By Ananya Chandhok
Medill Reports, Feb. 20, 2024
How ocean currents circulate heat over thousands of miles is critical for University of Washington oceanographer Channing Prend to understand ice melt in Antarctica.
Prend’s research on the West Antarctic ice sheet revealed that heat from water thousands of miles to the north can lead to ice melt onshore in Antarctica due to circulation from ocean currents.
Prend presented his findings to top scientists and their students gathered at the annual Comer Climate Conference held in southwestern Wisconsin this fall.
The oceanographer’s research focused on the Southern Ocean, also known as the Antarctic Ocean, because it “plays a disproportionately important role in global climate processes,” Prend said.
The region is the only area on the planet with no continental boundaries.
Its lack of boundaries creates a single current of water circulation called the Ross Gyre — a rotating system of ocean currents, according to the National Ocean Service.
Gyres’ strength varies based on wind intensity, which varies between the seasons and is impacted by long-term atmospheric changes that occur in the atmosphere, Prend said.
These changes include ozone depletion, or reduction of the barrier between ultraviolet radiation and living beings, according to the Environmental Protection Agency.
Prend described the Ross Sea ice as the liaison between the atmosphere and the ocean.
“The [sea] ice determines when the winds can enter the ocean and when they cannot,” Prend said.
In sea ice covered areas, such as West Antarctica, the ice behaves like a barrier between the ice and the wind.
With higher sea ice concentration in the winter, more wind-energy enters during this time rather than during the summer.
This leads to strengthened water circulation through the gyre system.
Understanding these ocean dynamics led Prend and his team to an unexpected finding: changes in wind-energy entering the water thousands of kilometers away and the Ross Gyre’s strength control how much heat enters the Antarctic ice shelf cavity.
Prend challenged previous assumptions that far-away ocean heat does not cause melt.
His research uncovered that even without climate-change related fluctuations in temperature, the ocean circulation leads to large changes in the heat that reaches the ice sheet.
The circulation pattern led to changes in where exactly the heat ended up, in this case under the Antarctic ice shelf where water can speed melting on the exposed underbelly of the ice, Prend said.
However, Prend said these findings are not hard and fast rules across the entire ice sheet.
“There are a lot of processes happening at the local scale,” Prend said. “There might be different processes driving melt in one location in Antarctica versus another.”
Prend and his team encountered data-collection-challenges because of how remote the area was and how rough the waves could get.
However, the team recently reached a new milestone by having access to ocean currents through technological advancements.
The answer to their challenge was floating “robots,” Prend said.
The team used autonomous floats, which allowed the team to collect ocean profile data remotely via satellite, Prend said.
Another challenge for Prend’s research is how the heat from the water makes its way into the ice cavities, which ultimately results in melt.
While it is unclear which factor is most responsible for the heat variability in the ice shelf, Prend said his study aimed to clarify how the water made its way from the open ocean to the shelf.
Variability in this area had not been considered before.
Prend now hopes to help expand the current climate framework for future studies, since more data would paint a clearer picture of how melt occurs globally.
“Climate models have a horizontal model that can vary like a pixel in a photograph,” Prend said. “A higher resolution model would help resolve the physics and other factors associated with ocean currents resulting in melt.”
Not only are Prend’s findings significant for scientists trying to understand variability among the various ice sheet models, they also reinforce the general public’s understanding of climate change.
“This is one more piece of the puzzle, of trying to understand what’s causing melting of the Antarctic ice sheet, which is significant to people all over the world because of the global contribution to sea level rise,” Prend said.
Prend’s call to action for the global community includes building a shared identity rooted in understanding the climate crisis.
“One of the most important things people can do is talk about climate change with their friends and family because creating a movement of people that value and care about the climate crisis is the most valuable way to actually make change,” Prend said.
Photo at top: The Southern Ocean where Prend’s research on the West Antarctic ice sheet revealed that heat from water thousands of miles to the north can lead to ice melt onshore in Antarctica due to the circulation of ocean currents. Photo by Channing Prend.
