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| Seasonality of Abrupt Climate Change over Greenland: Direct Tests for the Younger Dryas and 8.2 ka event using Paleolimnology | |
| 项目编号 | 2002515 |
| Yarrow Axford (Principal Investigator) | |
| 项目主持机构 | Northwestern University |
| 开始日期 | 2020-09-01 |
| 结束日期 | 2023-08-31 |
| 英文摘要 | The Younger Dryas (YD) is the best documented example of abrupt climate change in Earth?s history, yet fundamental traits of the YD remain enigmatic. Greenland sat at the epicenter of YD climate change, with intense cooling registered in ice cores, but nevertheless the Greenland Ice Sheet retreated during the YD. An influential hypothesis suggests that North Atlantic abrupt climate changes were characterized by extreme seasonality, with mild summers that explain counterintuitive YD glacier retreat. Resolving seasonality is crucial to understanding the impacts of past and future climate change on all aspects of the Arctic system ? including the ice sheet, because summer temperatures drive surface melt. This study will directly assess seasonality of the YD on Greenland for the first time by developing quantitative summer and winter temperature reconstructions. This study will also assess seasonality of the major cold snap over Greenland 8,200 years ago. Intriguingly, despite being shorter and smaller in annual magnitude than the YD, that event drove glacier advances around Greenland. This research will clarify how abrupt climate change affects the Arctic/subarctic North Atlantic region, especially Greenland and its ice sheet. By resolving seasonality of air temperatures during the YD, when the ice sheet retreated despite evidence for extremely cold (annual) air temperatures, this study will also clarify the competing roles of precipitation and ocean temperatures in driving past ice sheet behavior ? with implications for projections of future ice sheet mass loss. This study will test whether the Holocene 8.2 ka event was essentially a mini YD, or fundamentally different. The latter could make the YD a poor analog for future abrupt climate change, which would unfold in an interglacial world. The 8.2 ka event has been described as an ideal target for testing climate models, but the quantitative reconstructions of associated terrestrial climate changes needed to optimize such tests are rare. Another major contribution of this work is calibration and advancement of season-specific methods for reconstructing arctic climate. Such methods are needed to address questions about seasonality on diverse Quaternary timescales, providing essential tests for climate models. The proposed work will also enable more sophisticated interpretations of stable isotope records and paleotemperature reconstructions from the Greenland ice cores by providing direct comparisons. This may yield new insights from those iconic records, once seasonality of the climate changes they capture is clarified. This project will utilize classic sites that preserve rare, readily dateable YD lake sediment records. Multiple calibrated, season-specific proxies in sediment cores ? including insect and pollen assemblages, terrestrial leaf wax ?2H, and aquatic insect ?18O ? will test and complement one another and provide new comparisons to annually integrated records from ice cores. This work will build upon the research team?s experience calibrating and applying these proxies in Greenland. A new calibration study will verify the seasonality of leaf wax ?2H in a range of Greenland climates. The possibility of future abrupt climate change is a major societal concern. As evidence accumulates for recent and ongoing changes in North Atlantic Ocean circulation, past abrupt changes in the subpolar North Atlantic are increasingly relevant to the future. This project will train two Ph.D. students and at least six undergraduates. In addition to conducting research during the academic year, students will participate in mentored summer research institutes to build research and communication skills. To share science beyond academia and hone outreach skills, students will conduct outreach (a) in Greenland near the study site, and (b) in a Chicago area high school serving a diverse population of >3200 students, in partnership with teachers who participated in the PI?s 2018 climate science workshop for high school teachers. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. |
| 学科分类 | 08 - 地球科学 |
| 资助机构 | US-NSF |
| 项目经费 | 640580 |
| 项目类型 | Standard Grant |
| 国家 | US |
| 语种 | 英语 |
| 文献类型 | 项目 |
| 条目标识符 | http://gcip.llas.ac.cn/handle/2XKMVOVA/191028 |
| 推荐引用方式 GB/T 7714 | Yarrow Axford .Seasonality of Abrupt Climate Change over Greenland: Direct Tests for the Younger Dryas and 8.2 ka event using Paleolimnology.2020. |
| 条目包含的文件 | 条目无相关文件。 | |||||
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