Changes in the Sea Ice-Ocean Drag Coefficient Due to the Decrease in Antarctic Sea Ice

Despite the ongoing decline in Arctic sea ice extent over the past 30 years, an increase had been observed in Antarctic sea ice until 2016. That year, however, the sea ice melt season started unusually early, leading to a decrease in sea ice extent. Since then, this decline has continued, culminating in a record low sea ice extent in 2023. This reduction in sea ice is primarily linked to changes in atmospheric patterns, along with the impact of rising ocean surface temperatures. Additionally, it has been identified that the decrease in Antarctic sea ice extent significantly affects the atmosphere by increasing the surface heat loss from the Southern Ocean. Simultaneously, a continuous thinning of the sea ice has been observed. This decline in ice thickness is expected to lower the drag coefficient between the sea ice and the ocean, which would, in turn, enhance the influence of wind on the flow of sea ice. Notably, increased sea ice flow during the melting season could accelerate the melting process and increase seasonal sea ice variability. We analyzed the changes in the sea ice-ocean drag coefficient using satellite-observed sea ice concentration and thickness, along with reanalysis wind data over the past 20 years. Although regional differences exist, the overall trend indicates a clear decline in the sea ice-ocean drag coefficient.