According to researchers from NASA and the National Snow and Ice Data Center (NSIDC), the Arctic ice likely reached its minimum extent on September 19th. Thus, 2023 becomes the sixth year with the least ice since satellite data has been available.
Scientists monitor seasonal and yearly fluctuations because sea ice shapes Earth‘s polar ecosystems and plays a significant role in global climate. NSIDC and NASA researchers use satellites to measure ice as it melts and refreezes.
Polar ice loss
Between March and September 2023, Arctic ice cover reduced from a maximum area of 14.62 million square kilometers to 4.23 million square kilometers. This is approximately 1.99 million square kilometers below the 1981-2010 average minimum. The amount of lost sea ice is sufficient to cover all of the continental United States.
Sea ice around Antarctica reached its lowest extent on September 10th, 2023, at 16.96 million square kilometers. This is 1.03 million square kilometers below the previous historical minimum reached in 1986. “This is a record level of sea ice in Antarctica” said Walt Meier, an NSIDC sea ice scientist. “Sea ice growth appears low across almost the entire continent compared to any other region”.
This year in the Arctic, scientists observed particularly low ice levels. Regarding the Northwest Passage, Meier added (ref.), “It’s more open than before. It also appears that there is much more loose ice with lower concentration. Areas that were previously fairly compact and solid ice floes during the summer. The phenomenon has been occurring more frequently in recent years”.
Influence on climate change
Meier stated that the changes are a fundamental, decade-long response to global warming. Since satellite observation began in 1979, Arctic ice has not only been diminishing but also getting younger. Earlier spring melting and later autumn freezing lead to longer melting seasons (ref.). Research has shown that, on average across the Arctic Ocean, freezing occurs approximately a week later every decade, or a month later compared to 1979.
Nathan Kurtz, head of NASA’s Cryospheric Sciences Laboratory, stated that while the Arctic is warming about four times faster than the rest of the planet, the ice is also thinning. “The thickness at the end of the growth season largely determines the survival of sea ice. New research is using satellites like NASA’s ICESat-2 to monitor ice thickness throughout the year”.
Kurtz emphasized that long-term ice measurements are crucial for studying what is happening in real-time at the poles. “At NASA, we are interested in conducting cutting-edge measurements, but we are also trying to connect them to historical documentation to better understand what is driving some of these changes that we are seeing”.
Reduction in solar reflectivity
Scientists are working to understand the cause of the poor growth of Antarctic ice, which could include a combination of factors such as El Niño, wind distribution, and warming ocean temperatures. New research published in Nature (ref.) has shown that ocean heat likely plays a significant role in slowing ice growth in the cold season and promoting melting in the warm season.
This low extent so far in 2023 (ref.) is a continuation of a downward trend in Antarctic sea ice that began after a record level in 2014. Prior to 2014, the ice surrounding the continent was increasing slightly by about 1% every decade.
The melting of sea ice at both poles reinforces warming due to a cycle called the ice albedo feedback. While sea ice reflects most of the solar energy back into space, the ocean absorbs 90% of it. With more areas of the ocean exposed to solar energy, more heat can be absorbed, which warms the ocean waters and further delays sea ice growth.