Landfalling Atmospheric Rivers in the Antarctic Peninsula: Synoptic Evolution and Oceanic Feedback

Atmospheric rivers (ARs), increasingly recognized for their substantial influence on polar regions, are characterized as long, narrow corridors of intense moisture transport that play a crucial role in the redistribution of heat and water vapor toward higher latitudes. These systems profoundly affect precipitation regimes, surface melt dynamics, and, consequently, the surface mass balance of Antarctica (Wille et al., 2021). Additionally, ARs interact with oceanic processes, influencing wave activity, sea spray aerosol production, and feedback mechanisms that can impact cloud microphysics and precipitation. In the Antarctic Peninsula (AP), ARs have been associated with anomalous snowfall, extreme melting events, and transitions between snowfall and rainfall. A notable example occurred in February 2022, when an intense AR event resulted in unprecedentedly high temperatures, extensive surface melting across the AP and anomalously high rainfall amounts in the northern AP, underscoring their significant role in regional climate variability (Gorodetskaya et al., 2023).

Building on prior findings, this study examines a February 2023 AR event using observations at King Sejong Station, King George Island (radiosondes and precipitation radar MRR-PRO), ERA5 reanalysis and WAVEWATCH III model. The AR was driven by a deep low-pressure system west of the AP and a high-pressure ridge to the northeast, creating strong moisture advection and cyclonic uplift. Integrated Vapor Transport (IVT) values exceeded 400–600 kg/m−1 s−1 during peak days, with a distinct influence of baroclinic zones and fronts identified using wet-bulb potential temperature gradients at 850-hPa level. These conditions facilitated enhanced vertical motion, cloud development, and significant precipitation, primarily as snowfall in inland and higher- altitude regions of the AP. Concurrently, the strong winds associated with the AR enhanced wave activity and whitecapping in the surrounding Southern Ocean, increasing sea spray aerosol production, which could potentially influence cloud microphysical properties.

Furthermore, thermodynamic conditions during the AR were characterized by pronounced baroclinicity and the interaction of warm, moist subtropical air with cold polar air, which sustained cloud formation and moisture convergence. Later in February, as cyclonic activity weakened and IVT values decreased below 200 kg/m−1 s−1, precipitation became less intense and spatially confined. However, residual moisture flux and localized thermodynamic forcing supported light snowfall, even as synoptic features transitioned toward zonal flow. The dynamic interplay between AR-driven moisture transport, cyclonic uplift, oceanic feedback, and synoptic transitions underscores the significant role of ARs in modulating cloud and precipitation properties over the AP.

Acknowledgements: We are grateful for financial and logistical support via FCT projects MAPS and MICROANT, PROPOLAR and KOPRI

References:

Gorodetskaya, I.V. et al. “Record-high Antarctic Peninsula temperatures and surface melt in February 2022: a compound event with an intense atmospheric river” (2023) https://www.nature.com/articles/s41612-023-00529-6

Wille, J. D. et al. (2021) “Antarctic atmospheric river climatology and precipitation impacts” J. Geophys. Res. Atmos. 126, e2020JD033788