Researchers have created a mathematical model that demonstrates how the movement of brine within sea ice can improve heat transfer, potentially aiding climate change forecasts for polar areas.
A new mathematical theory could significantly enhance our comprehension of the role of sea ice in the global climate system, potentially leading to improved climate predictions.
A recent study published in the Proceedings of the Royal Society A on August 28 provides fresh insights into the way heat moves through sea ice—a vital aspect of regulating the polar climates on Earth.
Dr. Noa Kraitzman, a Senior Lecturer in Applied Mathematics at Macquarie University and the main author of the study, indicates that this research fills a critical void in current climate models.
“Sea ice covers roughly 15 percent of the ocean’s surface during the cold season when it is most expansive,” explains Dr. Kraitzman. “It forms a thin barrier between the atmosphere and ocean, playing a crucial role in heat transfer between both.”
Sea ice functions like an insulating blanket over the ocean by reflecting sunlight and controlling heat exchange. As global temperatures continue to rise, comprehending the behavior of sea ice will be increasingly essential for making climate change predictions.
The research centers on the thermal conductivity of sea ice, a vital factor utilized in numerous global climate models. The prior models overlooked the impact of liquid brine movement within sea ice, which can enhance heat transport.
According to Dr. Kraitzman, the unique composition of sea ice, along with its sensitivity to temperature and salinity, makes it challenging to evaluate and predict its properties, particularly thermal conductivity.
“When examining sea ice closely, its fascinating structure stands out, as it consists of ice, air bubbles, and brine inclusions.”
“When the air above the ocean plummets to extreme cold—down to minus 30 degrees Celsius, while the ocean water maintains about minus two degrees—a significant temperature gradient occurs, causing freezing from the top layer downward.”
“As the water freezes swiftly, the salt is expelled, leading to an ice framework composed of solidified water that traps air bubbles and very salty water pockets, known as brine inclusions, within nearly pure ice.”
These concentrated brine inclusions, being denser than fresh ocean water, lead to convective flow in the ice, forming large ‘chimneys’ where salty liquid escapes.
This research builds upon previous work by Trodahl in 1999, which suggested that fluid movement within sea ice could enhance its thermal conductivity. Dr. Kraitzman and her team have now mathematically confirmed this effect.
“Our mathematical results clearly indicate that such an enhancement in thermal conductivity is to be expected as convective flow begins within the sea ice,” Dr. Kraitzman remarks.
The model also establishes a connection between the thermal characteristics of sea ice and its temperature and saltiness, thus allowing theoretical findings to be compared against empirical measurements.
More specifically, it offers a method to incorporate these insights into large-scale climate models, potentially improving the accuracy of future climate predictions for polar regions.
Arctic sea ice has seen a rapid decline in recent decades. This reduction can trigger a feedback loop where increased exposure of dark ocean water leads to greater sunlight absorption, resulting in further warming and loss of ice.
The melting of sea ice can significantly impact weather patterns, ocean circulation, and marine ecosystems far beyond the polar regions.
Dr. Kraitzman emphasizes that understanding the thermal conductivity of sea ice is crucial for forecasting its future behavior.
The researchers conclude that while their model lays a theoretical groundwork, further experimental research is necessary to incorporate these findings into larger climate models.
