Evidence is accumulating that climate change is having a significant effect on a wide range of organisms spanning the full range of biodiversity found on this planet. This study investigates the ecological role of climate change, the North Atlantic Oscillation (NAO) and habitat change on British insect populations. Despite the NAO having a considerable effect on British weather, the role of the NAO on British insects has not previously been studied in great detail. The World's two best entomological time series datasets were used – the United Kingdom Butterfly Monitoring Scheme (UKBMS) and the Rothamsted Insect Survey of aphids – both surveys with very large sample sizes and high quality data. Summary of main findings: 1. Warm weather associated with a positive NAO index caused the spring migration of the green spruce aphid (Elatobium abietinum), a pest species of spruce trees (Picea) to start earlier, continue for longer and contain more aphids. An upward trend in the NAO index during the period 1966-2006 is associated with an increasing population size of E. abietinum. 2. The NAO does not affect the overall UK butterfly population size. However, the abundance of bivoltine butterfly species, which have a longer flight season, were more likely to respond positively to the NAO compared to univoltine species, which show little or a negative response. 3. A positive winter NAO index was associated with warmer weather and earlier butterfly flight dates. For bivoltine (two generations in a year) species, the NAO affects the phenology of the first generation, and then the timing of the second generation is indirectly controlled by the timing of the first generation. The NAO influences the timing of the butterfly flight seasons more strongly than it influences population size. 4. Butterfly data from Monks Wood National Nature Reserve in Cambridgeshire showed that the NAO does not affect the abundance of the whole butterfly community, but it does affect the population size of some species. The NAO does not affect butterfly diversity, but there were decreases in butterfly diversity and number of species with time. 5. The total number of butterflies counted at Monks Wood was constant for most of the time series. However, the population size of the ringlet (Aphantopus hyperantus) increased from very low numbers to more than half the total number of butterflies counted each year. Therefore the total population size of all the other species has decreased considerably. 6. The NAO was more important than climate change in determining the flight phenology of the meadow brown butterfly (Maniola jurtina) at Monks Wood. In conclusion, the NAO affects the abundance of some species of British butterfly, and an aphid species, with a stronger effect on the timing of flight rather than abundance. There was evidence for a long-term decrease in the biodiversity of butterflies at Monks Wood and this decrease is likely to continue.

In this thesis, the role of mid-latitude cyclones in air pollution transport in the Northern Hemisphere is quantified. The storm tracking model, TRACK, is used to study the mechanisms through which pollution, specifically ozone (O3) and carbon monoxide (CO), are vented from the boundary layer to the free troposphere and thus transported over large distances, as well as the introduction of O3 from the stratosphere into the troposphere. The relationship between mid-latitude cyclones and air pollution transport of O3 and CO is explored for the first time using the Monitoring Atmospheric Composition and Climate (MACC) reanalysis, a combined meteorology and composition reanalysis dataset. A comparison between springtime surface ozone measurements at rural background sites on the west coast of Europe and cyclone track frequency in the surrounding regions was used to first establish the correlation between cyclone location and surface air quality. The focus is on spring as it tends to be the season of maximum intercontinental transport of O3. The surface observations were compared to the MACC O3 values at the same locations and case studies of how cyclones can influence surface O3 measurements are described. When cyclones track north of 53°N, there is a significant probability that the surface O3 will be high (> the 75th percentile), due to the close proximity to stratospheric intrusions and the transport at low levels across the North Atlantic Ocean. The most intense spring cyclones (95th percentile) were selected for two regions, the North Atlantic and the North Pacific, for further investigation into the mechanisms which impact O3 and CO concentrations near cyclones. These intense cyclones ( 60 over each region) often tracked over the major emission sources of eastern North America and East Asia. The distributions of MACC O3 and CO within a "typical" intense cyclone are examined by compositing the cyclones together. The cyclone-centered composites were compared to background composites of "average conditions" created by sampling the reanalysis data of the previous year to the cyclone locations. Mid-latitude cyclones are found to redistribute concentrations of O3 and CO horizontally and vertically throughout the cyclone. This is clearly shown to occur through two main mechanisms: (1) vertical lifting of CO-rich and O3-poor air isentropically from near the surface to the mid- to upper-troposphere in the region of the warm conveyor belt; and (2) descent of O3-rich and CO-poor air isentropically in the vicinity of the dry intrusion, from the stratosphere toward the mid-troposphere. This work was expanded to identify the links between teleconnection patterns, mainly the North Atlantic Oscillation (NAO), that affect the major storm track pathways in the North Atlantic sector and the distribution of MACC O3 and CO throughout the troposphere and lower stratosphere. For this analysis, TRACK was used to calculate seasonal weighted-average O3 and CO distribution maps based on the monthly NAO index. During positive NAO phase, the persistence of low pressures over the North Atlantic coupled with the Azores High promotes transport across the North Atlantic throughout the troposphere. During negative NAO phase, blocking high pressure in the eastern North Atlantic are known to occur, which shifts transport pathways to a more southerly zonal flow. This work demonstrates the complex relationship between the horizontal and vertical distribution of pollution, including surface concentrations, and synoptic-scale systems.

Recent changes in climate have increased public attention and scientific evaluation of climate impacts on wild animals and plants. Variation in local weather and regional climate may affect breeding success in birds. Migratory species may be sensitive to these changes as breeding and wintering areas may experience different climate variations; some insectivorous species may be unable to alter timing of migration or laying dates and experience a mismatch between timing of nesting and peak insect availability for their nestlings. Therefore, I investigated the influence of local weather variables and regional climate on breeding performance of an insectivorous migrant songbird, the Tree Swallow (<i>Tachycineta bicolor</i>), and tried to examine effects of a mismatch between the timing of breeding and food availability.<p>I used a 14 year data set from St. Denis, Saskatchewan, Canada, 1991-2004, to evaluate correlations among local weather, wetland conditions, aerial insects and regional climate indices and their relationships with variation in clutch initiation date, clutch size, and fledging success. Swallows returned to the study site in late April each year. Annual variation in median clutch initiation date was best explained by mean minimum temperatures during 1-15 May. Larger clutches were laid in years with higher pond water levels (possibly an indication of increased insect availability) and when the Southern Oscillation Index (SOI) was positive (representing La Niña conditions). Fledging success was not influenced greatly by any explanatory variable; however, fledging success tended to increase in years with higher average temperatures. Individual variation in clutch initiation date was examined using path analysis. I found high correlations between initiation date and both local environmental variables and regional climate indices; earlier nesting was associated with warmer temperatures (increased local temperatures, more positive North Atlantic Oscillation Index (NAOI) values and more negative SOI values) and decreased moisture (more positive NAOI values). Two reduced data sets, including female age or insect abundance, were also examined. Clutches were initiated earlier by older females and during springs with higher abundance of aerial insects.<p>I applied two heating treatments to nest boxes used by pre-laying swallows and compared reproductive measures (timing of nesting, laying sequence, clutch size, egg weight and fledging success) of birds using heated boxes to those of females attending unheated control boxes. However, I was unable to directly examine the predictions of the mismatch hypothesis because nest box heating failed to advance laying dates. Furthermore, no increases in clutch size, egg weight and fledging success were detected between treatment and control nests. Although box heating increased nest temperatures an average of 6.1C (+ 0.8 SE) over controls, length of time females spent in heated boxes may have been too short to alleviate energetic constraints on egg production, or energy savings associated with box use were insufficient to supersede the influence of ambient environmental conditions that control food availability and energy expenditure of foraging swallows. My results demonstrated that local and regional climate variation strongly affected timing of nesting in swallows, likely via their effects on food supply.

Recent changes in climate have increased public attention and scientific evaluation of climate impacts on wild animals and plants. Variation in local weather and regional climate may affect breeding success in birds. Migratory species may be sensitive to these changes as breeding and wintering areas may experience different climate variations; some insectivorous species may be unable to alter timing of migration or laying dates and experience a mismatch between timing of nesting and peak insect availability for their nestlings. Therefore, I investigated the influence of local weather variables and regional climate on breeding performance of an insectivorous migrant songbird, the Tree Swallow (<i>Tachycineta bicolor</i>), and tried to examine effects of a mismatch between the timing of breeding and food availability.<p>I used a 14 year data set from St. Denis, Saskatchewan, Canada, 1991-2004, to evaluate correlations among local weather, wetland conditions, aerial insects and regional climate indices and their relationships with variation in clutch initiation date, clutch size, and fledging success. Swallows returned to the study site in late April each year. Annual variation in median clutch initiation date was best explained by mean minimum temperatures during 1-15 May. Larger clutches were laid in years with higher pond water levels (possibly an indication of increased insect availability) and when the Southern Oscillation Index (SOI) was positive (representing La Niña conditions). Fledging success was not influenced greatly by any explanatory variable; however, fledging success tended to increase in years with higher average temperatures. Individual variation in clutch initiation date was examined using path analysis. I found high correlations between initiation date and both local environmental variables and regional climate indices; earlier nesting was associated with warmer temperatures (increased local temperatures, more positive North Atlantic Oscillation Index (NAOI) values and more negative SOI values) and decreased moisture (more positive NAOI values). Two reduced data sets, including female age or insect abundance, were also examined. Clutches were initiated earlier by older females and during springs with higher abundance of aerial insects.<p>I applied two heating treatments to nest boxes used by pre-laying swallows and compared reproductive measures (timing of nesting, laying sequence, clutch size, egg weight and fledging success) of birds using heated boxes to those of females attending unheated control boxes. However, I was unable to directly examine the predictions of the mismatch hypothesis because nest box heating failed to advance laying dates. Furthermore, no increases in clutch size, egg weight and fledging success were detected between treatment and control nests. Although box heating increased nest temperatures an average of 6.1C (+ 0.8 SE) over controls, length of time females spent in heated boxes may have been too short to alleviate energetic constraints on egg production, or energy savings associated with box use were insufficient to supersede the influence of ambient environmental conditions that control food availability and energy expenditure of foraging swallows. My results demonstrated that local and regional climate variation strongly affected timing of nesting in swallows, likely via their effects on food supply.

Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisor: Daniel J. Leathers, Dept. of Geography. Includes bibliographical references.

Storm-induced open-ocean convective mixing is one of the primary processes controlling the supply of nitrate to the sunlit layer of the oligotrophic North Atlantic Subtropical Gyre (NASG). Yet, the magnitude and timing of nitrate fluxes during winter convection is poorly understood due to an absence of targeted process studies. In the northwest NASG, multiple quasi-Lagrangian studies were conducted during the boreal winters of 2004 and 2005 in an effort to sample strong winter convection. During each of the time-series studies, inventories of vertically fluxed nitrate were quantified approximately every twelve hours using the distribution of helium isotopes ([delta]�He) and nitrate in the water column. This method is known as the Helium Flux Gauge Technique (HFGT). Large variability in surface forcing and density structure of the upper ocean was observed between the two years; however, only winter 2005 experienced convective mixing to depths greater than 150 m. In winter 2004, mild atmospheric conditions coincided with a positive phase in the winter North Atlantic Oscillation (NAO), consistent with the dominant regime experienced during the previous decade. On average 36 � 9 mmol m[-2] of fluxed nitrate was inferred by excess �He in the mixed layer of the ocean during the winter 2004 study period. This inventory of physically transported nitrate is attributed to the sampling of waters laterally advected from nearby eddy features. The sampling of multiple water masses is likely due to the inability of the drogue to persistently follow water masses efficiently. Although physical evidence indicates spatial variability within the time-series data, the length scales of convective mixing appear to be greater than those associated with spatial aliasing as a result of drogue performance. This observation provides us with increased confidence that the objectives for the present study are not compromised by spatial variability in the data. In contrast, winter 2005 experienced a negative NAO, strong physical forcing and convective mixing to depths > 250 m. Two convectively modified water masses, most likely resulting from a single storm event, were sampled at different stages of development. These two water masses exhibit large variability in the magnitude of nitrate entrained in the convective layer from the thermocline. An average inventory of 247 � 56 mmol NO₃[-]m[-2] was entrained in the rapidly expanding convective layer of the first water mass in the first few days following the storm approach. In contrast, ongoing entrainment of nitrate was absent from the second water mass, sampled two weeks later when the depth of the surface mixed layer was consistently ~ 300 m. These results indicate that surrounding fluid is entrained into the convective layer when it is actively expanding in the vertical. On the other hand, significant fluid entrainment does not occur at the base of the plume once sinking waters have reached a level of neutral buoyancy. The persistence of elevated nitrate stocks (~ 100 mmol m[-2]) in the convective layer two to three weeks after the inferred injection event, suggests sub-optimal nitrate uptake by resident phytoplankton. Phytoplankton growth was most likely resource limited by light or a micronutrient such as iron. Despite the implied biolimitation, changes in chlorophyll-a, a proxy for phytoplankton biomass, indicate net production within the convective layer. On average, the convective layer was observed to support an inventory of 62 � 6mg chlorophyll-a m[-2], increasing at an average rate of 3.4mg m[-2] d[-1]. This inventory indicates a slow build-up of phytoplankton biomass to near bloom levels, ahead of the main spring bloom that typically follows formation of the seasonal thermocline near Bermuda. Net production in the convective layer was likely due to transient periods of increased (weak) surface stability that were observed to support high phytoplankton biomass, following the cessation of thermocline fluid entrainment. When nitrate and excess �He in samples collected from the thermocline were regressed for the purpose of quantifying nitrate fluxes, the results showed that between 1.6 - 2.0 [mu]mol kg[-1] of dissolved nitrate was present during formation of the water mass. This suggests the source of this excess (above Redfield ratios) nitrate in the thermocline of the NASG is not local, and has ramifications for local nitrogen fixation budgets determined using geochemical approaches. Thesis supervisors: William J. Jenkins, Senior Scientist, WHOI (United States of America); Philip W. Boyd, Senior Scientist, NIWA (New Zealand); Michael W. Lomas, Senior Scientist, BIOS (Bermuda)

Storm-induced open-ocean convective mixing is one of the primary processes controlling the supply of nitrate to the sunlit layer of the oligotrophic North Atlantic Subtropical Gyre (NASG). Yet, the magnitude and timing of nitrate fluxes during winter convection is poorly understood due to an absence of targeted process studies. In the northwest NASG, multiple quasi-Lagrangian studies were conducted during the boreal winters of 2004 and 2005 in an effort to sample strong winter convection. During each of the time-series studies, inventories of vertically fluxed nitrate were quantified approximately every twelve hours using the distribution of helium isotopes ([delta]�He) and nitrate in the water column. This method is known as the Helium Flux Gauge Technique (HFGT). Large variability in surface forcing and density structure of the upper ocean was observed between the two years; however, only winter 2005 experienced convective mixing to depths greater than 150 m. In winter 2004, mild atmospheric conditions coincided with a positive phase in the winter North Atlantic Oscillation (NAO), consistent with the dominant regime experienced during the previous decade. On average 36 � 9 mmol m[-2] of fluxed nitrate was inferred by excess �He in the mixed layer of the ocean during the winter 2004 study period. This inventory of physically transported nitrate is attributed to the sampling of waters laterally advected from nearby eddy features. The sampling of multiple water masses is likely due to the inability of the drogue to persistently follow water masses efficiently. Although physical evidence indicates spatial variability within the time-series data, the length scales of convective mixing appear to be greater than those associated with spatial aliasing as a result of drogue performance. This observation provides us with increased confidence that the objectives for the present study are not compromised by spatial variability in the data. In contrast, winter 2005 experienced a negative NAO, strong physical forcing and convective mixing to depths > 250 m. Two convectively modified water masses, most likely resulting from a single storm event, were sampled at different stages of development. These two water masses exhibit large variability in the magnitude of nitrate entrained in the convective layer from the thermocline. An average inventory of 247 � 56 mmol NO₃[-]m[-2] was entrained in the rapidly expanding convective layer of the first water mass in the first few days following the storm approach. In contrast, ongoing entrainment of nitrate was absent from the second water mass, sampled two weeks later when the depth of the surface mixed layer was consistently ~ 300 m. These results indicate that surrounding fluid is entrained into the convective layer when it is actively expanding in the vertical. On the other hand, significant fluid entrainment does not occur at the base of the plume once sinking waters have reached a level of neutral buoyancy. The persistence of elevated nitrate stocks (~ 100 mmol m[-2]) in the convective layer two to three weeks after the inferred injection event, suggests sub-optimal nitrate uptake by resident phytoplankton. Phytoplankton growth was most likely resource limited by light or a micronutrient such as iron. Despite the implied biolimitation, changes in chlorophyll-a, a proxy for phytoplankton biomass, indicate net production within the convective layer. On average, the convective layer was observed to support an inventory of 62 � 6mg chlorophyll-a m[-2], increasing at an average rate of 3.4mg m[-2] d[-1]. This inventory indicates a slow build-up of phytoplankton biomass to near bloom levels, ahead of the main spring bloom that typically follows formation of the seasonal thermocline near Bermuda. Net production in the convective layer was likely due to transient periods of increased (weak) surface stability that were observed to support high phytoplankton biomass, following the cessation of thermocline fluid entrainment. When nitrate and excess �He in samples collected from the thermocline were regressed for the purpose of quantifying nitrate fluxes, the results showed that between 1.6 - 2.0 [mu]mol kg[-1] of dissolved nitrate was present during formation of the water mass. This suggests the source of this excess (above Redfield ratios) nitrate in the thermocline of the NASG is not local, and has ramifications for local nitrogen fixation budgets determined using geochemical approaches. Thesis supervisors: William J. Jenkins, Senior Scientist, WHOI (United States of America); Philip W. Boyd, Senior Scientist, NIWA (New Zealand); Michael W. Lomas, Senior Scientist, BIOS (Bermuda)

abstract: ABSTRACT Famine is the result of a complex set of environmental and social factors. Climate conditions are established as environmental factors contributing to famine occurrence, often through teleconnective patterns. This dissertation is designed to investigate the combined influence on world famine patterns of teleconnections, specifically the North Atlantic Oscillation (NAO), Southern Oscillation (SO), Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO), or regional climate variations such as the South Asian Summer Monsoon (SASM). The investigation is three regional case studies of famine patterns specifically, Egypt, the British Isles, and India. The first study (published in Holocene) employs the results of a Principal Component Analysis (PCA) yielding a SO-NAO eigenvector to predict major Egyptian famines between AD 1049-1921. The SO-NAO eigenvector (1) successfully discriminates between the 5-10 years preceding a famine and the other years, (2) predicts eight of ten major famines, and (3) correctly identifies fifty out of eighty events (63%) of food availability decline leading up to major famines. The second study investigates the impact of the NAO, PDO, SO, and AMO on 63 British Isle famines between AD 1049 and 1914 attributed to climate causes in historical texts. Stepwise Regression Analysis demonstrates that the 5-year lagged NAO is the primary teleconnective influence on famine patterns; it successfully discriminates 73.8% of weather-related famines in the British Isles from 1049 to 1914. The final study identifies the aggregated influence of the NAO, SO, PDO, and SASM on 70 Indian famines from AD 1049 to 1955. PCA results in a NAO-SOI vector and SASM vector that predicts famine conditions with a positive NAO and negative SO, distinct from the secondary SASM influence. The NAO-famine relationship is consistently the strongest; 181 of 220 (82%) of all famines occurred during positive NAO years. Ultimately, the causes of famine are complex and involve many factors including societal and climatic. This dissertation demonstrates that climate teleconnections impact famine patterns and often the aggregates of multiple climate variables hold the most significant climatic impact. These results will increase the understanding of famine patterns and will help to better allocate resources to alleviate future famines. / Dissertation/Thesis / Doctoral Dissertation Geography 2017

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