Ocean Surfaces on Snowball Earth

摘要/论文题目：雪球地球上的海洋表面知识价值：新元古代（6 -8亿年前）极端冰川作用的证据导致了20世纪90年代初雪球地球假说的提出。这一假说的一个核心但有争议的观点是，在长达数百万年的时间里，冰几乎覆盖了整个海洋。气候模型对这一时期的模拟差异很大，从无冰的热带海洋，到“硬”雪球或完全冻结的海洋，再到介于两者之间的“泥泞”情景，应有尽有。众所周知，气候模型对规定的反照率高度敏感，尽管建模者尚未确定一种首选处理方法，部分原因是可能表面的全光谱反照率是不确定的。为了在这一领域提供更清晰的指导，南极综合系统科学计划极地项目办公室授予该奖项，以研究冰雪表面的反照率，这可能对冰覆盖海洋的形成和维持至关重要。反照率也可能是决定海冰厚度的关键因素，因此光传输到下面的水，因此为已知在这个时期幸存下来的更微妙的真核生物形式提供了可能的避难所。有人认为，今天只有南极洲提供了足够的类似于被认为在雪球地球情景下出现的专门的冰表面。为了检验雪球地球假说的可行性，将进行低温（低于-23℃）无雪海冰、盐包覆海冰表面和蓝色（受净消融影响）冰川的实地观测、实验室实验（各种盐包覆冰表面）和模拟（在地中海等边缘海域薄而能透射光的冰下潜在避难所所需的辐射传输和条件）。与气候建模者合作，实地和实验室结果将应用于更好地约束雪球地球的全球尺度模型。更广泛的影响：这个基础研究项目旨在了解地球上过去的极端气候条件。这种情况对生物进化有影响；虽然原核生物可以很容易地在这种挑战中生存下来，但尚不清楚更容易受到影响的真核生物是如何生存下来的。这些测量还应提供有关现代环境中海冰和冰川的信息，这些信息可能与预测未来气候有关。它们还可能为了解木星和土星卫星上的冰和盐表面提供见解。该项目将涉及一名本科生进行实验室观察，一名研究生的博士论文将来自于这项研究。这个研究项目综合了大气科学家、海冰科学家和冰川学家的专业知识。其中一名copi是海冰物理学中一个代表性不足的群体（女性）的成员。海冰部分与新西兰国际极地年项目合作，重点关注海冰特性的季节性演变。

AbstractPI: Stephen G. WarrenProposal Number: 0739779 Title: Ocean Surfaces on Snowball EarthIntellectual merit: Evidence of episodes of extreme glaciation during the Neoproterozoic time (600-800 million years ago) lead to formulation of the Snowball Earth hypothesis in the early 1990's. A central but controversial idea of this hypothesis is that ice covered nearly the entire ocean for periods of up to several million years. Climate models differ greatly in their simulations of this time period suggesting everything from an ice free tropical ocean, to a "hard" snowball or fully frozen ocean to "slushy" scenario in between. It is known that climate models are highly sensitive to prescribed albedos although modelers have yet to settle on a preferred treatment in part because the full spectral albedos of the likely surfaces are uncertain. To provide clearer guidance in this realm, the Office of Polar Programs, Antarctic Integrated System Science Program has made this award to study the albedo of snow and ice surfaces that may have been pivotal to initiation and maintenance of an ice-covered ocean. Albedo may have also been key factor in determining sea ice thickness, thus light transmission to the water below and so governing possible refugia for the more delicate eukaryotic life forms that are known to have survived this time period. It is argued that today only Antarctica provides sufficiently analogous ice surfaces to the specialized ones that are thought to have occurred under a Snowball Earth scenario. A combination of field observations of cold (meaning less than -23C) snow-free sea ice, salt encrusted sea-ice surfaces and blue (subject to net ablation) glacial ice, laboratory experiments (various salt encrusted ice surfaces) and modeling (of radiative transfer and conditions required for potential refugia under thin, light transmitting ice in marginal seas such as the Mediterranean) will be carried out to test the viability of the Snowball Earth hypothesis. In collaboration with climate modelers, the field and laboratory results will be applied to better constraining global scale models of Snowball Earth. Broader impacts: This basic research program is aimed at understanding past extreme climate conditions on Earth. Such conditions have implications for biological evolution; while prokaryotes could readily survive the challenge, it is not clear how the more susceptible eukaryotes did. The measurements should also provide information for sea-ice and glacial-ice in the modern environment that may be relevant to projecting future climate. They might also provide insights for the understanding of ice and salts surfaces on the moons of Jupiter and Saturn. The project will involve an undergraduate in laboratory observations and a graduate student whose PhD thesis will derive from this study. This research program integrates the expertise of an atmospheric scientist, sea-ice scientist and glaciologist. One of the coPIs is a member of an underrepresented group (female) in sea ice physics. The sea-ice component is collaborative with a New Zealand International Polar Year project focused on seasonal evolution of sea-ice properties.