Stability of Land Surfaces in the Dry Valleys: Insights Based on the Dynamics of Sub-Surface Ice and Sand Wedge Polygons

该奖项由国家科学基金会极地计划办公室提供，支持一个研究南极洲干旱山谷地区景观和土壤特征的项目，以期更全面地了解过去的气候和环境条件。由于最近看似极端的天气事件的发生，以及人们对变暖的日益担忧，气候的动态性质越来越受到公众的关注。厄尔尼诺现象和全球温室效应已成为人们耳熟能详的新闻话题。在这种背景下，了解地球气候的内在变异性以及人类如何影响地球环境变得越来越重要。要提高我们对地球气候系统的认识，一个重要的方法就是把地球当作一个天然的实验室，研究它过去的行为。在过去的几百万年里，地球气候系统中最极端的变化之一是从上新世的暖期过渡到冰河时代的世界。在南极洲，人们认为在这段时间里，相对温和的条件迅速让位于强烈的冰川条件，这种条件催化了地球上最大的冰盖的生长。这一推断是基于过去气候的地质指标，一些科学家认为，大约300-400万年前(上新世的部分时期)，南极东部相对温暖，基本上没有冰川。温和的气候条件突然结束，因为冰盖的快速增长和非常寒冷、干燥的气候的发展，现在是该地区的特征。基于大量地质证据的一种截然不同的观点表明，南极洲东部一直很冷，冰盖稳定了至少800万年，甚至更长时间。这些观点导致了对地球气候稳定性的截然不同的解释。该项目将通过引入独立的新证据和对南极洲干燥山谷地面冰和陆地表面稳定性研究得出的见解，有助于解决这一重要难题。这个项目将研究现代过程，这些过程对理解最近在Beacon山谷发现的埋藏冰的发生具有重要意义。这块冰可能是地球上最古老的冰，如果是这样的话，它为南极东部冰盖的长期稳定性提供了强有力的证据，并可能提供一个罕见的机会，让人们得以一窥数百万年前的大气状况。要研究的具体过程包括：影响地面温度的地面能量交换、水蒸气输送和导致土壤中冰形成或消失的其他过程，以及冬季冻土快速冷却时收缩引起的霜裂及其对土壤的破坏。

This award, provided by the Office of Polar Programs of the National Science Foundation, supports a project to study features of the landscape and soils of the Dry Valley region of Antarctica toward a fuller understanding of past climatic and environmental conditions. The dynamic nature of climate has received growing public attention because of the occurrence of seemingly extreme weather events recently, and growing concerns about warming. El Nino and global greenhouse warming have become familiar topics in the news. In this context, it is increasingly important to understand the inherent variability of Earth's climate and how humans affect can affect Earth's environment. One important means of improving our understanding of the Earth's climate system is to treat the Earth as a natural laboratory and examine it's past behavior. One of the most extreme changes in the Earth climate system during the last few million years is the transition from a warm period in the Pliocene to an ice age world. In Antarctica, this interval of time is thought to have seen relatively mild conditions give way rapidly to intense glacial conditions that catalyzed the growth of the largest ice sheet on Earth. This inference is based on geologic indicators of past climate from which some scientists suggest that East Antarctica was relatively warm and largely free of glaciers about 3-4 millions years ago (during parts of the Pliocene). The mild conditions ended abruptly by rapid ice-sheet growth and development of the very cold, dry climate that now characterizes this region. A contrasting view, based on substantial geologic evidence, suggests that East Antarctica has been cold and the ice sheet stable for at least 8 million years, and perhaps considerably longer. These views lead to drastically different interpretations of the stability of Earth's climate. This project will contribute to a resolution of this important dilemma by introducing independent new evidence and insights der ived from studies of the stability of ground ice and land surfaces in the Dry Valleys, Antarctica. This project will study modern day processes that have important implications for understanding the occurrence of buried ice found recently in Beacon Valley. This ice may be the oldest ice on Earth and, if so, provides strong evidence of long-term stability of the East Antarctic ice sheet and may provide a rare glimpse at atmospheric conditions millions of years ago. Specific processes to be investigated include: energy exchange at the ground surface that affect ground temperature, water vapor transport and other processes leading to the formation or loss of ice in the soil, and frost cracking due to contraction during rapid cooling of the frozen ground in the winter and its resulting disruptions of the soil.