7亿年前“雪球地球”海洋温度低至-15℃

Core Findings - An international research team led by 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 -15°C with extremely high salinity [1][3] - The "Snowball Earth" refers to a period between 720 million and 635 million years ago when the Earth experienced two phases of global glaciation, covering the planet from poles to equator in ice, including the oceans [1] Research Methodology - The research team analyzed ancient iron formations, which are sedimentary rocks composed of alternating iron-rich and silica-rich layers, to decode the ocean temperature signals from that era [3] - The findings indicated that iron isotopes during the "Snowball Earth" period were more "positively skewed" than at any other time in Earth's history, suggesting that lower temperatures correspond to a more positive signal [3] Environmental Conditions - Despite the extremely low temperatures, the study found that seawater did not completely freeze due to the high salinity of local water bodies, which was over four times that of modern seawater, lowering the freezing point to approximately -11°C [3] - The extreme cold and high salinity conditions likely formed beneath massive ice shelves, similar to the "ice pump" circulation observed under modern Antarctic ice shelves [3] Scientific Significance - This research provides the first direct quantitative evidence of the extreme marine environment during the "Snowball Earth," revealing that special microenvironments of liquid water may have existed even under global ice cover [3] - The findings offer new insights into how early life could have survived in extreme climates and hold significant scientific value for understanding the dramatic changes in Earth's climate system [3]