The relative influence of ENSO and SAM on Antarctic Peninsula climate

Previous studies documented that El Niño (EN) events are in general associated with negative phases of the Southern Annular Mode (SAM). EN 2015–2016 (EN15–16) was one of the three strongest events ever recorded. However, it was associated with a SAM positive phase of extreme intensity. Furthermore, while the negative linear relationship between ENSO and SAM during the most recent period (1986–2014) was significant and associated with a narrow uncertainty band, the combined condition of both climate patterns in the EN15–16 event was an outlier. The EN15–16 influence on the austral summer circulation anomalies at the extratropical and polar regions of the Southern Hemisphere was considerably altered by the strong SAM positive phase, which was evident not only at the troposphere but also at the stratosphere. Such circulation changes resulted in unusual regional impacts, such as negative anomalies of surface air temperature in western Antarctic Peninsula and negative precipitation anomalies in southeastern South America, ever recorded for previous strong EN events. Further research is needed to better understand the mechanisms explaining the SAM behaviour during 2015–2016 and its implication for climate predictability on seasonal timescales.

Section: Impact On Surface Air Temperature In the Antarctic Peninsulasupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Activity of the Southern Annular Mode during 2015–2016 El Niño event and its impact on Southern Hemisphere climate anomalies

Vera

Osman

2018

“…Sea ice variability is very important in dictating annual mean temperature at these two stations and the regional processes influencing sea ice variability at the two sites are often decoupled . Moreover, meridional wind anomalies and thermal advection play a dominant role on the western Peninsula, while zonal wind anomalies and Föhn events are more important on the eastern Peninsula (Clem et al, 2016).…”

Section: The Antarctic Peninsulamentioning

confidence: 98%

Antarctic temperature variability and change from station data

Turner

Marshall

Clem

et al. 2019

164

115

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

“…The SAM development explained 35% of the variability of the zonal group relative frequency (Figure a, r = .59). Since both the high value of SAM as well as high frequencies of the zonal group patterns indicate more intensive westerlies in the AP region, the relationship corresponds well to the essential principle of this mode (Thompson and Solomon, ; Clem et al ., ; Clem et al ., ). Furthermore, the variability of the low‐pressure system in the Weddell Sea ([1, 3]) showed a significant positive correlation with the ENSO Index ( r = .79), while there was a negative correlation ( r = −.52) with synoptic pattern [5, 1].…”

Section: Synoptic Patterns Over the Ap Regionmentioning

confidence: 99%

Multi‐year assessment of atmospheric circulation and impacts on air temperature variation on James Ross Island, Antarctic Peninsula

Ambrožová

Láska

Kavan

2019

The influence of synoptic‐scale circulation on air temperature variation in the ice‐free and glaciated areas on the eastern side of the Antarctic Peninsula (AP) has been analysed. For this purpose, a new classification of atmospheric circulation with 15 synoptic patterns in the AP region was developed using the self‐organizing maps technique. The synoptic patterns were compared with air temperature observations from coastal and glacial sites on James Ross Island, northeastern AP, in the period 2005–2015. The most frequent synoptic pattern with a frequency of 13.7% was dominated by a low‐pressure centre in the northwestern Bellingshausen Sea, which extended over the AP to the Weddell Sea. On the other hand, the largest inter‐annual variability was observed for a synoptic pattern with a low‐pressure centre in the southern Bellingshausen Sea. This synoptic pattern also had the highest air temperature anomalies at both investigated sites year‐round. Air temperature anomalies at the lower lying site (Mendel station) were the lowest during a high‐pressure ridge dominating the AP region due to a combination of local and synoptic‐scale processes. At Davies Dome, the glacial site, southerly barrier winds advecting cold air from the ice‐covered Weddell Sea during a strong low‐pressure system in the Weddell Sea ensured the coldest air temperature anomalies.