A significant decline in Earth’s freshwater levels began abruptly in May 2014 and has persisted ever since, according to an international study published in Surveys in Geophysics. Using data from NASA-German GRACE satellites, scientists discovered that from 2015 to 2023, the average amount of freshwater stored on land—including surface water, groundwater, and soil moisture—was 290 cubic miles (1,200 cubic kilometers) lower than the 2002–2014 average. This loss, equivalent to 2.5 times the volume of Lake Erie, signals a potentially long-term drying phase for Earth’s continents.
The GRACE mission (Gravity Recovery and Climate Experiment), operated by NASA and German partners, tracks changes in Earth’s gravity to measure fluctuations in water mass. The original GRACE satellites (2002–2017) and their successors, GRACE-FO (2018–present), revealed that the decline began with a massive drought in Brazil. This was followed by widespread droughts across regions like Australasia, North and South America, Europe, and Africa. A powerful El Niño event between 2014 and 2016 exacerbated the situation by altering jet streams and disrupting rainfall patterns. However, even after El Niño ended, global freshwater levels failed to recover.
Climate change plays a central role in this crisis. Warming temperatures lead to higher evaporation rates and allow the atmosphere to hold more water vapor, resulting in prolonged droughts punctuated by extreme precipitation events. These intense rainfalls often fail to replenish groundwater due to compacted soils, leading to increased runoff instead of absorption. This dynamic perpetuates water scarcity, particularly in regions that rely on steady groundwater supplies for agriculture and drinking water. As groundwater depletion accelerates during droughts, aquifers struggle to recover, creating a cycle of chronic water stress.
The implications of this freshwater loss are profound. The United Nations warns that declining water availability heightens the risk of famine, poverty, conflict, and disease, as communities are forced to rely on contaminated sources. Moreover, the study found that 13 of the 30 most intense droughts recorded by GRACE have occurred since 2015, underscoring the growing severity of the issue. While total global precipitation levels may not change significantly, irregular rainfall patterns and longer dry periods disrupt ecosystems and human water supplies.
The researchers suggest that global warming is a major driver of these changes, though definitive attribution is complicated by uncertainties in climate models. Matthew Rodell, a NASA hydrologist and study co-author, emphasized the striking correlation between rising temperatures and the abrupt freshwater decline. He noted that the nine warmest years on record coincided with this persistent drying, which may signal further challenges ahead.
The future of Earth’s freshwater remains uncertain. It is unclear whether levels will stabilize, recover, or continue to decline. However, the data from the GRACE satellites offer critical insights into the fragility of global water systems and the urgent need for improved management. As warming temperatures and shifting hydrological cycles intensify, addressing water scarcity will become increasingly essential to ensure the well-being of communities, ecosystems, and economies worldwide.
https://phys.org/news/2024-11-nasa-satellites-reveal-abrupt-global.html