Atmospheric blocking key to arctic melting and extreme weather, shows study

Lake Linné, on the west coast of Svalbard, where much of the field work was done. Credit: UMass Amherst.

Scientists have discovered that a weather phenomenon called “atmospheric blocking” significantly influences Arctic melting and extreme weather.

François Lapointe, a research associate at the University of Massachusetts Amherst, led a team that combined data from the past 2,000 years with advanced computer models and field research to uncover this connection.

Their study, focusing on the Norwegian Arctic archipelago of Svalbard, was published in Nature Communications.

The Arctic is warming faster than the global average, a phenomenon known as Arctic Amplification.

However, Svalbard has experienced an even more rapid warming trend since 1991, with temperatures rising twice as fast as the rest of the Arctic. This rapid warming has led to massive ice loss, extreme rainfall, and landslides.

“We wanted to understand why Svalbard is warming so much faster than the rest of the Arctic,” said Raymond Bradley, Distinguished Professor at UMass Amherst and co-author of the study, “and to determine if these trends will continue.”

To investigate, the researchers studied lake sediments from Lake Linné on Svalbard’s west coast. This lake has been monitored by instruments deployed since 2012 by UMass Amherst alumnus Michael Retelle, now a professor at Bates College.

These instruments track the timing of sediment entering the lake during intense rainstorms.

Lapointe and his team analyzed the calcium levels in the lake’s sediments. The surrounding terrain is rich in carbonate, and heavy rains wash these carbonates into the lake.

By examining sediment cores, the team could track rainfall over the past 2,000 years.

The researchers found a strong link between major rain and warming events and atmospheric blocking over Scandinavia and the Ural Mountains. Atmospheric blocking occurs when a high-pressure system stalls over a region, in this case, northern Scandinavia.

This high-pressure system is often paired with a low-pressure system over Greenland, creating a gear-like effect.

The two systems draw warm, moist air from the mid-Atlantic Ocean into the Arctic, causing heavy rain in Svalbard. Since records began, the frequency of atmospheric blocking and Arctic warming have both increased.

“It will be fascinating to see how atmospheric blocking changes with further warming,” said Lapointe. “Any increase will likely worsen floods and natural hazards in Svalbard.”

The future projections for Svalbard are concerning. Although the archipelago has a small year-round population of just 2,650 people, it attracts over 130,000 visitors annually due to its stunning landscapes and unique wildlife.

Understanding the role of atmospheric blocking in Arctic warming and weather extremes is crucial for predicting and preparing for future changes in the region.

This study highlights the importance of atmospheric blocking in driving extreme weather and rapid warming in the Arctic. As climate change progresses, monitoring and understanding this phenomenon will be vital in addressing the impacts on regions like Svalbard.

Source: University of Massachusetts Amherst.