Hendy Test Stable Isotope Data

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HIGH-RESOLUTION SPELEOTHEM-BASED PALAEOCLIMATE RECORDS FROM NEW ZEALAND REVEAL ROBUST TELECONNECTION TO NORTH ATLANTIC DURING MIS 1-4 A thesis submitted as required for the degree of Doctor of Philosophy in Chemistry and Earth and Ocean Sciences at The University of Waikato by THOMAS EDWARD WHITTAKER _______________ The University of Waikato 2008 Abstract Growth rates, δ18O and δ13C of five stalagmites from the west coasts of North and South Islands, New Zealand, provide records of millennial-scale climate variability over the last ~75 kyr. Thirty-five uranium-series ages were used to provide the chronology. δ18O of stalagmite calcite was influenced by changes in moisture source region, temperature and both δ18O and δ13C primarily display a negative relationship with rainfall. To assist interpretation of climatic signals δ18O profiles were adjusted for the ice-volume effect. Changes in these proxies reflect changes in the strength of the circumpolar westerly circulation and the frequency of southwesterly flow across New Zealand. MIS 4 was a period of wet and cool climate lasting from 67.7 to 61.3 kyr B.P., expressed in the stalagmites by an interval of strongly negative isotope ratios and increased growth rate. This contrasts with less negative δ18O and δ13C, and slow growth, interpreted as dry and cold climate, during much of MIS 2. This difference between MIS 2 and MIS 4 provides an explanation for why glacial moraines in the Southern Alps of MIS 4 age lie beyond those deposited during the last glacial maximum (MIS 2). Heinrich events, with the exception of H0 (the Younger Dryas), are interpreted from high-resolution South Island stalagmite HW05-3, from Hollywood Cave, West Coast, as times of wetter and cooler climate. Minima in δ18O and δ13C (wet periods) occurred at 67.7-61.0, 56-55, 50.5-47.5, 40-39, 30.5- 29, 25.5-24.3 and 16.1-15. kyr B.P. matching Heinrich events H6-H1 (including H5a) respectively. This demonstrates a robust teleconnection between events in the North Atlantic and New Zealand climate. Minima in δ18O also occurred at similar times in less well-dated North Island stalagmite RK05-3 from Ruakuri Cave, Waitomo. Speleothems from low-latitudes have revealed that Heinrich events forced southerly displacement of the Intertropical Convergence Zone. This caused steepening of the temperature gradient across mid-southern latitudes, increased westerly circulation and resulted in wet conditions on the west coast of both islands. Immediately following H1 in the HW05-3 stable isotope profiles is another excursion to more negative isotopic values, suggesting wet and cold climate, lasting from 14.6 to 13.0 kyr B.P. Such a climate on the West Coast at this time has been previously suggested from glacier advance (e.g. Waiho Loop moraine) and decreased abundance of tall trees on the landscape. This event occurred too early to be a response to H0, but is synchronous with a return to cool climate in Antarctica. Thus West Coast climate appears to have been sensitive to changes in Antarctica as well as the North Atlantic. Isotopic minima (wet and cool climate) in South Island stalagmite GT05-5, which formed during the Holocene, first occurred 4.6 kyr B.P. This began a series of four oscillations in isotope ratios, the last terminating when the stalagmite was collected (2006). Onset of these oscillations is associated with initiation of ice advance in the Southern Alps, and beginning of the Neoglacial. The last oscillation displays enriched isotope ratios lasting from 1.2 to 0.8 kyr B.P. succeeded by depleted ratios lasting until 0.15 kyr B.P., mirroring the Medieval Climate Optimum and Little Ice Age, respectively, of European palaeoclimate records. Acknowledgements Completion of this thesis would not have been possible without the help and support of a great many people. First and foremost this project would not have existed but for the vision and financial support of Gary Comer. I hope that the work contained within this thesis is a rewarding result for his investment in abrupt climate change research through grants from the Gary Comer Educational Foundation. Second, I would like to thank my primary supervisor Chris Hendy for providing me with the opportunity to be involved in such an exciting project. Third, I doubt that the fieldwork for this project could ever have gone so well, so smoothly, or with so much fun without the inextinguishable enthusiasm of Russell Bromley. Thank you also to Cam Nelson for providing invaluable advice when things didn’t run so smoothly and for ensuring that the manuscript was suitable for submission; Deborah Carden (Buller-Kawatiri Office, Department of Conservation) for assistance in the permit application process; Jane Furkert and Dawn Mazzagetti for help in the field; Steve Cooke for teaching me more mass spectrometer operating idiosyncrasies than I ever thought possible; John Hellstrom for dedicating time to teach me the ins and outs of uranium-thorium dating; and to Marcus Vandergoes for many discussions on current thinking of New Zealand palaeoclimate research and for assisting in editing the manuscript. I wish to acknowledge John Ash and Van Watson (tourism Holdings Limited) and Dave Smith (Department of Conservation for the generous access to stalagmites recovered during the redevelopment of Ruakuri Cave, Waitomo. I also acknowledge Timberlands West Coast (Greymouth office) for allowing access to the land surrounding Whiskey Cave and Mr and Mrs Hunter of Springs Junction for granting permission to cross their land in order access Guillotine Cave. Lastly, I am especially grateful to my wife, Amber, for her unending support throughout this project. I only hope I can return in kind when she does her Ph.D. iv Table of Contents ACKNOWLEDGEMENTS ................................................................................... iv TABLE OF CONTENTS.........................................................................................v LIST OF FIGURES ............................................................................................... ix LIST OF TABLES ............................................................................................... xiii GLOSSARY OF ABBREVIATED TERMS....................................................... xiv Chapter 1 BACKGROUND ..................................................................................................1 1.1 Milankovitch Theory and Global Climate (A)Synchrony......................1 1.2 New Zealand Climate History................................................................3 1.3 Speleothems ...........................................................................................5 1.4 Research Objectives ...............................................................................5 2 LITERATURE REVIEW .....................................................................................7 2.1 Climate Events of Last Glacial-Interglacial Cycle.................................7 2.1.1 Background .............................................................................7 2.1.2 Last Glacial Period (~115-10 kyr B.P.) ................................10 2.1.3 Last Glacial Maximum (LGM) .............................................15 2.1.4 Deglaciation ..........................................................................17 2.1.5 Holocene ...............................................................................19 2.1.6 Summary ...............................................................................21 2.2 Speleothems .........................................................................................23 2.2.1 Introduction...........................................................................23 2.2.2 Speleothem Formation ..........................................................24 2.2.3 Speleothems as Archives of Past Climate.............................27 2.2.3.1 Factors Influencing Speleothem δ18O ....................28 2.2.3.2 Factors Influencing Speleothem δ13C ....................32 2.2.3.3 Chronology.............................................................34 2.2.3.4 Trace Elements.......................................................36 2.2.3.5 Other Proxies..........................................................40 2.2.4 Speleothem Collection ..........................................................42 v 2.2.5 Summary ...............................................................................43 2.3 Review of Southern Hemisphere Speleothem Records .......................44 2.3.1 Introduction...........................................................................44 2.3.2 New Zealand .........................................................................44 2.3.2.1 Introduction............................................................44

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