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

ABSTRACTMillerOPP-0454662BrinerOPP-0454601Intellectual优点：仪器记录显示，在过去的一个世纪里，地球变暖了约0.7摄氏度，这是自20世纪60年代以来几十年来最显著的增长。北极经历了类似的模式，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。直接观测的时间跨度很短，因此很难评估自然气候变异性和温室气体强迫在解释这些观测中的作用，但这种变化模式与全球气候模型(GCM)对温室气体增加后果的模拟是一致的。首席调查人员将提供20世纪北极变暖的全新世背景。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范围内还是史无前例的？北极仪器记录在时间和空间上是有限的，因此必须利用替代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的大面积、薄而冷的冰盖，自小冰期(LIA)达到最大值以来，面积已经减少了97%。20世纪60年代和80年代初研究的一个冰盖现在已经完全融化；其他许多冰盖预计将在未来五到十年内消失，所有冰盖预计都将在2050年之前消失。这项研究将确定这些冰盖可能有助于北极变暖辩论的三种方式：1)将根据航空照片和卫星图像确定过去50年冰盖消退的空中速率，根据这些图像可以预测它们的最终消失；2)将通过沿从冰缘到冰分界线的横断面钻穿冰来收集保存在现有高原冰盖下的植物遗骸。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边缘以外的横断面上采集的石英中原位产生的14C将确定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融以来，高原无冰的比例，为当前的变暖提供了一个更长远的视角。更广泛的影响：为什么北极正在变暖，以及它可能变暖多少是具有巨大社会意义的问题。定义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。这一奖项下的研究活动将通过将目标和最终成果翻译成因努基特语，制作描述研究的海报，并在努纳武特首府伊卡卢伊特和研训所外地基地克莱德河举办公开讲座，使土著人民能够了解。该研究项目将培养一名博士生，并在前几年成功传统的基础上，为本科生提供参与研究的机会。这个项目是联合研究本科教学的直接结果。2003年，在更新一堂关于北极变暖的讲座时，米勒发现，他在20世纪80年代研究的冰盖出人意料地消失了，根据这一线索，他提出了这个建议。

ABSTRACTMillerOPP-0454662BrinerOPP-0454601Intellectual 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.