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Recent studies have investigated the hydrological and geochemical characteristics of karst aquifers in different settings; however, telogenetic karst aquifer processes remain poorly understood. In south-central Kentucky, the iconic Lost River Cave and Valley represents a large, complex telogenetic karst drainage basin with a series of discharge points along a collapsed section of the cave. Two Campbell Scientific® CR1000 automated dataloggers were installed at Blue Hole Four, a primary discharge point of the Lost River Karst Aquifer (LRKA). These dataloggers recorded spring discharge, water temperature, specific conductance (SpC), and pH at ten-minute intervals from January to November, 2013. During the year, data for 34 storm events were captured, including water samples that were analyzed for major cation/anion concentrations. These concentrations were correlated to SpC to yield a continuous record of ionic concentrations. Rainfall data were acquired from the Kentucky Mesonet’s Warren County Site within the LRKA basin. Dissolution rates, Ca2+/Mg2+ ratios, and a mass flux of dissolved CaCO3were calculated to assess aquifer evolution processes and identify seasonal and storm event variability throughout the year. A two end member mixing analysis (EMMA) is used to analyze storm flow conditions versus baseflow conditions, and a predictive model is presented that is used to predict peak springflow based upon rainfall totals. A detailed water budget analysis and comparison to historical data is used to assess groundwater storage and aquifer complexity. The annual data reveal both seasonal and storm event patterns in geochemical and hydrologic conditions of the aquifer. The data indicate distinct responses to storm events. These responses, as well as EMMA results, indicate that storm event flows are composed initially of water formerly stored in the aquifer flushed through the aquifer by incoming meteoric water; this gradually gives way to a mixture of meteoric water and storage water that becomes gradually more similar to pre-storm conditions as discharge recedes to baseflow levels. The highest proportion of meteoric water is coincident with the highest potential for CaCO3 dissolution, indicating that storm events drive dissolution in the LRKA. Water budgeting for the full study period and individual storm events indicate that a large proportion of water in the LRKA is not discharged at Blue Hole Four, but rather is stored in the aquifer or follows another flowpath through the aquifer. Additionally, the higher rainfall totals during storm events tend to increase the proportion of water discharged from the aquifer rather than that stored within it. The predictive model indicates a strong correlation between total rainfall and peak discharge. The results overall indicate two critical times at which contaminant transport may occur: first, any contaminants stored in the aquifer will be flushed out first with storage water as discharge peaks, followed by a period in the falling limb of the discharge hydrograph that coincides with the peak proportion of meteoric water carrying contaminants that entered the aquifer during this event. This study helps to improve understanding of telogenetic karst aquifer processes and evolution, particularly in large, complex drainage basins. Future research is necessary to understand the dynamics of these important groundwater reserves and their response to continuing pressures from climate change, human impacts, and natural processes.

Several species of North American migratory songbirds reportedly experience seasonal diet shifts involving a shift from an insect diet during the breeding season to one incorporating fruits during migration and non-breeding periods but the extent to which dietary plasticity occurs in migratory songbirds is poorly quantified. Thus, I used stable carbon (ä13C) and nitrogen (ä15N) isotope analyses to evaluate the timing and extent of frugivory throughout the annual life cycle of 16 species of migratory songbirds, representing wide ranges in body size and reported diets. Birds were sampled during spring and fall migration at the Delta Marsh Bird Observatory in 2003. To investigate dietary patterns, I sampled multiple tissues (muscle, liver, whole blood, claws, bone collagen, feathers) as these represent different periods of diet integration due to varying elemental turnover rates.<p>Assuming that relatively low ä15N values represent a fruit diet and relatively high ä15N values represent an insect diet, I expected tissues representing fall migration (liver, blood, and muscle from fall-captured birds) and winter (greater coverts and claws from spring-captured birds) to have lower ä15N values than tissues representing spring migration (liver, blood, and muscle from spring-captured birds) and summer (tail feathers and claws from fall-captured birds) when fruits are presumed to be less common in songbird diets. Based on blood and claw ä15N values, there was no isotopic segregation of species I classified a priori as insectivores or omnivores. For most species, tissue ä15N values showed either no seasonal change or a shift opposite to my prediction (e.g., ä15N values higher in fall birds compared to spring birds). Boreal fruit ä15N values were lower than those for insects; however, ä15N values of agricultural fruits overlapped both boreal fruit and insect values suggesting that food web baselines did not conform to a simple (single) linear trophic-enrichment model. In Yellow-rumped Warblers (Dendroica coronata), within-tissue seasonal comparisons for liver, muscle and blood indicated a fruit diet during fall and winter and an insect diet during spring and summer; claws and feathers of birds captured in spring (representing winter diet) had unexpectedly high ä15N values. Diet-tissue isotopic discrimination factors associated with both a fruit diet and insect diet were taken from the literature and used to correct stable isotope values of tissues to putative diet because, currently, little is known about the nature of factors influencing discrimination factors to be used in simple linear dietary mixing models. There were differences in tissue ä13C and ä15N values depending on which discrimination factor was used. Based on mixing model results for tissue ä15N values, a higher proportion of insects vs. fruits was detected in the diet of Yellow-rumped Warblers for all tissues except muscle and claws. <p>My interpretations are contingent on the fact that the available natural history information, on which guild classifications were based, was correct and that elemental turnover rates and discrimination factors used were accurate. However, much uncertainty remains about the appropriate diet-tissue isotopic discrimination factors corresponding to fruit and insect diets. Due to extensive natural variability of stable nitrogen isotope values in food sources, possible anthropogenic influences and a lack of knowledge of the metabolic processes that can potentially affect stable isotope values, I caution against using stable isotope analysis alone to track frugivory in temperate North American migratory songbirds. Future research should focus on captive studies aimed at determining and validating discrimination factors of various tissues, particularly claws and feathers, for birds feeding on varying proportions of fruits and insects. Additionally, more information on the dietary habits of these migratory songbirds is needed, as previous estimates of insectivory and frugivory in songbirds may not be accurate.

One of the world’s largest freshwater deltas (~4000 km2), the Peace-Athabasca Delta (PAD), is located at the convergence of the Peace and Athabasca rivers and Lake Athabasca in northern Alberta, Canada. Since the early 1970s, there has been increasing concern regarding the ecological impacts on the PAD after flow regulation of the Peace River began in 1968, decreased discharge in the Peace and Athabasca rivers as a result of hydroclimatic changes in Western Canada, and increased Athabasca River water usage by oil sands development to the south. This thesis is part of an ongoing, multi-disciplinary project assessing current and past hydrological and ecological conditions in the PAD. Research conducted in this thesis aims to better understand the processes controlling water balance of lakes in the PAD using mainly stable water isotope data collected from lakes and their input sources. Isotope data are used to describe and quantify hydrological processes for individual lakes (seasonal and annual) and across the delta and are supported by other chemical and hydrometric data. An isotopic framework in d18O-d2H-space is developed for the PAD using evaporation-flux-weighted local climate data, and isotopic data collected from a reference basin, lakes throughout the PAD, and lake input sources (i.e., snowmelt, rainfall, and river water). The framework is comprised of two reference lines, the Local Meteoric Water Line, which is based on measured isotopic composition of precipitation, and the Local Evaporation Line, which is based on modelled isotopic composition of reference points. Evaporation pan data is used to assess short-term variations in key isotopic reference values, which are important for addressing short-term changes in the isotopic signature of shallow basins. This framework is used in subsequent chapters including assessment of seasonal and annual water balance of two hydrologically-contrasting shallow lakes, and to quantify the impacts of flood water and snowmelt on a set of 45 lakes in spring 2003. Five years of isotope data using time-series analysis and the isotopic framework suggested that a perched (isolated) lake and its catchment (forest and bedrock) in the northern, relict Peace sector captured sufficient rain, snow, and runoff to maintain a relatively stable water balance, and also that a low-lying lake in the southern, active Athabasca sector was regularly replenished with river water in both spring and summer. Snowmelt and rainfall were found to have diluted the perched basin by an average of 16% and 28 % respectively, while spring and summer floods were found to almost completely flush the low-lying lake. Using the spring 2003 regional dataset, flooded lakes were separated from snowmelt-dominated lakes through use of suspended sediment concentrations, isotope data, and field observations. Application of an isotope mixing model translated d18O values into a range of replenishment amount by either river water or snowmelt, which compared well with hydrological conditions at the time of sampling and previously classified drainage types of the lakes. Spatial mapping of replenishment amounts illustrated flooding of much of the Athabasca sector due to ice-jams, except for two sub-regions isolated from flooding by artificial and natural northern diversion of flow from the Athabasca River. It is also shown that most of the relict landscape of the Peace sector was replenished by snowmelt except for a few low-lying lakes close to the Peace River and its tributaries. Overall, improved understanding of lake and regional hydrology in the PAD, especially the ability to quantify the affects of various lake inputs, will improve the ability to develop effective guidelines and management practices in the PAD as lakes respond to future changes in climate and river discharge.

One of the world’s largest freshwater deltas (~4000 km2), the Peace-Athabasca Delta (PAD), is located at the convergence of the Peace and Athabasca rivers and Lake Athabasca in northern Alberta, Canada. Since the early 1970s, there has been increasing concern regarding the ecological impacts on the PAD after flow regulation of the Peace River began in 1968, decreased discharge in the Peace and Athabasca rivers as a result of hydroclimatic changes in Western Canada, and increased Athabasca River water usage by oil sands development to the south. This thesis is part of an ongoing, multi-disciplinary project assessing current and past hydrological and ecological conditions in the PAD. Research conducted in this thesis aims to better understand the processes controlling water balance of lakes in the PAD using mainly stable water isotope data collected from lakes and their input sources. Isotope data are used to describe and quantify hydrological processes for individual lakes (seasonal and annual) and across the delta and are supported by other chemical and hydrometric data. An isotopic framework in d18O-d2H-space is developed for the PAD using evaporation-flux-weighted local climate data, and isotopic data collected from a reference basin, lakes throughout the PAD, and lake input sources (i.e., snowmelt, rainfall, and river water). The framework is comprised of two reference lines, the Local Meteoric Water Line, which is based on measured isotopic composition of precipitation, and the Local Evaporation Line, which is based on modelled isotopic composition of reference points. Evaporation pan data is used to assess short-term variations in key isotopic reference values, which are important for addressing short-term changes in the isotopic signature of shallow basins. This framework is used in subsequent chapters including assessment of seasonal and annual water balance of two hydrologically-contrasting shallow lakes, and to quantify the impacts of flood water and snowmelt on a set of 45 lakes in spring 2003. Five years of isotope data using time-series analysis and the isotopic framework suggested that a perched (isolated) lake and its catchment (forest and bedrock) in the northern, relict Peace sector captured sufficient rain, snow, and runoff to maintain a relatively stable water balance, and also that a low-lying lake in the southern, active Athabasca sector was regularly replenished with river water in both spring and summer. Snowmelt and rainfall were found to have diluted the perched basin by an average of 16% and 28 % respectively, while spring and summer floods were found to almost completely flush the low-lying lake. Using the spring 2003 regional dataset, flooded lakes were separated from snowmelt-dominated lakes through use of suspended sediment concentrations, isotope data, and field observations. Application of an isotope mixing model translated d18O values into a range of replenishment amount by either river water or snowmelt, which compared well with hydrological conditions at the time of sampling and previously classified drainage types of the lakes. Spatial mapping of replenishment amounts illustrated flooding of much of the Athabasca sector due to ice-jams, except for two sub-regions isolated from flooding by artificial and natural northern diversion of flow from the Athabasca River. It is also shown that most of the relict landscape of the Peace sector was replenished by snowmelt except for a few low-lying lakes close to the Peace River and its tributaries. Overall, improved understanding of lake and regional hydrology in the PAD, especially the ability to quantify the affects of various lake inputs, will improve the ability to develop effective guidelines and management practices in the PAD as lakes respond to future changes in climate and river discharge.

Several species of North American migratory songbirds reportedly experience seasonal diet shifts involving a shift from an insect diet during the breeding season to one incorporating fruits during migration and non-breeding periods but the extent to which dietary plasticity occurs in migratory songbirds is poorly quantified. Thus, I used stable carbon (ä13C) and nitrogen (ä15N) isotope analyses to evaluate the timing and extent of frugivory throughout the annual life cycle of 16 species of migratory songbirds, representing wide ranges in body size and reported diets. Birds were sampled during spring and fall migration at the Delta Marsh Bird Observatory in 2003. To investigate dietary patterns, I sampled multiple tissues (muscle, liver, whole blood, claws, bone collagen, feathers) as these represent different periods of diet integration due to varying elemental turnover rates.<p>Assuming that relatively low ä15N values represent a fruit diet and relatively high ä15N values represent an insect diet, I expected tissues representing fall migration (liver, blood, and muscle from fall-captured birds) and winter (greater coverts and claws from spring-captured birds) to have lower ä15N values than tissues representing spring migration (liver, blood, and muscle from spring-captured birds) and summer (tail feathers and claws from fall-captured birds) when fruits are presumed to be less common in songbird diets. Based on blood and claw ä15N values, there was no isotopic segregation of species I classified a priori as insectivores or omnivores. For most species, tissue ä15N values showed either no seasonal change or a shift opposite to my prediction (e.g., ä15N values higher in fall birds compared to spring birds). Boreal fruit ä15N values were lower than those for insects; however, ä15N values of agricultural fruits overlapped both boreal fruit and insect values suggesting that food web baselines did not conform to a simple (single) linear trophic-enrichment model. In Yellow-rumped Warblers (Dendroica coronata), within-tissue seasonal comparisons for liver, muscle and blood indicated a fruit diet during fall and winter and an insect diet during spring and summer; claws and feathers of birds captured in spring (representing winter diet) had unexpectedly high ä15N values. Diet-tissue isotopic discrimination factors associated with both a fruit diet and insect diet were taken from the literature and used to correct stable isotope values of tissues to putative diet because, currently, little is known about the nature of factors influencing discrimination factors to be used in simple linear dietary mixing models. There were differences in tissue ä13C and ä15N values depending on which discrimination factor was used. Based on mixing model results for tissue ä15N values, a higher proportion of insects vs. fruits was detected in the diet of Yellow-rumped Warblers for all tissues except muscle and claws. <p>My interpretations are contingent on the fact that the available natural history information, on which guild classifications were based, was correct and that elemental turnover rates and discrimination factors used were accurate. However, much uncertainty remains about the appropriate diet-tissue isotopic discrimination factors corresponding to fruit and insect diets. Due to extensive natural variability of stable nitrogen isotope values in food sources, possible anthropogenic influences and a lack of knowledge of the metabolic processes that can potentially affect stable isotope values, I caution against using stable isotope analysis alone to track frugivory in temperate North American migratory songbirds. Future research should focus on captive studies aimed at determining and validating discrimination factors of various tissues, particularly claws and feathers, for birds feeding on varying proportions of fruits and insects. Additionally, more information on the dietary habits of these migratory songbirds is needed, as previous estimates of insectivory and frugivory in songbirds may not be accurate.

Soot prediction in realistic systems is one of the most challenging problems in theoretical and applied combustion. Soot formation as a chemical process is very complicated and not fully understood up to the moment. The major difficulty stems from the chemical complexity of the soot formation processes as well as its strong coupling with the other thermochemical and fluid processes that occur simultaneously. Soot is a major byproduct of incomplete combustion, having a strong impact on the environment, as well as the combustion efficiency. Therefore, it needs to be predicted in realistic configurations in an accurate and yet computationally efficient way. In the current study, a new soot formation subgrid model is developed and reported here. The new model is designed to be used within the context of the Large Eddy Simulation (LES) framework, combined with Linear Eddy Mixing (LEM) as a subgrid combustion model. The final model can be applied equally to premixed and non-premixed flames over any required geometry and flow conditions in the free, the transition, and the continuum regimes. The soot dynamics is predicted using a Method of Moments approach with Lagrangian Interpolative Closure (MOMIC) for the fractional moments. Since, no prior knowledge of the particles distribution is required, the model is generally applicable. The effect of radiation is introduced as an optically thin model. As a validation the model is first applied to a non-premixed non-sooting flame, then a set of canonically premixed flames. Finally, the model is validated against a non-premixed jet sooting flame. Good results are predicted with reasonable accuracy.

As ever-increasing levels of carbon dioxide alter the chemistry of the Earth’s atmosphere, understanding the global carbon cycle becomes increasingly important. A particularly important component is the riverine carbon cycle, as rivers are the primary conduits for dissolved inorganic carbon from terrestrial watersheds to ocean basins. Stable carbon isotopes (13C/12C) were collected weekly and input into the mixing model IsoSource to delineate seasonal carbon sourcing along two nested basins in the upper Green River System, Kentucky. In the more siliciclastic upstream catchment, dissolved inorganic carbon (DIC) was primarily derived from soil respiration (34%). Groundwater dissolving carbonate bedrock and carbonate dissolution/precipitation reactions contributed 31% and 11%, respectively. The more carbonate-dominated downstream catchment also was influenced greatly by soil respiration (35%). Due to the more pronounced levels of carbonate bedrock, carbonate reactions contributed double that of the upstream catchment (20%), with groundwater contributing 22%. Seasonally, the upstream basin gathered most DIC from soil respiration from late spring to winter. Early spring precipitation and still limited photosynthesis caused the primary carbon sourcing to shift to groundwater. Downstream, the primary source throughout the entire study period was soil respiration. Collectively, this study provides insight into the carbon cycling process in a mid-latitude, karstic river using carbon isotope sourcing to aid in the quantification of global carbon flux in the critical zone.

Dados EASE-grid do Special Sensor Microwave-Imager (SSM/I) e imagens classificadas ASAR wideswath (WS), cobrindo a Península Antártica (PA), foram processadas e usadas em um Modelo Linear de Mistura Espectral (MLME), para a análise subpixel da Zona Superficial de Neve Úmida (ZSNU) em imagens SSM/I. As proporções dos componentes puros (imagens-fração) da área de estudo (ZSNU, Zona Superficial de Neve Seca e rochas) foram derivadas das imagens ASAR classificadas. As imagens-fração e imagens SSM/I co-registradas de mesma data (bandas 19H, 19V, 37H e 37V) foram usadas no MLME para estimar as assinaturas espectrais desconhecidas (i.e., temperatura de brilho em cada banda SSM/I). Essas assinaturas espectrais foram então usadas no MLME para estimar as imagens-fração da ZSNU, as quais foram comparadas com as imagens-fração ASAR correspondentes, por meio do cálculo do coeficiente de correlação. Foram identificadas as duas assinaturas espectrais que resultaram nos dados mais correlacionados, sendo também calculadas as correlações das imagens-fração da ZSNU resultantes do uso no MLME dos valores médio e mediano das assinaturas espectrais mais similares. Os valores medianos dessas assinaturas espectrais produziram as imagens-fração da ZSNU mais correlacionadas, que tiveram uma precisão global de classificação média (PGCM) de 95,6% e 97,3%, nas imagens de primavera e outono, respectivamente (amplitude de classes de 0,1), e uma PGCM de 72,6% nas imagens de verão (amplitude de classes de 0,2). Essas assinaturas espectrais medianas foram então usadas no MLME para estimar, com esses níveis de precisão global, a intensidade e extensão da ZSNU na PA, pelo uso de imagens calibradas SSM/I e SMMR (Scanning Multichannel Microwave Radiometer), possibilitando assim a análise diária e em nível subpixel dessa fácie superficial, de 1978 a 2008. Na análise espacial das imagens-fração da ZSNU estimadas, observou-se que o derretimento superficial médio começava no final de outubro e terminava no final de março, com auge em 7 de janeiro (cerca de 172.237 km2 ou 31,6% da área da PA). A área total mediana da ZSNU no verão foi de aproximadamente 105.100 km2. A análise de regressão com as imagens-fração dos verões entre 1978-1979 a 2007-2008 revelou a tendência de redução da área da ZSNU, totalizando 330,854 km2 nesse período. Todavia, essa tendência não é estatisticamente significante, devido à alta variabilidade interanual da área da ZSNU na PA. Forte derretimento superficial ocorreu nos verões de 1984-1985 (176.507,289 km2) e 1989-1990 (172.681,867 km2), enquanto fraco derretimento, nos verões de 1993-1994 (26.392,208 km2) e 1981-1982 (23.244,341 km2). O mais persistente e intenso derretimento superficial foi observado nas plataformas de gelo Larsen, Wilkins, George VI e Wordie e isto foi relacionado com os eventos de fragmentação e desintegração dessas massas de gelo, ocorridos nas últimas décadas. O derretimento superficial está intimamente relacionado com a estabilidade do sistema glacial antártico e com mudanças no nível médio dos mares. Esse poderia ser monitorado em toda a Antártica, por meio da análise subpixel de imagens SMMR e SSM/I proposta neste estudo. / Special Sensor Microwave-Imager (SSM/I) EASE-grid data and classified ASAR wideswath (WS) images, covering the Antarctic Peninsula (AP), were processed and used in a Spectral Linear Mixing Model (SLMM) for a subpixel analysis of the Wet Snow Zone (WSZ) in SSM/I images. The components’ proportions (fraction images) of the endmembers in the study area, namely WSZ, Dry Snow Zone and rock outcrops, were derived from classified ASAR images. These fraction images and co-registered SSM/I images (bands 19H, 19V, 37H and 37V), acquired on the same date, were used in the SLMM to estimate the unknown spectral signatures (i.e., brightness temperature on each SSM/I band). These spectral signatures were used to estimate WSZ fraction images, which were compared with the ASAR fraction images, by calculating the correlation coefficients. This work identified two spectral signatures that produced the most correlated data, and determined the WSZ fraction images correlations resulting from the use, in the SLMM, of the mean and median values of the most similar spectral signatures. The median values of these spectral signatures produced the most correlated WSZ fraction images, which had an average overall classification accuracy (AOCA) of 95.6% and 97.3% for spring and autumn fraction images, respectively (class range of 0.1), and an AOCA of 72.6% for summer fraction images (class range of 0.2). These median spectral signatures were then used in a SLMM to estimate accurately the WSZ intensity and its extension on the AP, by using calibrated SSM/I and SMMR (Scanning Multichannel Microwave Radiometer) imageries, allowing a daily subpixel analysis of this glacier facie on the AP from 1978 to 2008. Based on the spatial analysis of the WSZ fraction images, it was observed that melt primarily takes place in late October and ends in late March, with peak on January 7th (about 172,237 km2 or 31,6% of the AP area). The WSZ median total area in summer was about 105,100 km2. Regression analysis over the 1978-1979 to 2007-2008 summers, revealed a negative interanual trend in surface melt of 330.854 km2. Nevertheless, this trend inference is not statistically significant, due to the high WSZ interanual variability. Extremely high melt occurred in the 1984-1985 (176,507.289 km2) and 1989-1990 (172,681.867 km2) summers, while extremely weak melt occurred in the 1993-1994 (26,392.208 km2) and 1981-1982 (23,244.341 km2) summers. The most persistent and intensive melt was observed on Larsen, Wilkins, George VI and Wordie ice shelves and it was related to the break-up and disintegration events that occurred on these glaciers in the last decades. Surface melting is closely related to the stability of the Antarctic glacial system and global sea level changes. It could be monitored for the whole Antarctica, by using the WSZ subpixel analysis in SMMR and SSM/I imageries proposed by this study.

Dados EASE-grid do Special Sensor Microwave-Imager (SSM/I) e imagens classificadas ASAR wideswath (WS), cobrindo a Península Antártica (PA), foram processadas e usadas em um Modelo Linear de Mistura Espectral (MLME), para a análise subpixel da Zona Superficial de Neve Úmida (ZSNU) em imagens SSM/I. As proporções dos componentes puros (imagens-fração) da área de estudo (ZSNU, Zona Superficial de Neve Seca e rochas) foram derivadas das imagens ASAR classificadas. As imagens-fração e imagens SSM/I co-registradas de mesma data (bandas 19H, 19V, 37H e 37V) foram usadas no MLME para estimar as assinaturas espectrais desconhecidas (i.e., temperatura de brilho em cada banda SSM/I). Essas assinaturas espectrais foram então usadas no MLME para estimar as imagens-fração da ZSNU, as quais foram comparadas com as imagens-fração ASAR correspondentes, por meio do cálculo do coeficiente de correlação. Foram identificadas as duas assinaturas espectrais que resultaram nos dados mais correlacionados, sendo também calculadas as correlações das imagens-fração da ZSNU resultantes do uso no MLME dos valores médio e mediano das assinaturas espectrais mais similares. Os valores medianos dessas assinaturas espectrais produziram as imagens-fração da ZSNU mais correlacionadas, que tiveram uma precisão global de classificação média (PGCM) de 95,6% e 97,3%, nas imagens de primavera e outono, respectivamente (amplitude de classes de 0,1), e uma PGCM de 72,6% nas imagens de verão (amplitude de classes de 0,2). Essas assinaturas espectrais medianas foram então usadas no MLME para estimar, com esses níveis de precisão global, a intensidade e extensão da ZSNU na PA, pelo uso de imagens calibradas SSM/I e SMMR (Scanning Multichannel Microwave Radiometer), possibilitando assim a análise diária e em nível subpixel dessa fácie superficial, de 1978 a 2008. Na análise espacial das imagens-fração da ZSNU estimadas, observou-se que o derretimento superficial médio começava no final de outubro e terminava no final de março, com auge em 7 de janeiro (cerca de 172.237 km2 ou 31,6% da área da PA). A área total mediana da ZSNU no verão foi de aproximadamente 105.100 km2. A análise de regressão com as imagens-fração dos verões entre 1978-1979 a 2007-2008 revelou a tendência de redução da área da ZSNU, totalizando 330,854 km2 nesse período. Todavia, essa tendência não é estatisticamente significante, devido à alta variabilidade interanual da área da ZSNU na PA. Forte derretimento superficial ocorreu nos verões de 1984-1985 (176.507,289 km2) e 1989-1990 (172.681,867 km2), enquanto fraco derretimento, nos verões de 1993-1994 (26.392,208 km2) e 1981-1982 (23.244,341 km2). O mais persistente e intenso derretimento superficial foi observado nas plataformas de gelo Larsen, Wilkins, George VI e Wordie e isto foi relacionado com os eventos de fragmentação e desintegração dessas massas de gelo, ocorridos nas últimas décadas. O derretimento superficial está intimamente relacionado com a estabilidade do sistema glacial antártico e com mudanças no nível médio dos mares. Esse poderia ser monitorado em toda a Antártica, por meio da análise subpixel de imagens SMMR e SSM/I proposta neste estudo. / Special Sensor Microwave-Imager (SSM/I) EASE-grid data and classified ASAR wideswath (WS) images, covering the Antarctic Peninsula (AP), were processed and used in a Spectral Linear Mixing Model (SLMM) for a subpixel analysis of the Wet Snow Zone (WSZ) in SSM/I images. The components’ proportions (fraction images) of the endmembers in the study area, namely WSZ, Dry Snow Zone and rock outcrops, were derived from classified ASAR images. These fraction images and co-registered SSM/I images (bands 19H, 19V, 37H and 37V), acquired on the same date, were used in the SLMM to estimate the unknown spectral signatures (i.e., brightness temperature on each SSM/I band). These spectral signatures were used to estimate WSZ fraction images, which were compared with the ASAR fraction images, by calculating the correlation coefficients. This work identified two spectral signatures that produced the most correlated data, and determined the WSZ fraction images correlations resulting from the use, in the SLMM, of the mean and median values of the most similar spectral signatures. The median values of these spectral signatures produced the most correlated WSZ fraction images, which had an average overall classification accuracy (AOCA) of 95.6% and 97.3% for spring and autumn fraction images, respectively (class range of 0.1), and an AOCA of 72.6% for summer fraction images (class range of 0.2). These median spectral signatures were then used in a SLMM to estimate accurately the WSZ intensity and its extension on the AP, by using calibrated SSM/I and SMMR (Scanning Multichannel Microwave Radiometer) imageries, allowing a daily subpixel analysis of this glacier facie on the AP from 1978 to 2008. Based on the spatial analysis of the WSZ fraction images, it was observed that melt primarily takes place in late October and ends in late March, with peak on January 7th (about 172,237 km2 or 31,6% of the AP area). The WSZ median total area in summer was about 105,100 km2. Regression analysis over the 1978-1979 to 2007-2008 summers, revealed a negative interanual trend in surface melt of 330.854 km2. Nevertheless, this trend inference is not statistically significant, due to the high WSZ interanual variability. Extremely high melt occurred in the 1984-1985 (176,507.289 km2) and 1989-1990 (172,681.867 km2) summers, while extremely weak melt occurred in the 1993-1994 (26,392.208 km2) and 1981-1982 (23,244.341 km2) summers. The most persistent and intensive melt was observed on Larsen, Wilkins, George VI and Wordie ice shelves and it was related to the break-up and disintegration events that occurred on these glaciers in the last decades. Surface melting is closely related to the stability of the Antarctic glacial system and global sea level changes. It could be monitored for the whole Antarctica, by using the WSZ subpixel analysis in SMMR and SSM/I imageries proposed by this study.