Researcher Willem van der Bilt was surprised when a project on Arctic storminess revealed ‘the opposite of what was expected’. But if ‘disasters become more frequent when the disparity between the temperature at the equator and the temperature at the Earth’s poles increases’, as this climatologist explains, perhaps the real surprise was that researchers were surprised to find exactly that. “Civilization has always done better under warmer conditions,” because “a warmer world is a less volatile weather world”. Maybe their assumptions were somehow influenced by alarmist voices predicting ever greater weather ‘extremes’ of all kinds under gradually warming conditions? In any case, convincing evidence for such assertions is in short supply.
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A recent study has uncovered surprising patterns in Arctic storminess, challenging the common assumptions about the relationship between warming temperatures and increased wind activity, says the University of Bergen @ ScienceNorway.
Willem van der Bilt is a researcher at the University of Bergen and the Bjerknes Centre for Climate Research. As part of an international research team, he has developed new methods for extracting climate hazard information from geological archives like lake sediments.
Studying sediments to track storminess
To do this, the research team used detailed scanning methods and combined the results in a structured way to analyse patterns and relationships in the data.
The researchers examined sediments from a coastal lake on Svalbard, focusing on particles transported by wind and waves. These particles, which include sand grains and sea salt carried into lakes by storms, allow researchers to trace changes in wind strength and wave height over time.
Using advanced geological tools, the team refined methods typically used for studying glacier behaviour and flood frequency, adapting them to reconstruct wind history.
“We used a toolbox of techniques that are typically applied to extract other past information from geological records. And then I thought; we might as well look at the wind, right?” says van der Bilt.
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Wind history
The study focused on a coastal lake on Svalbard, chosen for its ability to consistently record wind patterns over time.
The team ended up sampling cores from a few lakes shielded by a rocky ridge and started analysing these sediments. They applied a proven set of methods, making refinements, and introducing some enhancements to improve accuracy.
Van der Bilt explains that from these sediments, they extracted a clear storm signal.
“We started to understand that we could tie different signals that we recorded in these sediments to both wind systems that prevail in the area – the Westerlies and Easterlies – and get 10,000 years of wind history,” he says.
Surprising patterns in Arctic storminess
As the team started to analyse their findings, the plot thickened. The results were the opposite of what the researchers thought they would be.
“The assumption is that a less icy, warm Arctic will be windier, but the sediments show us that it’s the other way around. We learned that the stormy phases that we see in our record actually overlap with phases of colder climate conditions in the North Atlantic Ocean. That was a big surprise,” says van der Bilt.
Another thing they observed was a form of cyclicity in storminess.
“We find that storminess exhibits a 1,500-year cyclicity. This periodicity is a widespread feature of many North Atlantic climate records and acts like a bit of a heartbeat of the region’s climate system,” he says.
Van der Bilt adds that the team found both of the region’s main wind systems – the Polar Easterlies and the Westerlies – move in synchrony, weakening and strengthening together over time.
Full article here.
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Image: Svalbard Map [credit: theoceanadventure.com]
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November 20, 2024 at 11:40AM
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