Rapid Increase in Sea Level Rise: Understanding the Accelerating Rates

The rate of sea level rise has dramatically accelerated since 2012, as measured by satellites, and this trend has persisted.

While these sudden increases may result from natural fluctuations, they could also signify a response to exacerbated global warming, as noted by Lancelot Leclerc from the University of Toulouse, France.

Over the past 15 years, global average sea levels have risen by more than 0.2 meters due to multiple contributing factors. The melting of mountain glaciers and the ice sheets of Greenland and Antarctica, alongside the thermal expansion of warming oceans, play significant roles.

Satellite monitoring of sea levels commenced in the 1990s, revealing a previously stable rise estimated at approximately 3.6 mm per year. However, significant data collected by Leclerc’s team highlights a shift post-2012, with the average increase accelerating from 2.9 mm/year to 4.1 mm/year.

Jonathan Bamber from the University of Bristol, who was not involved in the study, comments, “That’s not a robust signal. We’re not observing centimeters per year.”

Despite this, Bamber acknowledges that analyzing satellite data alongside century-old tide gauge records indicates a clear acceleration in sea level rise.

The researchers believe this increase stems frommultiple factors rather than a single cause. In addition to ice sheets melting at an accelerated rate, there’s a notable decrease in freshwater stored on land, which contributes more water to the oceans.

Moreover, the rate of global warming has intensified since around 2010, primarily due to reduced aerosol pollution in countries like China. Aerosols have a cooling effect, historically mitigating the impact of rising CO2 levels.

Leclerc presented findings at the European Geosciences Union (EGU) conference in Vienna, suggesting that decreasing air pollution contributes to accelerating sea level rise, highlighted in research published on May 5th.

Team member Annie Cazenave from the University of Toulouse remarked, “The trend change observed around 2012 seems related, in part, to an increase in anthropogenic radiation forcing linked to reduced aerosol emissions.”

Another study at the EGU meeting indicated that ocean water deeper than 2 kilometers has begun warming and expanding within the last decade, contributing further to the rise.

Prior to 2016, all recognized causes of sea level increase accounted for the observed global average rise. However, Yang Chunxue from Italy’s National Research Council indicates that these factors alone no longer explain the total increase observed since.

Yang proposed that we’ve overlooked significant contributors, likely including deep ocean warming—an area lacking systematic temperature measurements below 2 kilometers depth. Presently, around 4,000 robotic probes measure oceanic temperatures, but none extend this deep.

Using ocean models, Yang and their collaborators suggest that warming within shallower depths may help clarify the gap in sea level measurements. Their study indicates substantial deep ocean warming is occurring, particularly in the North Atlantic off the US east coast.

“Research suggests deep ocean warming began around 2016,” states Kazunabe, another study contributor. “Further investigation is necessary to confirm its correlation with the early 2010s trend change.”

The research team has estimated that deep ocean warming contributes an estimated 0.4 mm per year to sea level rise, accounting for roughly 10 percent of overall increases.