Meltwater pulse 1A (MWP-1A) is the largest land ice melt event of the last deglaciation. In a period of no more than 340 years, between 14.65 and 14.31 ka (Dechamps et al, 2012), ~10% of the total deglacial sea-level rise occurred (Hanebuth et al, 2000; Peltier and Fairbanks, 2006; Deschamps et al, 2012), resulting in the highest reported rate of global mean sea-level rise in the geological record, which may have exceeded 4 m per century (Deschamps et al, 2012). Yet, the implications of MWP-1A for constraining the rates of the underlying processes and its role in the sequence of climate events during Termination 1 remain unclear due to the lack of information on its melt source distribution. While glacial isostatic adjustment (GIA) modelling experiments (Clark et al, 2002; Bassett et al, 2005; Deschamps et al, 2012) and recent assessments of ice-sheet histories (Carlson and Clark, 2012) suggest that at least 50% of the event may have come from Antarctica, other interpretations of Antarctic ice-extent and sea-level records suggest a substantially smaller (including zero) Antarctic contribution (Ackert et al, 2007; Mackintosh et al, 2011; Whitehouse et al, 2012). In this study, we show that after reassessments of local MWP-1A amplitudes at Barbados and Sunda Shelf based on the well-constrained timing derived from the Tahiti sea-level record (Deschamps et al, 2012), the sea-level data from Barbados, Sunda Shelf, and Tahiti do not provide as tight of a constraint on the Antarctic contribution as previously thought. We find that between 1 to 10 m sea-level equivalent (sle) could have melted from the Antarctic, compared to 7 to 15 m sle from previous analyses (Clark et al, 2002; Bassett et al, 2005; Deschamps et al, 2012). To better constrain the source of MWP-1A, we also consider sea-level data from Scotland (Shennan et al, 2000), which have, until now, been excluded from MWP-1A fingerprinting experiments because they are strongly influenced by local ice unloading. To overcome this, we isolate the elastic MWP-1A amplitude (i.e. fingerprint signal) at this location using a suite of models that provide optimal fits to the Scottish data, and thereby remove near-field contamination. Preliminary results show that the inclusion of these data leads to an improved MWP-1A source distribution constraint compared to that obtained using the far- and intermediate-field data alone.

No description available.

This study develops techniques for the preparation and counting of testate amoebae for Holocene sea-level reconstructions. In addition, this study provides a ~3000 year relative sea-level reconstruction for south Hinnøya in the Vesterålen islands off mainland Norway, adding new data to a poorly defined period of the Holocene sea-level history of north-western Norway. This is important to quantify rates of glacial-isostatic adjustment (GIA), to refine GIA models, and to establish baseline (pre-industrial) rates of relative sea-level change. Surface sediments from two salt marshes (Storosen and Svinøyosen) in south Hinnøya are used to assess the effects of using different preparation procedures and count totals when analysing for testate amoebae. Analytical efficiency can be improved upon by using a mild alkali, chemical disaggregant (5 % KOH) to break up fibrous salt-marsh sediment and concentrate tests prior to counting. A count total of 100 individuals, rather than 150, can be used to make time gains with little or no effects on assemblages. Training sets of salt-marsh surface testate amoebae, foraminifera and elevational data are established for the two field sites. For testate amoebae, species – elevation relationships are constructed using regression modelling and applied to downcore fossil samples using a transfer function to derive estimates of sea level for the past ~100 years. The greater water depths reconstructed between ~3000 and ~100 years ago are not covered by modern foraminiferal training sets and are therefore estimated qualitatively from the fossil foraminiferal assemblages supplemented by information derived from fossil molluscs. Chronology is based on a combination of AMS14C, 210Pb, 137Cs and a suite of geochemical markers. At south Hinnøya, sea level has been falling at a rate of ~0.5 mm yr-1 over the last 3000 years.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Global warming will result in a sea level rise of between 0.25 and 0.82 m by 2090, as well as an increase in intensity and frequency of both extreme sea level and extreme rainfall events. In consequence, low-lying areas will be permanently inundated, extreme waves will penetrate further inland and flood intensity and frequency will increase. Estuaries are subject to the effect of both extreme sea levels and extreme floods and water levels in estuaries are expected to increase, under both open and closed conditions. As a response to expected higher flood levels, setback lines have been legislated in South Africa. For cases where a flood level study has not been undertaken, a minimum setback line at the 5 m above mean sea level (MSL) contour is prescribed in terms of the National Environmental Management Act (Act 107 of 1998). This study assessed the adequacy of the 5 m setback line, under the effects of climate change, for Great Brak estuary. Local features of the Great Brak estuary may influence flood levels. Specifically, the lagoon of the Great Brak estuary, below the N2 Bridge, is small at 1.1 x 0.7 km. Further, it is constrained at the upstream end by road and rail embankment, and on the left bank by steep slopes. A sand barrier at the mouth is at times breached, both naturally and artificially. Artificial breaching is initiated when the sand barrier is between 1.5 and 2.0 m high, or when a flood is forecast. The barrier has previously reached 2.7 m, higher than the still water level of the sea, which has not exceeded 2 m above MSL. There is a populated island about 180 m upstream of the mouth. The greater extent of the island is below 2.5 m above MSL. Mike11 software was used to generate flood levels on which the conclusions of this study are based. The study determined that the influence of the increased sea levels does not extend much beyond the N2 Bridge. This may be a peculiarity of the Great Brak estuary, due to the influence of the three bridges and the road and rail embankments. For the scenario where Mean High Water Springs coincides a with an extreme sea storm and there is a 100-year riverine flood, the flood level in the estuary is 3.16 m at the mouth, increasing to 4 m upstream of the N2 bridge. In the scenario where the barrier height was raised to 4 m above MSL, the flood levels were 4.52 m downstream of, and 5 m upstream of, the N2 Bridge. Extensive inundation of properties in the floodplain and on the Island will occur, as well as the inundation of the N2 embankment. The probability of such an extreme sea level event occurring at the same time as peak runoff of a 100-year riverine flood is unlikely. It is the conclusion of this study that, for the Great Brak River, the 5 m setback line, as prescribed, is sufficient for an extreme situation where a future 100-year flood coincides with the MHWS coincides and an extreme sea storm raising the sea level to 2.65 above current MSL. / AFRIKAANSE OPSOMMING: Aardverwarming sal lei tot 'n styging van seevlakke van tussen 0.25 en 0.82 m teen 2090, sowel as 'n toename in intensiteit en frekwensie van beide stormseevlak en reënval. Gevolglik sal laagliggende gebiede permanent oorval word, stormgolwe verder in die binneland dring en vloed intensiteit en frekwensie toeneem. Riviermondings is onderhewig aan die effek van beide hoë seevlakke en vloede. Om die negtaiewe effekte van hoër vloedvalktes te bekamp word ‘n minimum terugsetlyn van 5 m bo seevlak voorgeskryf, in terme van die Wet op Nationale Omgewingsbestuur (Wet 107 van 1998). Hierdie is van toepassing waar ‘n vloedlyn studie nie onderneem is nie. Hierdie studie beoordeel die geskiktheid van die 5 m terugsetlyn, onder die invloed van klimaatsverandering, vir Groot Brak rivier monding. Plaaslike kenmerke van die Groot Brak monding mag vloed vlakke beïnvloed. Spesifiek, die Groot Brak monding meer het ‘n oppervak van net 1,1 x 0,7 km; is in die stroomop rigting beperk deur pad en spoor walle; en word op linkeroewer deur steil hellings vesper. Die sandversperring by die word kunsmatig oopgemmak wanneer die sand versperring tussen 1,5 en 2,0 m hoog is, of wanneer 'n vloed voorspel word. Hierdie sandversperring het al voorheen 2.7 m hoogte beriek, hoër as die 2 m maksimum historiese stilwater vlak van die seë. Daar is 'n bevolkde eiland sowat 180 m stroomop van die mond. Die die eiland is meestelik onder 2.5 m bo seevlak. Mike11 sagteware is gebruik om vloed vlakke, waarop die bevindinge van hierdie studie gebaseer is, te bepaal. Hiedie studie bevind dat die effek hoër voedvlakke trek nie veel verder stroomop as die N2 brug, oontlike weens die voorkoms van die drie bruë. In die geval waar ‘n uiterste seëstorm terselfde tyd voorkon as die lente hoogwater gety endie 100 jaar river vloed, sal die watervlak in the mondingsmeer tot 3.16 m bo huidiglike seëvlak styg by die mond, en tot 4 m bo huidiglike seëvlak by die N2 brug. In die geval waar die sandversperring by the riviersmond 4 m verhoog is, sal die watervlak in the mondingsmeer tot 4.5 m bo huidiglike seëvlak styg by die mond, en tot 5 m bo huidiglike seëvlak by die N2 brug. Faktore nie in ag geneem in hierdie studie sluit in die uitwerking van die verhoogde afloop, sediment verandering en die effek van windgolwe oor die ondingsmeer. Wydverspreide vloeding van ontwikkelde areas aangrensend to vloedvlakte sal voorkom, insluitend die oorstroing van die N2 padwal. Die waarskynlikheid is klein dat ‘n uiterste seëstorm terselfde tyd voorkom as the lengte hoogwater gety en die 100 yaar rivier vloed. Dit is dus die gevolgtrekking van hierdie studie dat die 5 m terugsetlyn soos voorgeskryf, voldoende is vir Groot Brak rivier vir so ‘n uiterste geval.

This work examines the use of pedo-properties to identify dune soil system responses to environmental change on the Sefton coast, based on the development of conceptual pedogenic models. Previous environmental change and shoreline dynamics are determined through O.S. maps and aerial photographs, while present day processes are investigated through a dune-toe photographic survey and seasonal monitoring by fixed point photography. Topsoil (0-5 cm) physico-chemical characteristics are presented in a series of baseline GIS maps, displaying spatial pedo-property variation across the dune landscape. Combined with vegetation data, topsoil analysis identifies 10 distinct pedo-environments. Physico-chemical characteristics of associated National Soil Resources Institute (NSRI) soil profile classifications and an exposed stratigraphic section are presented graphically in a proposed sequence of development. Topsoil and soil profile samples are analysed for soil pH, soil organic matter (SOM) content, particle size, geochemical composition and mineral magnetism. Significant differences (p <0.05) are apparent for the suite of topsoil characteristics collated, indicating discrete dune environments are influenced by specific soil properties. Distinct down-profile variations in soil characteristics are also apparent between dune environments, highlighting pedological dynamism. Multivariate Factor analysis groups bare sand and mobile dune communities into ‘frontal dunes’ and fixed dune community, pasture, scrub, deciduous woodland and coniferous plantations into ‘hind dunes’, separating these topsoil environments from heath and slack communities. Factor analysis also identifies linkages between pedo-characteristics within soil profile horizons, suggesting pedogenesis on the Sefton dunes initiates as raw sand, progressing to sand-pararendzinas through leaching of nutrients. Desalinization and decalcification processes lead to brown earth development, followed by increased acidicification, subsequently, resulting in micro-podzol formation. Groundwater gley soils are associated with dune slacks, where drainage is inhibited and anaerobic conditions prevail. Analysis of buried soils suggests such pedo-environment formations are cyclic, responding to phases of shoreline regression/transgression, dune activity and stabilization. Conceptual models are designed to graphically demonstrate pedogenesis under both erosion and deposition regimes on the Sefton coast. Regression equations and correlation coefficients between pedo-properties and distance from mean high water are used as a proxy for soil age, which represent lateral soil maturity from the unstable frontal dunes to the stable hind dunes inland. The models simulate formation and process of the full array of soil properties, accounting for geomorphological impacts and anthropogenic influences. This has great implications for dune managers by raising awareness of pedogenesis as an integral part of nature and associated habitats, which could be incorporated in future shoreline management plans (SMPs).

Shallowly-buried channel systems have been imaged on the New Jersey Shelf with high-resolution seismic imaging. These channels formed as riverine systems that occupied the exposed shelf during the Last Glacial Maximum, ~18 ka. Subsequent sea level rise ~15-12 ka modified the valleys, forming estuaries and filling the channels with estuarine sediments. The infill sediments within the channel provide evidence for the response of the shelf to the Late Pleistocene glacio-eustatic sea level rise, but little work has been done on samples from these strata. This study aids in the ground-truthing of previous stratigraphic results by analyzing the cores collected within the infill sediments. The seismic stratigraphy of fill sediments from the mid-shelf and outer-shelf channels are structurally dissimilar. The mid-shelf channel fill stratigraphy is dominated by finely-laminated U-shaped reflectors throughout the section, with cut and fill geometries. In contrast, the outer shelf channel fill stratigraphy is a well-ordered sequence of 4 identifiable, primarily flat-lying seismic units. We collected five cores in mid-shelf channels (~30 m water depth), one in an outer shelf channel (~80 m of water depth) and one core in the trangressive ravinement surface. Cores were logged for density and seismic velocity. Grain size analysis was conducted by settling column and laser particle size analyzer. Radiocarbon analysis of the stratigraphy was conducted with the shell fragments and organic mud within the samples. The foraminiferal assemblages aided in determining the depositional environment. Using these data I investigated the differences in depositional environment of the mid- and outer-shelf channels systems, and consider these results in the context of sedimentary models for estuarine processes. The radiocarbon dates and foraminiferal are consistent with channel infill in an estuarine environment. Grain size and density log data indicate that the mid-shelf channel fills are sandier than the outer-shelf channel fills, which leads me to infer that the sediment from the mid-shelf channels was deposited in a higher energy environment than that of the sediment in the outer shelf channels. The stratigraphic differences and locations of the channel systems are similar to the Zaitlin (1994) model of incised valley infill, but infill of the mid-shelf channel system could possibly be the result of a catastrophic meltwater flood event occurring ~14 ka as glacial lakes to the north broke their dams and flooded the mid-shelf. / text

The rapid development of space geodesy over the last two decades has had a profound effect on geologic studies by allowing measurements of crustal motion with sub-millimeter per year precision. The focus of this work is to better understand microplate kinematics, intraplate deformation and sea level rise in Europe by use of Global Positioning System (GPS) measurements of crustal deformation. This is accomplished in three separate studies. The first study focuses on crustal motion and sea level rise along the eastern margin of Adria. We use data from tide gauge and continuous GPS (CGPS) stations. We develop a new method to separate common-mode relative sea level from spatially variable signals. From tide gauge data, we find uniform relative sea level rise along the coast that is 2-4 times lower than the estimates for global average sea level rise. In constrast, vertical motion of coastal rocks determined by CGPS varies appreciably from an average of -1.7 ± 0.4 mm/yr in the southern Adria to 0.0 ± 0.4 mm/yr in northern Adria. The most enigmnatical result of this study is that the combination of tide gauge and CGPS data shows that absolute sea level varies in such a way that relative sea level remains constant. The second study focuses on diffuse intraplate deformation of western Eurasia measured by CGPS. We find that our preferred model involves four subplates, separated by the Pyrenees, Rhine Graben, and Trans European Suture Zone, and yields residual velocities indistinguishable from random samples. We interpret the intraplate dormation as the surface manifestation of downwelling mantle lithosphere. The final component of this work is a study of the Northern and Southern Adria microplates' internal stability and tectonic motion. Results show that both Adria microplates are kinematically distinct from one another and from the slowly converging Eurasia and Nubia plates, with implications for the dynamics of the Nubia-Eurasia plate boundary zone. We also find that internal strain within the Adria microplates is statistically insignificant. We estimate appreciable fault slip rates around the periphery of Adria, with implications for slip rates and seismic hazards associated with circum-Adria fault zones.

During 1998-2012, climate change and sea level rise (SLR) exhibit two notable features: a slowdown of global surface warming (hiatus) and a rapid SLR in the tropical western Pacific. To quantify their relationship, we analyze the long-term control simulations of 38 climate models. We find a significant and robust correlation between the east-west contrast of dynamic sea level (DSL) in the Pacific and global mean surface temperature (GST) variability on both interannual and decadal time scales. Based on linear regression of the multimodel ensemble mean, the anomalously fast SLR in the western tropical Pacific observed during 1998-2012 indicates suppression of a potential global surface warming of 0.16 degrees 0.06 degrees C. In contrast, the Pacific contributed 0.29 degrees 0.10 degrees C to the significant interannual GST increase in 1997/1998. The Pacific DSL anomalies observed in 2015 suggest that the strong El Nino in 2015/2016 could lead to a 0.21 degrees 0.07 degrees C GST jump.

A detailed record of the Late Holocene sea level rise and landscape evolution that has taken place on the Georgia coast is contained within the sedimentary stratigraphy of its salt marsh depositional basins. Global relative sea level (RSL) has risen during the Late Holocene, and the rate of rise has accelerated during the Anthropocene. Jones Narrows marsh stratigraphy and radiocarbon analysis indicate increasing rates of RSL rise for the late Holocene on the Northern Atlantic Coast of Georgia, while FPXRF analysis of the marsh sediments facilitates a chemostratigraphic study of Jones Narrows salt marsh deposition and landscape evolution. Sedimentation and hydrology at the site have been heavily influenced by recent local anthropogenic impacts, which are examined through stratigraphic and spatial methods.

Magister Artium - MA / This thesis investigates the influence of climate change and climatic variability on wetland ecosystems (coastal and inland wetlands) on the Agulhas coastal plain. Firstly, this research examines coastal wetland ecosystem resilience to sea level rise by modelling sea level rise trajectories for the Droё River wetland. The rate of sediment accretion was modelled relative to IPCC sea level rise estimates for multiple RCP scenarios. For each scenario, inundation by neap and spring tide and the 2-, 4- and 8-year recurrence interval water level was modelled over a period of 200 years. When tidal variation is considered, the rate of sediment accretion exceeds rising sea levels associated with climate change, resulting in no major changes in terms of inundation. When sea level rise scenarios were modelled in conjunction with the recurrence interval water levels, flooding of the coastal wetland was much greater than current levels for the 1 in 4 and 1 in 8 year events. The study suggests that for this wetland, variability of flows may be a key factor contributing to wetland resilience. Secondly, the thesis examines the variability of open wetland water surface areas and their relation to rainfall to determine wetland hydrological inputs for the Nuwejaars wetland system and respective wetlands. A remote sensing approach was adopted, Landsat 5 TM and 8 OLI multispectral imagery were used to detect changes of water surfaces for the period 1989 to 2017. Water surfaces were enhanced and extracted using the Modified Normalized Difference Water Index of Xu (2006). The coefficient of variation of wetland water surface area was determined. The variability ranges from low to high for respective wetlands. A correlation analysis of wetland water surfaces and local and catchment rainfall for the preceding 1, 3, 6, 9, 12 and 24 months was undertaken. The preceding month and associated inputs explains the annual variability of surface waters. The study suggests that, the variability of wetland water surface area are related to variations to water inputs and groundwater, as well as variations in water outputs such as evapotranspiration and an outlet channel.