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| 說明 | 1 online resource (76 pages) |
| 文字 | text |
| 無媒介 | computer |
| 成冊 | online resource |
| 附註 | Source: Masters Abstracts International, Volume: 56-06 |
| Adviser: Meredith A. Kelly |
| Thesis (M.S.)--Dartmouth College, 2016 |
| Includes bibliographical references |
| It is uncertain as to how the Greenland Ice Sheet (GrIS) will respond to future climate changes. One means of assessing the sensitivity of the GrIS to projected climate conditions is to determine its response to past conditions. I reconstructed late glacial and Holocene (̃15 ka-present) GrIS extents in the Nunatarssuaq, northwestern Greenland. I applied geomorphic mapping, 10Be surface exposure dating, and 14C dating of subfossil plants to determine a chronology of past GrIS extents. I also analyzed sediment cores from a glacially fed lake. 10Be ages of boulders and bedrock exposed during deglaciation from the Last Glacial Maximum (LGM; ̃26-19.5 ka) are apparently old due to 10Be inherited from prior periods of exposure. The youngest 10Be age (̃15 ka) may also contain inherited 10Be but approximates the time of deglaciation. Subfossil plants transported to the GrIS margin on shear planes date to ̃4.6 cal ka BP and indicate a less extensive GrIS during middle Holocene time. Geomorphic mapping documents higher levels of Nordso, a glacial lake dammed by a more extensive GrIS margin. I constrain the age of this GrIS extent to ̃3-2 ka using 14C ages of in situ subfossil plants on nunataks and 10Be ages of boulders on the drift deposited during the advance. A fresh drift occurs ̃30-50 m beyond the present GrIS margin. 10Be ages of this fresh drift range from 2.2 to 0.5 ka. I interpret the youngest 10Be age (̃0.5 ka) as the time the drift was exposed. 14C ages of in situ subfossil plants indicate that the GrIS was at or behind its present margin at AD ̃1662-1897 |
| I compare my record of GrIS extents to other glacial fluctuations and climate records. I find that the GrIS margin in Nunatarssuaq fluctuated at similar times as local ice masses and other GrIS margins. The middle Holocene GrIS recession occurred during relatively warm conditions registered by regional climate records and the late Holocene GrIS advances occurred during cooler conditions. I also document asynchronous GrIS margin fluctuations in Nunatarssuaq. These require further investigation to determine whether they were influenced by climate conditions or ice dynamics |
| Electronic reproduction. Ann Arbor, Mich. : ProQuest, 2018 |
| Mode of access: World Wide Web |
| 主題 | Geology |
| Paleoclimate science |
| Geomorphology |
| Electronic books. |
| 0372 |
| 0653 |
| 0484 |
| ISBN/ISSN | 9780355156249 |
