• Soil moisture dropped sharply between 2000 and 2002.
• Global water loss exceeded Greenland’s ice melt during that time.
• Earth’s axis and sea level shifts support findings.

Monday, March 31, 2025 — A new study published March 27 in Science reveals that Earth’s land-based water storage has undergone a major and potentially irreversible change in the 21st century. Researchers led by Hyungjun Seo used satellite measurements, sea level data, and Earth’s polar motion to assess soil moisture trends going back four decades. Their findings point to a dramatic and continuing decline in terrestrial water reserves.

A Steep Decline Early in the Century.

Between 2000 and 2002, global soil moisture plummeted by approximately 1614 gigatonnes. The researchers note that this is “much larger than Greenland’s ice loss of about 900 gigatonnes” recorded between 2002 and 2006. Even after the initial sharp drop, the loss continued. From 2003 to 2016, an additional 1009 gigatonnes disappeared from the soil.

This decline was identified using the ERA5 dataset—an advanced climate reanalysis model that tracks soil moisture from space. To cross-verify the trend, the team also examined sea level rise and polar motion. They found both indicators reflected the shift in water mass from land to ocean.

Supporting Clues from Sea Level and Earth’s Axis.

The study notes that sea levels rose by roughly 4.4 millimeters during the same period. At the same time, Earth’s rotational axis shifted about 45 centimeters. These changes align with a global redistribution of water—moving away from land surfaces and into the oceans.

According to the researchers, this massive water loss was likely driven by persistent precipitation deficits, paired with stable rates of evapotranspiration—the process by which water evaporates from the soil and transpires from plants.

A Lasting Change in the Water Cycle.

Perhaps the most concerning aspect of the findings is their long-term outlook. According to the study, “SM  (soil moisture) has not recovered as of 2021, with future recovery unlikely under present climate conditions.” This suggests the observed soil moisture depletion is not a temporary fluctuation but part of a broader, lasting shift in how water moves and is stored across the planet.

In a related perspective article, hydrologist Luis Samaniego wrote that the study “reveals a dramatic decline” in global land water storage, signaling what may be a new hydrological regime for the Earth.

As climate conditions continue to change, scientists say tracking soil moisture and water storage from space will remain vital for understanding how the planet’s water cycle is evolving—and what that means for ecosystems, agriculture, and human water use worldwide.

Source:
Seo, H. et al. (2025). “Abrupt sea level rise and Earth’s gradual pole shift reveal permanent hydrological regime changes in the 21st century.” Science. https://www.science.org/doi/10.1126/science.adq6529

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