Periodic Reporting for period 3 - SHExtreme (Estimating contribution of sub-hourly sea level oscillations to overall sea level extremes in changing climate)
Reporting period: 2023-09-01 to 2025-02-28
Coping with sea level rise caused by climate change is one of the most important challenges facing modern society. Mean sea level (MSL) is projected to rise 40 to 60 cm worldwide by the end of the 21st century. Higher mean sea level means that flood risks associated with extreme sea levels (ESL) will also increase, with 100-year return values of extreme events on European coasts projected to increase by 50 to 90 cm by 2100. ESLs occur due to a superposition of numerous oceanic phenomena acting at different temporal (from seconds to millennia) and spatial scales (from bays to oceans). The SHExtreme project will, for the first time, investigate in depth the contribution of under-researched sub-hourly sea level oscillations to ESLs along the European coast. High-resolution 1-min sea level data measured at more than 100 tide gauge stations, as well as reanalyses, hindcasts, and future climate simulations, will be analysed to achieve the project goals of (i) assessing the present-day distribution of sub-hourly sea level oscillations and estimating their contribution to total ESLs; (ii) linking sub-hourly ESLs to governing atmospheric conditions; (iii) estimating the future strength and distribution of sub-hourly ESLs. The SHExtremes project will, thus, provide the first comprehensive estimate of the intensity, frequency, and spatial and temporal distribution of current and future sub-hourly ESLs along European coasts.
The main outcomes of the project, so far, are:
1. Creation of a database of high-quality 1-min measurements of sea level. This is a database of unprecedented quality for European sea level data measured at time steps of 1-20 minutes, and it is likely to be used for numerous research activities in the future. The database will be made publicly available through existing sea level data services.
2. Improved understanding of the importance of sub-hourly sea level oscillations. Traditionally, extreme sea levels have been studied using either low-frequency (hourly) sea level series (when studying storm surges) or high-frequency series (when studying various forms of tsunamis, including meteotsunamis). In SHExtreme, we examine the joint effect of low-frequency and high-frequency sea-level oscillations, and show that processes at both scales can contribute significantly to overall extremes and should be evaluated together when assessing hazards caused by extreme sea levels.
3. Research on tsunamis caused by the eruption of the Hunga Tonga-Hunga Ha'apai volcano. The eruption occurred on January 15, 2022, and triggered two types of tsunamis: a tsunami generated by the initial displacement of the water level due to the submarine eruption (this tsunami reached heights of up to 90 m and was felt along the coasts of the Pacific Ocean), and tsunamis triggered by atmospheric waves that circled the Earth several times. As part of the project, we conducted some of the first published research on this topic.
4. Educational activities for local island communities. As part of the SHExtreme project, we have made significant efforts to promote marine research at the local level. We do this through an activity called " Oceanographers on the island" (https://www.facebook.com/oceanografi/(opens in new window)). We visit islands and organise one- to two-day workshops for school children, game nights on oceans and ecology, and popular lectures for local people. So far, we have visited six Croatian islands, reaching several hundred children and islanders. We plan to continue these activities throughout the project and beyond.
5. Meteotsunami catalogue - a unique meteotsunami catalogue was created for the Adriatic coast (https://projekti.pmfst.unist.hr/floods/meteotsunamis/(opens in new window)). This is one of the first meteotsunami catalogues, and we hope that it will serve as a base catalogue to which meteotsunami events from other European coasts will be added. The catalogue contains detailed information on 36 meteotsunami events measured along the Adriatic coast. A source is given for each event, along with descriptions of atmospheric and sea level variability and detailed synoptic analyses.
In summary, the SHExtreme project is the first to comprehensively investigate the contribution of under researched sub-hourly sea-level oscillations to extreme sea levels along European coasts. Our initial published analyses, as well as ongoing research, have shown that sub-hourly sea level oscillations have been unfairly omitted from sea level extremes analysis - an omission that must be corrected as soon as possible in the face of accelerated sea level rise.
1. Creation of a database of high-quality 1-min measurements of sea level. This is a database of unprecedented quality for European sea level data measured at time steps of 1-20 minutes, and it is likely to be used for numerous research activities in the future. The database will be made publicly available through existing sea level data services.
2. Improved understanding of the importance of sub-hourly sea level oscillations. Traditionally, extreme sea levels have been studied using either low-frequency (hourly) sea level series (when studying storm surges) or high-frequency series (when studying various forms of tsunamis, including meteotsunamis). In SHExtreme, we examine the joint effect of low-frequency and high-frequency sea-level oscillations, and show that processes at both scales can contribute significantly to overall extremes and should be evaluated together when assessing hazards caused by extreme sea levels.
3. Research on tsunamis caused by the eruption of the Hunga Tonga-Hunga Ha'apai volcano. The eruption occurred on January 15, 2022, and triggered two types of tsunamis: a tsunami generated by the initial displacement of the water level due to the submarine eruption (this tsunami reached heights of up to 90 m and was felt along the coasts of the Pacific Ocean), and tsunamis triggered by atmospheric waves that circled the Earth several times. As part of the project, we conducted some of the first published research on this topic.
4. Educational activities for local island communities. As part of the SHExtreme project, we have made significant efforts to promote marine research at the local level. We do this through an activity called " Oceanographers on the island" (https://www.facebook.com/oceanografi/(opens in new window)). We visit islands and organise one- to two-day workshops for school children, game nights on oceans and ecology, and popular lectures for local people. So far, we have visited six Croatian islands, reaching several hundred children and islanders. We plan to continue these activities throughout the project and beyond.
5. Meteotsunami catalogue - a unique meteotsunami catalogue was created for the Adriatic coast (https://projekti.pmfst.unist.hr/floods/meteotsunamis/(opens in new window)). This is one of the first meteotsunami catalogues, and we hope that it will serve as a base catalogue to which meteotsunami events from other European coasts will be added. The catalogue contains detailed information on 36 meteotsunami events measured along the Adriatic coast. A source is given for each event, along with descriptions of atmospheric and sea level variability and detailed synoptic analyses.
In summary, the SHExtreme project is the first to comprehensively investigate the contribution of under researched sub-hourly sea-level oscillations to extreme sea levels along European coasts. Our initial published analyses, as well as ongoing research, have shown that sub-hourly sea level oscillations have been unfairly omitted from sea level extremes analysis - an omission that must be corrected as soon as possible in the face of accelerated sea level rise.
The SHExtreme project will provide the first comprehensive estimate of the intensity, frequency, and spatial and temporal distribution of present and future sub-hourly extreme sea levels along European coasts. From a practical point of view, it will also enable more detailed hazard assessment studies related to extreme sea levels, thus making an important contribution to coastal planning and management.
The main expected outcomes of the SHExtreme project can be summarized as follows: (i) creation of a high quality database of 1-minute sea level measurements; (ii) assessment of the current distribution of sub-hourly sea level oscillations and estimation of their contribution to the total extreme sea level events on the European coasts; (iii) development of novel algorithms for the detection of atmospheric synoptic conditions associated with sub-hourly extreme sea levels; (iv) estimation of the future magnitude and distribution of extreme sea levels associated with sub-hourly sea level oscillations at European coasts.
The main expected outcomes of the SHExtreme project can be summarized as follows: (i) creation of a high quality database of 1-minute sea level measurements; (ii) assessment of the current distribution of sub-hourly sea level oscillations and estimation of their contribution to the total extreme sea level events on the European coasts; (iii) development of novel algorithms for the detection of atmospheric synoptic conditions associated with sub-hourly extreme sea levels; (iv) estimation of the future magnitude and distribution of extreme sea levels associated with sub-hourly sea level oscillations at European coasts.