Scientists used more than 120 years of data to decipher how melting ice, dwindling groundwater, and rising seas are nudging the planet’s spin axis and lengthening days.

Recent studies reveal that Earth’s days are lengthening, a trend accelerating due to climate-driven changes such as glacier melt and aquifer depletion. These alterations in mass distribution not only shift the planet’s axis but also decelerate its rotation. Research utilizing advanced measurement techniques and spanning the last century details how human-induced changes are exacerbating these natural phenomena, with potential long-term impacts on timekeeping and technology reliant on precise timings.

Days Lengthening Due to Climate Change

Days on Earth are growing slightly longer, and that change is accelerating. The reason is connected to the same mechanisms that also have caused the planet’s axis to meander by about 30 feet (10 meters) in the past 120 years. The findings come from two recent NASA-funded studies focused on how the climate-related redistribution of ice and water has affected Earth’s rotation.

This redistribution occurs when ice sheets and glaciers melt more than they grow from snowfall and when aquifers lose more groundwater than precipitation replenishes. These resulting shifts in mass cause the planet to wobble as it spins and its axis to shift location — a phenomenon called polar motion. They also cause Earth’s rotation to slow, measured by the lengthening of the day. Both have been recorded since 1900.

Polar Motion: Decades of Analysis

Analyzing polar motion across 12 decades, scientists attributed nearly all of the periodic oscillations in the axis’ position to changes in groundwater, ice sheets, glaciers, and sea levels. According to a paper published recently in Nature Geoscience, the mass variations during the 20th century mostly resulted from natural climate cycles.

The same researchers teamed on a subsequent study that focused on day length. They found that, since 2000, days have been getting longer by about 1.33 milliseconds per 100 years, a faster pace than at any point in the prior century. The cause: the accelerated melting of glaciers and the Antarctic and Greenland ice sheets due to human-caused greenhouse emissions. Their results were published July 15 in Proceedings of the National Academy of Sciences.