Ocean Surfaces on Snowball Earth

建议编号：0739779标题：雪球地球上的海洋表面智力价值：新元古代(6-8亿年前)极端冰川事件的证据导致了1990年代初S提出了雪球地球假说。这个假说的一个核心但有争议的观点是，冰覆盖了几乎整个海洋，时间长达数百万年。气候模型在对这段时间段的模拟中存在很大差异，它们提出了从没有冰的热带海洋到“硬”雪球或完全冻结的海洋，再到介于两者之间的“泥泞”情景。众所周知，气候模型对规定的反照率高度敏感，尽管建模人员尚未确定更好的处理方法，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方案办公室颁发了这一奖项，以研究冰雪表面的反照率，这可能是启动和维持冰盖海洋的关键。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中，从而决定了已知在这一时期幸存下来的更微妙的真核生命形式的可能避难所。有人争辩说，今天只有南极洲提供的冰面与被认为是在雪球地球情景下发生的专门冰面足够相似。将结合对寒冷(指低于-23摄氏度)的无雪海冰、盐渍覆盖的海冰表面和蓝色(可净消融)冰川冰的现场观测、实验室实验(各种盐渍覆盖的冰面)和模拟(在地中海等边缘海域薄而透光的冰下进行辐射传输和潜在避难所需的条件)来检验Snowball Earth假说的可行性。在与气候建模人员的合作下，现场和实验室结果将被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：这项基础研究计划旨在了解地球上过去的极端气候条件。这些条件对生物进化有影响；虽然原核生物可以轻易地从挑战中幸存下来，但更容易受到影响的真核生物是如何做到这一点的尚不清楚。这些测量还应提供现代环境中的海冰和冰川冰的信息，这些信息可能与预测未来气候有关。它们还可能为理解木星和土星卫星上的冰和盐表面提供洞察力。该项目将涉及一名实验室观察专业的本科生和一名研究生，他们的博士论文将来自这项研究。这项研究计划融合了大气科学家、海冰科学家和冰川学家的专业知识。其中一名COPIS是海冰物理学中代表性不足的群体(女性)的成员。海冰部分是与新西兰国际极地年项目合作的，该项目侧重于海冰属性的季节性演变。

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.