Sea ice levels in the Arctic Ocean are declining rapidly, thanks to global warming. Now, to understand and predict ice growth and decay, researchers from Japan and collaborating countries conducted a survey in the Arctic Ocean to study the influence of ocean heat on sea ice in the boundary layer. ice-ocean. Their findings provide insight into the mechanisms of Arctic sea ice decline to make accurate future predictions of global climate.
Sea ice (a term for ice that is not attached to the shore) in the Arctic Ocean is currently at an all-time low, due to global warming. Scientists have previously attempted to study the ice in this region; however, due to its constant movement by strong surface winds and ocean currents, it is difficult to continuously monitor it.
The growth and breakdown of sea ice can be influenced by the interaction of drift ice and the near-surface ocean layer, where turbulent heat and salt fluctuations govern ice formation. Turbulence at the ice-ocean boundary layer (IOBL), which is the transition zone between sea ice and seawater, is also shaped by freshwater intrusion from the melting of the sea ice and the physical exclusion of brine during ice formation. Although some research has been conducted on the mechanisms of sea ice formation, the combined effect of mechanical forces and buoyancy on this process remains poorly understood.
Now, a joint team of researchers from the University of Tokyo, Hokkaido University and the National Polar Research Institute have used data collected during the international ship-based MOSAiC observation expedition. , to examine the arctic IOBL as it transitioned from melting to refreezing in real time. The team was led by Dr. Yusuke Kawaguchi of the University of Tokyo’s Institute of Atmospheric and Oceanic Research and included Dr. Daiki Nomura of Hokkaido University and Dr. Jun Inoue of the National Research Institute polar.
“Due to the complex patterns of heat and energy transfer, the physics of cold oceans is complicated. Our goal was to quantify the thermodynamic growth and decay of sea ice while incorporating the effects of heat exchange and salt with near-surface water due to turbulent forces,” says Kawaguchi about his motivation to complete this work. The team’s findings were published in the Journal of Geophysical Research-Oceans.
The team combined various datasets, including observations of air, sea ice and ocean properties from the sea ice. These were collected during the final stage of the MOSAiC study, which was an international project undertaken to study the climate, ocean and sea ice characteristics of the Arctic Ocean.
From their investigation, the team concluded that the current Arctic sea ice was more likely to melt in summer and freeze in autumn and early winter than before. Asked about the main discoveries, Kawaguchi, the lead author, talks about the characteristics of seawater and sea ice that are responsible for this fascinating phenomenon. “Our first finding was that in summer, strong winds cause water to mix where the ice and ocean meet. We were able to show that the enhanced heat transfer occurs just below the ice. of sea”, he explains.
Their second discovery concerns the drop in salinity of seawater when it mixes with the melting water of the pack ice. “As meltwater accumulates under the sea ice, the salinity of the seawater decreases and then the freezing temperature increases. This ends the melting of sea ice at an earlier time because the water becomes easier to freeze. Kawaguchi said.
The team is excited about the implications of their findings for the field of polar oceanography, particularly in the context of climate change. Currently, the team is developing a device that simultaneously measures sea ice movement and salinity at IOBL, in the hope that it will collect more data to paint a clearer picture of sea ice fluctuations. Arctic.
“The extent of Arctic sea ice can affect regional climate in remote locations, such as Japan, via atmospheric disturbances. We believe that studying sea ice will allow us to better predict future changes in Earth’s climate” , concludes Kawaguchi.
– This press release was provided by the Information and Systems Research Organization