New Study 'Closes the Gap' in Understanding Sea-Level Rise

A groundbreaking study published in the journal *Earth's Future* is providing crucial insights into the complexities of global sea-level rise, a critical indicator of our planet's changing climate. For years, scientists have observed a discrepancy, a 'gap,' in the data since 2016, where the measured heat absorbed by the oceans, particularly in the upper layers, did not fully account for the observed rise in sea levels. This new research, led by Anny Cazenave, a collaborator at the LEGOS laboratory in Toulouse, offers a compelling explanation: the warming of deep ocean waters.

This research highlights that thermal expansion in ocean layers below 2,000 meters is now a significant factor, contributing approximately 0.4 millimeters per year to sea-level rise. This accounts for about 10% of the total rise observed between 2005 and 2022, a contribution that can no longer be ignored. The findings underscore the interconnectedness of Earth's systems and the need for comprehensive monitoring, extending beyond the well-established Argo float network, which typically measures only down to 2,000 meters.

To overcome the limitations of direct measurement in these deep ocean layers, the international research team employed sophisticated 'reanalysis' techniques. This method combines observational data with numerical models to create a more complete picture of oceanic changes. As the development of technologies like the 'Deep Argo' floats, designed to probe depths down to 6,000 meters, is still in its early stages, reanalysis becomes an indispensable tool. This study is vital for refining our climate models and improving predictions of future sea-level rise, a phenomenon with profound implications for coastal communities worldwide. It demonstrates that understanding climate change requires looking deeper, both literally and figuratively.

“

The thermal expansion of water below 2,000 meters almost fully explains the sea-level rise after 2016.