- July 28, 2026
- By Cazzy Medley
“Hot, sticky, miserable weather” might sound like a description of typical Maryland summer, but those words were written in 1954 by a glaciologist working on the vast, frozen expanse of the Greenland Ice Sheet.
The scientist, Carl Benson, and his colleagues had no idea at the time why sultry temperatures had taken hold on the ice. Now, however, a science team that includes a University of Maryland researcher who was a longtime collaborator of Benson has discovered the answer by piecing together records of a dramatic atmospheric phenomenon unknown decades ago. Their findings, published in the Journal of Glaciology, reveal how today’s technology can help scientists better understand Greenland’s past and monitor its future.
The study’s lead author was Benson, a longtime University of Alaska Fairbanks (UAF) researcher who died in January at age 98; UMD Earth System Science Interdisciplinary Center snow and ice scientist Dorothy Hall and Rick Thoman and Matthew Sturm, both of UAF, rounded out the research team.
The mystery unfolded 72 years ago this month, when a research team working for the U.S. government ventured out from Thule Air Base (now Pituffik Space Base) in northwestern Greenland to study the structure, behavior and geologic history of the ice sheet. Over four years, the team, led by Benson, dug pits into the snow, collected samples, and carefully documented the physical properties of the ice sheet, work that would provide a fundamentally new understanding of ice sheets and glaciers.
On July 11, 1954, the weather turned, and it began to rain. Suddenly, the glacier’s surface temperature rose considerably—above freezing. This persisted for over 60 hours, melting the glacier’s surface into slush.
“Solid overcast, surface snow very wet, good for making snowballs,” wrote Benson in that day’s field notes, which also included his complaints about heat.
The slushy surface made traversing the glacier impossible, leaving the team stranded. But it also presented a rare scientific opportunity to trace surface water as it flowed through the snow and firn—dense, granular snow not yet compacted into ice—in a part of the ice sheet that rarely melts. They saw firsthand how meltwater trickles through channels to create dense, clear “ice lenses” and layers upon refreezing.
The warm, wet weather persisted for three days. But even years afterward, evidence of this melt event was visible in the stratigraphy of the glacier as refrozen slush layers and meltwater columns. The melt event had permanently changed its geological makeup.
A year later, the team drilled a cylindrical sample of ice, known as an ice core, about 48 km away. The sample revealed that the 1954 melt was the heaviest in 68 years. They also learned that melt events were limited from 1886 to the 1920s, then became much more frequent.
The researchers also discovered that evidence of the 1954 melt event appeared clearly on two walls of a three-meters-deep snow pit but was absent on the other two, showing that meltwater had flowed through isolated channels rather than spreading evenly throughout the snowpack.
“Ice cores, though extremely valuable, may greatly underestimate the extent of melt throughout a column of Greenland ice,” said Hall, who met Benson, a pioneering researcher of frozen northern expanses, while doing graduate-level field work in Alaska in 1978. “Thus we cannot know for certain the extent of historical melt events even when ice cores are available.”
While ice cores provide detailed, localized information, satellite sensors are far more effective than ice cores when it comes to mapping the extent of melting across an ice sheet.
“At that time, there was no way to view the ice sheet from above, so [the team’s] ability to understand and explain the perplexing melt event was limited,” said Hall. “We can use today’s technology to help explain some decades-old problems such as, ‘Why was there rain at such a high latitude on the Greenland Ice Sheet in July of 1954?’”
After seven decades, today’s research team can finally answer that particular question, pointing to an atmospheric river as the cause. These are long, narrow bands of water vapor in the atmosphere that typically carry enough water vapor to equal the flow of the Mississippi River; strong atmospheric rivers can carry up to 15 times that amount. The phenomenon was not identified until the early 1990s, but today it is widely recognized as a key mechanism for transporting warm, moist air to Greenland.
The study highlights how dramatically scientists’ ability to monitor Greenland has changed since Benson’s expeditions. During his fieldwork, Benson developed the glacier-facies concept, which divides the ice sheet into distinct “melt zones” (facies) based on how much snow melts and refreezes at different elevations. Today, satellites allow scientists to map those facies across the entire ice sheet and watch the facies boundaries change over time.
As Earth’s climate warms, the boundaries between glacier facies are shifting uphill and farther inland. Areas that once remained frozen year-round are increasingly experiencing seasonal melting and refreezing. Tracking these shifting boundaries helps scientists measure whether the Greenland Ice Sheet is gaining or losing ice, providing critical insight into how climate change is reshaping the Arctic and contributing to global sea-level rise.
Hall said she was glad to be able help her friend and colleague of nearly 50 years publish his last study, so many years in the making.
“He always thought things through very thoroughly, so it took a while to get that final paper written though we had been discussing it for about 15 years. When Carl realized he didn’t have much time left, the work speeded up,” Hall said. “Carl was fully engaged and provided important input even in his last weeks.”
Benson crosses the ice in Alaska's Wrangell Mountains in 1987.