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

Abstract

The Antarctic Peninsula (AP) experienced a new extreme warm event and record high surface melt in February 2022, rivaling the recent temperature records from 2015 and 2020, and contributing to an alarming series of extreme warm events there. The northern/northwestern AP was directly impacted by an intense atmospheric river (AR) bringing anomalous heat and rainfall, while AR-enhanced foehn effect further warmed its northeastern side. The event was triggered by multiple large-scale atmospheric circulation patterns linking the AR formation to tropical convection anomalies and stationary Rossby waves, with anomalous Amundsen Sea low and record-breaking blocking high. The cascade of impacts culminated in widespread and intensive surface melt across the AP. The event was statistically attributed to global warming. Increasing frequency of such events can undermine the stability of the AP ice shelves, with multiple local to global impacts, including acceleration of the AP ice mass loss and changes in sensitive ecosystems.

Strong Warming Over the Antarctic Peninsula During Combined Atmospheric River and Foehn Events: Contribution of Shortwave Radiation and Turbulence

“…In the 2018 case, the surface melting was mainly over the remaining Larsen B Ice Shelf (max ∼30 mm of water equivalent; see Figure 3c). By contrast, in the 2022 case, surface melting affected the whole northern AP (Figure 3d), including the upwind side (e.g., Anvers Island, Graham Coast, and Adelaide Island; see also Gorodetskaya et al, 2023). The South Shetland Islands also experienced strong melting, whereas no melting was detected there in the 2018 case.…”

“…An increasing AR frequency over the AP may occur in the future under climate change, as well as the positive SAM trend (Espinoza et al, 2018;Wille et al, 2021). Consequently, more intense and complicated foehn cases may occur, which can lead to extreme weather, such as record-breaking temperature and intense precipitation (e.g., Bozkurt et al, 2018;González-Herrero et al, 2022;Gorodetskaya et al, 2023). In addition, the upper Southern Ocean has warmed due to anthropogenic activities since the 1950s, and drastic reductions of ice-shelf extent and surface height over the AP are associated with the basal melting (Armour et al, 2016;Cook & Vaughan, 2010;Li et al, 2021;Paolo et al, 2015).…”

“…The collapse of ice shelves over the AP is the consequence of multiple factors, including rapid regional atmospheric warming and an extended melting period (Mulvaney et al, 2012;Scambos et al, 2000). During the austral summer, warming over the northeast AP is strongly associated with strengthening westerly winds due to the positive Southern Annular Mode (SAM) trend (Clem et al, 2016(Clem et al, , 2022Elvidge & Renfrew, 2016;Marshall et al, 2006). Stronger summer westerly winds have led to a higher frequency of air masses being advected eastward over the orographic barrier of the northern AP (Marshall et al, 2006), contributing to foehn-induced surface melt of ice shelves on the eastern side of the Peninsula (Bozkurt et al, 2018;González-Herrero et al, 2022).…”

“…Deep convection in the central tropical Pacific often leads to prolonged cyclone activity over the South Pacific and blocking highs/anticyclones over the Drake Passage, which helps transport warm marine air toward the southwest AP (Clem et al, 2022). This circulation pattern may be associated with strong atmospheric rivers (ARs) and foehn warming on the leeside of the AP due to orographic lifting on the upwind side (Clem et al, 2022). However, the surface warming/melting pattern depends on the strength and landfall location of an AR, as well as its modification by the local topography.…”

“…Also, associated with a warming tropical Atlantic sea surface temperatures, a deepened Amundsen Sea Low favors warm air advection and the surface warming over the AP (Li et al, 2021). Deep convection in the central tropical Pacific often leads to prolonged cyclone activity over the South Pacific and blocking highs/anticyclones over the Drake Passage, which helps transport warm marine air toward the southwest AP (Clem et al, 2022). This circulation pattern may be associated with strong atmospheric rivers (ARs) and foehn warming on the leeside of the AP due to orographic lifting on the upwind side (Clem et al, 2022).…”