Global mean sea-level (GMSL) has risen significantly due to climate change, threatening coastal populations and ecosystems. This rise, caused by thermal expansion of oceans, ice melt, and variations in land and water storage, is projected to accelerate. The resulting hazards include increased coastal flooding, habitat loss, coastal erosion, and saltwater intrusion. These impacts threaten infrastructure, economies, human livelihoods, and cultural heritage. To address these risks, integrated management strategies are crucial, requiring collaboration across disciplines. Research on SLR science has grown exponentially, making comprehensive analysis challenging. This study aims to provide a systematic evaluation of SLR science from 1990 to 2021, analyzing trends, research streams, and disciplinary contributions to identify understudied areas and inform research and policy.

The authors reviewed nearly 15,000 SLR-related articles from the Web of Science database published between 1990 and 2021. Early IPCC reports reviewed far fewer documents. This substantial increase in literature necessitates a systematic approach to understand global trends and developments in SLR research. Previous bibliometric analyses have been conducted on related topics such as climate change, coastal flooding, and adaptation strategies, but a comprehensive analysis specifically focused on the totality of SLR science was lacking. This study aims to fill this gap, providing insights into spatial and temporal trends, research streams, disciplinary involvement, and emerging management requirements.

The study employed a bibliometric approach using a term-based search strategy in the Web of Science database. The search terms included "sea-level rise" and "sea level rise" in titles, abstracts, and keywords. The analysis focused on titles, abstracts, keywords, and references of the identified articles. Keyword analysis, co-occurrence analysis, and co-citation analysis were used to identify major research themes (clusters) and sub-themes. Geographical distribution of articles was analyzed based on author affiliations. Temporal trends were analyzed to understand the evolution of research focus over time. The average number of citations per term was calculated to assess the significance of different research areas. Co-citation analysis was used to identify 16 sub-themes, ranked by the number of cited and influential references. The analysis also examined the age and persistence of these sub-themes, exploring the maturity of knowledge bases and identifying growth patterns, emergence of new sub-themes, and decline in others.

The study identified 14,951 unique SLR articles published between 1990 and 2021. Developed nations, particularly the USA, UK, Australia, and Germany, dominated research output. Four major research themes emerged: (I) geological dynamics and sea-level interactions, (II) risks and adaptation, (III) physical components of sea-level change, and (IV) coastal systems and planning. Sixteen sub-themes were identified within these clusters, including coastal wetlands and estuaries, Quaternary sea-level change, global sea-level projections, high-end sea-level rise, coastal erosion, vulnerability and adaptation, and others. Analysis revealed a shift in research focus over time, from geological aspects and pure science to solution-oriented research related to risks and adaptation. Articles focusing on high-end sea-level rise, extreme events, and ecosystem services received more citations, reflecting the increasing societal relevance of this work. There is a notable imbalance in geographical representation, with limited contributions from developing nations most vulnerable to SLR impacts. The growth rate of SLR literature was high (doubling time of 4.8 years) suggesting that the volume of SLR research is expected to continue expanding rapidly.

The findings highlight the evolution of SLR science from a predominantly geological and physical focus to a more interdisciplinary field encompassing social sciences, economics, and engineering. The shift towards solution-focused research reflects the increasing urgency to address the risks posed by SLR. The identified research gaps highlight the need for greater engagement with vulnerable communities in developing nations, incorporating local knowledge and expertise. The study emphasizes the need for improved methods for integrating diverse research outputs to inform effective adaptation strategies. This requires improved methods for literature synthesis and review, particularly given the rapid growth in publications. Addressing the mismatch between research output and regional needs, including equity, requires further research that prioritizes local contexts and incorporates community expertise. The large and growing body of research requires more advanced review methodologies capable of incorporating various data types and perspectives.

This study provides a comprehensive overview of the evolution of SLR science from 1990 to 2021. The findings reveal a shift in research focus, geographical imbalances, and significant growth in publications. The identification of key themes and sub-themes, along with the temporal trends, offers valuable insights for future research priorities and policy development. Future research should focus on bridging the gap between research and action, addressing regional disparities, integrating diverse knowledge systems, and developing more robust assessment methodologies. Addressing the challenges associated with the vast and rapidly growing body of SLR literature is crucial for effective adaptation and mitigation efforts.

While the study analyzed a large dataset, it is limited to the Web of Science database, potentially excluding relevant grey literature and publications from non-indexed journals. The categorization of research themes and sub-themes is subjective and may vary depending on interpretation. The analysis focuses on publication counts and citations, which may not fully capture the quality or impact of individual research studies. Finally, the analysis relied on keyword analysis, which can be limited in capturing the nuances of research topics and cross-disciplinary studies.