Antarctic sea ice is a vital component of the Earth’s climate system, as it insulates the ocean, reflects heat, drives currents, supports ecosystems and protects ice shelves. However, in recent years, Antarctic sea ice has experienced a sudden and dramatic loss of coverage, reaching record low levels in 2023.
According to a new study published in Communications Earth & Environment, Antarctic sea ice may have entered a new state of diminished coverage, driven by ocean warming. The study, conducted by Australian scientists, describes a “breakdown” in the link between sea ice and the atmosphere over Antarctica.
The study used a statistical algorithm to identify three different periods in the sea-ice record: a neutral sea-ice period from November 1978 to August 2007, a high sea-ice period from September 2007 to August 2016, and a low sea-ice period from September 2016 until now.
The researchers found that the low sea-ice period was characterized by a weak relationship between sea ice and the Southern Annular Mode (SAM), a measure of the strength and position of the westerly winds that circulate around Antarctica. The SAM influences the amount of heat and moisture that reaches the Antarctic continent and the surrounding ocean.
The study suggests that ocean warming has weakened the influence of the SAM on sea ice, making it more vulnerable to other factors, such as regional variability and extreme events.
The consequences of low sea ice
The loss of Antarctic sea ice has serious implications for the climate, the environment and the wildlife of the region. For example, low sea ice can expose the ice shelves that fringe the Antarctic coast to warmer water, increasing the risk of melting and collapse. Ice shelves act as buttresses that slow down the flow of glaciers into the ocean, and their loss can contribute to sea level rise.
Low sea ice can also affect the marine ecosystems that depend on it, such as krill, fish, seals, penguins and whales. Sea ice provides a habitat, a refuge, a source of food and a platform for breeding and resting for many species. In 2022, a tragic event occurred when 10,000 emperor penguin chicks died after the sea ice they lived on melted before they had grown their waterproof feathers.
Moreover, low sea ice can alter the ocean circulation and the carbon cycle, as sea ice formation and melting affect the salinity, density and nutrient content of the water. Sea ice also plays a role in regulating the exchange of heat, moisture and carbon dioxide between the ocean and the atmosphere, which can have feedback effects on the climate.
The outlook for the future
The study warns that the low sea-ice state may be the “new abnormal” for Antarctica, as the ocean warming that caused it is expected to continue or intensify in the future. The study calls for more research and monitoring to understand the causes and consequences of the low sea-ice state, and to improve the projections of sea-ice changes under different scenarios of greenhouse gas emissions.
The study also highlights the need for more international cooperation and action to reduce the greenhouse gas emissions that are driving the ocean warming and the sea-ice loss. The Antarctic Treaty System, which governs the use and protection of Antarctica, is an example of a successful framework for peaceful and scientific collaboration in the region. However, more efforts are needed to address the challenges and opportunities posed by the changing Antarctic environment.