Refining the climate, glacier, and volcanic history of Iceland during the Holocene

• Main Author: Harning, David
• Other Authors: Áslaug Geirsdóttir, Jarðvísindadeild (HÍ), Faculty of Earth Sciences (UI), Verkfræði- og náttúruvísindasvið (HÍ), School of Engineering and Natural Sciences (UI), Háskóli Íslands, University of Iceland
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Iceland, School of Engineering and Natural Sciences, Faculty of Earth Sciences 2019
• Subjects: Iceland; Holocene; Paleoclimate; Glaciers; Lakes; Marine; Tephra; Organic geochemistry; Nýlífsöld; Veðurfarsbreytingar; Fornveðurfræði; Jöklar; Stöðuvötn; Hafið; Gjóska; Jarðfræði; Jarðefnafræði; Doktorsritgerðir; Drangajökull; glacier; Ice cap
• Online Access: https://hdl.handle.net/20.500.11815/1047

Iceland’s position at the confluence of major oceanic and atmospheric fronts results in a highly sensitive climate evident in both instrumental and paleo records. However, open questions still remain regarding the pre-instrumental evolution of climate, glacier, and volcanic activity at this hemispherically relevant location. This dissertation capitalizes on and merges a range of analytical techniques in an effort to refine our understanding of Icelandic climate variability, glacier extent, and tephrochronology during the Holocene epoch, with a focus on Northwest Iceland. In order to provide robust age control in our records, this research required the development of a tephrochronological framework for West Iceland, a region that lacks the otherwise widely-dispersed rhyolitic marker tephras. Glacier proxies (threshold lake sediment records and emerging dead vegetation from receding ice margins) provide firm constraints on the Holocene activity of Drangajökull, an ice cap in northwest Iceland, and high-resolution lake sediment proxy records (TOC, δ13C, C/N and biogenic silica) collected adjacent to the glacier elucidate the concomitant climate. Furthermore, we explore two lipid biomarker paleothermometers (alkenones and branched glycerol dialkyl glycerol tetraether, GDGTs) in one of these lakes and its catchment soils for the first time in Iceland to quantify the evolution of Holocene summer temperature. Similar to other Icelandic ice cap histories, our records collectively illustrate that a warm early Holocene (2 to 5 oC above modern) likely resulted in the complete demise of Drangajökull shortly after 9 ka. Subsequent to peak early Holocene summer warmth, lake sediment climate proxies indicate punctuated declines in algal productivity and increases in soil erosion alongside steadily decreasing northern hemisphere (NH) summer insolation. As summers continued to cool, Drangajökull re-nucleated by ~2.3 ka and episodically expanded to its maximum dimension during the Little Ice Age (0.7-0.1 ka), when summer ...