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Hydrology controls lithium isotopes in rivers and seawater

Hydrologie controleert lithiumisotopen in rivieren en zeewater7li, 87sr/86Sr, and hydrometeorological data from the NE Tibetan Plateau. Weekly variations of δ7Li and 87sr/86Sr in the carbonate-dominated BH (a) and silicate-dominated SL (b) watersheds (Supplementary Figure 2) along with daily Qw and precipitation, with inverse trends between δ7Li and Qw in every river. When plotting weekly data from the two rivers together (c), there is still an overall negative association, indicating strong hydrological control of rivers δ7Li. (d) 87sr/86Sr vs Qw, with major differences between the two rivers, due to their different lithology (Supplementary Figure 3). The dotted lines in a and b represent the melting times of the ice. Errors for7Li are < 0.9‰. The shaded areas in c show 95% confidence intervals. Black-bordered symbols in c and d represent wet seasons, and others are dry seasons. Credit: Nature Communications (2022). DOI: 10.1038/s41467-022-31076-y” width=”800″ height=”366″/>

High resolution river water δ7li, 87sr/86Sr, and hydrometeorological data from the NE Tibetan Plateau. Weekly variations of7Li and 87sr/86Sr in the carbonate-dominated BH (a) and silicate-dominated SL (b) watersheds (Supplementary Figure 2) along with daily Qwith whom and precipitation, with inverse trends between δ7Li and Qwith whom in every river. When plotting weekly data from the two rivers together (c), there is still an overall negative association, indicating strong hydrological control of rivers δ7Li. (d) 87sr/86Sr vs Qwith whom, with major differences between the two rivers, due to their different lithology (Supplementary Figure 3). The dotted lines in a and b represent the melting times of the ice. Errors for7Li are Nature Communications (2022). DOI: 10.1038/s41467-022-31076-y

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


More information:
Fei Zhang et al, Hydrological control of river and seawater lithium isotopes, nature communication (2022). DOI: 10.1038/s41467-022-31076-y

Provided by the Chinese Academy of Sciences


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

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