In a groundbreaking study, researchers from The Hong Kong Polytechnic University (PolyU) have revealed alarming data concerning global sea levels, using advanced satellite laser ranging techniques. The investigation, which spans three decades from 1993 to 2022, presents the first precise long-term record of global ocean mass change. This work is crucial as it underscores the accelerated rise in global mean sea level (GMSL), now estimated to be increasing at a rate of approximately 3.3 mm per year. As climate change continues to intensify, these findings are significant for understanding future projections regarding sea-level rise.
GMSL acts as an important indicator of climate change, influenced primarily by two driving elements: thermal expansion of seawater, as the oceans absorb a staggering 90% of the excess heat related to climate change, and the increase in global ocean mass due to freshwater influx from melting land ice. This highlights a vital area of research as monitoring global ocean mass changes is essential for accurately assessing present-day GMSL rise. With the implications of rising sea levels on coastal communities and ecosystems, understanding this phenomenon is more crucial than ever.
The research team, which includes Prof. Jianli Chen, a renowned expert in Space Geodesy and Earth Sciences at PolyU, and Dr. Yufeng Nie, the lead author and research assistant professor, has illuminated the direct observations of global ocean mass estimates for the first time through the innovative use of time-variable gravity field data derived from satellite laser ranging (SLR). This advancement marks a significant step forward in the quest to understand and quantify the factors contributing to sea-level rise around the world.
Historically, scientists primarily relied on satellite altimetry for assessing sea-level rise projections. However, with the historical data from satellite gravimetry becoming available only after 2002 with the Gravity Recovery and Climate Experiment (GRACE) mission, it has limited comparative studies. SLR, a traditional and proven technique that measures the distance between satellites and ground stations using laser ranging, faced challenges relating to its direct application in estimating ocean mass change. The study effectively overcomes these limitations through its cutting-edge forward modeling technique, which improves spatial resolution by incorporating detailed geographic information about ocean-land boundaries.
The researchers discovered that between 1993 and 2022, an estimated global average sea-level rise of approximately 90 mm occurred, with around 60% of this rise attributed to the increase in ocean mass. A critical observation points to the period post-2005, where the acceleration of GMSL was predominantly driven by the rapid increase in ocean mass due to significant land ice melting events, particularly in Greenland. The study reveals that over 80% of the total increase in ocean mass during this timeframe was a direct result of melting polar ice sheets and mountain glaciers.
Prof. Chen stressed that climate warming over recent decades has significantly intensified land ice loss, emerging as a key factor in global sea-level rise. He emphasized the importance of their findings, which facilitate the precise quantification of ocean mass increase and provide a vital assessment regarding its long-term impacts on the sea-level budget. The data produced from this study promises to play a crucial role in validating coupled climate models, enhancing the accuracy of predictions regarding future sea-level rise scenarios.
Dr. Nie highlighted the success of their research, noting the alignment between ocean mass changes derived from SLR analysis and the total sea level changes observed through satellite altimeters, once the effects of ocean thermal expansion have been considered. This synchronization provides strong evidence that traditional SLR techniques can now be applied effectively as a potent and innovative tool in the ongoing study of long-term climate changes.
The successful integration of satellite laser ranging into this field of research not only sets a new standard for analyzing ocean mass changes but also signifies a major shift towards more robust methodologies for climate research. With the interconnectedness of natural systems, better understanding of these elements is paramount as humanity grapples with the increasingly complex challenges posed by climate change.
As the ongoing impacts of climate change become ever more pronounced, accurate data on sea-level changes becomes indispensable. This research equips scientists with valuable insights into the extent of ocean mass changes and provides a framework for continuous monitoring, which is critical for both immediate assessments and long-range climate modeling.
Through this pioneering study, PolyU researchers have unveiled informative trends that could shape policies and strategies towards mitigating the anticipated impacts of sea-level rise. These findings are a call for urgent action and awareness regarding climate-related issues that will affect millions globally. The implications of this research point towards a pivotal shift in understanding and responding to the rising tides that threaten our coastal communities.
As more information emerges about the interplay between melting ice and rising sea levels, the urgency to address climate change impacts on a global scale becomes apparent. Research such as that conducted by the team at PolyU is not just academic; it serves as a clarion call to policymakers, stakeholders, and the global community to engage in proactive measures in response to scientific evidence.
The documentation of these pivotal findings furthers the pain of acknowledgment of climate shifts while simultaneously fostering hope through scientific innovation and collaboration. Continued investigation and implementation of these technologies will pave the way for a better understanding of our planet’s future as we navigate the challenges of global warming and its repercussions on sea levels.
In conclusion, as we herald the significance of these findings, let them serve as a basis for ongoing dialogue and action surrounding climate change and its direct impact on global sea levels. The research done by these PolyU scientists not only sheds light on an urgent issue but also reinforces the critical intersection of science and society. As we look toward the future, may this study inspire increased engagement across disciplines and communities to combat and adapt to the challenges we face.
Subject of Research: Ocean Mass Change and Global Sea Level Rise
Article Title: Elevated Ocean Mass: New Insights on Global Sea Level Rise from Advanced Satellite Techniques
News Publication Date: 30-Jun-2025
Web References: Proceedings of the National Academy of Sciences
References: DOI: 10.1073/pnas.2425248122
Image Credits: © 2025 Research and Innovation Office, The Hong Kong Polytechnic University. All Rights Reserved.
Keywords
Sea Level Rise, Climate Change, Ocean Mass, Satellite Laser Ranging, Global Warming, Melting Ice, Environmental Research, Climate Modeling, Geodesy, Oceanography.
