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

Abstract

The Antarctica Peninsula (AP) has experienced more frequent and intense surface melting recently, jeopardizing the stability of ice shelves and ultimately leading to ice loss. Among the key phenomena that can initiate surface melting are atmospheric rivers (ARs) and leeside foehn; the combined impact of ARs and foehn led to moderate surface warming over the AP in December 2018 and record‐breaking surface melting in February 2022. Focusing on the more intense 2022 case, this study uses high‐resolution Polar WRF simulations with advanced model configurations, Reference Elevation Model of Antarctica topography, and observed surface albedo to better understand the relationship between ARs and foehn and their impacts on surface warming. With an intense AR (AR3) intrusion during the 2022 event, weak low‐level blocking and heavy orographic precipitation on the upwind side resulted in latent heat release, which led to a more deep‐foehn like case. On the leeside, sensible heat flux associated with the foehn magnitude was the major driver during the night and the secondary contributor during the day due to a stationary orographic gravity wave. Downward shortwave radiation was enhanced via cloud clearance and dominated surface melting during the daytime, especially after the peak of the AR/foehn events. However, due to the complex terrain of the AP, ARs can complicate the foehn event by transporting extra moisture to the leeside via gap flows. During the peak of the 2022 foehn warming, cloud formation on the leeside hampered the downward shortwave radiation and slightly increased the downward longwave radiation.

Atmospheric River Brings Warmth and Rainfall to the Northern Antarctic Peninsula During the Mid‐Austral Winter of 2023

“…The implications of this rapid warming are profound, affecting changes in the cryosphere and ecosystem processes (Convey & Smith, 2006;Scambos et al, 2004;Siegert et al, 2023). This warming includes extreme weather events, exemplified by the February 2020 record temperature of 18.3°C in the northern AP, causing widespread ice melt (Clem et al, 2022;González-Herrero et al, 2022;Gorodetskaya et al, 2023;Orr et al, 2023;Wille et al, 2022;Xu et al, 2021;Zou et al, 2023). Rainfall on the cryosphere, particularly during such extreme events, can accelerate ice melt and impact the structural integrity of ice sheets and glaciers, further exacerbating the effects of temperature rise (Vignon et al, 2021;Wille et al, 2022).…”