Dramatically suppressed climate signals in the Yellow River

Human activities have greatly changed the natural flow of mega rivers globally, with potentially devastating consequences for human and ecosystems. Previous budget and regime studies, however, have overlooked an important dimension of the changes that human disturbances can also suppress or even eliminate the natural climate signals archived in the river water-sediment periodicities. Here, using a 68-year basin-wide record, we quantify for the first time how much of natural climate signals has been lost in the Yellow River, China. Our results show that systematic engineering in the watershed between 1986 and 2019 has eliminated over 90 % of the monsoon signal and over 80 % of the El Niño/Southern Oscillation (ENSO)-Pacific Decadal Oscillation (PDO) signals from the Yellow River's hydrology in comparison with the period of 1952–1968, despite the powerful monsoon and ENSO-PDO that still drive basin-wide annual and multi-annual precipitation periodicities during this period. We conclude that the Yellow River has turned into a mega river with an anthropogenic flow regime. Such losses of natural climate signals represent an un-recognized aspect of decreasing ‘naturalness’ of mega rivers, which might also take place in other mega rivers in response to future human activities.