The continent of Antarctica is surrounded by sea ice. The amount of ice grows in the winter and shrinks in summer. The total area is covers changes from year to year. And it just set a new record in January, the National Oceanic and Atmospheric Administration reports. That month, Antarctic sea ice shrunk to the lowest monthly extent ever recorded.
Antarctic sea ice averaged just 4.04 million square kilometers (1.6 million square miles). That’s 1.19 million square kilometers (0.46 million square miles) below the 1981 through 2010 average. And that’s 280,000 square kilometers (108,000 square miles) smaller than the previous record low, set in 2006.
The new record comes just two years after the largest January Antarctic sea ice extent on record. Southern Hemisphere sea ice had been growing by about 3 percent per decade since recordkeeping began in 1979. However, there is a lot of year-to-year variation.
The cause of the record-low ice — and whether future years will similarly buck the growing trend — is unclear, James Pope said in a statement. He is a climate scientist with the British Antarctic Survey in Cambridge, England. “It is difficult to identify what is causing the record minimum and whether anything significant has changed” so close to the record-setting event, he said. Researchers may not understand for years what caused the decline in sea ice. “We will now study the data with interest and look at what is causing this minimum,” he said.
Meanwhile, in the Northern Hemisphere, where it is winter, Arctic sea ice is growing. But sea ice there set another record. It had its smallest January extent on record. That edges out the previous record — set just last year.
Antarctica A continent mostly covered in ice, which sits in the southernmost part of the world.
Arctic A region that falls within the Arctic Circle. The edge of that circle is defined as the northernmost point at which the sun is visible on the northern winter solstice and the southernmost point at which the midnight sun can be seen on the northern summer solstice.
Arctic sea ice Ice that forms from seawater and that covers all or parts of the Arctic Ocean.
average (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.
climate The weather conditions prevailing in an area in general or over a long period.
continent (in geology) The huge land masses that sit upon tectonic plates. In modern times, there are six geologic continents: North America, South America, Eurasia, Africa, Australia and Antarctica.
data Facts and/or statistics collected together for analysis but not necessarily organized in a way that gives them meaning. For digital information (the type stored by computers), those data typically are numbers stored in a binary code, portrayed as strings of zeros and ones.
National Oceanic and Atmospheric Administration (or NOAA) A science agency of the U.S. Department of Commerce. Initially established in 1807 under another name (The Survey of the Coast), this agency focuses on understanding and preserving ocean resources, including fisheries, protecting marine mammals (from seals to whales), studying the seafloor and probing the upper atmosphere.
sea An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.
square (in geometry) A rectangle with four sides of equal length. (In mathematics) A number multiplied by itself, or the verb meaning to multiply a number by itself. The square of 2 is 4; the square of 10 is 100.
survey (v.) To ask questions that glean data on the opinions, practices (such as dining or sleeping habits), knowledge or skills of a broad range of people. Researchers select the number and types of people questioned in hopes that the answers these individuals give will be representative of others who are their age, belong to the same ethnic group or live in the same region. (n.) The list of questions that will be offered to glean those data.