Late Holocene (0–6 ka) sea-level changes in the Makassar Strait, Indonesia

The Spermonde Archipelago, off the coast of southwest Sulawesi, consists of more than 100 small islands and hundreds of shallow-water reef areas. Most of the islands are bordered by coral reefs that grew in the past in response to paleo relative sea-level changes. Remnants of these reefs are preserved today in the form of fossil microatolls. In this study, we report the elevation, age, and paleo relative sea-level estimates derived from fossil microatolls surveyed in five islands of the Spermonde Archipelago. We describe 24 new sea-level index points, and we compare our dataset with both previously published proxies and with relative sea-level predictions from a set of 54 glacial isostatic adjustment (GIA) models, using different assumptions on both ice melting histories and mantle structure and viscosity. We use our new data and models to discuss Late Holocene (0–6 ka) relative sea-level changes in our study area and their implications in terms of modern relative sea-level estimates in the broader South and Southeast Asia region

Validation of Recent Altimeter Missions at Non-Dedicated Tide Gauge Stations in the Southeastern North Sea

Consistent calibration and monitoring is a basic prerequisite for providing a reliable time series of global and regional sea-level variations from altimetry. The precisions of sea-level measurements and regional biases for six altimeter missions (Jason-1/2/3, Envisat, Saral, Sentinel-3A) are assessed in this study at 11 GNSS-controlled tide gauge stations in the German Bight (SE North Sea) for the period 2002 to 2019. The gauges are partly located at the open water, and partly at the coast close to mudflats. The altimetry is extracted at virtual stations with distances from 2 to 24 km from the gauges. The processing is optimized for the region and adjusted for the comparison with instantaneous tide gauge readings. An empirical correction is developed to account for mean height gradients and slight differences of the tidal dynamics between the gauge and altimetry, which improves the agreement between the two data sets by 15–75%. The precision of the altimeters depends on the location and mission and ranges from 1.8 to 3.7 cm if the precision of the gauges is 2 cm. The accuracy of the regional mission biases is strongly dependent on the mean sea surface heights near the stations. The most consistent biases are obtained based on the CLS2011 model with mission-dependent accuracies from 1.3 to 3.4 cm. Hence, the GNSS-controlled tide gauges operated operationally by the German Waterway and Shipping Administration (WSV) might complement the calibration and monitoring activities at dedicated CalVal stations

The ‘Wickedness’ of Governing Land Subsidence: Policy Perspectives From Urban Southeast Asia

Drawing on Jakarta, Metro Manila and Singapore as case studies, we explore the paradox of slow political action in addressing subsiding land, particularly along high-density urban coastlines with empirical insights from coastal geography, geodesy analysis, geology, and urban planning. In framing land subsidence as a classic ‘wicked’ policy problem, and also as a hybrid geological and anthropogenic phenomenon that is unevenly experienced across urban contexts, the paper uses a three-step analysis. First, satellite-derived InSAR maps are integrated with Sentinel-1A data in order to reveal the socio-temporal variability of subsidence rates which in turn pose challenges in uniformly applying regulatory action. Second, a multi-sectoral mapping of diverse policies and practices spanning urban water supply, groundwater extraction, land use zoning, building codes, tenurial security, and land reclamation reveal the extent to which the broader coastal governance landscape remains fragmented and incongruous, particularly in arresting a multi-dimensional phenomenon such as subsidence. Finally, in reference to distinct coastal identities of each city–the ‘Sinking Capital’ (Jakarta), ‘Fortress Singapore’, and the ‘Disaster Capital’ (Manila) the paper illustrates how land subsidence is portrayed across the three metropolises in markedly similar ways: as a reversible, quasi-natural, and/or a highly individualized problem

Fossil Java Sea corals record Laurentide ice sheet disappearance

The Laurentide ice sheet was the largest late Pleistocene ice mass and the largest contributor to Holocene pre-industrial sea-level rise. While glaciological dates suggest final ice sheet melting between 8 and 6 ka, inversion of sea-level data indicates deglaciation at ca. 7 ka. Here, we present new chronostratigraphic constraints on Laurentide ice sheet disappearance based on Holocene relative sea-level observations from the tectonically stable north coast of Java, Indonesia. Age-elevation data from the flat upper surfaces of 13 fossil intertidal corals (i.e., microatolls) indicate that the Java Sea experienced a relative sea level of 1.3 ± 0.7 m above present between 6.9 and 5.3 ka. To determine uncaptured relative sea-level trends within the observational uncertainties of this apparently constant highstand, we analyzed the internal structure of three sliced microatolls from the same site to produce a high-resolution data set. These data were used to statistically model relative sea-level rates and trends. Employing the data with the model provided evidence for a short-lived rise of relative sea level from 1.0 ± 0.3 m above present at 6.7 ± 0.1 ka to 1.9 ± 0.3 m above present at 6.4 ± 0.1 ka. The end of this rise likely represents the last input of meltwater from the vast Laurentide ice sheet, which, consequently, collapsed at least 400 yr later than assumed by some widely used models of glacial isostatic adjustment. Incorporating these new results into such predictive models will help to better understand the geographical variability of future sea-level rise as a result of global warming

On the Scientific Applications of IGS Products: An Assessment of the Reprocessed TIGA Solutions and Combined Products

Global sea levels have risen since the early 19th century and this rise is likely to accelerate through the 21st century and beyond. Much of the past information on sea level rise stems from the instrumental records of tide gauges, which measure changes in sea level relative to a tide gauge benchmark (TGBM) situated on land. In order to assess regional or global sea level changes the vertical land movements (VLM) at the tide gauge and its TGBM need to be monitored. GNSS, in particular GPS, has been recognized as one space-geodetic technique to provide highly accurate estimates of VLM in a geocentric reference frame for tide gauges and their TGBMs. As it turned out, this scientific application of GNSS poses the most stringent requirements on the consistency and homogeneity on the data, processing strategies, satellite products, bias models and reference frames used in the analysis of GNSS measurements. Under the umbrella of the International GNSS Service (IGS), the Tide Gauge Benchmark Monitoring (TIGA) Working Group (WG) has the objective to provide highly-accurate positions and VLM estimates for a global network of tide gauges contributing to the Global Sea Level Observing System (GLOSS) and the Permanent Service for Mean Sea Level (PSMSL). As such TIGA forms an important contribution of the IGS to the goals of the Global Geodetic Observing System (GGOS), the Global Climate Observing System (GCOS) and the World Climate Research Programme (WCRP). To achieve the TIGA-WG objectives, five TIGA Analysis Centers (TACs) contributed re-processed global GPS network solutions to TIGA, employing the latest bias models and processing strategies in accordance with the second IGS re-processing campaign (repro2). These individual TAC solutions were then used to compute the combined products by the TIGA Combination Centre (TCC) at the University of Luxembourg using an in-house modified version of the CATREF software package. In this study, we present and internally evaluate the individual TAC and TIGA combined products. We investigate station positions, scale and origin biases, including their frequency content. We also externally evaluate the combined products, particularly the VLM estimates, using solutions from the ITRF2008, ITRF2014 and the glacial isostatic adjustment model ICE-6G (VM5a). Finally, we draw some conclusions on the recent advances and remaining limitations of the various IGS products required for the challenging application to sea level studies

A Global Vertical Land Movement Data Set from a Combination of Global Navigation Satellite System Solutions

Coastal sea-level measurements by tide gauges provide the longest instrumental records of sea-levels with some stretching from the 19th century to present. The derived mean sea-level (MSL) records provide sea-level relative to a nearby tide gauge benchmark (TGBM), which allows for the continuation of this record in time after, for example, equipment modifications. Any changes in the benchmark levels induced by vertical land movements (VLM) affect the MSL records and hence the computed sea-levels. In the past, MSL records affected by VLM were often excluded from further analyses or the VLM were modelled using numerical models of the glacial isostatic adjustment (GIA) process. Over the last two decades Global Navigation Satellite System (GNSS), in particular Global Positioning System (GPS), measurements at or close to tide gauges and the development of the associated processing strategies, have made it possible to obtain estimates of VLM in a geocentric reference system, such as the International Terrestrial Reference Frame release 2008 (ITRF2008) that approach the required accuracy for sea-level studies. Furthermore, the GPS-derived VLM estimates have been shown to improve estimates of sea-level change compared to those using the aforementioned GIA models as these models cannot predict local subsidence or uplift. The International GNSS Service (IGS) Tide Gauge Benchmark Monitoring (TIGA) Working Group has recently re-processed the global GNSS data set from its archive (1000+ stations for 1995-2014) to provide VLM estimates tuned for the sea-level community. To achieve this, five TIGA Analysis Centers (TAC) contributed their reprocessed global GPS network solutions to the WG, all employing the latest bias models and processing strategies in accordance with the second re-processing compaign (repro2) of the IGS. These individual solutions were then combined by the TIGA Combination Center (TCC) to produce, for the first time, a TIGA combined solution (Release 0.99). This combined solution allows an evaluation of each individual TAC solution while also providing a means to gauge the quality and reliability of the combined solution, which is generally regarded as superior to the individual TAC solutions. Using time series analysis methods, estimates of VLM can then be derived from the daily position estimates, which are sub-sequentially employed to investigate coastal sea-levels. In this study, we show results from the evaluation of the relevant solutions, provide an evaluation of the TIGA VLM estimates and give examples of their impact on sea-level estimates for selected tide gauges from around the world. The TAC and TIGA combined solutions, as well as the derived VLM data sets are available from the IGS TIGA WG and will be accessible through SONEL (www.sonel.org) in the near future

Next Generation Train: Dynamisches Flügeln, Beschreibung eines Betriebskonzepts auf Basis der zukünftigen LST, MS 2420 1712

Im Rahmen des Arbeitspakets 2420 von NGT 3 wurde eine Leit- und Sicherungstechnik skizziert, die die die Möglichkeiten und Vorteile des in NGT betrachteten dynamischen Flügelns für den operativen Eisenbahnbetrieb umsetzen soll. Diese LST wurde VCTCS genannt (Virtual Coupling Train Control System) und grob in zwei Ausbaustufen aufgebaut: a) VCTCS Level 1 (Fahren im relativen Bremswegabstand mit herkömmlichen Weichen) und b) VCTCS Level 2 (Nutzung passiver Weichen und weitgehender Selbstorganisation der Fahrwegsicherung). Im Rahmen des Generischen Betriebskonzepts wurde gezeigt, welche Effekte bereits die Einführung von dynamischem Flügeln mit Hilfe von VCTCS Level 1 auf den tatsächlichen Eisenbahnbetrieb haben könnte. Im Rahmen des hier vorliegenden Berichts wurde untersucht, welche weitreichenden Effekte das vollumfängliche Ausrollen von VCTCS Level 2 auf die Eisenbahnwelt haben wird. Auf Basis dessen wurden Überlegungen angestellt, welche Effekte sich daraus für den Eisenbahnbetrieb der Zukunft ergeben. Dabei wurde bewusst darauf geachtet, die Betrachtungen unabhängig von den heutigen etablierten Verfahrensweisen und historisch gewachsenen Prozessen zu halten. Ausgangspunkt war die Idee, mit der neuen Sicherungstechnik und den Passivweichen einen spontanen selbstorganisierten Betrieb mit kurzen Fahrzeugen auf die Gleise zu bringen. Nach dem Betrachten mehrerer Szenarien sind allerdings einige Einschränkungen gegenüber dem freien Autobahnverkehr zu erwarten. Eine These hierzu ist: Es ist eine zentrale regelnde Instanz erforderlich, die für einen sichereren und effizienteren Eisenbahnbetrieb sorgt. Da die Bremswege im Bahnverkehr länger sind, muss jeder Zug von einer anderen Instanz Informationen über die Gleisbelegung erhalten. Diese andere Instanz können keine anderen Züge sein, da diese durch Kommunikationsstörungen o. ä. verschwinden können. Eine weitere These ist: Es wird im Eisenbahn-Personenverkehr auch in Zukunft eine Art Fahrplan geben müssen. Ursache dafür ist hauptsächlich die Existenz von Weichen, die in jedem Falle weniger Gleiswechsel ermöglichen, als dies bei Spurwechseln auf Straßen möglich ist. Dadurch ergibt sich immer die Tendenz Eisenbahnfahrzeuge zu längeren Einheiten zusammenzukuppeln. Da die Züge länger sind als ein Pkw werden Zeitvereinbarungen für die Abfahrt erforderlich sein, was einem Fahrplan entspricht

Abstract Wind Speed and SWH Calibration for Radar Altimetry in the North Sea

Satellite altimetry is a valuable tool for the determination of instantaneous sea level or mean sea surface height. Beside these quantities, the returning waveform and the backscatter coefficient can be used for computing the significant wave height (SWH) and wind speed. Both values are only raw estimates and have to be calibrated properly for useful operational services, like weather forecasting, ship routing or storm warnings. The accuracy of the satellite derived wind speed and SWH is degraded due to insufficient in-situ data used for calibration or the large distance between the in-situ sensors and the measurements. Only a few locations worldwide, oil platforms or buoys, exist for calibrations. The limited geographical distribution causes problems due to the different sea state behavior in different regions. In some studies ECMWF wind fields are used for calibration, but the local wind may vary more rapidly than computed from the models. In addition, the wind speed retrieval algorithm as used today was developed for Geosat and has to be calibrated and inter-calibrated between different satellites, e.g. to ERS-2 and TOPEX/Poseidon in order to get comparable values. Also for ENVISAT the algorithm of Witter & Chelton [16] will be used. The German Weather Service (DWD) is operating weather stations onshore and offshore, achieving highly accurate wind speed, wind direction and air pressure data. Moreover, the Federal Agency for Maritime Service (BSH) is operating a network of waverider buoys, estimating the SWH every 3 hours. Both data sets are available since 1992 an