This undated handout photo provided by NASA shows Thwaites Glacier in the West Antarctic. Two new studies indicate that part of the vast West Antarctic ice sheet is beginning to slow collapse in an unstoppable way. Worried scientists say this means more sea level rise than they thought. , Photo Credit: AP
February 19 limit sea ice in antarctica It has come down to its lowest level ever. This is in continuation of a worrying trend where sea ice cover is shrinking as global temperatures rise. Sea ice melts during Antarctica’s summer, which begins around October and ends in March, and then freezes again during the winter months.
The data show that there has been a significant decline in Antarctic sea ice cover over the past six years. Melting sea ice leads to global sea level rise, which is a major threat to coastal cities. According to NASA, meltwater from the Antarctic ice sheet accounts for about a third of the global average rise in sea level since 1993.
Chart 1 | Chart showing Antarctic sea ice extent in million square kilometers
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Except for March and April, sea ice extent was the lowest ever recorded for all other days of the year. For example, the 8.73 million km² snow extent recorded on 20 May was the lowest recorded for that date since 1950. Now the second lowest summer sea ice extent in Antarctica.
Such a drastic reduction in ice also changes the way water flows around the world, affecting global weather and underwater ecosystems. The Southern Ocean is important for the transfer of heat from the atmosphere to the global oceans, according to a report by the Intergovernmental Panel on Climate Change. Scientists say the increase in cold, fresh water from melting ice is hindering the flow of warm, cold, fresh and salt water around the world. This change in temperature and density can subsequently affect weather patterns, and alter deep water nutrient flows. In addition to underwater nutrients, algae that feed on tiny crustaceans such as krill, which feed on whales, seals, penguins and other birds, are found growing on sea ice. Less sea ice means less food is available to support the Antarctic food chain.
Map 2 | Map showing the extent of Antarctic sea ice as of May 21, 2023. The areas in white are the sea ice extent as of 21 May and the boundary line indicates the mean sea ice extent between 1981 and 2010.
The map shows that the current sea ice extent has decreased significantly compared to the median.
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With the rise in global temperature, the Antarctic region saw higher air temperatures this year. Less sea ice also means that more of the Sun’s heat, which would otherwise be reflected back, is absorbed by the darker ocean. The heat is trapped in what is known as the ice-albedo feedback cycle.
Chart 3 | The chart shows global temperature anomaly data for the Antarctic region.
Anomalies have been observed in the temperature of Antarctica in the last few years. The graph shows the increase/decrease in temperature (in °C) over the region for the month of April of each year compared to the 1910–2000 average. In 2023, the April temperature in the region was 0.93 °C above the 1910–2000 average for that month – the second largest increase in the millennium.
While the ice sheets melt every summer, the record-breaking decline seen this year far exceeds the lowest levels recorded in the past.
Chart 4 | The chart shows the minimum Antarctic sea ice extent recorded (in million sq km) each summer since 1980.
On February 19, 2023, the Antarctic sea ice area of 1.76 million sq km was recorded, the lowest ever. Although ice does re-form in the winter months, freshly formed ice is generally thinner than multi-year ice, which renders Antarctica’s overall surface area in a more fragile state.
sonikka.l@thehindu.co.in
Source: National Snow and Ice Data Center and National Oceanic and Atmospheric Administration
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