Past Sea Ice Variability Derived from Ice Cores: The Bromine Approach

Sea ice is a crucial parameter in the climate system, and it is declining at a faster rate than models predicted. Bromine plays a central role in sea ice chemistry, from where it is released as BrO during springtime, enriching its abundance in the polar atmosphere. Therefore, bromine enrichment in snow, with respect to the sodium ratio in seawater, can be been linked to first year sea ice variability at the Poles. Measurements of Bromine enrichment (Brenr) have been carried out in Greenland (NEEM and Renland ice cores), Svalbard, Severnaya Zemlya and Antarctica (Talos Dome, Law Dome and Dome C). These climate ice archives investigated, cover both the satellite era and the older climate periods back to the last glaciation. The results obtained from deep drilling in the Arctic suggest that during the Holocene climate optimum (9- 10 ky BP) in summer time open water was present in the Canadian Arctic, whilst multi-year sea ice was present during the last glaciation, with rapid interstadial periods able to changes the sea ice structure. The Antarctic results (except Talos Dome) were mainly focussed on covering the last 200 years, the Talos Dome ice core covered back to the previous glaciation (150 ky BP). The results obtained from the Law Dome and Dome C ice core, support the idea that Br enrichment can also be used in Antarctica and suggests that the variability of sea ice, especially in the Indian sector, might be explained by the changes in the SAM (Southern annular mode).