An international team of climate scientists has made significant strides in explaining the factors contributing to global sea level rise over the past sixty years, addressing a long-standing challenge in understanding one of the most pressing issues of climate change.
Accelerating Sea Levels
A recent study published in Science Advances reveals that global sea levels have risen at an average rate of 2.06 millimeters annually since 1960. However, this rate has surged in recent decades, reaching an alarming 3.94 millimeters per year between 2005 and 2023.
The research identifies warming oceans as the primary driver, accounting for 43% of this increase. As ocean temperatures rise, the seawater expands, leading to higher sea levels worldwide. Additionally, melting ice has emerged as a crucial factor, with mountain glaciers contributing 27% to sea level rise since 1960, while the Greenland Ice Sheet adds 15% and the Antarctic Ice Sheet contributes 12%. Changes in land water storage make up the remaining 3%.
The study also clarifies why sea level rise has accelerated over time. While ocean warming and reduced land water storage were significant factors since 1960, the rapid melting of glaciers and ice sheets in Greenland and Antarctica has become increasingly influential since 1993.
Bridging the Measurement Gap
For years, researchers faced a perplexing mismatch between observed sea level rise and estimates based on known causes. Satellite measurements and coastal tide gauge data often did not align with calculations derived from ocean warming and ice melting.
This new research appears to reconcile that discrepancy. "For years, there has been a frustrating gap between how much the oceans were observed to be rising and how much we could explain from the individual causes. This work shows that, with better instruments, processes, and smarter analysis, this knowledge gap can be closed," stated Prof. John Abraham from the University of St. Thomas and co-author of the study.
The team was spearheaded by scientists from the Institute of Atmospheric Physics at the Chinese Academy of Sciences, collaborating with researchers from Tulane University, the NSF National Center for Atmospheric Research, and the University of St. Thomas, along with scientific partners from France.
Technological and analytical advancements were key to resolving the discrepancies, including updated corrections to satellite measurements, improved methods for assessing land movement at coastal tide gauges, and more precise estimates of ice loss from Greenland and Antarctica.
Long-Term Sea Level Rise
The findings underscore a significant reality regarding climate change. Even with potential stabilization of greenhouse gas emissions, sea level rise is expected to persist for centuries. The oceans absorb heat slowly, continuing to warm over prolonged periods, while substantial ice sheets and glaciers melt long after temperatures have increased. This planetary inertia suggests that sea levels will continue to rise for many generations to come.