Future average water levels – Based on data from IPCC AR6 WG 1 (2021)

Future mean water levels in RH 2000 and the approximate future location of the shoreline along Sweden’s coastline are calculated for several different scenarios and for each decade from 2030 to 2150. The data are based on regional projections from the IPCC compilation “AR6 Interim Report 1 – The Science Foundation” published in August 2021. The calculations are adjusted for the local land uplift. The calculations are based on projections, which the IPCC considers likely, for five different emission scenarios: SSP1-1.9, SSP1-2,6, SSP2-4,5, SSP3-7.0 and SSP5-8.5. In addition to these, there are two calculations based on projections that the IPCC deems less likely, as they include processes associated with deep uncertainty related to inland ice instability: SSP1-2.6 less likely and SSP5-8.5 less likely. Three different levels are given for each scenario and decade. The three levels are the median and the 17th and 83 rd percentiles. The extremes are not shown, i.e. neither the highest possible level nor the lowest possible. Data on future mean water levels in cm in RH 2000 are available for download in CSV format for each coastal municipality in Sweden (87). The levels can also be seen in an interactive table at https://www.smhi.se/klimat/stigande-havsnivaer/framtida-medelvattenstand-1.165493 . Data on the future location of the shoreline are available for download in SHAPE format for each year and likely, or less likely scenario. These can also be consumed through a WMS service. The average water level in cm in RH 2000 is available for download in TIFF format for each year and likely, or less likely scenario. The above map layer is still produced, i.e., map layers from all years and scenarios are not yet available, but will be replenished gradually until all are in place. So far, map layers for the years 2050, 2070, 2100, 2110, 2120, 2130, 2140 and 2150 have been developed. RESTRICTIONS The geographical distribution of the map layers is limited to the area between about 10 km off the shoreline and 1-1.5 km within the shoreline. Larger rivers and lakes located within this area can have a sharp limit in the map layers. Islands less than 1 000 km² are filtered out and are not included in the map layers. Comment on data in CSV format The future mean water level for each SSP scenario and year may vary between grid squares within a coastal municipality. This is mainly due to variations in the pace of land elevation, especially in municipalities that are spreading north-south direction. Gotland has the greatest difference in long-term land elevation within its coastal area, where it differs just under 1.8 mm/year between different areas. This makes a difference of 9 centimeters in 50 years. The average water level during the reference period (1995-2014) may also vary within a municipality’s coastal area, but these are minor variations of up to about 4 centimeters. The future mean water level is therefore provided as an average for each coastal municipality. Comments on: 1. Average water levels are combined with topographic information from Lantmäteriet. Areas with an altitude level lower than the calculated mean water level are classified as permanently flooded. Any variation in the accuracy of the topographic information may affect the outcome of the map layers. There may also be newer or more detailed topographic information than the one used when the map layers were created. 2. In the topographic map data used in the calculations, there may be a lack of detailed information on where natural or constructed obstacles or passages between land and sea exist or are missing. This means that land areas that are lower than the future sea level can be shown as flooded even though in reality there may be obstacles for the sea to reach it. 3. It occurs that the land rise in parts of Sweden is larger than the sea level rise. This means that in the near future sea level will be lower than it is today. In these places, where land rises faster than the sea rises, the future sea level is shown as if it were unchanged, i.e. at the same level as today. 4. Any effects on the coastline of a change in mean water level (e.g. erosion) cannot be inferred from the map layers. USE The average water level determines where the sea surface and the shoreline are normally located. The data can be used to study possible future mean water levels based on different emission scenarios and years. The data provides a comprehensive basis for information on future sea levels. The aim is not to provide a full basis for decision-making, but to provide an indication of the areas in which a more detailed basis should be produced. When there is a lot of wind, the sea can rise sharply above the average water level for a short period of time. This is called a high-water event. In the planning context, there may be a need to take into account high-water events, wave effects and the like. High-water events and wave effects are not included in the data on future mean water levels. Read more about this on the following website: https://www.smhi.se/klimat/stigande-havsnivaer/hogvattenhandelser-och-extremnivaer-1.165445. Production of the CSV files has been completed. Map warehouses are still produced and launched gradually.针对瑞典海岸线沿线的2000年参考高程（RH 2000）下的未来平均水位，以及海岸线的近似未来位置，本数据集针对多种不同情景，计算了2030年至2150年每十年的对应结果。数据基于政府间气候变化专门委员会（IPCC）2021年8月发布的《AR6临时报告1——科学基础》（AR6 Interim Report 1 – The Science Foundation）中的区域投影，且计算过程已针对当地陆地抬升进行了校正。 本次计算基于IPCC认定为大概率发生的五种不同排放情景的投影，即SSP1-1.9、SSP1-2.6、SSP2-4.5、SSP3-7.0与SSP5-8.5。除此之外，另有两种基于IPCC认定为低概率情景的投影开展的计算，这类情景包含与内陆冰不稳定性相关的深度不确定性过程，分别为低概率SSP1-2.6情景与低概率SSP5-8.5情景。 每种情景与每十年的结果均提供三个不同水平值，分别为中位数、17百分位数与83百分位数，未展示极端值，即既未包含最高可能水位，也未包含最低可能水位。 瑞典各沿海市镇（共87个）的RH 2000下未来平均水位数据（单位：厘米）可通过逗号分隔值（CSV）格式下载获取。用户也可在以下交互式表格中查看相关数据：https://www.smhi.se/klimat/stigande-havsnivaer/framtida-medelvattenstand-1.165493。 海岸线未来位置的数据可按年份与大概率/低概率情景分类，以SHAPE格式下载获取，也可通过网络地图服务（WMS）调用。以RH 2000为基准的平均水位数据（单位：厘米）可按年份与大概率/低概率情景分类，以标签图像文件格式（TIFF）下载获取。上述地图图层仍在制作中，即目前尚未提供所有年份与所有情景的地图图层，但将逐步补充完善直至全部上线。截至目前，已完成2050年、2070年、2100年、2110年、2120年、2130年、2140年与2150年的地图图层开发。 ## 使用限制 地图图层的地理分布范围限定于海岸线外约10公里至海岸线内1至1.5公里的区域。该区域内的大型河流与湖泊在地图图层中会存在清晰的边界阈值。面积小于1000平方公里的岛屿将被过滤，不会纳入地图图层。 ### CSV格式数据说明 针对某一SSP情景与某一年份，沿海市镇内的不同网格单元的未来平均水位可能存在差异，这主要源于陆地抬升速率的差异，尤其在呈南北向延伸的市镇中更为明显。哥特兰岛（Gotland）沿海区域的长期陆地抬升差异为瑞典各沿海市镇中最大，不同区域的抬升速率差异接近1.8毫米/年，这将在50年内造成约9厘米的水位差异。参考时段（1995年至2014年）内的平均水位在沿海市镇范围内也可能存在小幅波动，最大差异约为4厘米。因此，未来平均水位以各沿海市镇的平均值形式提供。 ### 补充说明 1. 平均水位与瑞典土地测量局（Lantmäteriet）提供的地形信息相结合。海拔低于计算所得平均水位的区域将被归类为永久性淹没区域。地形信息的精度差异可能会影响地图图层的生成结果，且可能存在比制作地图图层时所使用的地形数据更新、更详细的地形资料。 2. 本次计算所使用的地形地图数据中，可能缺乏关于海陆间天然或人工障碍物、通道的详细信息，这意味着实际存在阻碍海水侵入的障碍时，海拔低于未来海平面的陆地区域仍可能被标注为淹没区域。 3. 瑞典部分区域的陆地抬升速率高于海平面上升速率，这意味着在不久的将来，当地海平面将低于当前水平。在这类陆地抬升速率超过海平面上升速率的区域，未来海平面将被标注为与当前持平。 4. 地图图层无法反映平均水位变化对海岸线造成的各类影响（例如海岸侵蚀）。 ## 使用指南 平均水位决定了海面与海岸线的常规位置。本数据集可用于研究不同排放情景与不同年份下的未来平均水位情况。 本数据为未来海平面相关信息提供了全面的参考基础，其目的并非为决策提供完整依据，而是用于指示需要进一步开展详细研究的区域。 当出现强风时，海平面可能在短时间内大幅高于平均水位，此类现象被称为高潮位事件。在规划工作中，可能需要考虑高潮位事件与波浪效应等因素，但未来平均水位数据并未涵盖此类内容。相关详细信息可访问以下网站：https://www.smhi.se/klimat/stigande-havsnivaer/hogvattenhandelser-och-extremnivaer-1.165445。 CSV文件的制作已全部完成，地图图层仍在逐步制作并上线发布。