【科技日报】7亿年前“雪球地球”海洋温度低至-15℃

Core Insights - An international team led by researchers from the Chinese Academy of Sciences has innovatively used iron isotopes as a "paleothermometer" to directly measure ocean temperatures during the "Snowball Earth" period approximately 700 million years ago, revealing that local ocean temperatures could drop to as low as -15°C with extremely high salinity [1][2]. Group 1: Research Findings - The study published in "Nature Communications" indicates that during the "Snowball Earth" period, the ocean was entirely covered in ice, with temperatures significantly lower than previously estimated [1]. - The research team successfully decoded the ocean temperature signals by analyzing iron isotopes in ancient iron-rich sedimentary rocks, which are key to understanding historical ocean temperatures [1]. - The iron isotopes from this period showed a "positive shift," indicating lower temperatures, with the signal being more pronounced at lower temperatures [1]. Group 2: Salinity Impact - The study found that despite the extremely low temperatures, seawater did not completely freeze due to the high salinity levels, which were over four times that of modern seawater, lowering the freezing point to approximately -11°C [2].