Rising global mean sea level (GMSL) is one of the clearest signs of a warming planet. Researchers at The Hong Kong Polytechnic University (PolyU) have produced the first highly precise 30-year (1993-2022) record of changes in global ocean mass, also known as barystatic sea level. Their findings show that the growing mass of the oceans has played a leading role in pushing sea levels higher.
Over this period, GMSL increased at an average rate of about 3.3 mm per year, and the rate itself has been speeding up, underscoring the intensifying impact of climate change. The study was published in the Proceedings of the National Academy of Sciences, as reported by The Science Daily portal.
Sea level rise is mainly driven by two processes. One is the expansion of seawater as it warms, since the oceans absorb roughly 90% of the excess heat trapped in Earth’s climate system.
The other is the addition of water from melting land ice, which increases the total mass of the oceans. Tracking long-term changes in ocean mass is therefore essential for understanding why sea levels are rising today.
The research team was led by Prof. Jianli Chen, Chair Professor of Space Geodesy and Earth Sciences in the PolyU Department of Land Surveying and Geo-Informatics (LSGI) and a core member of the PolyU Research Institute for Land and Space.
Dr. Yufeng Nie, Research Assistant Professor of LSGI, served as the lead and corresponding author. Together, they provided the first direct estimates of global ocean mass change spanning 1993 to 2022 using time-variable gravity field data collected through satellite laser ranging (SLR).
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