EAGER: An Oasis for Surface Life on the Ocean of Snowball Earth

EAGER：雪球地球海洋上的地表生命绿洲

• 批准号: 2041491
• 负责人: Stephen Warren
• 金额: $ 22.5万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2041491&HistoricalAwards=false
• 关键词: EAGER; Oasis; Surface; Life; Ocean

There is now compelling evidence for times in the distant past when the Earth was in a deep freeze, with ice sheets hundreds of meters thick covering the world's oceans. These "snowball earth" episodes lasted for millions of years during the Cryogenian period, between 720 and 630 million years ago. Somehow, despite thick ice cover and surface temperatures 30 Celsius below zero, life survived on snowball earth. Among the survivors were multicellular species of algae which rely on photosynthesis and must have lived at the surface or below ice thin enough to transmit sunlight. Given the harsh conditions it is natural to look for refugia, special places which remained unusually hospitable due to favorable local conditions.Research under this award considers the possibility that the refugia of snowball earth were bays at the far ends of protected tropical seas similar to the Red Sea today. Previous work by the Principal Investigators (PIs) shows that such a sea could keep out the "sea glaciers" that covered the open oceans. But the sea would also need to be in an unusually warm region to prevent thick ice from growing locally. The PIs hypothesize that such warmer conditions could occur if the sea were surrounded by bare land with a relatively dark (or low albedo) surface to promote solar absorption. Warmer local climate could also occur due to favorable configurations of mountain ranges around the sea.Work performed here tests the protected sea refugia hypothesis using climate model simulations configured to represent conditions on snowball earth. The continental configuration is adjusted to include a protected sea, and the albedo of the surrounding land is varied to determine if a darker land surface can produce a regional climate warm enough to allow open water. Other aspects of the configuration are also varied, such as the size of the sea and the presence of mountain ranges around it.The work has broader impacts due to the importance of the problem for understanding life on earth, and it also has implications for efforts to find evidence of life on other planets. Results of the research are presented to the public through several outreach activities, and the PIs use the snowball earth problem as a way to motivate K-12 students to learn more about earth science during class visits to the University of Washington campus.This project is jointly funded by the Climate and Large-scale Dynamics Program (PD 06-5740) and the Arctic Natural Sciences Program (PD 16-595).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

现在有令人信服的证据表明，在遥远的过去，地球处于深度冰冻状态，数百米厚的冰盖覆盖了世界海洋。 这些“雪球地球”事件在距今 720 至 6.3 亿年前的成冰纪持续了数百万年。不知何故，尽管冰层覆盖很厚，表面温度低于零下​​ 30 摄氏度，生命仍然在雪球地球上生存下来。 幸存者中有一种多细胞藻类，它们依赖光合作用，必须生活在足够薄的冰层表面或下方，以传输阳光。 考虑到恶劣的条件，寻找避难所是很自然的事情，因为当地条件有利，这些特殊的地方仍然异常热情好客。该奖项的研究考虑了雪球地球避难所可能是位于受保护的热带海洋远端的海湾，类似于今天的红海。首席研究员（PI）之前的工作表明，这样的海洋可以阻挡覆盖公海的“海洋冰川”。 但海洋也需要位于异常温暖的地区，以防止局部厚冰生长。 PI 假设，如果海洋被光秃秃的土地包围，并且表面相对较暗（或低反照率）以促进太阳光吸收，那么这种温暖的条件就会出现。 由于海洋周围山脉的有利构造，当地气候也可能会出现。这里进行的工作使用配置为代表雪球地球条件的气候模型模拟来测试受保护的海洋保护区假说。 调整大陆配置以包括受保护的海洋，并改变周围陆地的反照率，以确定较暗的陆地表面是否可以产生足够温暖的区域气候以允许开放水域。 配置的其他方面也各不相同，例如海洋的大小和周围山脉的存在。由于该问题对于理解地球上生命的重要性，这项工作具有更广泛的影响，并且它也对寻找其他行星上生命证据的努力产生了影响。 研究结果通过多项外展活动向公众展示，PI 们利用雪球地球问题作为激励 K-12 学生在华盛顿大学校园课堂参观期间更多地了解地球科学的方式。该项目由气候和大尺度动力学计划 (PD 06-5740) 和北极自然科学计划 (PD 16-595) 联合资助。该奖项反映了 NSF 的法定奖项 使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。