Holocene Glacial History of Renland, East Greenland Reconstructed from Lake Sediments Aaron Medford
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The University of Maine DigitalCommons@UMaine Electronic Theses and Dissertations Fogler Library 5-2013 Holocene Glacial History of Renland, East Greenland Reconstructed From Lake Sediments Aaron Medford Follow this and additional works at: http://digitalcommons.library.umaine.edu/etd Part of the Climate Commons Recommended Citation Medford, Aaron, "Holocene Glacial History of Renland, East Greenland Reconstructed From Lake Sediments" (2013). Electronic Theses and Dissertations. 1934. http://digitalcommons.library.umaine.edu/etd/1934 This Open-Access Thesis is brought to you for free and open access by DigitalCommons@UMaine. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of DigitalCommons@UMaine. HOLOCENE GLACIAL HISTORY OF RENLAND, EAST GREENLAND RECONSTRUCTED FROM LAKE SEDIMENTS By Aaron Medford B.S. Lafayette College, 2011 A THESIS Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science (in Earth and Climate Sciences) The Graduate School The University of Maine August 2013 Advisory Committee: Brenda L. Hall, Professor, School of Earth and Climate Sciences and Climate Change Institute, Advisor George H. Denton, Professor, School of Earth and Climate Sciences and Climate Change Institute Daniel F. Belknap, Professor, School of Earth and Climate Sciences, Cooperating Professor, Climate Change Institute Ann C. Dieffenbacher-Krall, Assistant Research Professor, Climate Change Institute THESIS ACCEPTANCE STATEMENT On behalf of the Graduate Committee for Aaron Medford I affirm that this manuscript is the final and accepted thesis. Signatures of all committee members are on file with the Graduate School at the University of Maine, 42 Stodder Hall, Orono, Maine. ________________________________________________________________________ Dr. Brenda Hall, Professor of Sciences and Quaternary and Climate Studies 6/25/2013 ii LIBRARY RIGHTS STATEMENT In presenting this thesis in partial fulfillment of the requirements for an advanced degree at the University of Maine, I agree that the Library shall make it freely available for inspection. I further agree that permission for “fair use” copying of this thesis for scholarly purposes may be granted by the Librarian. It is understood that any copying or publication of this thesis for financial gain shall not be allowed without my written permission. Signature: Date: HOLOCENE GLACIAL HISTORY OF RENLAND, EAST GREENLAND RECONSTRUCTED FROM LAKE SEDIMENTS By Aaron Medford Thesis Advisor: Dr. Brenda L. Hall An Abstract of the Thesis Presented in Partial Fulfillment of the Requirements for the Degree of Master of Science (in Earth and Climate Sciences) August 2013 The Arctic is responding to the modern increase in temperature, resulting in ice loss and consequent sea-level rise. In order to understand present-day changes, we need to understand how the Arctic has reacted in the past to natural variations in climate forcing. To begin to identify the mechanisms behind climate change, I produced a Holocene glacial and climate record for the Renland Ice Cap, Scoresby Sund, East Greenland, from sediments in glacially fed lakes. I cored Rapids and Bunny Lakes, which are fed by meltwater from the Renland Ice Cap, as well as Raven Lake, which does not receive glacial influx at present. The presence or absence of glacial sediments in Rapids and Bunny Lakes gives information on the size of the Renland Ice Cap. I studied multiple sediment characteristics in the cores, including magnetic susceptibility (MS), grain size, organic and carbonate content, and color intensity. In general, I identified glacial sediment as grey, inorganic, and with high MS. Non-glacial material was black or brown with high organic content and low MS. Chronology for the cores came from radiocarbon dating of macrofossils and sieved organic fragments. My results suggest that the region may have deglaciated as early as ~12.5 ka. The high organic content in all three lakes suggests that the early- to mid-Holocene was warm with periods of limited ice extent, consistent with the Holocene thermal maximum, which has been documented elsewhere. After this warmth, the area cooled during the Neoglaciation that culminated in the largest glacial event of the Holocene during the Little Ice Age. Superimposed on the long-term climate change were multiple centennial- to-millennial-scale glacial advances at ~ 9.4, 8.6-8.8, 8.1-8.3, 7.6-7.8, 7.0-7.5, 5.8-6.0, 4.7-5.0, 3.7-4.0, 3.0-3.6, and ~1.0 (AD 600 and 900) cal. kyBP. My reconstruction of variations in the Renland Ice Cap matches well with other glacial records from Scoresby Sund and from the wider Northern Hemisphere. In addition, comparison with other glacial records from the Scoresby Sund region suggests that elevation exerts a strong control on the timing, size, and number of glacial advances exhibited at each site. This highlights the need for caution when comparing glacial records from large geographic areas. The Renland record, along with other Northern Hemisphere data, indicates pervasive millennial-scale climate change throughout the Holocene, with the largest magnitude glacial advance occurring during the Little Ice Age. This pattern favors a cyclical forcing mechanism, such as solar variability or a 'wobbly ocean conveyor,' rather than unique events, such as volcanic eruptions or outburst floods, as a cause of millennial-scale climate change. ACKNOWLEDGMENTS I would like to begin by thanking my advisor, Dr. Brenda Hall, for this great opportunity, as well as for the guidance and knowledge she has passed on. I also want to thank my committee Dr. George Denton, Dr. Daniel Belknap, and Dr. Ann Dieffenbacher-Krall for their expertise and help in improving my thesis. I owe the National Science Foundation, the University of Maine Graduate School Government, and School of Earth and Climate Science for funding my master’s work. Thank you to the School of Earth and Climate Science, the Climate Change Institute, Dartmouth College, and the University of Minnesota Limnological Research Center for the use of lab space and material. In addition, the work in Scoresby Sund, would not have happened without the support of the late Gary Comer. I was fortunate to join an ongoing project, and I am excited to add my record to the already stellar work done by this group. I want to especially thank my field team Dr. Brenda Hall, Dr. Meredith Kelly, Dr. Tom Lowell, Dr. Yarrow Axford, Paul Wilcox, and Laura Levy for help in collecting and analysis of the data. In addition, I would like to thank Krista Slemmons and Karen Marysdaughter for help in processing the cores. I am grateful to my family for their support throughout the last two years, giving me unconditional support. I would like to thank the faculty and staff in the Climate Change Institute and School of Earth and Climate Sciences; it has been a great and rewarding experience being able to work with you. I would like to thank my fellow graduate students, especially the game night group, for support and encouragement. Finally, I would like to acknowledge the geology department at Lafayette College, who laid the foundation that allowed me to accomplish what I did. iii TABLE OF CONTENTS ACKNOWLEDGMENTS............................................................................................ iii LIST OF TABLES.......................................................................................... ……… vii LIST OF FIGURES...................................................................................................... viii CHAPTER 1. INTRODUCTION………………………………………........................................ 1 1.1 Overview………………………………………………………………… 1 1.2 Background……………………………………………………................ 4 2. METHODS………………………………………………………………………... 7 2.1 Field Work……………………………………………………………….. 7 2.2 Lab Work……………………………….................................................... 10 3. RESULTS…………………………………………………………………………. 16 3.1 Lake Setting……………………………………………………………… 16 3.1.1 Glacial Lakes………………………………………………....... 16 3.1.2 Conceptual Model……………………………………………... 23 3.1.3 Non-Glacial Lake……………………………………................ 26 3.2 Sediment Core Descriptions………………….………………………….. 31 3.2.1 Rapids Lake……………………….…………………................ 31 3.2.1.1 RPD11-1B-1…………………………………………... 31 3.. 3 3. 3 iv 3.2.2 Bunny Lake……………………………………......................... 37 3.2.2.1 Southern Basin: BNL11-1A-1………………................ 37 3.2.2.2 Southern Basin: BNL11-1B-1........................................ 42 …………………… 3.2.2.3 Northern Basin: BNL11-2A-1………………………… 43 3.2.2.4 Northern Basin: BNL11-2A-2………………………… 48 3.2.3 Raven Lake………………………….……………..................... 50 3.2.3.1 RAV11-1A-1………………………………………….. 50 3.2.3.2 RAV11-1A-2………………………………………….. 54 3.2.3.3 RAV11-2A-1………………………………………….. 55 3.2.3.4 RAV11-3A-1………………………………………….. 58 4. DISCUSSION ……………………………………........................………………. 61 4.1 Age Model……………………….............................................................. 61 4.1.1 Radiocarbon Date Quality……………………………………... 61 4.1.2 Rapids Lake…………………….............................................. 62 4.1.3 BNL11-1………………………….............................................. 62 4.1.4 BNL11-2………………………………...................................... 63 4.1.5 Raven Lake………………………………................................. 65 4.2 Lake History……………………………………………………………... 67 4.2.1 Raven Lake…………………………………………………….. 67 4.2.2 Rapids Lake…………………………………............................. 69 4.2.3 Bunny Lake…………………………………………................. 73 4.3 Glacial History of Raven, Rapids,