A 147cm sediment core from Lake DV09, northern Devon Island, Nunavut, Canada (75° 34’34”N, 89° 18’55”W) contains annually-laminated (varved) sediments, providing a 1600-year record of climate variability. A minerogenic lamina deposited during the annual thaw period and a thin deposit of organic matter deposited during the summer and through the winter, together form a clastic-organic couplet each year. The thinnest varves occur from AD800-1050, and the thickest from AD1100-1300, during the Medieval Warm Period. The relative sediment density is also highest during this period suggesting increased sediment transport energy. The coldest period of the Little Ice Age appears to be during the AD1600s. Varve widths over the past century indicate climate warming in the region. / This research program was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC), and the Canadian Foundation for Climate and Atmospheric Sciences (CFCAS). A tuition bursary from Ultramar Inc. also helped in making this research possible. Logistical support was provided by the Polar Continental Shelf Project (PCSP Contribution number 04508).

The intent of the research described in this thesis was to reconstruct and document Holocene glacier activity in the central British Columbia Coast Mountains. Despite ongoing efforts to describe glacier fluctuations in the southern and northern Coast Mountains, only limited attention has been directed to revealing the Holocene histories of glaciers in the central Coast Mountain region. The goals of this research were twofold: firstly, to describe mid-Holocene glacier advances at five remote glacier sites in the central Coast Mountains, and secondly, to detail Little Ice Age (LIA) glacier fluctuations at four glacier sites in the central Coast Mountains. The mid-Holocene behaviour of Canoe, Fyles, Jacobsen, Tchaikazan and Icemaker glaciers was investigated using dendroglaciological techniques and stratigraphic analysis. Subfossil wood evidence suggests these glaciers were expanding into standing forests prior to 6.63, 4.90 and 4.20 ka. Stratigraphically constrained woody detritus at Fyles Glacier records the progradational history of a Gilbert-type delta forming in response to glacial expansion between 7.02-5.47 ka. Glacial expansion occurring between 7.50-4.00 ka has regional correlatives, suggesting coherent broad-scale climate forcing mechanisms influenced glacial mass balance at this time. Insight into the LIA behaviour of central Coast Mountain glaciers was provided by conducting lichenometric surveys of Rhizocarpon spp. across LIA moraines at Pattullo, Fyles, Deer Lake and Jacobsen glaciers. The presence of a second, lesser known, lichen species at some sites necessitated the construction of a Xanthoria elegans growth curve. An assessment of lichenometric measurements from the southern and central Coast Mountains provided the opportunity to build a X. elegans growth curve constrained by 18 control points. Lichenometric surveys revealed dominant moraine building episodes at 890-1020, 1280-1320, 1490-1530, 1680-1720, 1780 and 1820-1870 AD, highlighting the complex nature of glacier fluctuations during the LIA. A regional subalpine fir tree-ring chronology (1610-2010 AD) was developed from four stands located in the central Coast Mountains for dendroclimatological investigations. Correlation analyses show that the radial growth of trees corresponded to variations in the mean June/July air temperature and May 1st snowpack. This relationship was used to reconstruct these climate parameters for the duration of the tree-ring record. Intervals of cooler summer air temperatures and above average snowpack were found to broadly correspond with dominant periods of LIA moraine building from 1610-1930 AD. This reconstruction of mid-Holocene and LIA glacial history offered insights consistent with the emerging record of glacial activity described for the southern Coast Mountain glaciers. It also provides the first evidence for mid-Holocene glacial expansion in the central and northern Coast Mountains. The application of lichenometry in the central Coast Mountains documents the regional LIA behaviour of glaciers and the construction of a Xanthoria elegans growth curve for the Coast Mountains provides a framework for future geobotanical dating using this species. / Graduate

Les glaciers des Alpes françaises subissent un recul généralisé depuis la fin du Petit Âge Glaciaire (PAG). Dans le contexte actuel d'élévation de la température et du fait des nombreux enjeux auxquels ils sont associés, l'amélioration de leur suivi apparaît indispensable. Avant ce travail, il n'existait pas d'étude exhaustive récente concernant l'ensemble des glaciers des Alpes françaises, les travaux de Mougin et de Vivian datant respectivement du milieu des années 1920 et 1970. L'objectif de ce travail est de dresser un inventaire diachronique des glaciers des Alpes françaises et de leurs marges proglaciaires. Les données de cet inventaire servent ensuite de base à l'étude des modalités du retrait glaciaire depuis la fin du PAG et à l'établissement de méthodes pour détecter les secteurs susceptibles d'être affectés par des instabilités. L'inventaire diachronique des glaciers des Alpes françaises est réalisé à 3 dates : (i) 2006-2009 à partir des orthophotographies récentes de l'IGN, (ii) 1967-1971 à partir des premières éditions des cartes topographiques 1 :25 000 de l'IGN, et (iii) la fin du PAG (pour les massifs du Mont Blanc, de la Vanoise et des Ecrins), en croisant documents anciens et données géomorphologiques acquises sur le terrain et par photo-interprétation. Les données sont organisées dans un Système d'Information Géographique (SIG) qui permet d'associer cartographie et base de données. La superficie des glaciers était de 275 km² en 2006-2009, 369 km² en 1967-1971 et 544 km² à la fin du PAG pour les massifs du Mont Blanc, de la Vanoise et des Ecrins. A l'échelle régionale, les glaciers ont perdu 25 % de leur superficie depuis la fin des années 1960 et 50 % de leur superficie depuis la fin du PAG. La rétraction des glaciers est environ 2,5 fois plus rapide entre 1967-1971 et 2006-2009 qu'entre la fin du PAG et 1967-1971. A l'échelle individuelle, les glaciers ont perdu en moyenne 52 % de leur superficie entre 1967-1971 et 2006-2009, et 115 ont même disparu. A l'échelle régionale comme individuelle, le retrait glaciaire présente des tendances différentes selon les massifs, la taille des glaciers et leur exposition Des méthodes simples, basées sur les données des inventaires des glaciers et des marges proglaciaires sont établies afin d'identifier les lacs potentiellement instables, les secteurs englacés favorables à la formation de futurs lacs, au déclenchement d'avalanches de séracs ou susceptibles d'être déstabilisés en masse, et les marges proglaciaires favorables à l'occurrence de glissements ou de laves de débris. / French alpine glaciers are retreating since the end of the Little Ice Age (LIA). In the context of the increasing air temperature and because of issues that they represent, it is necessary to improve glacier monitoring. Before the present study, the only two inventories covering the entire French Alps were made by Mougin (1925) and Vivian (1975). The main goal of this study is to realise a multi-temporal glacier inventory of glaciers in the French Alps and of their proglacial margins. Data from this inventory are used to study glacial retreat since the end of the LIA and to develop methods to detect sector that could be affected by instabilities. Multi-temporal inventory of French Alpine glacier glaciers is made for 3 dates: (i) 2006-2009, based on IGN recent orthophotographs, (ii) 1967-1971, based on 1: 25 000 IGN topographic maps, and (iii) the end of the LIA (for Mont Blanc, Vanoise and Ecrins massifs), crossing old documents and geomorphologic data based on field work and interpretation of orthophotographs. Data are integrated in a Geographical Information System (GIS), combining mapping and data base. Glaciers in the French Alps covered 275 km² in 2006-2009, 369 km² in 1967-1971 and 544 km² at the end of the LIA for Mont Blanc, Vanoise and Ecrins massifs. At a regional scale, glaciers lost 25 % of their 1967-1971 area and 50 % of their LIA area. Glacier shrinkage between 1967-1971 and 2006-2009 is about 2.5 times higher than between the end of the LIA and 2006-2009. At an individual scale glaciers lost 52 % of their area between 1967-1971 and 2006-2009, and 115 disappeared. At regional or individual scale, different trends in glacier shrinkage are observed according to the massifs, size and aspect of the glaciers. Simple methods, based on glaciers inventory and proglacial margins data, are developed in order to identify potential unstable lakes, glaciated sectors prone to glacier lake formation, ice avalanche triggering or mass destabilization, and proglacial margins where sliding or debris flows could occur.

Palaeoenvironmental investigations from the Lake Plav catchment of the Prokletije Mountains in Montenegro and Albania, allowed primarily climatic change and anthropogenic influences during the Late Holocene and particularly the Little Ice Age (LIA) to be identified. Three sediment cores were analysed, two from Lake Plav (904 m a.s.l., cores LPCA and LPCB) and one from the upper catchment site of Lake C in Buni i Jezerces (1754 m a.s.l., core BJC1). These sediments were analysed for a variety of proxies including pollen, ostracoda, organic content, magnetic susceptibility and particle size. Chronologies for each sediment core were constructed using AMS radiocarbon, 210Pb and 137Cs dating techniques. The lower sites provided a record of past flood events, anthropogenic influences, lake development and infilling that have occurred since c. AD 500. Core BJC1 provided longer-term data since c. 2720 BC, providing complementary records of Pediastrum and thermophilous arboreal types, identified following a catchment vegetation survey. Glacial geomorphological mapping of the Maja e Koljaet glacier in Buni i Jezerces, Albania, enabled a catchment specific palaeotemperature record to be constructed from AD 1859 to the present. Glacial features were dated using lichenometry before degree-day modelling enabled temperature reconstruction. The palaeotemperature reconstruction for the Albanian Little Ice Age glacial maximum (LIAGM) suggests that temperatures were 0.9°C below the 1980-2008 annual temperature mean. This work also provided the first record of glacial extent during the LIA in Albania, indicating that the Albania LIAGM occurred c. AD 1859, around a decade after the European LIAGM and two decades before that of Montenegro. Anthropogenic indicators were used to reconstruct human activity in the catchment, which suggested that arable farming was pursued throughout the Medieval Warm Period (MWP; c. AD 800-1090) and continued during a period of transition to the LIA, between c. AD 1090 and AD 1300. The LIA (c. AD 1300 - 1860) was characterised by an abrupt Alnus decline, thought to be the result of anthropogenic clearance of the floodplain and reduction of both arable and thermophilous types. During the LIA sedimentation rates were up to 1.41 + 0.17 cm yr-1 at Lake Plav causing lake infilling and shallowing allowing wetland expansion c. AD 1570. The result of lake infilling is highlighted during the early 20th century, when the lake extent fell by around 42% as a result of climatic amelioration post-LIA causing lake levels to fall and wetland indicators to decline. The inferred past climatic changes from the Lake Plav catchment are compared to data from around the Mediterranean and Southern Europe. This allows identification of the climatic influences affecting the site during the Late Holocene. Catchment records have provided evidence of cooler and wetter conditions coeval to the occurrence of solar minima such as the Wolf, Spörer and Maunder minima. Overall, the records suggest that continental atmospheric circulation patterns such as the North Sea-Caspian Pattern (NCP) and East Atlantic-West Russia pattern (EA-WR), dominated the site until the late 1800s, when records become more synchronous with the NAO index and Mediterranean/Southern European data.

Accurate reconstruction of natural climate variability over the past millennium is critical for predicting responses to future climate change. In order to improve on current understanding of climate variability in the sub-tropical North Atlantic region over the past millennium, a rigorous study of Gulf of Mexico (GOM) sea surface temperature (SST) variability was conducted using both inorganic (foraminiferal Mg/Ca) and molecular organic (TEX86) geochemical proxies. In addition to generating multiple high-resolution climate records, the uncertainties of the SST proxies are rigorously assessed. There are 3 major research questions addressed: (1) What was the magnitude of GOM SST variability during the past 1,000 years, particularly during large-scale climate events such as the Little Ice Age (LIA) and the Medieval Warm Period (MWP). (2) Is the SST signal reproducible within the same sediment core, among different northern GOM basins, and using different geochemical SST proxies? (3) What are the ecological controls on the paleothermometers used to reconstruct SST variability in the GOM? Can differences in the ecology (i.e. seasonal distribution, depth habitat, etc.) of distinct paleothermometers be exploited to gain insight into changes in upper water column structure or seasonality in the GOM during the LIA and MWP? The major findings include: (1) The magnitude of temperature variability in the GOM over the past millennium is much larger than that estimated from Northern Hemisphere temperature reconstructions. The MWP (1400-900 yrs BP) was characterized by SSTs in the GOM that were similar to the modern SST, while the LIA (400-150 yrs BP) was marked by a series of multidecadal intervals that were 2-2.5°C cooler than modern. (2) This LIA cooling was replicated in the Mg/Ca-SST records from three different well-dated northern GOM basins (Pigmy, Garrison and Fisk Basins), as well as in two different geochemical proxies. (3) It is determined that foraminiferal test size has a significant effect on shell geochemistry. Using core-top calibration, discrepancies in the seasonal/depth habitats between different planktonic Foraminifera, and between Foraminifera and Crenarchaeota are inferred. Downcore differences are used to make inferences about changes in GOM mixed layer depth and seasonality over the past millennium.

Savanna systems are complex and dynamic in space and time. Climate, fire, herbivory and nutrients have been identified as structuring agents of savanna form and function, but their interactions and feedbacks with one another and vegetation are poorly resolved. Increasing the spatial and temporal scope of studies will help to improve this situation, as demonstrated in recent studies in the spatial dimension in particular. This study aims to investigate vegetation and Nitrogen cycling changes over time in a diverse patch mosaic landscape in Hluhluwe-iMfolozi Park to identify drivers of vegetation structure and their dynamism over time. Sediment from a 150cm core (taken using a Russian corer) was analyzed for stable ¹³C and ¹⁵N isotope abundances, and C:N ratio of soil organic matter. The base of the core was dated at 2380±40cal.Yr.BP. δ¹³C, δ¹⁵N and C:N of soil organic matter was found to be variable over time. δ¹³C followed a pattern of stable periods of distinct abundance separated by abrupt changes; δ¹⁵N and C:N underwent changes over the same periods as δ¹³C. Vegetation follows a pattern of phase and transition as predicted by resilience theory. An aquatic vegetation phase persists around 2000cal.Yr.BP to about 500cal.Yr.BP, coinciding with a warm, wet period (including the Medieval Warm Period) with an open Nitrogen cycle. A C₄ grassland phase follows alter a transition to cool, dry conditions coinciding with the Little Ice Age, and decreasing openness of the N cycle. Recent increasing C₃ vegetation and N-openness were attributed to atmospheric CO₂ increase and Nitrogen deposition respectively. Climate is concluded to be the major driver of vegetation at this site, and a combination of climate and vegetation are responsible for changes in Nitrogen availability. Findings are discussed in relation to landscape management. Multi-proxy evidence in future studies would be useful in validating the findings of this study.

Sclerochronology affirms the well-established fact that banded growth increments in marine molluscs accurately record oscillations in climate and environment for the past millennia or more. This study considers how such records can enhance understanding of environmental shifts across the 18th to 20th centuries. Specifically, it investigates whether sclerochronological data are fundamentally associated with stable carbon and oxygen isotope values and if the climate phenomenon of the Little Ice Age impacts the marine radiocarbon reservoir effect. Furthermore, this study compares the North Sea and the Irish Sea to discover whether observed environmental changes are equivocal or not. Three shells of Arctica islandica were retrieved from the Dutch natural history museum "Naturalis" in Leiden, the Netherlands, to construct a chronology dating back to the 18th century from growth increments. Collection dates for the three shells vary between 1882 and 1954 in the North Sea and the Irish Sea. Shells were prepared, photographed and milled for calcium carbonate material. Digital images allowed counting of increments while the milled material was measured for stable carbon and oxygen isotopes and was radiocarbon dated. The ontogenetic bias was removed from sclerochronological data using MATLAB software to produce a purely environmental growth signal. The results agreed with the proposed hypothesis that there is a link between growth increments and the stable isotope data. However, further analysis is required to validate the presence of the Little Ice Age in the radiocarbon reservoir effect. These results indicate that the stable carbon and oxygen isotopes and growth increments are a good indicator of favourable growth conditions for Arctica islandica. Therefore, this study highlights that Arctica islandica is a suitable proxy for the North Sea and Irish Sea palaeoenvironment reconstructions. On this basis, future climate research can accurately depend on sclerochronological data to aid in understanding the patterns of anthropogenic climate change.

A 147cm sediment core from Lake DV09, northern Devon Island, Nunavut, Canada (75° 34’34”N, 89° 18’55”W) contains annually-laminated (varved) sediments, providing a 1600-year record of climate variability. A minerogenic lamina deposited during the annual thaw period and a thin deposit of organic matter deposited during the summer and through the winter, together form a clastic-organic couplet each year. The thinnest varves occur from AD800-1050, and the thickest from AD1100-1300, during the Medieval Warm Period. The relative sediment density is also highest during this period suggesting increased sediment transport energy. The coldest period of the Little Ice Age appears to be during the AD1600s. Varve widths over the past century indicate climate warming in the region. / This research program was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC), and the Canadian Foundation for Climate and Atmospheric Sciences (CFCAS). A tuition bursary from Ultramar Inc. also helped in making this research possible. Logistical support was provided by the Polar Continental Shelf Project (PCSP Contribution number 04508).

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