Hydrology controls lithium isotopes in rivers and seawater
Seawater lithium isotopes (δ7Li) record changes in Earth’s history, including an increase of ~9 during the Cenozoic, which is interpreted as reflecting either a change in continental silicate weathering rate or the strength of the weather feedback, associated with tectonic uplift. However, mechanisms that control the dissolved7Li continue to be debated.
Researchers from the Institute of Earth Environment of the Chinese Academy of Sciences and their collaborators from the UK, France and Australia have found a clear link between δ7Li and hydrology based on river sample data collected during seasonal changes in river flow.
The findings were published in nature communication on June 10.
Adding this new data to a global compilation of rivers (across latitudes and basin sizes), they found a consistent story: When the climate is dry, river δ7Li values are high, and when the climate is wet, river δ7Li values are low. They interpreted this result in an emerging theme related to continental weathering: that water residence time controlled river δ7Li values.
Then they examined the geologic data of shifts in δ. again7Li (from the last ice age to >106 years) and found that the data set can be explained by a similar mechanism: shifts in the residence time of liquids associated with changes in continental hydrology and the water cycle.
The researchers showed for the first time that a hydrological control mechanism can explain everything7Li records several climatic transitions during the last ~445 million years, leading to a provocative conclusion: the Cenozoic seawater δ7Li record reflected the overall drying out of the continental climate over millions of years, rather than control by tectonic uplift.
First multi-year flow variability of the Karnali River
Fei Zhang et al, Hydrological control of river and seawater lithium isotopes, nature communication (2022). DOI: 10.1038/s41467-022-31076-y
Quote: Hydrology monitors lithium isotopes in rivers and seawater (2022, June 23) retrieved June 23, 2022 from https://phys.org/news/2022-06-hydrology-lithium-isotopes-rivers-seawater.html
This document is copyrighted. Other than fair dealing for personal study or research, nothing may be reproduced without written permission. The content is provided for informational purposes only.