The variability of Antarctic fast ice extent related to tropical sea surface temperature anomalies

Abstract. While numerous studies have examined the influence of meteorological variables on fast ice, the mechanistic linkages between fast-ice variability and large-scale climatic oscillations have remained inadequately explored. Empirical Orthogonal Function (EOF) analysis is applied to circumpolar Antarctic fast-ice extent data (March 2000–February 2018) to investigate seasonal-scale teleconnections between fast ice anomalies and tropical sea surface temperature (SST) variability. Results demonstrate a fluctuating but increasing trend in fast-ice extent during austral winter and spring, with spatially predominant anomalies concentrated in the West Antarctic. A physical pathway linking tropical and subtropical SST anomalies to fast-ice variability is elucidated through multiscale interactions: SST anomalies modulate outgoing longwave radiation (OLR), subsequently perturbing the 200 hPa geopotential height field and triggering atmospheric Rossby wave trains. These planetary waves propagate from the tropics towards the Antarctic coastal zone, generating anomalies in the Southern Annular Mode (SAM) and other patterns of mean-sea-level pressure (MSLP) and surface wind field. These atmospheric adjustments directly regulate fast-ice mechanical formation/disintegration processes while indirectly influencing thermodynamic ice evolution through air temperature modifications. Tropical SST anomalies predominantly exciting planetary waves during austral autumn, whereas the subtropical South Pacific SST dipole mode emerges as the primary forcing mechanism during austral winter and spring. Seasonal variations in atmospheric forcing on fast ice are identified. By tracing how remote SST forcing propagates through atmospheric wave dynamics to influence regional fast-ice conditions, this study advances process-level understanding of tropical and subtropical impacts on the Antarctic.