced an increase in temperature, although the only trends that were significant were at Vostok, Scott base, Vernadsky and Amundsen-Scott. In this season, much of the Peninsula/West Antarctic warming can be attributed to tropical Pacific forcing through the IPO/PDO. K E Y W O R D SAntarctica, climate change, climate variability, temperature

Recent warming of the Antarctic Peninsula during austral autumn, winter, and spring has been linked to sea surface temperature (SST) trends in the tropical Pacific and tropical Atlantic, while warming of the northeast Peninsula during summer has been linked to a strengthening of westerly winds traversing the Peninsula associated with a positive trend in the Southern Annular Mode (SAM). Here we demonstrate that circulation changes associated with the SAM dominate interannual temperature variability across the entire Antarctic Peninsula during both summer and autumn, while relationships with tropical Pacific SST variability associated with the El Niño–Southern Oscillation (ENSO) are strongest and statistically significant primarily during winter and spring only. We find the ENSO‐Peninsula temperature relationship during autumn to be weak on interannual time scales and regional circulation anomalies associated with the SAM more important for interannual temperature variability across the Peninsula during autumn. Consistent with previous studies, western Peninsula temperatures during autumn, winter, and spring are closely tied to changes in the Amundsen Sea Low (ASL) and associated meridional wind anomalies. The interannual variability of ASL depth is most strongly correlated with the SAM index during autumn, while the ENSO relationship is strongest during winter and spring. Investigation of western and northeast Peninsula temperatures separately reveals that interannual variability of northeast Peninsula temperatures is primarily sensitive to zonal wind anomalies crossing the Peninsula and resultant leeside adiabatic warming rather than to meridional wind anomalies, which is closely tied to variability in the zonal portion of the SAM pattern.

After 1979, statistically significant warming in Antarctica is only observed in austral spring (September-November, SON) across West Antarctica and the Antarctic Peninsula. While previous work has linked this warming to reductions in sea ice cover, we note that a substantial (30-