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Late Quaternary Ice Dynamics of the Monte San Lorenzo Ice Cap Late Quaternary ice dynamics of the Monte San Lorenzo ice cap, Patagonia Julian Rodney Victor Martin Department of Geography Royal Holloway, University of London Thesis submitted for the degree of Doctor of Philosophy (PhD) Royal Holloway, University of London September 2019 1 Declaration ROYAL I HOLLOWAY �J' Declaration of Authorship for Co-Authored Work . If you are presenting partlyco-authored work, please indicate below your individual contribution to the thesis. Name of candidate: .�.��!.A.N..... lb?.��F..!..... Y.!f:.!.t?.�..... t1.f.!.f?:T./�................. Thesis title: l-A.1.f........ <£!!: fl:.[§&._�!!.tt .... Jf.�........ �Y.!Y.!.!.d.l��-·•··•·.Of. .... T.fl.P................ •••••••••••••••••••••••••••••••0••••••••••••••r10Nrt >AN L.ollE.Nz.o •••••••••••••• •••••••••••••••n••••••••••••••• 1c:E c.AP•••••Jr•••••••••••••••••••••••••••••••••••••••••••• PA7Affo1-J1A ••OOoooooU,OOoOOOOO I confirm that the thesis that I am presenting has been co-authored with: .��_fl{//AJ . .. J)flV I l.5 .... �-"-\... ... VIIR.. 'IL- ..... THD�N P1 c.g..11 F, ............................................ Within this partly co-authored work, I declare that the following contributions are entirely my own work: (Here you should indicate, in precisstyle, the datasets that you gathered, interpretedand discussed; methods thatyou developed; complete first drafts that you wrote; content that is entirelyyour own work; etc. It is oftenappropriate to organise this statement by chapter) cJ.-..��(L.r 4- o.,.� �be..r u; t,� (:::h.;> U.es:s �vL be.a.,.._ "'-½tel.jrt, ,.,.,.__ M.-b,._ eJ ..J.. Z..DICI l Se...,a_ An�� iC.e..!:.) ' Wro�e. 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If)✓.ef.:' �?..... ���-=• -..� .': .....(:J ..k.'l>-..-U:�� ... ............ Date: ..............2.t/.... (/1.. J /'.{.'.?.Q ~r (Supervisor) This fom, should be signed by the candidate and the candidate's supervisorand returned to Student Administration, Royal Holloway, Egham, Surrey TW20 OEX with the copies of the thesis. 2 Acknowledgements First and foremost, I would like to thank my supervisors Bethan Davies and Varyl Thorndycraft. Their support, help, guidance and patience has been invaluable and their commitment to teaching and enthusiasm for the subject has provided much needed encouragement and energy. From their support with fieldwork, to day to day queries, to their final assistance bringing this thesis together, I am very thankful to have had Bethan and Varyl as supervisors. I would like to acknowledge Dr Richard Jones for his invaluable assistance in setting up, initialising and running PISM. Dr Jan Leanarts is gratefully thanked for processing the RAMCO 2.3 climatic dataset for use in PISM. Dr Nick Golledge is thanked for his assistance in running PISM. I am very grateful to all the academic, technical and administrative staff within the Department of Geography, who welcomed me into the department and have always been available and keen to help with any questions or problems. The close, friendly, encouraging community within the department has really made the last four years. Likewise, I am extremely grateful to the fantastic group of PhD students past and present who made PhD life so enjoyable. I have had a great time and great laugh with more people than I can name, but in particular to Rachel and Dave who have been there on the DTP since day one. To Rhys, Jacob, Paul and Ash who made my first months in EMU, and the years since, so much fun. Richard, Lizzy, Angharad, Simon, Alice, Josh, Amy, Jen and many more who I spent so many days with. All those on the DTP, too many to mention, who made the first 6 months of my PhD a time I will always look back on so fondly. I am grateful to have had this group of people around me. To Rachael whose constant support, motivation and laughter I will be forever grateful. Finally, to my parents and brother George, thank you for your unending support and unconditional willingness to do whatever you can to help and support me. This thesis was supported by a Natural Environment Research Council award NE/ L002485/1, as well as numerous organisations including the Quaternary Research Association (QRA), Geologists Association (GA), British Society for Geomorphology (GSB) and INQUA, for funding fieldwork and supporting conference attendance. Cosmogenic nuclide ages were supported by NERC Cosmogenic Isotope Analysis Facility (CIAF), grant number 9174/0417. 3 Abstract Glaciers of small ice caps have short response times and high climate sensitivity, making them a useful proxy for understanding palaeoclimate. Past changes in climate and glacier dynamics can provide an analogue for present-day and future rapid climate and glacier change. Land- terminating glaciers are of particular interest, since their extent is largely a function of temperature and precipitation. Constraining the past behaviour of these glaciers from the geological record and glacier mass-balance sensitivities from numerical modelling can yield insights into past climate change. This is of particular interest in Patagonia to help elucidate the behaviour of the precipitation bearing Southern Westerly Winds, which are changed dynamically during the Late Pleistocene and Holocene. Key climatic constraints on glaciers east of the Northern Patagonian Icefield are also poorly understood, complicated by a lack of understanding of interactions between glaciers and ice-dammed palaeolakes. This study presents a new reconstruction of the deglaciation of the northern Monte San Lorenzo ice cap, southern South America, during a period of accelerated warming following the Antarctic Cold Reversal. Detailed geomorphological mapping of the valleys north of Monte San Lorenzo reveals 14 primary ice limits, two of which were dated to 12.5 ± 0.4 ka and 12.1 ± 0.4 ka by cosmogenic nuclide dating. Glacial landsystem analysis enables and formalises the reconstruction of Antarctic Cold Reversal and Holocene glacier dynamics and glacier-lake interactions. This work underpins a numerical model (PISM) of the ice cap to evaluate palaeoclimate drivers. Climatic and physical parameter sensitivity experiments and climatic response time tests provide, for the first time, an important insight into the controls of glacier change and the response of temperate Patagonian glaciers to rapidly-warming climate. Forcing the model using temperature and precipitation combinations to match reconstructed ice limits provides estimates of past climate conditions following the Antarctic Cold Reversal. 4 Contents Acknowledgements …………………………………………………………………………………………………………………3 Abstract …………………………………………………………………………………………………………………………………..4 Contents ………………………………………………………………………………………………………………………………….5 List of Figures …………………………………………………………………………………………………………………………10 List of Tables ………………………………………………………………………………………………………………………….19 1. Introduction ……………………………………………………………………………………………………………………….22 1.1. Rationale ......................................................................................................................22 1.2. Previous work and gaps in knowledge ..........................................................................25 1.3. Research questions .......................................................................................................26 1.4. Aims & objectives .........................................................................................................27 1.4.1. Aims ......................................................................................................................27 1.4.2. Objectives ..............................................................................................................27 1.5. Study area ....................................................................................................................28 1.6. Thesis structure and results ..........................................................................................30 1.6.1. Chapter 4: Sediment-landform assemblages and landsystems of the northern MSL region ..............................................................................................................................30 1.6.2. Chapter 5: Glacier chronology and post-ACR recession ..........................................30 1.6.3. Chapter 6: Palaeoglacier and ELA reconstruction ...................................................31 1.6.4. Chapter 7: Numerical modelling of the MSL ice cap................................................31 1.6.5. Chapter 8: Discussion .............................................................................................31 2. Literature review ……………………………………………………………………………………………………………….33 2.1.
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