Westerly winds, as they do now, have passed poleward in the past.
Westerlies – or westerly winds – play an important role in local and global weather and climate by affecting rainfall patterns, influencing ocean circulation, and regulating tropical cyclones. It is therefore important to find a way to predict how they would change as the climate warms.
Westerly winds usually blow from west to east at the mid-latitudes of the Planet.
Nevertheless, scientists have found that in recent decades these winds have moved and migrated poleward. Researchers suspect that climate change is responsible for this.
However, if temperatures and atmospheric carbon dioxide (CO2) continue to increase under potential warming scenarios, scientists question whether the poleward movement of westerly winds will continue.
This scientific issue has been difficult to answer because our knowledge of westerly winds in past warm climates has been minimal.
Climate researchers at the Lamont-Doherty Earth Observatory of Columbia University identify a new approach for tracing the ancient past of westerly winds in a paper published today (Jan. 6, 2021) in Nature – an example of what we might expect in a potential warming environment.
The lead author, Lamont graduate student Jordan Abell, and his supervisor, Gisela Winckler, developed a framework for applying paleoclimatology to the issue of how westerly winds behave, observing the past environment, and found evidence that as the climate warms, air circulation patterns will change.
In our understanding of how winds have changed in the past and how they can change in the future, the outcome represents a breakthrough.
Researchers were able to recreate wind patterns that occurred three to five million years ago by using dust in ancient deep-sea sediments as an indirect predictor of wind. The authors analyzed cores from the North Pacific, recognizing that winds-in this scenario, westerlies-transport dust from desert regions to distant locations.
This area is downwind of East Asia, one of today’s largest sources of dust and for the last few million years a known dust-producing region.
The researchers were able to map shifts in the dust and, in turn, the westerly winds, by measuring dust in cores from two separate sites thousands of kilometers away.
“We were able to clearly see the trends.
“The information is so clear. Our work is consistent with modern observations and suggests that as the climate warms, wind patterns will change,” Abell said.
They discovered that during the warm portions of the Pliocene (three to five million years ago, when the Planet was around two to four degrees Celsius warmer than today, but had about the same concentration of CO2 in the atmosphere as we do today), westerly winds were closer to the poles worldwide than during the colder periods that followed.
“Using the Pliocene as an analog for global warming today, it seems likely that the movement of westerly winds toward the poles observed in modern times will continue with further human-induced warming,” Winckler states.
For storm systems and precipitation trends, the movement of these winds has huge consequences.
And while this study doesn’t indicate specifically where it will rain more or less, it does confirm that as the climate warms, wind and precipitation patterns will change.
“In the records of Earth’s history, it was hard to track wind patterns and how they were changing because we didn’t have a tracer for it,” Winckler says. “Now we do.”
Reference: Nature, January 6, 2021.
The research was co-authored by Robert Anderson of the Lamont-Doherty Earth Observatory at Columbia University and Timothy Herbert of Brown University.