120,000 years of Arctic sea ice evolution reconstructed: its average extension, closely related to changes in climate, would have reached its minimum value in the last 11,000 years. This is indicated by the analysis of the sea salts contained in a 584 meter long ice core, extracted in 2015 from a glacier on the east coast of Greenland. The study was conducted by the Institute of Polar Sciences of the National Research Council (CNR-ISP) as part of the European 'ice2ice' project, and is published in the journal Climate of the Past.
The results show "that the period of maximum extension and thickness of the ice occurred about 20,000 years ago, during the last glacial maximum", explains Niccolo Maffezzoli, researcher of the CNR-ISP and author of the research. "The ice then began to melt some 17,500 years ago, in conjunction with many other climate changes that occurred during the deglaciation that led to the current interglacial state."
The history of Arctic sea ice in a 584 meter ice core (source: CNR-ISP)
The ice formed by the freezing of sea water in winter is a fundamental climatic variable, deeply involved in the processes that link the atmosphere, the oceans and the biosphere. "It is a very sensitive parameter to climate change: proof of the contraction we have been witnessing in the Arctic ocean in recent decades, due to the anthropogenic warming that influences air temperatures especially in these latitudes", continues Maffezzoli. "Satellite observations in the Arctic have been available since the 1980s and climate models predict an Arctic Ocean free from ice in the summer in a few decades."
Chemical analyzes performed with mass spectroscopy on the ice core "have quantified bromine, sodium and other elements trapped in the ice matrix up to levels of one part per trillion", underlines Maffezzoli. "We look forward to being able to measure the carrot that will be extracted from the Antarctic ice sheet in the Beyond-Epica project, which is estimated to cover the last million and a half of Earth's climatic history."