Atmospheric precursors to the Antarctic sea ice record low in February 2022

Abstract

Antarctic sea ice expansion and recession are asymmetric in nature, with regional and temporal variations. The decade-long overall increase in the Antarctic sea ice extent (SIE) until 2015 showed a decrease in recent years since satellite records were available. The present study focused on determining the atmospheric forcing and climate fluctuations responsible for the lowest SIE record in February 2022. Here, the lowest SIE record was assumed to result from the sea ice recession that began in September 2021. The SIE reached a record low of 2.16 × 106 km2 in February 2022, which was 43% lower than the mean extent of the previous February months since the satellite era. However, the second-lowest SIE was recorded from November 2021 to January 2022. The Weddell Sea, Ross Sea, and Bellingshausen/Amundsen Seas (ABS) sectors experienced the maximum sea ice change on a regional scale. The record-low SIE occurred when the Amundsen Sea Low (ASL) pressure center was intensified, with the Southern Annular Mode (SAM) at its positive phase. Together, these two climate fluctuations played a role in modifying the pressure and wind patterns in Antarctica. Further, the study investigated the Polar Cap Height (PCH), which demonstrates a strengthening of the stratospheric polar vortex and positive polarity of the SAM. Regions dominated by warm northerly winds produced decreased SIE. However, sea ice increased due to wind-driven sea ice drift towards the north.

Record low Antarctic sea ice coverage indicates a new sea ice state

“…Individual extreme sea ice events have been linked to anomalous atmospheric circulation events. For example, the strong meridional circulation associated with zonal wave number three contributed to the low sea ice in spring 2016 17 , while a strong Amundsen Sea Low circulation in spring 2021 influenced the low spring/summer sea ice conditions in 2021/22 18,19 . However, the phase of the Southern Annular Mode cannot account for the low Antarctic sea ice over recent years: the positive phase of the Southern Annular Mode has historically been associated with colder sea surface temperatures and increased sea ice extent 7 , and in line with this, the 2017 record summer sea ice minimum (Fig.…”

Atmospheric drivers of Antarctic sea ice extent summer minima

“…Holland et al, 2017;, and previous works examining the 2017 and 2022 minima also considered this season (e.g. Purich and England 2019;Yadav et al 2022). Furthermore, as seen in the previous section, the sea ice anomalous conditions are already set up in January at the latest, indicating the important role of surface winds during the previous months.…”

“…More recently, Yadav et al (2022) specifically focused on the atmospheric precursors of this event during the preceding months, i.e. since September 2021.…”

Compound drivers behind new record high temperatures and surface melt at the Antarctic Peninsula in February 2022

“…Sea-ice extent remained close to record low levels during most of the summer 2021-22. Yadav et al [62] showed that the sea ice deficit around the AP was linked to persistent warm northerly flow in the Amundsen/Bellingshausen sector throughout the summer 2021/2022 (from November 2021 until February 2022) linked to the anomalously deep Amundsen Sea Low, while sea ice anomalies in the northern Weddell Sea were to a large extent caused by stronger westerlies associated with positive SAM during the entire summer season. Wang et al [61] emphasized that the Amundsen Sea sea ice loss was more dynamically related, while a strong surface melt contributed to the Weddell Sea sea ice minimum.…”