During late February, Antarctic sea ice breached the previous all-time record low for extent coverage since measurements began in 1978. And in the following days, sea ice extent measures near the South Pole have continued to creep lower, gradually extending into unprecedented ranges.
Record Melt During a Period of Considerable Global Heat
(This February, according to JAXA, the Antarctic sea ice extent measure hit a new all time record low. Image source: JAXA.)
Hitherto unseen global heat — driven primarily by human fossil fuel emissions — appears to be the chief contributor to this melting. During 2016, global average surface temperatures rose to 1.2 degrees Celsius above 1880s ranges. This global reading likely represents the warmest surface temperatures the world has experienced in the last 115,000 years. At the same time, the global ocean system has been rapidly accumulating warmth and transferring it through the surface and deep layers of the world’s waters.
Such pervasive heat is producing an ongoing trend of considerable sea ice melt in the Arctic — a trend that has been in place since record-keeping began in 1978. One that, all by itself, is strong enough to drag global sea ice measures lower and lower. The warmth is also producing land ice melt around the world — including glaciers in Antarctica, Greenland and across numerous mountain ranges.
(Global warming produced an identifiable global sea ice melt trend during the post year 2000 period. By 2016, that trend had become glaringly obvious. See final paragraph for further discussion. Image source: Wipneus.)
Mild Antarctic Ice Growth Trend Reversed
Sea ice melt in the Antarctic, however, is a possible new feature. In the past, it is thought that fresh water outflow from glaciers in Antarctica and strong winds encircling the Southern Hemisphere sea ice helped to protect it from the initial pulse of human-forced warming. And as recently as 2014 and 2015, Antarctic sea ice experienced new record high readings even as the long-term trend hinted at a possible slow expansion of sea ice near the South Pole. Researchers had indicated that the protection for Southern Hemisphere sea ice might only last as long as fragile wind patterns around the South Pole remained.
For 2016 and 2017, however, that thin veil of protection appears to have fallen. Previous record lows for Antarctic sea ice extent set in 1997 at 2.26 million square kilometers sea ice coverage during the austral summer month of February have now been exceeded by 100,000 square kilometers. As of yesterday, according to JAXA, the new record low stood at 2.16 million square kilometers.
(More above average temperatures predicted this week for Antarctica may extend sea ice record lows somewhat before refreeze sets in. Image source: Climate Reanalyzer.)
Antarctic refreeze typically starts during mid-February as seasonal cooling sets in. However, 2017’s warmth has driven an extension of late season melt with Antarctic sea ice continuing to decline through the end of February. At some point during the next week or two, however, refreeze is likely to finally kick in. But this return to rising ice coverage may be still be delayed somewhat by very warm Antarctic temperatures predicted to range as high as 2.9 C above average through the next five days.
Global Sea Ice Coverage Falling Rapidly
This year’s all time record low for Antarctic sea ice extent also comes at a time when the Arctic has been experiencing daily, monthly and seasonal record lows. Highly unseasonable temperatures have dominated Arctic Fall and Winter during 2016 and 2017 — producing never before see low extent coverage during the period. As a result of record lows occurring at the same time in the north and in the south, overall global sea ice coverage has taken a considerable beating and the larger global sea ice trend is now strongly negative.