A sea-level database following a new protocol of quality evaluation standards has been constructed and is used for a comparative analysis to reconcile conflicting hypotheses about Holocene relative sea-level change in the Gulf of Mexico. Sea-level data are assessed quantitatively by assigning errors to both sample elevation and radiocarbon age. Sources of elevation uncertainty include sample thickness, indicative range, sampling errors, and surveying errors. Radiocarbon ages are corrected for bulk peat contamination, reservoir effects, and isotopic fractionation. Error calculations are performed as conservatively as possible. Furthermore, other variables such as sediment compaction are considered, in part relying on descriptive and semi-quantitative information that can prove useful for future studies. Overall, this database is valuable as a guideline for sea-level database standardization. A relative sea-level database has been compiled for coastal Louisiana following the proposed protocol. Comparing relative sea-level records from the Mississippi Delta and the southwest Louisiana Chenier Plain reveals that local sea-level change in both areas exhibits the same trend. This result challenges a recent model used to reconcile the smooth trend of rising sea level in the Mississippi Delta with a mid-Holocene highstand elsewhere along the US Gulf Coast, which advocated cyclic uplift and subsidence of the Mississippi Delta caused by sediment excavation and filling of the Lower Mississippi Valley, respectively. Therefore, it is concluded that vertical crustal movements in coastal Louisiana (i.e., subsidence) are mainly controlled by glacio-isostasy, associated with the melting of the Laurentide Ice Sheet. / acase@tulane.edu

The main outcome of this dissertation is a highly detailed RSL record constructed for the time interval 600 to 1600 AD to explore the eustatic response of sea level to the atmospheric warming that occurred during the Medieval Warm Period (∼900 to ∼1200 AD) and the transition into the Little Ice Age (∼1400 to ∼1900 AD). This new record was obtained in the microtidal Mississippi Delta and contains 28 sea-level index points that track ∼60 cm of relative sea-level rise. Basal peat was used as a tracer of sea-level, and age control was obtained by AMS 14C dating. All data were plotted as error boxes using 2 sigma confidence levels. A clustering of index points between 1000 and 1200 AD suggests an increase in the rate of sea-level rise. While this suggests a fluctuating eustatic sea level, any centennial-scale fluctuation could not have had an amplitude larger than ~30 cm. Rates of sea-level change calculated from the first derivative of a third-order polynomial function fitted through the central point of each error box (r2=0.96) indicate that the maximum rate of sea-level rise occurred around 1100 AD, which slightly postdates peak Medieval warmth according to most Northern Hemisphere paleotemperature records. The dominant control of the long-term rate (0.56 mm yr-1) of RSL rise obtained from the new reconstruction is glacial isostasy in the form of forebulge collapse. Subtracting the rate of eustatic sea level rise for the 20th century (1.7 mm yr-1) (Church and White, 2006) from the rate of sea level rise captured by the Pensacola (Florida) tide gauge (2.2 mm yr-1), an area that is considered tectonically stable, yields a residual of 0.5 mm yr-1. This figure is in agreement with the long-term rate obtained in this study. This value is also very close to what some geophysical models predict as the present-day rate of glacial isostatic adjustment for the north central Gulf Coast. Taking the ratio of the instrumental rate for the last 90 years captured by the Pensacola tide gauge (2.2 mm yr-1) to the long-term geologic rate (0.56 mm yr-1) indicates a four-fold increase in the rate of relative sea level rise during the 20th century compared to that of the previous millennium. Given that at time scales of one-thousand years processes like glacial isostasy and tectonic subsidence behave essentially linearly, and that both records are free of compaction, the increase can only result from an acceleration in the rate of global sea level rise. / acase@tulane.edu

¡@¡@The impacts of global warming and climate change were the important issue in the last few decades. The sea level rising was one of most discussion topics of physical impact which derived from global warming. In this study, about forty year¡¦s sea level records (from Harbor & Marine Technology Center) were used to analysis the long term water level trends at Keelung Harbor, Taichung Harbor and Kaohsiung Harbor in the western Taiwan. ¡@¡@We rearranged the records format, filtered out error data, and then sorted the data by the logged time. Three kinds of analysis method were applied to investigate the trend of water level change. The first one was harmonic analysis which was used to eliminate the effects of astronomical tide. The second method was spectrum analysis and it assisted to obtain the amplitudes and phases of tidal component. Finally, we used the moving average method to smooth data and discussed the tendency of water level change. ¡@¡@The result showed no evidence of sea level rising along the western coast of Taiwan. The average water level raised and declined evenly in the duration of forty years, and the general trends of water level varied near the zero level. The result also showed the variation of water level that affected by the measurement instruments was more over the physical effects.

Οι μεταβολές της στάθμης της θάλασσας τα τελευταία 20.000 χρόνια και η εμφάνιση καταστροφικών φαινομένων (σεισμοί, παλιρροιακά κύματα) έχουν οδηγήσει στην καταβύθιση αρχαίων πόλεων, οικισμών και λιμενικών εγκαταστάσεων. Οι περισσότερες των αρχαιολογικών παράκτιων θέσεων σήμερα, βρίσκονται βυθισμένες στη θάλασσα και η μελέτη τους απαιτεί τη χρήση σύγχρονων συστημάτων θαλάσσιας γεωφυσικής διασκόπησης. Τις τελευταίες δύο δεκαετίες οι θαλάσσιες γεωφυσικές μέθοδοι έχουν αναδειχθεί σε εξαιρετικά αποτελεσματικό μέσο στη μελέτη τέτοιων περιοχών καθώς είναι εφικτό: (α) να εντοπίζουν και να χαρτογραφούν με ακρίβεια και σε σύντομο χρονικό διάστημα μεγάλης έκτασης περιοχών αρχαιολογικής σημασίας, (β) να εντοπίζουν και να χαρτογραφούν γεωμορφές σχετιζόμενες με το περιβάλλον ανάπτυξης των αρχαιολογικών θέσεων έτσι ώστε να αναπαριστούν την εξέλιξη της παράκτιας παλαιογεωγραφίας. Επιπλέον, οι γεωφυσικές μέθοδοι χρησιμοποιούνται πλέον συστηματικά για τον εντοπισμό και τη μελέτη κινητών μαρτυριών (ναυάγια) της ανθρώπινης δραστηριότητας στον πυθμένα. Στην παρούσα εργασία παρουσιάζονται τα προκαταρκτικά αποτελέσματα από την εφαρμογή των μεθόδων θαλάσσιας γεωφυσικής διασκόπησης στην ευρύτερη περιοχής Μοδίου – Πόρου. Στη βορειοδυτική πλευρά της νησίδας Μόδι, το Ινστιτούτο Ενάλιων Αρχαιολογικών Ερευνών (ΙΕΝΑΕ) εντόπισε φορτίο ναυαγίου που χρονολογείται τον 12ο αιώνα π.Χ. Επιπλέον, η περιοχή μελέτης αποτελεί μεγάλο αρχαιολογικό ενδιαφέρον για τον Ελληνικό θαλάσσιο χώρο διότι στην αρχαιότητα αποτελούσε σημαντικό εφαλτήριο και βρίσκονταν σε ενδιάμεσους πολυσύχναστους θαλάσσιους πλόες του Αργοσαρωνικού κόλπου. Τα όργανα γεωφυσικής διασκόπησης που χρησιμοποιήθηκαν στην συγκεκριμένη έρευνα ήταν o τομογράφος υποδομής πυθμένα υψηλής διακριτικής ικανότητας και ο ηχοβολιστής πλευρικής σάρωσης. Η επεξεργασία και η ανάλυση των δεδομένων επέτρεψε την αποτύπωση της θέσης του ναυαγίου με σύγχρονες μεθόδους διασκόπησης, την κατασκευή λεπτομερών χαρτών βυθομετρίας και γεωμορφολογίας του πυθμένα, τον εντοπισμό ιχνών (scarps) καταβυθισμένων παλαιοακτών και τον προσδιορισμό της στρωματογραφικής υποδομής του πυθμένα στην περιοχή μελέτης. Με βάση τα παραπάνω δεδομένα έγινε προσπάθεια ανάπλασης της παλαιογεωγραφικής εξέλιξης στην ευρύτερη περιοχή μελέτης για τα τελευταία 18.000 χρόνια. Επιπλέον εντοπίστηκε στην ευρύτερη περιοχή έρευνας, ένας σημαντικός αριθμός στόχων πιθανής αρχαιολογικής σημασίας. / The changes in sea level over the last 20,000 years and the emergence of catastrophic events (earthquakes, tidal waves) have led to the submergence of ancient cities, settlements and port facilities. Most of the archaeological coastal positions today are immersed in the sea and their study requires the use of modern systems of marine geophysical surveys. Over the past two decades, marine geophysical methods have become an extremely effective tool in studying such areas as practicable: (a) to identify and map out accurately and in a short period of large areas of archaeological importance, (b) to identify and mapping landforms associated with the development environment of the sites to represent the evolution of the coastal Paleogeography. In addition, geophysical methods are now used routinely to detect and study mobile testimonies (wrecks) of human activity on the sea floor. This paper presents preliminary results from the application of marine geophysical methods in the wider region Modi Rocky Islet and Poros Isl. On the northwestern side of the rocky islet of Modi, the Hellenic Institute of Marine Archaeology (H.I.M.A) identified a cargo of a shipwreck dating to the 12th century BC Furthermore, the study area forms great archaeological interest in the Greek sea area because in ancient times was an important springboard and was located in intermediar and frequented sea voyages of the Saronic Gulf. The geophysical instruments used in this study was the subbottom profiler and side-scan sonar. The processing and data analysis enabled mapping the location of the wreck using modern marine geophysical methods, build detailed bathymetry maps and maps with the geomorphology of the seabed, detect traces (scarps) of submerged palaeocoast and determine the stratigraphic infrastructure of sea floor in the study area. Based on these data attempted reconstruction of the palaeogeographic evolution of the study area for the past 18,000 years. In addition, in the study area, was identified a significant number of potential targets with archaeological importance.

Sea level rise (SLR) threatens coastal communities, infrastructure, and ecosystems. Worldwide, stakeholders critically depend on SLR projections with the associated uncertainty for risk assessments, decision-making and coastal planning. Recent research suggests that the Antarctic ice sheet mass loss during the 21st century may contribute up to an additional one meter of global SLR by year 2100. While uncertainty still exists, this value would double the ‘likely’ (> 66% probability) range of global SLR (0.52-0.98 m) by the year 2100, as found by Chapter 13 on Sea Level Change in the Fifth Assessment Report by the Intergovernmental Panel on Climate Change. Here, we present three studies that assess mechanisms relevant to 21st century local, regional, and global SLR. Appendix A examines the effect of large-scale oceanic and atmospheric circulation variability on extreme sea levels along the East Coast of North America. Appendices B and C analyze ocean warming on the Antarctic shelf and its implications for future ice shelf basal melt and Antarctic Ice Sheet mass loss. These studies will contribute to more accurate projections of local, regional, and global SLR. In Appendix A, we analyze long-term tide gauge records from the North American eastern seaboard and find an extreme SLR event during 2009-2010. Within this two-year period, coastal sea levels spiked between Montauk, New York and Southern Canada by up to 128 mm. This two-year spike is unprecedented in the tide gauge record and found to be a 1-in-850 year event. We show that a 30% reduction in strength of the Atlantic meridional overturning circulation (AMOC) and a strong negative North Atlantic Oscillation (NAO) index caused the extreme SLR event. Climate models project that the AMOC will weaken and NAO variability will remain high over the 21st century. Consequently, extreme SLR events on the Northeast Coast could become more frequent during the 21st century in response to climate change and SLR. In Appendix B, we use a fine-resolution global climate model (GFDL CM2.6) that resolves an eddying ocean. With this state-of-the-art coupled model, we quantify the mechanisms contributing to ocean warming on the Antarctic continental shelf in an idealized experiment of doubling of the atmospheric CO2 concentration. The results show that the CO2 forcing leads to the shelf region warming both in the upper 100 m ocean and at depths near the sea floor. These warming patterns are controlled by different mechanisms. In the upper 100 m, the heat anomalies are primarily controlled by increased heat transport into the shelf region associated with the warmer near-surface waters from lower latitudes. Below 100 m, the heat anomalies develop due to increased onshore intrusions of relatively warm Circumpolar Deep Water and reduced vertical mixing of heat in the water column. A complete heat budget analysis is performed for the Antarctic shelf region as well as for six subdomains and three depth ranges (0-100 m, 100-700 m, and 700-1000 m). The results show that certain regions of the Antarctic shelf are more susceptible to large CO2-forced warming. These findings have implications for future Antarctic Ice Sheet mass loss and SLR, and can provide more detailed and accurate ocean boundary conditions for dynamical ice sheet models. In Appendix C, we use CM2.6 to examine the connections among ocean freshening and the magnitude and location of ocean warming on the Antarctic shelf. We find that CO2 forcing freshens the Antarctic shelf seas via increases in local precipitation, sea ice loss, liquid runoff, and iceberg calving. The freshening induces three heat budget-relevant responses: (1) reduced vertical mixing; (2) strengthening of the Antarctic Slope Front (ASF); and (3) increased eddy kinetic energy (EKE) near the ASF. First, heat can accumulate at depth (100-1000 m) as freshening increases the vertical stratification on the shelf and reduces upward mixing of heat associated with diffusion and convective processes. Second, freshening near the shelf break strengthens the ASF by increasing the lateral density gradient and by steepening and deepening the associated isopycnals. This response limits cross-ASF onshore heat transport at many locations around Antarctica. Third, EKE increases near the ASF may contribute to shelf warming by increasing cross-ASF onshore eddy heat transport. These results demonstrate the importance of shelf freshening to the development of positive heat anomalies on the Antarctic shelf. The findings provide new insight to the location of future shelf warming and ice shelf basal melting as well as provide significant information for projecting regional and global SLR.

This thesis investigates sea-level changes in order to test the hypothesis that the main contribution to early 20th century sea-level rise was Northern Hemisphere land-based ice melt. Multiproxy sea-level reconstructions were established for the Falkland Islands, a location where models suggest sea-level rise from Northern Hemisphere ice melt produces the largest signal. The Falklands reconstruction indicated sea levels in the early 20th century accelerated compared to the long-term rate, synchronous with accelerations observed globally. The magnitude of the acceleration in the Falklands reconstruction was greater than Northern Hemisphere rates, consistent with the spatial pattern from a Northern Hemisphere melt source, but likely less than in New Zealand and Australia. It is therefore not possible rule out other contributions to the observed sea-level acceleration. The Falklands reconstruction indicated a rapid sea-level jump around 8.4 ka BP, synchronous with a jump observed in the Northern Hemisphere, which has been attributed to the sudden drainage of Laurentide proglacial lake Agassiz-Ojibway associated with the 8.2 ka BP climatic downturn. A maximum estimate of 0.89 ± 0.22 m for this jump in the Falklands is considerably less than estimates from Northern Hemisphere records. This difference could indicate additional contributions from the Southern Hemisphere are being recorded in the Northern Hemisphere signal. This thesis also focused on developing testate amoebae as sea-level indicators. In the Falklands, testate amoebae transfer functions were able to reconstruct sea level with precision (±0.08 m) comparable to diatoms (±0.07 m). However, preservation issues were indicated in the fossil testate amoebae assemblages which limits their use as tools for sea-level reconstruction. In addition, contemporary distributions of salt-marsh testate amoebae were investigated over one annual cycle. Seasonal variations in the live assemblages were observed to be asynchronous between taxa. Variations in the death assemblages were also observed which were correlated with variations in the live assemblages. This observation suggests the commonly applied assumption in palaeoenvironmental studies that analysing the death population negates temporal bias is invalid. Further research is required to investigate the impact these observed variations have on reconstructive performance.

This study contributes to developing terrestrial and marine palynological indicators of winter or summer monsoon signals as well as oceanographic environments of the South China Sea (SCS). The high-resolution reconstructions of Holocene East Asian Monsoon (EAM) climate and oceanographic condition of the northern SCS provide insights into regional climate events in the western low-latitude Pacific Ocean and their impacts on local oceanography and ecology. Sediment trap samples from the southwest Taiwan waters of the SCS in winter monsoon (March-April) and summer monsoon (July-August) seasons identify abundances of Pinus and Ulmus pollen as indicators of the winter monsoon whereas fern spores appeared to be indicators of the summer monsoon. The increased fluxes of dinoflagellate cyst (DC) taxa during summer are correlated with decreased sea-surface salinity (SSS) associated with nutrient-rich river inputs. DC distributions across the SCS show that some taxa are good indicators of changes in sea-surface temperature (SST), SSS, water depth and chlorophyll-a (chl-a) concentrations associated with EAM and oceanographic conditions. In particular, the concenrations of Brigantedinium spp. and cysts of Protoperidinium together with Echinidinium spp. are positively correlatd with SST in January and SST in July, and chl-a concentrations, respectively, which are linked to past monsoon strength and primary productivity. In total, four high cyst concentration regions have been observed off southern Vietnam, Borneo, Hainan, and South China. High-resolution palynological records from a sediment core in the northern SCS reflect several EAM climatic and oceanographic events over the last 12.5 kyr. A short-term Impagidinium decrease implied that the Taiwan Strait opened at ~11.7–11.0 cal kyr BP, with reduced Kuroshio Current influence when the East China Sea waters entered through the strait. Three Holocene relative sea-level stages were identified in the palynomorph records. The highest herb pollen abundances were observed before ~10.4 cal kyr BP, reflecting the shortest distance from the grassland sources on the exposed shelf at the low sea-level stand. High Brigantedinium and cysts of Protoperidinium abundances also indicate a near-shore environment. During ~10.4- ~6.8-6.0 cal kyr BP at the rising sea-level stage, fern spore abundances increased and DC abundances decreased. Consistently low total DC concentrations and high fern spore abundance were observed after ~6.8-6.0 cal kyr BP when the present oceanographic conditions were formed. Increased abundances of Pinus pollen reflected three strengthened winter monsoon intervals at ~5.5, 4.0 and 2.5 cal kyr BP under the present oceanographic conditions. The highest Dapsilidinium pastielsii abundances reflected the warmest interval at ~6.8-5.5 cal kyr BP of the northern SCS. / Graduate / 2019-12-13

<p>Denna rapport ger förslag på olika metoder att automatiskt justera flytläget på en statiskt förankrad boj, en överblick över de processer som styr ändringen av vattennivån och en statisktisk analys på vattennivåförändringarna vid Stockholm, Kungsholmsfort och Kungsvik.</p><p>Beroende på vattenivåns variation finns olika metoder för justering. Områden med små variationer av vattennivå lämpar det sig bäst utan någon som helst justering av flytläget. Områden med inte för stora tidvattensförändringar bör justeras med ett system bestående av vinsch, växellåda med en utväxling på 10 000:1, en 12 V DC motor, ett skötselfritt 12 V batteri, en luftlindad linjärgenerator och en trådtöjningsgivare. Områden med stora variationer i tidvatten behöver en avlastning för motorn i form av en fjäder och dämpare. De monteras horizontellt inuti bojen för att skyddas från den yttre miljön.</p><p>Den statistiska analysen påvisade de största vattennivåändringarna vid både Kungsviks och Kungsholmsforts mätstationer, båda uppvisade ett intervall på 1,6 m mellan minimum och maximum. Kungsvik var den station med de största dagliga variationerna, detta på grund av tidvattnets påverkan i området.</p> / <p>This thesis gives examples of different methods of automated adjustment of floatation level for a static moored buoy, an overview of the theories behind water level change and a statistical analysis of the water level changes for Stockholm, Kungsholmsfort and Kungsvik.</p><p>Depending on the range and frequency of the water level change different methods of adjustment are recommended. For areas with small changes in sea level the best choice would be no adjustment of the floatation level. Areas that are influenced by moderate tidal ranges should incorporate a system of regulation consisting of a winch, gearbox with a gear ratio of around 10,000:1, 12 V DC motor, 12 V maintenance free battery, air coiled linear generator and a strain gauge. For areas with large tidal ranges the previous system should be complimented with a horizontally mounted spring, inside the buoy, to lessen the loads on the motor.</p><p>The statistical analysis found the largest extremes in water level of the three sites to be at Kungsvik and Kungsholmsfort, both exhibiting a range of almost 1.6 m. Kungsvik was the station with the largest daily variations, this is because this is the only station influenced by tidal variations.</p>

Denna rapport ger förslag på olika metoder att automatiskt justera flytläget på en statiskt förankrad boj, en överblick över de processer som styr ändringen av vattennivån och en statisktisk analys på vattennivåförändringarna vid Stockholm, Kungsholmsfort och Kungsvik. Beroende på vattenivåns variation finns olika metoder för justering. Områden med små variationer av vattennivå lämpar det sig bäst utan någon som helst justering av flytläget. Områden med inte för stora tidvattensförändringar bör justeras med ett system bestående av vinsch, växellåda med en utväxling på 10 000:1, en 12 V DC motor, ett skötselfritt 12 V batteri, en luftlindad linjärgenerator och en trådtöjningsgivare. Områden med stora variationer i tidvatten behöver en avlastning för motorn i form av en fjäder och dämpare. De monteras horizontellt inuti bojen för att skyddas från den yttre miljön. Den statistiska analysen påvisade de största vattennivåändringarna vid både Kungsviks och Kungsholmsforts mätstationer, båda uppvisade ett intervall på 1,6 m mellan minimum och maximum. Kungsvik var den station med de största dagliga variationerna, detta på grund av tidvattnets påverkan i området. / This thesis gives examples of different methods of automated adjustment of floatation level for a static moored buoy, an overview of the theories behind water level change and a statistical analysis of the water level changes for Stockholm, Kungsholmsfort and Kungsvik. Depending on the range and frequency of the water level change different methods of adjustment are recommended. For areas with small changes in sea level the best choice would be no adjustment of the floatation level. Areas that are influenced by moderate tidal ranges should incorporate a system of regulation consisting of a winch, gearbox with a gear ratio of around 10,000:1, 12 V DC motor, 12 V maintenance free battery, air coiled linear generator and a strain gauge. For areas with large tidal ranges the previous system should be complimented with a horizontally mounted spring, inside the buoy, to lessen the loads on the motor. The statistical analysis found the largest extremes in water level of the three sites to be at Kungsvik and Kungsholmsfort, both exhibiting a range of almost 1.6 m. Kungsvik was the station with the largest daily variations, this is because this is the only station influenced by tidal variations.

No description available.