Blustering westerly winds, which are an important feature of the climate in Central Asia, have blown with little disruption in the region for the past 42 million years, scientists have said. This discovery could help map out future climate projections, as the findings indicate that these wind are resilient to climate change and are likely to remain unchanged for years to come.
Westerly winds carry with them dust – an accumulation of which influences the location of deserted areas and the patterns of dry climate in parts of Central Asia.
Previously, researchers had shown that dust accumulation began some 25 million years ago, with an increase of these winds over the past three million years.
In the latest study, published in Nature Communications, scientists have studied rocks from China showing the process of dust accumulation, and the presence of westerly winds to bring them, may have started much before that.
Unlike what was thought, they emerged before the formation of the Tibetan Plateau.
The story in the rocks
To study past climates, scientists usually resort to models and simulations. The problem is that these can lack precision so the team from the University of Washington used rock samples dating back to between 42 and 33 million years ago, from an area around Xining, the largest city at the north-eastern corner of the Tibetan Plateau. These rocks were thus present during the Eocene period, at a time when the Tibetan Plateau was less developed, the Paratethys sea – an ancient, large, shallow sea – still existed in central Asia and atmospheric CO2 was much higher.
The presence of the dust in these rocks suggests that the region was already dry at this time and not subtropical like previous findings had hinted. Chemical analysis show that dust was carried in the region from areas in western China and along the northern edge of the Tibetan Plateau. This trajectory is likely the result of the gusting of westerly winds blowing in a very similar way to those seen today in Central Asia.
"The origin of the dust hasn't changed for the last 42 million years," lead author Alexis Licht explained. Even when the region experienced dramatic climate shifts, the same windy patterns remained.
"Neither Tibetan uplift nor the decrease in atmospheric carbon dioxide concentration since the Eocene seem to have changed the atmospheric pattern in Central Asia. Wind patterns are influenced by changes in the Earth's orbit over tens or hundreds of thousands of years, but over millions of years these wind patterns are very resilient."
This is interesting for geologists and climate change scientists because it may allow them to better predict how climate will evolve in the future, what impact the westerly winds may have, and whether they will have an impact on droughts and rainfall.