Extreme intra-seasonal anomalies in the Amundsen and Bellingshausen sea-ice area, Antarctica, during the austral winter

Abstract

We examine the role of the propagation of atmospheric mid-latitudes wave trains in modulating the Amundsen and Bellingshausen sea-ice area (SIA), Antarctica, on intra-seasonal timescales (20-100 days). Spectral analysis of passive microwave estimates of SIA in the Amundsen and Bellingshausen Seas for 1979-2004 shows significant peaks on intra-seasonal timescales. Previous studies have suggested that variations in SIA are linked to disturbances in atmospheric circulation and sea surface temperature. We show that extreme SIA anomalies on intra-seasonal timescales lag the propagation of subtropical wave trains in the Southern Hemisphere by approximately 10-15 days. The sign of the SIA anomaly depends on the phase of the wave. We present evidence that the number of disturbances that cause extreme anomalies of SIA on intra-seasonal timescales has increased in the last 14 years.

Variabilidade Intrassazonal Extrema Da Temperatura Do Ar À Superfície Na Península Antártica

“…Yu et al (2011) identificaram dois períodos importantes na variabilidade da temperatura do ar a 2m na Antártica e no Oceano Austral em 29 invernos utilizando dados das reanálises II do NCEP/NCAR: 26-30 dias e 13-14 dias. No entanto, Lima e Carvalho (2008) observaram o mesmo sinal encontrado no presente estudo nas anomalias de gelo marinho nos mares de Amundsen e Bellingshausen. Pelo fato do pico espectral IS estar próximo da escala temporal da MJO (entre 20-100 dias), os EIF e EIQ foram separados em MJO e NMJO (ver a explicação em "Dados e Metodologia") para avaliar a influência desta oscilação nos eventos IS de Tsup na Península Antártica em cada estação do ano (Tabela 2).…”

The intraseasonal variability of winter semester surface air temperature in Antarctica

“…By means of complex empirical orthogonal functions (CEOFs), Baba et al (2006) reported that the largest amplitudes in variability along the marginal sea-ice zone occurred around West Antarctica, especially in the Amundsen and Bellingshausen seas, and that the spatial phase of the meridional wind velocity preceded that of sea-ice concentration by about 908. Lima & Carvalho (2008) demonstrated the relationship between mid-latitude atmospheric wave train and sea-ice area in the Amundsen and Bellingshausen seas and showed that the extreme sea-ice area anomalies on intraseasonal timescales (20 Á 100 days) lag behind the propagation of subtropical wave train in the Southern Hemisphere by approximately 10 Á 15 days.…”

“…Mo & Higgins (1998) related the PSA to tropical convection and outgoing longwave radiation (OLR). The intraseasonal variation in tropics and subtropics is associated with atmospheric and oceanic variability in the Southern Ocean (Matthews & Meredith 2004;Lima & Carvalho 2008).…”

“…Those anomalies consistently propagate eastward correspondingly with the evolution of the modes. The wind vector anomaly also influences the sea-ice anomaly (Baba et al 2006;Lima & Carvalho 2008). In most cases the effect is confined to the Southern Ocean and Antarctic marginal sea regions.…”

The high‐frequency variability of Antarctic sea ice and polar cold air incursions over Amazonia

“…In this way, the persistence of the extremes was considered as the consecutive occurrence of 2 days or more, satisfying the conditions for SIE HF extremes, and as independent events, only those with at least 2 days apart (cf. Lima and Carvalho, 2008).…”