Collaborative Research: A Holocene Context for Current Arctic Warming Derived from the Vanishing Plateau Ice Caps of North-Central Baffin Island

知识价值：仪器记录显示，地球已经变暖约。0.7在过去的世纪里，气温上升了摄氏度，是自20世纪60年代以来几十年来最急剧的上升。北极也经历了类似的模式，但幅度更大，自20世纪60年代以来，北极部分地区的年平均气温上升了2至5摄氏度。由于直接观测的时间跨度很短，因此很难评估自然气候变率和温室气体强迫在解释这些观测中的作用，但变化的模式与全球气候模式对温室气体增加后果的模拟是一致的。 主要研究人员将提供一个全新世的背景下，20世纪世纪北极变暖。这种变暖的速度和幅度有多不寻常？北极上一次像现在这样温暖是什么时候？这种温暖程度是在自然变化的范围内，还是前所未有的？北极的仪器记录在时间和空间上都是有限的，因此必须利用代用气候数据的自然档案来解决这些问题。覆盖在加拿大巴芬岛中北部高原上的广泛、薄、冷的冰盖，自小冰期（LIA）最大以来，面积已经缩小了97%。20世纪60年代和80年代初研究的一个冰帽现在已经完全融化;预计其他许多冰帽将在未来5到10年内消失，预计所有冰帽都将在2050年之前消失。这项研究将确定这些冰盖可以促进北极变暖辩论的三种方式：1）过去50年冰盖退缩的空中速度将通过航空照片和卫星图像来确定，从而可以预测它们的最终消失; 2）保存在现存高原冰盖下的植物遗骸将通过从冰缘到冰分水岭的沿着断面钻穿冰来收集。埋藏植被的放射性碳年龄定义了北极最后一次足够温暖以完全融化这些冰盖的时间，3）从当前冰缘到LIA边缘以外的边缘的沿着横断面收集的石英中原位产生的14 C将定义整个高原的暴露历史。地表暴露的持续时间决定了自区域冰川消退以来高原在全新世中没有冰的比例，为当前的变暖提供了一个更长期的视角。更广泛的影响：为什么北极变暖，以及它可能会变得多么温暖是具有巨大社会重要性的问题。确定目前的温暖有多不寻常，并量化冰盖融化的速度，将有助于集中讨论温室气体和全球变暖的潜在后果。将向土著人民提供该奖项下的研究活动，办法是将目标和最终结果翻译成因纽特语，制作介绍研究的海报，并在努纳武特首府伊卡卢伊特和研究所外地基地克莱德河举办公开讲座。该研究计划将培养一名博士生，并为本科生提供参与研究的机会，建立在前几年的成功传统基础上。这个项目是将研究纳入本科教学的直接结果。2003年，在为一个新生班级更新关于北极变暖的讲座时，米勒发现他在20世纪80年代研究的冰盖出乎意料地消失了，并遵循这一线索，导致了这个提议。

Intellectual merit: Instrumental records show that the Earth has warmed ca. 0.7 degreesC over the past century, with the most dramatic increase in the decades since the 1960s. The Arctic has experienced a similar pattern, but the magnitude is greater, with average annual temperature increases of 2 to 5 degreesC across portions of the Arctic since the1960s. The short time span of direct observations makes it difficult to evaluate the roles of natural climate variability and greenhouse gas forcing in explaining these observations, but the pattern of change is consistent with Global Climate Model (GCM) simulations of the consequences of increased greenhouse gases. The Principal Investigators will provide a Holocene context for 20th century Arctic warming. How unusual is the rate and magnitude of this warming? When was the Arctic last as warm as it is now? Is this degree of warmth within the range of natural variability or is it unprecedented? The Arctic instrumental record is limited in time and space, so natural archives of proxy climate data must be exploited to address these questions. Extensive, thin, cold-based ice caps mantling the north-central plateau of Baffin Island, Canada, have receded by 97% in area since their Little Ice Age (LIA) maxima. One ice cap studied in the 1960s and early 1980s has now completely melted; many others are predicted to vanish in the next five to ten years, and all are expected to be gone before 2050. This research will identify three ways that these ice caps can contribute to the Arctic warming debate: 1) Aerial rates of ice-cap retreat over the past 50 years will be defined from air photo and satellite imagery, from which their final disappearance can be predicted; 2) Plant remains preserved beneath extant plateau ice caps will be collected by boring through the ice along transects from the ice margin to the ice divide. Radiocarbon ages of the entombed vegetation define the last time the Arctic was warm enough to completely melt these ice caps, 3) In situ 14C produced in quartz collected along transects from the current ice margins to beyond the edge of the LIA margin will define exposure histories across the plateau. The duration ofsurface exposure defines what proportion of the Holocene the plateaus have been ice-freesince regional deglaciation, providing a longer-term perspective on current warming.Broader impacts: Why is the Arctic warming, and how much warmer it may become are questions of immense societal importance. Defining how unusual is the present warmth, and quantifying the rates of ice-cap melt, will help focus the debate over greenhouse gases and the potential consequences of global warming. Research activities under this award will be made accessible to indigenous peoples by translating the goals and eventual results into Inuktitut, making posters that describe the research, and by offering public lectures in Iqaluit, the capital of Nunavut, and at Clyde River, the INSTAAR field base. This research program will train a PhD student, and provides opportunities for undergraduates to become involved with research, building on successful traditions from previous years. This projectl is a direct consequence ofincorporating research into undergraduate teaching. While updating a lecture on Arcticwarming for a freshman class in 2003, Miller discovered that the ice cap he studied inthe1980s was unexpectedly gone, and following that lead, led to this proposal.