Antarctica and the Southern Ocean, b. Atmospheric circulation and surface observations [in "State of the Climate in 2022"]

Many of the major climate themes over Antarctica and the surrounding Southern Ocean in 2022 were a continuation of those seen during 2021. Most notable was the persistence of a deep
Amundsen Sea Low (Clem et al. 2022) over the South Pacific, which produced another warm year on the Antarctic Peninsula; it was the second-warmest year on record for all five of the long-term staffed weather stations located on the Peninsula. Coupled with above-normal pressure over much of the southern middle latitudes and generally weak- to below-average pressure elsewhere over Antarctica, the Southern Annular Mode (SAM; Marshall 2003), the difference in pressure anomalies between the southern middle latitudes and Antarctica, remained in a strongly positive state through most of the year (except June), and 2022 saw the third-highest annual-mean SAM index on record (since 1957). This reflects a remarkably persistent positive SAM pattern over the Southern Hemisphere that dates back to October 2020: 24 of the past 27 months have recorded a
positive monthly-mean SAM index. Furthermore, the persistence of La Niña through all of 2022 (see section 4b for details), combined with positive SAM conditions, enhanced the deepening
and expansion of the Amundsen Sea Low (Fogt et al. 2011), especially from July onward when La Niña strengthened. This contributed to three of the five Peninsula stations recording their warmest July−December period on record. Lastly, there were two exceptional warming events in 2022 due to strong atmospheric rivers: one in early February on the Antarctic Peninsula (not shown; Gorodetskaya et al. 2023) and one in March on the East Antarctic plateau (see Sidebar 6.1 for details). A detailed overview of other noteworthy climate and circulation anomalies across Antarctica in 2022 is provided below.