The Arctic Ocean’s rapidly shrinking cover of sea ice has raised alarms about the far-reaching consequences on ecosystems, economies, and climate systems. But understanding the factors that determine how quickly this ice disappears is far from simple.
Now, a new method for tracking sea ice and its movements across the seasons could help researchers predict the fates of both older ice and the new floes that form each year. Much like a river’s flow shaping its course and where it ends up, the route sea ice travels plays a crucial role in its survival.
“There’s this long-standing idea that sea ice loss is inevitable with warming,” said climate scientist Patrick Taylor of NASA’s Langley Research Center. “Our study shows that where the ice starts and how far it travels can make a huge difference” in how fast we lose sea ice. Taylor and his colleagues will present their findings at AGU’s Annual Meeting 2024 in Washington, D.C., on 9 December.
The Ebbs and Floes of Melting Sea Ice
Arctic sea ice melt is driven by a combination of factors, including rising temperatures, changing ocean currents, and increased absorption of the Sun’s warmth by exposed Arctic Ocean waters.
Previous studies analyzing the extent of ice loss have primarily focused on monthly averages of sea ice extent. However, these measurement methods overlook the dynamic nature of the ice. Parcels of old and new ice move constantly and are influenced by environmental stressors such as heat and salinity. Monthly average data cannot capture how individual ice floes respond to these variables, nor can the data account for year-to-year variability in ice loss.
In contrast, Taylor’s group aimed to track individual sea ice parcels over multiple years to understand how their survival was affected by the paths they traveled. The researchers used satellite data from sources including from the National Snow and Ice Data Center to capture weekly movements of individual units of sea ice.
The team layered satellite data about sunlight exposure, radiation levels, ice movement, albedo, snow cover, and ice thickness onto their analysis to identify the roles each factor played in influencing sea ice melt. They statistically examined millions of floes, focusing on the likelihood of individual floes enduring the summer melt season to reveal insights beyond aggregate sea ice extent measurements.
To follow the floes, the researchers used a feature tracking algorithm that identified common features between consecutive satellite images taken 1 to 3 days apart. This algorithm also integrated data about winds from weather forecasts and observations of sea ice motion from buoys deployed on the sea ice.
“They have a comprehensive database covering nearly 20 years,” said Linette Boisvert, a climate and cryosphere scientist at NASA’s Goddard Space Flight Center who was not involved with the research. “This is the first time that all these datasets are together in one place, so now, we can easily look at what factors might cause the sea ice to survive the summer melt or not.”
The team found that the likelihood of a parcel of sea ice surviving the summer melt varied significantly depending on where it traveled. Overall, parcels that drifted from their starting regions into warmer and more southern regions were less likely to survive. The researchers defined regions as subbasins of the Arctic, such as the Beaufort Sea. The research also found that though thicker ice parcels are more likely to survive the summer in general, the opposite is true in regions such as the East Siberian Sea, perhaps because of the movement patterns of warm water.
The results offer newly detailed insights into the variability of sea ice in the Arctic, where some regions are much more vulnerable than others to seasonal melting. Understanding those differences is key to predicting how much ice will remain in future years—and where, Taylor said.
The Arctic’s Worldwide Ripple Effects
The loss of sea ice is already disrupting ecosystems that depend on it, affecting animal feeding and migration, weather patterns, global sea levels, and even geopolitics as new shipping routes open up in areas formerly covered by ice.
“What happens in the Arctic doesn’t stay in the Arctic.”
“What happens in the Arctic doesn’t stay in the Arctic,” said Boisvert. The region acts as a thermostat for the planet, she noted. As it warms, the cascading effects can be felt worldwide.
For example, reduced sea ice leads to greater heat absorption by the ocean because the darker open water lets in more warmth from the Sun. This increased heat creates a feedback loop that accelerates warming. Ebbs and flows in ice cover also influence the circulation of polar atmospheric patterns overhead, which can spawn extreme weather events in regions far from the Arctic.
Climate models predict anywhere from 5°C to 15°C of Arctic warming within the next 100 years, according to Taylor. How much ice will persist in those vastly different scenarios is an open question, but Taylor thinks his team’s new approach will help. Few studies have looked closely at sea ice circulation patterns within climate models or the potential effects of these patterns, and that’s just what Taylor’s group plans to do next.
—Mahima Samraik (@mahimasamraik_), Science Writer
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