Distribution of icebergs in the Atlantic and Indian ocean sectors of the Antarctic region and its possible links with ENSO

The spatial distribution and multiyear variability of iceberg concentration in the Atlantic and Indian ocean sectors of the Antarctic region have been studied using ship-borne observations of iceberg occurrence. The collected dataset includes more than 40,000 reports predominantly from Russian and Australian research vessels made over the last 36 years (1970 - 2005). The analysis of the data has revealed a gradual decrease in the iceberg concentration away from the coast of Antarctica and a substantial variation along the coast line. Large concentration of icebergs was found in the Weddell Sea and north-east of the Antarctic Peninsula. Several regions in the Atlantic and Indian Ocean sector of Antarctica have been identified where yearly anomalies of the iceberg occurrence exhibit a noticeable correlation with El Nino/Southern Oscillation (ENSO) events. The strongest ENSO effect was observed in the region east of Drake Passage where the iceberg concentration increased by about 50% during years of the negative Southern Oscillation Index (SOI) phase. The change in the iceberg amount is explained by an increased iceberg drift into this region from the southern part of Weddell Sea and from Pacific Ocean. The latter is caused by anomalous surface pressure High and associated anticlockwise circulation around the pressure anomaly developing in the south-eastern part of Pacific Ocean during the negative phase of ENSO.