This study is a test of a methodology to predict changes in elevation and shoreline position of coastal wetlands in Trinity Bay, Texas, in response to projected sea level rise. The study combines numerical modeling and a geographic information system. A smoothing technique is used on a United States Geographical Survey (USGS) digital elevation model to obtain elevation profiles that more accurately represent the gently sloping wetlands surface. The numerical model estimates the expected elevation change by raster cell based on input parameters of predicted sea level rise, mineral and organic sedimentation rates, and sediment autocompaction rates. A GIS is used to display predicted elevation changes and changes in shoreline position as a result of four projected sea level rise scenarios over the next 100 years. Results demonstrate that this numerical model and methodology are promising as a technique of modeling predicted elevation change and shoreline migration in wetlands. The approach has potential utility in coastal management applications.

Cette thèse a pour objectif d’identifier les trajectoires plurimillénaires des écosystèmes de Corse à basse et moyenne altitude sous la triple influence des forçages climatiques, eustatiques et anthropiques à travers l’étude des assemblages d’insectes fossiles et des données paléobotaniques disponibles ou nouvellement acquises. Cette approche multidisciplinaire a été appliquée sur trois séquences sédimentaires prélevées à l’étang du Greco sur l’île Cavallo, au marais de Cannuta et à la tourbière de Bagliettu.Les résultats obtenus révèlent des changements majeurs dans la structuration du couvert végétal. Des signes d’ouverture du paysage apparaissent sur Cavallo et à Cannuta dès 5500-5000 cal. BP. Ils coïncident avec des indices d’activités des sociétés insulaires, lesquelles s’intensifient après 3000 cal. BP et plus particulièrement depuis 1000 ans à Bagliettu. Notre étude suggère que la sensibilité et la réponse des zones humides littorales face à la remontée relative du niveau marin dépend du contexte géomorphologique. Sur l’île Cavallo où le relief est faible, la transgression marine induit une augmentation de la salinité dans l’étang du Greco vers 3700 cal. BP, qui provoque une chute irréversible de la diversité des coléoptères aquatiques et hygrophiles. Au marais de Cannuta, où l’érosion des versants a favorisé la progradation de la plaine alluviale, notre étude montre une diminution de l’influence marine après 5000 cal. BP et une diversification de cette même entomofaune à partir de 1200 cal. BP. À Bagliettu, nous avons démontré l’importance des changements hydro-morphologiques des rivières dans la dynamique des écosystèmes tourbeux attenants et de leur entomofaune. / This thesis aims to define the multi-millennial trajectories of Corsican ecosystems under the climatic, eustatic and anthropic factors via the study of fossil insect assemblages and previous or new palaeobotanical data. This multidisciplinary approach was carried out at low and middle elevation on three sedimentary archives from the Greco pond on Cavallo Island, the Cannuta marsh and the Bagliettu peat-bog. The results reveal major changes in the structure of the vegetation cover over the last 7000 years. Signs of more open landscapes occurred on Cavallo and in Cannuta from 5500-5000 cal. BP. They coincide with bio-markers of insular societies activities, which increased from 3000 cal. BP onward and more particularly during the last 1000 years at Bagliettu.This study also suggests that the sensitivity and the response of coastal wetlands to the relative sea-level rise depend on the geomorphological context. On the low-lying Cavallo Island, marine transgression induced an increase of salt conditions in the Greco pond from 3700 cal. BP, which in turn, caused an irreversible loss of aquatic and hygrophilous beetle diversity. In Cannuta marsh, erosion on catchment slopes favoured the progradation of the coastal floodplain and the results reveal a progressive decrease of the marine influence from 5000 cal. BP as well as a diversification of this entomofauna over the last 1200 years. In Bagliettu, the results show how hydro-morphological changes of the rivers impact the dynamics of adjacent peaty ecosystems and beetle diversity.

Havsnivåhöjning och kraftigare stormar är två konsekvenser av klimatförändringarna som i sin tur leder till ökad erosion och översvämning. När kustområdena omvandlas, och i värsta fall försvinner, påverkas människors möjligheter att bo och leva där. För att minska risken att sociala, ekonomiska och ekologiska värden går förlorade krävs att vi planerar skyddsåtgärder för havsnivåhöjning, erosion och översvämning samt planerar för hur vi kan anpassa oss efter dessa föränderliga förutsättningar.  Syftet med denna studie är att undersöka hur svenska kommuner planerar för klimatanpassning idag och hur planerad reträtt skulle kunna användas som strategi i Sverige. Flexmark, en idé som tagits fram i ett projekt lett av SGI, inkluderades i studien för att ta reda på om den kan underlätta planeringen för klimatanpassning i Sverige. För att genomföra undersökningen valdes de skånska kommunerna Ystad, Trelleborg och Lomma ut samt Länsstyrelsen Skåne och Region Skåne för djupare studie. I studien undersöktes plandokument rörande klimatanpassning framtagna av kommunerna, regionen och länsstyrelsen. En intervjustudie med informanter från samtliga organisationer kompletterade studien. Resultatet visade att de valda kommunerna jobbar med klimatanpassning men än så länge inte med planerad reträtt. Osäkerhet kring vad som är möjligt enligt PBL, motstånd hos kommuninvånare samt frågan om vem som skulle ansvara för och finansiera reträtten angavs som några av de aspekter som gör strategin svår att införa.  Naturbaserade lösningar och vallar är klimatanpassningsåtgärder som används inom kommunerna idag. Majoriteten av de intervjuade anser att planerad reträtt kommer behövas i svensk planering i framtiden men att det idag inte finns möjlighet eller vilja att utföra en sådan åtgärd. För att ge inspiration till hur reträtt kan planeras och hanteras presenteras tre internationella exempel som en referensram för vad som varit framgångsfaktorer för lyckade reträtter i andra länder. De internationella fallen tillsammans med intervjuerna och dokumentstudien analyseras för att undersöka hur planerad reträtt skulle kunna användas som strategi i Sverige. Idéen om flexmark fick ett generellt positivt mottagande bland informanterna i intervjustudien och skulle med fördel kunna användas som verktyg inom strategin planerad reträtt.  Tillvägagångssätt för planerad reträtt i en svensk kontext analyserades utifrån styrningsmodellerna hierarkisk styrning, samarbetsstyrning samt självstyrning som presenterar olika alternativ för initiativ, styrning och finansiering av planerad reträtt. Samarbetsstyrd planerad reträtt, med initiativtagande och styrning på lokal nivå samt rätt till ekonomisk stöttning från nationell nivå, är enligt forskarna i den här studien, den strategi som lämpar sig bäst inom svensk planering. För att planerad reträtt ska få ett lyckat resultat krävs att berörda parter involveras tidigt och att kontinuerlig dialog förs mellan dem under processen. / Sea level rise and increased intensity of storms are two consequences of climate change which in turn lead to increased erosion and flooding. When coastal areas are transformed, and in the worst case disappear, many people's everyday life will be affected. To reduce the risk of social, economic and ecological values ​​being lost, we need to plan for protection against sea level rise, erosion and flooding and plan for how we can adapt to these changing conditions. The purpose of this study is to investigate how Swedish municipalities plan for climate change adaptation today and how planned retreats could be used as a strategy in Sweden. Flexmark, an idea developed in a project led by SGI, was included in the study to find out if it can facilitate planning for climate change adaptation in Sweden. To carry out the investigation, Skånes’s municipalities Ystad, Trelleborg and Lomma were selected, as well as the County Administrative Board of Skåne and Region Skåne for deeper study. The study examined planning documents concerning climate change adaptation produced by the municipalities, the region and the county administrative board. An interview study with informants from all organizations supplemented the study. The results showed that the selected municipalities are working with climate change adaptation but so far not with planned retreats. Uncertainties regarding what is possible according to the Planning and Building Act, opposition from municipal residents and the matter of who would be responsible for and finance the retreat were stated as some of the aspects that make the strategy difficult to implement. Nature-based solutions and dikes are climate change adaptation measures used in municipalities today. The majority of the interviewees believe that planned retreats will be needed in Swedish planning in the future, but today there is no opportunity or willingness to carry out such a measure. To provide inspiration for how retreats can be planned and managed, three international examples are presented as a reference framework for what have been key factors for successful retreats in other countries. The international cases together with the interviews and the document study are analyzed to investigate how planned retreats could be used as a strategy in Sweden. The responses to ​​flexmark were generally positive among the informants and the idea could be used as a tool within the strategy planned retreat. Approaches of planned retreat in a Swedish context were analyzed based on the governance modes hierarchical governance, co-governance and self-governance, which present various alternatives for initiative, governance and financing of planned retreats. Cooperative planned retreat, initiated and governed at local level with financial support from national level, is according to the researchers of this study, the strategy that is best suited in Swedish planning. In order for a planned retreat to generate a successful result, it is necessary that all affected parties are involved early and that a continuous dialogue is conducted between them during the process.

This study uses the predictive modeling program Sea-Levels Affecting Marshes Model (SLAMM) to evaluate sea-level rise hazards, such as erosion and inundation, on coastal archaeological sites with a vertical rise of sea level of .98 meters from 2006 to 2100. In total 177 archaeological site locations were collected and georeferenced over GIS outputs maps of wetlands, erosion presence, surface elevation, and accretion. Wetlands data can provide useful information about characteristics of the wetland classes, which make a difference in the ability for coastal archaeological sites to combat sea level rise. Additionally, the study evaluated predicted erosion of archaeological sites by presence or absence of active erosion on a cell-by-cell basis. Elevation map outputs relative to mean tide level allowed for a calculation of individual archaeological site datums to use NOAA tidal databases to identify the potential for their inundation. Accretion maps acquired from the SLAMM run determined the potential for the archaeological site locations to combat rising sea levels and potentially provide protection from wave effects. Results show that the most significant hazard predicted to affect coastal archaeological sites is inundation. Approximately 54% of the total archaeological sites are predicted to be inundated at least half the time by 2100. The hazard of erosion, meanwhile, is expected to affect 33% of all archaeological sites by the end of the century. Although difficult to predict, the study assumes that accretion will not be able to keep pace with sea-level rise. Such findings of hazards prove that SLAMM is a useful tool for predicting potential effects of sea-level rise on coastal archaeological sites. With its ability to customize and as it is complementary, it provides itself not only an economical choice but also one that is adaptable to many scenarios.

Bakgrund: Klimatförändringarna medför osäkerheter som är en utmaning för samhällsplaneringen. Utifrån Plan- och bygglagen (2010:900) har kommunerna ansvar att planlägga mark inom sitt geografiska område. Kustområden är i många fall högt utvecklade, tätbefolkade och ekonomiskt viktiga, men havsnivåhöjningen förväntas orsaka komplexa risker som kan innefatta förlust av liv, mark och försörjningsmöjligheter om inga åtgärder implementeras. Det är därför allmänt erkänt att klimatanpassningen inte kan vänta. I Sverige har den unika landhöjningen en mildrande effekt på havsnivåhöjningen. Studiens syfte är att undersöka hur svenska kommuner hanterar dessa osäkerheter i detaljplaneprocessen med utgångspunkt i olika teorier om beslutsfattande. Metod: Studien har utgått ifrån en flerfallsstudiedesign för att bygga upp fall som kan jämföras och ställas emot varandra för att få ut generaliserande kunskaper. Studien har följt en induktiv kvalitativ metod för att kunna sammanställa stora kvantiteter av underlag och för att ha datan i fokus under hela processen. Fallen Helsingborgs stad och Varbergs kommun har valts ut genom ett strategiskt urval, kommunerna har aktiva eller nyligen beslutade detaljplaner i kustområdet. Två datakällor har använts i studien: expertintervjuer från de utvalda fallen och dokumentation kopplat de utvalda fallen. Transkriberingen av expertintervjuerna och dokumenten har analyserats genom en kvalitativ innehållsanalys. Resultat: Båda kommuner har i detaljplanearbetet identifierat en risk med översvämning från havet. Helsingborgs stad har ett styrdokument, antaget av fullmäktige, med specificerade säkringsnivåer för byggnation i närheten av kusten. Denna nivå har använts fram tills idag, men den diskuteras i ett separat planuppdrag som finns inom kommunen på grund av nytillkommen forskningsbaserad kunskap. Hållbarheten för byggnationen är viktig och IPCC:s scenario RCP8,5 har använts för att ta fram nivåer och tidsperspektivet är år 2150. Befintlig bebyggelse kan medföra att ett kortare tidsperspektiv används för att passa in i området. Varbergs kommun identifierar att kunskapen förändrats sedan deras styrdokument antogs och tar kontakt med olika myndigheter för att få kunskap om hur de ska arbeta. Dessa myndigheter säger olika saker och till slut meddelar Länsstyrelsen att en expertutredning måste genomföras. Kommunen har valt att ta höjd för värsta scenariot år 2150, men kan inte höja marken tillräckligt mycket på grund av befintlig byggnation och har därför en föreskrift i detaljplanen om färdigt golv-nivå. Slutsats: Havsnivåhöjningen innebär att komplexa och kombinerade risker, men kusten är populärt att bosätta sig vid och kortsiktig tillväxt går före säkerhet även om områden identifieras som olämpliga av tjänstepersoner. Osäkerheten och ständigt tillkommande ny kunskap medför en utmaning för kommunerna. Kommunerna vill bidra till att skapa hållbara bostadsområden, men också att den befintliga platsens förutsättningar ska kunna inverka på klimatsäkringen. Detaljplaner påverkas tydligt av myndigheter och experter. Helsingborg använder sig av beslutsstrategierna försiktighetsprincipen och As Low As Reasonably Practicable (ALARP) i samhällsplaneringen, medan Varberg använder ALARP. Ett nytt teoretiskt ramverk har tagits fram under studiens process. / Background: Climate change brings uncertainties that pose challenges for urban planning. Under the Swedish Planning and Building Act (2010:900), municipalities are responsible for land-use planning within their defined geographical area. Coastal areas are in many cases highly developed, densely populated and economically important, and sea level rise is expected to expose these areas to complex risks that may result in loss of life, land and livelihoods if actions are not implemented. It is therefore widely recognised that climate adaptation cannot wait. Land elevation in Sweden have a mitigating effect on the sea level rise. The aim of this study is to investigate how Swedish municipalities deal with these uncertainties in the zone planning process based on different theories of decision making. Method: The study is based on a multi-case study design in order to build up cases that can be compared and weighed against each other in order to gain generalizable knowledge. Qualitative method was used as an inspiration to compile large amounts of evidence and to keep the focus on the collected data throughout the process. The cases Helsingborg City and Varberg Municipality have been selected through a strategic selection: the municipalities have active or recently adopted zone plans in the coastal area. Two data sources have been used in the study: expert interviews from the selected cases and documentation linked to the selected cases. The transcripts of the expert interviews and the documents have been analysed through a qualitative content analysis. Results: Both municipalities have identified a risk of flooding from the sea in the zone planning process. The city of Helsingborg has a policy document, adopted by the municipal council, with specified safety levels for construction near the coast. This level has been used for zone planning until now, but it is under discussion in a separate ongoing planning process within the municipality due to newly available research-based knowledge. The sustainability of the new construction is the most important factor for climate adaptation. The IPCC scenario RCP8.5 has been used as a safety measure during the process and the time perspective is set to 2150. In other areas a shorter time perspective might be used due to present development. Varberg municipality acknowledges that their current policy document is outdated due to new and accumulated knowledge on the effects of climate change. The municipality has been in contact with various governmental agencies to identify suitable actions. However, the prerequisites given by different authorities are conflicting, and the County Administrative Board announced that an expert study must be conducted. The municipality has chosen the worst-case scenario of the year 2150 as a condition in their planning. However, since the ground cannot be sufficiently raised due to existing development, they have a finished-floor-level ordinance in the zone plan.  Conclusion: Sea level rise poses complex and combined risks, but due to popularity, short-term growth takes precedence over safety in urban planning even when areas are identified as unsuitable by the civil servants. Uncertainty and the constant addition of new knowledge pose a challenge for local authorities. Municipalities want to build sustainable residential areas, but the conditions of the existing buildings at the location can have an impact on the climate adaptation. Helsingborg uses the precautionary principle and As Low As Reasonably Practicable (ALARP) decision-making strategies in their urban planning, while Varberg uses ALARP. During the process of the study a new theoretical framework have evolved.

The tidal prism, or the volume of water exchanged from the sea to an estuary from mean low to mean high tide, influences system hydrodynamics and ecological functioning. Since 1884, the tidal prism in Morro Bay, California has been estimated to be decreasing over time due to sedimentation from upstream practices. What is the current tidal prism in Morro Bay and how will that change with sea level rise? How will eelgrass respond to rising sea levels? For this study, inexpensive tidal gauges were deployed at four locations in Morro Bay from March to August 2023 to measure spatially varying tidal elevations and datums within the bay. I utilized a Digital Elevation Model (DEM) and tidal information to determine volumes of water in Morro Bay. Estimated sea level rise scenarios were utilized to project the 2022 tidal prism into the years 2050 and 2100. Additionally, I estimated the 2019 and 2022 viable eelgrass habitat area using the vertical growth range. I estimated the future potential viable habitat area in the years 2050 and 2100 using estimated sea level rise scenarios. Future projections were made assuming no change in bathymetry over time. Different instruments used to obtain water levels yielded up to ~4 percent differences in the tidal prism estimate. Measurement uncertainty in the monthly tidal datums produced ~3 percent uncertainty within the tidal prism estimate. Compared to the tidal prism in August 2019, the August 2022 tidal prism was lower by ~2 percent. Compared to the tidal prism in August 2019, the August 2023 tidal prism estimated from two nearly co-located tidal instruments at the mouth of Morro Bay were higher by ~5 and ~7 percent, respectively. Spatially varying tidal datums in Morro Bay were found to affect the tidal prism by up to ~3 percent, compared to tidal prism estimates using only a tidal datum near the estuary mouth. However, the effect of spatially varying tidal datums on the tidal prism is the same order of magnitude as measurement uncertainty and is thus not statistically significant. As sea levels rise, the tidal prism is projected to increase by ~40 percent by 2100 from 2022 under the most extreme scenario, H++. Initially, as sea levels rise, the potential viable eelgrass habitat area will increase from the area in 2022 (1108 acres (4.47E+06 m2)). After sea levels rise to 1.5 m above 2000 levels, the potential viable eelgrass area will have reached a maximum area of 1938 acres (7.82E+06 m2). However, under SLR scenario H++, potential viable habitat area is predicted to decrease by up to 59% by 2100 from 2022. The tidal prism, or the volume of water exchanged from a bay to the seathe sea to an estuary from mean lowhigh to mean highlow tide, influences system hydrodynamics and ecological functioning. Since 1884, the tidal prism in Morro Bay, California has been estimated to be decreasing over time due to sedimentation from upstream practices. What is the current tidal prism in Morro Bay and how will that change with sea level rise? How will eelgrass respond to rising sea levels? For this study, inexpensive tidal gauges were deployed at four locations in Morro Bay from March to August 2023 to obtain measure spatially varying tidal elevations and datums within the bay. I utilized a Digital Elevation Model (DEM) and tidal information from NOAA to determine volumes of water in Morro Bay at the estimated monthly mean tidal datums. Estimated sea level rise scenarios were utilized to project the 2022 tidal prism into the years 2050 and 2100. Additionally, I estimated the 2019 and 2022 viable eelgrass habitat area using the vertical growth range. I estimated the future potential viable habitat area in the years 2050 and 2100 using estimated sea level rise scenariosfor various sea level rise scenarios.Future projections were made assuming no change in bathymetry over time. Different instruments used to obtainwater levels yielded up to ~4 percent differences in the tidal prism estimate. Measurement uncertainty in the monthly tidal datums produced~3 percent uncertainty within the tidal prism estimate. Compared to the tidal prism in August 2019, the August 2022 tidal prism from Stilltek decreasedwas lower by ~2.05 percent. Compared to the tidal prism in August 2019, the August 2023 tidal prism estimated from the Stilltek gauge and the Cal Poly Coast Guard gaugetwo nearly co-located tidal instruments at the mouth of Morro Bay increased were higher by ~5.06 and ~6.777 percent, respectively. Spatially varying tidal datums in Morro Bay were found to affect the tidal prism by up to ~2.883 percent, compared to tidal prism estimates using only a tidal datum near the estuary mouth. However, the effect of spatially varying tidal datums on the tidal prism is the same order of magnitude as measurement uncertainty and is thus not statistically significant. As sea levels rise, the tidal prism is projected to increase by ~to a maximum of 40 percent by 2100 from 2022 under the most extreme scenario, H++. InitiallyInitially, as sea levels rise, the potential viable eelgrass habitat area will increase from the area in 2022 (1108 acres (4.47E+06 m2)). ABut after sea levels rise to 1.5 m above 2000 levels, the potential viable eelgrass areas will have reached the thresholda maximum area of 1938 acres (7.82E+06 m2). However, under SLR scenario H++, potential viable habitat area is predicted to decrease by up to 59% by 2100 from 2022.

This thesis examines the readiness and perception in the regions of Gothenburg and Bremen towards future sea level rise. It does so through the theoretical lens of risk psychology / policy research and of climate science research. Results are built on some of the most recent research of these fields, as well as interviews with 14 people on the local, regional and national level in Germany and Sweden. Key findings of this thesis are that both contexts struggle to deal with the great uncertainties inherent in sea level rise. On the German North Sea coast, there is long experience with sea level variation and extensive civil institutions created to deal with storm surges, dikes and sea level rise which may partially compensate for inherent vulnerability to future sea level rise in this region. The novelty of sea level rise in Gothenburg and Sweden means that it is in the process of creating similar institutions and national-regional divisions of responsibility from scratch. The great uncertainty around the pace and extent of future sea level rise is however an obstacle which may have to be overcome before a more coherent response may be developed. / Denna uppsats undersöker beredskap och uppfattningar kring framtida havsnivåhöjningar i Göteborg och Bremen. Detta görs med de teoretiska ansatserna riskpsykologi / beslutspsykologi och grundläggande klimatvetenskap. Uppsatsens resultat bygger på de senaste resultaten inom dessa fält, samt intervjuer med 14 personer på lokal, regional och nationell nivå i Tyskland och Sverige. Efter genomförd studie kan konstateras att bägge kontext har svårigheter att hantera de stora osäkerheter som havsnivåhöjningen medför. Tyska Nordsjökusten har mycket lång erfarenhet och kapabla offentliga institutioner vilka skapats för att hantera skyddsvallar, sjunkande landnivåer och stormfloder, vilket balanserar det prekära läge som området annars står inför. I Göteborg och i Sverige är havsnivåhöjning något fundamentalt nytt, vilket innebär att man nu försöker skapa liknande institutioner och ansvarsfördelning mellan nationellt och regionalt som de Bremen och Tyskland redan har. Ett hinder för detta är de stora osäkerheter som råder kring hastighet och absolut nivå på framtida havsnivåhöjningar. Dessa osäkerheter kan komma behöva reduceras innan problemet börjar hanteras på ett mer samordnat sätt.

Le niveau de la mer est une des variables climatiques essentielles dont la variabilité résulte de nombreuses interactions complexes entre toutes les composantes du système climatique sur une large gamme d'échelles spatiales et temporelles. Au cours du XXème siècle, les mesures marégraphiques ont permis d'estimer la hausse du niveau de la mer global entre 1,6 mm/an et 1,8 mm/an. Depuis 1993, les observations faites par les satellites altimétriques indiquent une hausse du niveau de la mer plus rapide de 3,3 mm/an. Grâce à leur couverture quasi-globale, elles révèlent aussi une forte variabilité du niveau de la mer à l'échelle régionale, parfois plusieurs fois supérieure à la moyenne globale du niveau de la mer. Compte tenu de l'impact très négatif de l'augmentation du niveau de la mer pour la société, sa surveillance, la compréhension de ses causes ainsi que sa prévision sont désormais considérées comme des priorités scientifiques et sociétales majeures. Dans cette thèse, nous validons d'abord les variations du niveau de la mer mesurées par la nouvelle mission d'altimétrie satellitaire, SARAL-AltiKa, en comparant les mesures avec celles de Jason- 2 et des marégraphes. Un autre volet de cette première partie de thèse a consisté à estimer les parts respectives des facteurs responsables des variations du niveau de la mer depuis 2003 en utilisant des observations issues de l'altimétrie satellitaire (missions altimétrique Jason-1, Jason-2 et Envisat), de la mission GRACE, et des profils de température et salinité de l'océan par les flotteurs Argo. Une attention particulière est portée à la contribution de l'océan profond non 'vue' par Argo. Nous montrons que les incertitudes dues aux approches du traitement des données et aux erreurs systématiques des différents systèmes d'observation nous empêchent encore d'obtenir des résultats précis sur cette contribution. Dans la deuxième partie de la thèse, en utilisant les données de reconstruction du niveau de la mer dans le passé, nous étudions la variabilité régionale du niveau de la mer et estimons sa hausse totale (composante régionale plus moyenne globale) de 1950 à 2009 dans trois régions vulnérables: l'océan Indien, la mer de Chine méridionale et la mer des Caraïbes. Pour les sites où l'on dispose de mesures du mouvement de la croûte terrestre par GPS, nous évaluons la hausse locale du niveau de la mer relatif (hausse du niveau de la mer totale plus mouvement de la croûte locale) depuis 1950. En comparant les résultats de ces trois régions avec une étude précédente sur le Pacifique tropical, nous constatons que le Pacifique tropical présente la plus forte amplitude des variations du niveau de la mer sur la période d'étude. Dans la dernière partie de la thèse, nous nous concentrons par conséquent sur le Pacifique tropical. Nous analysons les rôles respectifs de la dynamique océanique, des modes de variabilité interne du climat et du forçage anthropique sur les structures de la variabilité régionale du niveau de la mer du Pacifique tropical depuis 1993. Nous montrons qu'une partie importante de la variabilité régionale du niveau de la mer du Pacifique tropical peut être expliquée par le mouvement vertical de la thermocline en réponse à l'action du vent. En tentant de séparer le signal correspondant au mode de variabilité interne du climat de celui de la hausse régionale du niveau de la mer dans le Pacifique tropical, nous montrons également que le signal résiduel restant (c'est-à-dire le signal total moins le signal de variabilité interne) ne correspond probablement pas à l'empreinte externe du forçage anthropique. / Sea level is an integrated climate parameter that involves interactions of all components of the climate system (oceans, ice sheets, glaciers, atmosphere, and land water reservoirs) on a wide range of spatial and temporal scales. Over the 20th century, tide gauge records indicate a rise in global sea level between 1.6mm/yr and 1.8 mm/yr. Since 1993, sea level variations have been measured precisely by satellite altimetry. They indicate a faster sea level rise of 3.3 mm/yr over 1993-2015. Owing to their global coverage, they also reveal a strong regional sea level variability that sometimes is several times greater than the global mean sea level rise. Considering the highly negative impact of sea level rise for society, monitoring sea level change and understanding its causes are henceforth high priorities. In this thesis, we first validate the sea level variations measured by the new satellite altimetry mission, SARAL-AltiKa by comparing the measurements with Jason-2 and tide gauge records. We then attempt to close the global mean sea level budget since 2003 and estimate the deep ocean contribution by making use of observational data from satellite altimetry, Argo profiles and GRACE mission. We show that uncertainties due to data processing approaches and systematic errors of different observing systems still prevent us from obtaining accurate results. In the second part of the thesis, by making use of past sea level reconstruction, we study the patterns of the regional sea level variability and estimate climate related (global mean plus regional component) sea level change over 1950-2009 at three vulnerable regions: Indian Ocean, South China and Caribbean Sea. For the sites where vertical crustal motion monitoring is available, we compute the total relative sea level (i.e. total sea level rise plus the local vertical crustal motion) since 1950. On comparing the results from these three regions with already existing results in tropical Pacific, we find that tropical Pacific displays the highest magnitude of sea level variations. In the last part of the thesis, we therefore focus on the tropical Pacific and analyze the respective roles of ocean dynamic processes, internal climate modes and external anthropogenic forcing on tropical Pacific sea level spatial trend patterns since 1993. Building up on the relationship between thermocline and sea level in the tropical region, we show that most of the observed sea level spatial trend pattern in the tropical Pacific can be explained by the wind driven vertical thermocline movement. By performing detection and attribution study on sea level spatial trend patterns in the tropical Pacific and attempting to eliminate signal corresponding to the main internal climate mode, we further show that the remaining residual sea level trend pattern does not correspond to externally forced anthropogenic sea level signal. In addition, we also suggest that satellite altimetry measurement may not still be accurate enough to detect the anthropogenic signal in the 20 year tropical Pacific sea level trends.

Light Detection and Ranging (Lidar) data are used to report the temporal and spatial patterns of subsidence as well as the potential contributors to subsidence within the Barataria and Terrebonne Bays. In recent decades, subsidence in southeast Louisiana has become a topic of substantial and growing concern to the scientific community, the local residents, and all those invested in the region. Lidar data were acquired from the United States Geological Survey (USGS) and the LSU Center for Geoinformatics. The data has been manipulated to map the differenced Lidar, complete an instantaneous slope analysis, and determine the thickness of the Holocene sediments. The goal was to gain a more comprehensive understanding of the subsidence patterns and the dynamic processes driving subsidence within the study area. These efforts provide a better ability to plan for the future of the Louisiana working coast and mitigate against relative sea level rise and coastal land loss.

This study uses the storm surge sediment beds deposited by Hurricanes Audrey (1957), Carla (1961), Rita (2005) and Ike (2008) to investigate spatial and temporal changes in sedimentation rates on the McFaddin National Wildlife Refuge in Southeast Texas. Fourteen sediment cores were collected along a transect extending from 90 to 1230 meters inland from the Gulf Coast. Storm-surge-deposited sediment beds were identified by texture, organic content, carbonate content, the presence of marine microfossils, and Cesium-137 dating. The hurricane-derived sediment beds are marker horizons that facilitate assessment of marsh sedimentation rates from nearshore to inland locations as well as over decadal to annual timescales. Near the shore, on a Hurricane Ike washover fan, where hurricane-derived sedimentation has increased elevation by up to 0.68 m since 2005, there was no measurable marsh sedimentation in the period 2008-2014. Farther inland, at lower elevations, sedimentation for the period 2008-2014 averaged 0.36 cm per year. The reduction in sedimentation in the period 2008-2014 on the nearshore part of the marsh is likely due to reduced flooding in response to increased elevation from hurricane storm surge sediment deposition. These results provide valuable knowledge about the sedimentary response of coastal marshes subject to storm surge deposition and useful guidance to public policy aimed at combating the effects of sea level rise on coastal marshes along the Gulf of Mexico.