BEGIN:VCALENDAR VERSION:2.0 PRODID:-//pretalx//talks.staging.osgeo.org//foss4g-europe-2025//talk//7WXHL S BEGIN:VTIMEZONE TZID:CET BEGIN:STANDARD DTSTART:20001029T040000 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10 TZNAME:CET TZOFFSETFROM:+0200 TZOFFSETTO:+0100 END:STANDARD BEGIN:DAYLIGHT DTSTART:20000326T030000 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3 TZNAME:CEST TZOFFSETFROM:+0100 TZOFFSETTO:+0200 END:DAYLIGHT END:VTIMEZONE BEGIN:VEVENT UID:pretalx-foss4g-europe-2025-7WXHLS@talks.staging.osgeo.org DTSTART;TZID=CET:20250717T110000 DTEND;TZID=CET:20250717T113000 DESCRIPTION:Palaeogeography is the study of past geography\, focusing on th e physical landscapes\, climate\, and environments of the Earth in past ov er geological periods. It reconstructs the positions of continents\, ocean s\, mountain ranges\, and ecosystems over millions of years\, helping scie ntists understand plate tectonics\, past climates\, and the evolution of l ife.\nPalaeogeographic maps can be generated with qualitative to semi-quan titative methods\, for instance by discriminating between oceans\, coastal and land areas\, or can be fully quantified\, with each pixel of the map being assigned a specific elevation value. Unlike other plate tectonic mo dels\, PANALESIS is able to depict fully quantified palaeogeographic maps at 0.1° x 0.1° resolution from 545 million years ago until present-day\, in ca.10-million-year time steps.\nPalaeogeography can also be leveraged to estimate sea-level variations. By calculating the oceans volumes\, and comparing them to the present-day volume\, we can quantify the increase or decrease in sea-level required to match this reference. These sea-level v ariations can then be compared and validated against estimates from other plate tectonic models\, and with other methods such as stratigraphic studi es.\nAn initial sea-level curved based on PANALESIS was published in 2015 (Vérard et al.\, 2015). The methodology was never published in detail and was running on ArcGIS\, using a now obsolete system that cannot be run an ymore. This implies that it is not possible to reproduce or verify these r esults.\nTo address this\, we have entirely rewritten and enhanced the sou rce code into a QGIS plugin named TopoChronia. With this paper\, we presen t the new sea-level curve derived from the new palaeogeographic maps and c ompare them with other data from the literature\, including the 2015 PANAL ESIS data.\nWe also highlight critical issues that impacted this transitio n to open-source and open science in general\, including input data and so urce code management practices\, mismatch between published results\, inpu t data and code\, as well as methodological errors\, and the way towards F AIR compliance.\nWe use a straightforward methodology\, which converts the model input lines into points\, to each of which is assigned an elevation value based on modelling of the geological (or tectonic) setting they bel ong to (Vérard\, 2017). Settings include for instance collision and subdu ction zones\, active or passive margins and mid-oceanic ridges. \nA global raster is then interpolated form these points using the QGIS Triangulated Irregular Network (TIN) method\, as it has shown to perform well in these circumstances (Franziskakis et al.\, in prep). From this global raster\, we calculate the volume below the elevation of 0m and compare it with the present-day volume of oceans. \nAssuming a constant oceanic volume through time\, we can therefore estimate the required increase or decrease in sea -level required to match this volume\, using Allen & Allen (Allen & Allen\ , 2005) equations. These equations divide the newly added water column hei ght into an increase of water above initial sea-level (∆SL) and the subs idence (S) of oceanic floor caused by the added water. \nWe compare the PA NALESIS v0 results (spanning form 545Ma to present-day) and we also includ e the PANALESIS v1 results\, currently spanning form 888Ma to 330Ma.\nOver all\, both the original and the new v0 seem to follow similar tendencies\, but with differences in amplitude. The original PANALESIS curve shows low er values compared to the new one\, with a median value of +45m. This can be explained by a few factors\, including:\n1. The reference volume used i n 2025 is based on the ETOPO volume under z = 0m\, whereas the 2015 refere nce volume was the 000 Ma (present-day) PANALESIS reconstruction volume\, which was significantly higher than ETOPO.\n2. The method to calculate the required sea-level rise has changed. For the original version\, a 0.55 ra tio of the added water column height was used\, whereas now the rise is fo llowing Allen & Allen equations\, which approximates a higher ratio of 0.6 9. This leads to a 25% higher final sea-level increase.\n3. The input data has since changed. Modifications have been made to some features (e.g. as signing a younger age to a feature)\, leading to large areas being shallow er than previously\, as depth is primarily controlled by age. \n4. A diffe rent interpolation method was used\, previously Natural Neighbour from Arc GIS\, and now replaced by QGIS TIN.\nThe v1 curve also differs from the v0 ones as the newest version of the model has been strongly enhanced and co ntains much more details. However\, the v1 model only spans from 888 to 33 0 Ma\, allowing comparison only between 330 and 545 Ma.\nImprovements are still required on the palaeogegraphy\, including the incorporation of clim ate feedback: simulations for CO2 concentration and precipitation estimate s at global scale will help shape better sediment fluxes. It is also impor tant to consider ice sheets formation and melting\, strongly controlled by the presence or absence of land in polar regions.\nAnother aspect is the quantification of error propagation: starting with the input model (time + space)\, points distribution (space)\, interpolation (oceans volume\, sea -level)\, orbital parameters related to glacial/interglacial cycles (ocean s volume\, sea-level).\nFinally\, the transition to open-source and open d ata is necessary and underway to make input and output data available\, al ongside the processing software. This has already started by making the To poChronia code available online and will contribute to more transparency a nd reproducibility. DTSTAMP:20260527T042044Z LOCATION:PA01 (Quarticle) SUMMARY:Comparing 545 Million Years of Sea-Level Change: New insights from the TopoChronia QGIS Plugin - Florian Franziskakis URL:https://talks.staging.osgeo.org/foss4g-europe-2025/talk/7WXHLS/ END:VEVENT END:VCALENDAR