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Centennial-scale Reconstructions of Mountain Glacier Fluctuations During the Holocene, West Greenland
Başlık:
Centennial-scale Reconstructions of Mountain Glacier Fluctuations During the Holocene, West Greenland
Yazar:
Schweinsberg, Avriel D., author. (orcid)0000-0001-7374-5706
ISBN:
9780438061309
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (261 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-10(E), Section: B.
Advisors: Jason P. Briner Committee members: Beata Csatho; Gifford H. Miller; Elizabeth K. Thomas.
Özet:
Mountain glaciers and ice caps are an integral part of the Earth's climate system yet the Holocene history of mountain glacier variability remains poorly known, particularly in remote regions of the Arctic. In Greenland, for example, continuous records of Holocene alpine glacier change are extremely rare, and the majority of information regarding past glacier extents is fragmentary. While contemporary observations are critical for understanding the mechanisms driving present-day glacier change, geological reconstructions of former glacier fluctuations provide additional data on glacier behavior over longer timescales, and place much-needed constraints on the sensitivity of glacier response to climate change. Here, I employ a novel multi-proxy approach that combines glacier-fed lake sediments, radiocarbon dating of in situ moss that recently emerged along retreating ice cap margins, and cosmogenic in situ 10Be and 14C surface-exposure dating to reconstruct centennial-scale records of Holocene mountain glacier fluctuations in West Greenland. This investigation also merges pre-historic glacier records with contemporary observations; historical aerial photographs and satellite imagery provide 20-21st century glacier length histories that shed light on the intricate processes that link glaciers and climate.
The glacier-size records developed here reveal a dynamic response of mountain glaciers to Holocene climate variability in West Greenland; glaciers episodically advanced and retreated at centennial-timescales despite the progressive insolation-driven millennial-scale cooling trend during the Holocene in the Northern Hemisphere. Radiocarbon-dated glacier-fed lake sediments from two regions in West Greenland suggest that abrupt cooling at 9300 and 8200 years ago, recorded in Greenland ice cores, triggered advances of glaciers that are contemporaneous with advances/stillstands of the western GrIS margin. Following decreased glacier activity in the middle Holocene, several independent glacier-size proxies record an onset of Neoglaciation at ∼5 ka followed by substantial snowline lowering and glacier expansion at ∼3.7 ka. Frequent, high-amplitude glacier fluctuations superimposed on net glacier growth characterize the succeeding millennia; notable ice expansion phases occurred at ∼2.9 ka, 1.8 ka, between 1.4 and 1.2 ka, 1.0 ka, and during the Little Ice Age (LIA). The extensive build-up of ice during the late Holocene is further supported by a suite of 10Be surface-exposure ages that reveal some alpine glaciers in West Greenland achieved extents similar to their eventual LIA configurations before what is considered the classic LIA interval. Collectively, these results corroborate an emerging pattern of significant summer cooling and glacier expansion millennia before the LIA in the North Atlantic region. Some of these episodes coincide with multidecadal periods of low solar activity or explosive volcanism; thus, it is possible that multidecadal variations of solar and volcanic activity, supported by positive feedbacks in the climate system, played a critical role in late Holocene alpine glaciation in West Greenland. Finally, analysis of aerial and satellite imagery shows that glaciers advanced and retreated in concert with temperature trends in Greenland, implying that alpine glaciers responded most readily to changes in air temperature throughout the 20-21st centuries on decadal timescales.
These new data contribute critically needed geographic coverage to predominately fragmentary alpine glacier records for examining spatial and temporal centennial-scale Holocene climate variability in Greenland. In addition, the integrated geochronological approach applied in this study emphasizes that using a suite of techniques not only strengthens proxy interpretations, but also may result in a more comprehensive understanding of spatio-temporal glacier change.
Notlar:
School code: 0656
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(681728.1) | 681728-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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