This summer, Arctic sea ice reached near-historic lows, according to researchers at NASA, part of a decades-long trend of ice loss in the region as the world continues to warm from climate change.
And this is not just a problem for polar bears—the loss of sea ice impacts both global ocean circulation and daily weather patterns around the world, including North America, according to Melissa Gervais, associate professor of meteorology and atmospheric science and co-hire with the Institute for Computational and Data Sciences.
Gervais studies the complex, coupled interactions between sea ice, ocean, and atmosphere that may influence atmospheric circulation and impact daily weather.
“The atmosphere, ocean and sea ice are constantly influencing one another,” Gervais said. “Having a better understanding of these interactions can help us better understand and project changes in the daily weather that people experience. I think it’s a really important direction for us to go in terms of research, because people experience daily weather—and they can better understand the impacts in terms of changes in daily weather. And climate is really an amalgamation of daily weather.”
As a doctoral student at McGill University in Canada, Gervais had two advisers—a sea-ice dynamicist and a synoptic meteorologist—giving her a background in the formation and modeling of sea ice and the study of daily weather.
“My interests fell in the climate realm in between,” she said. “I’ve always existed between different research communities, and I really like that. I feel like this provides a unique perspective where you can see opportunities to understand things that we don’t normally think about.”
Anomaly in the Atlantic
While global temperatures continue to set record highs, an anomaly exists in the North Atlantic Ocean, referred to as the North Atlantic warming
hole. It is an area of the ocean just south of Greenland that is experiencing relative cooling compared to the rest of the seas.
The warming hole is linked to a slowdown of Atlantic Meridional Overturning Circulation (AMOC), the main ocean current system in the Atlantic Ocean, among other processes. AMOC acts like a conveyor belt, bringing warm, salty water north, where it cools and creates more dense water that sinks to the bottom of the ocean before returning south again. But cold, fresh water entering the ocean from melting glaciers may impact the circulation pattern.
Changes in the AMOC could have major climate and weather impacts in many parts of the world, and understanding potential long-term changes is important, Gervais said.
In a study published this year in the journal Nature Communications, Gervais and colleagues found climate model simulations of ocean temperatures in the coming decades begin to produce a wide gulf between possible temperatures in the North Atlantic by the 2050s.
The researchers traced the beginnings of the divergence to a time period just a few years
from now—around 2030 and found the different paths are likely triggered by positive climate feedbacks. Gervais’ former student Qinxue Gu, who received her doctorate from Penn State in 2023 and is now a postdoctoral researcher at Princeton, was the lead author on the study.
“Positive feedback means that if there is a change in one direction that might cause warming, then it will keep warming,” Gervais said. “Or if there is a forcing that causes it to cool, it will keep cooling. So when these positive feedbacks are set off, it helps the different tracks diverge.”
For example, cooler water temperatures would mean less sea ice melting. And the presence of ice on the ocean surface prevents the atmosphere and wind from interacting with the water. This further weakens the deep convection and can result in colder sea surface temperatures, Gervais said.
“How these systems all interact is so fascinating,” Gervais said. “The sea ice kind of acts like a cap on top of the ocean. The ocean can’t feel the stress from the atmosphere and so it stirs mechanically a little bit less, and that weakens the deep conduction more. That becomes a positive feedback.”
Monitoring conditions in the North Atlantic could help us understand what feedbacks are triggered and which of the divergent paths sea surface temperatures will take. This may give us a better idea of when the warming hole will form and where temperatures will end up several decades out, Gervais said.
This is important because sea surface temperatures can also impact winds—or the
North Atlantic jet—that cross the ocean and help determine the climate of Europe, the Mediterranean, and parts of North America.
“If people are used to a certain climate and all of a sudden you change the game, even just by a little bit, they’re not ready for whatever’s coming their way,” Gervais said. “And that’s a huge problem. This is why it can be really helpful to have some knowledge of where the climate state is heading.”
From climate change to daily weather
Traditional synoptic weather analysis of weather maps can allow us to summarize and understand the atmospheric conditions over large regions.
But this is difficult to do with large volumes of data from climate models. Instead, researchers like Gervais are turning to machine learning tools that can help with organizing the maps and classifying patterns.
“A lot of my work is looking at climate change from a weather perspective. I often use machine learning, a tool specifically called self-organizing maps, to do this,” Gervais said. “What it allows us to do is to take a huge volume of data of daily weather patterns and classify them so we can identify the main weather patterns that exist.”
Gervais uses the approach as part of a Faculty Early Career Development (CAREER) award she received from the National Science Foundation to investigate the impact of sea ice loss on large-scale patterns of atmospheric variability and cold air outbreaks.
Her CAREER award findings, reported this year in the Journal of Climate, teased out the impacts of ice sea loss on the future of large-scale meteorological patterns over North America.
Gervais and her colleagues found that ice sea loss de-amplified these patterns and their impact on temperature near the surface— meaning, for example, cold weather events may be less cold.
“My CAREER award is all about sea ice, atmosphere interactions, and how sea ice loss can impact daily weather,” she said. “It’s at the boundary between climate and synoptic meteorology, which personally I think is a really important direction for us to go in research.”