By Michael Le Page
Jan. 16, 2017
It’s a new low point. The area of the world’s oceans covered by floating sea ice is the smallest recorded since satellite monitoring began in the 1970s. That means it is also probably the lowest it has been for thousands of years.
The latest observations from the US National Snow & Ice Data Center in Boulder, Colorado, show how the ice extent has fallen to a new low this year (bright red trace in the graph below).
In the Arctic, the low in sea ice coverage is a result of both global warming and unusual weather events probably influenced by global warming.
But in the Antarctic, the current low in seasonal sea ice could just be a result of natural variability.
The extent of Arctic sea ice should be growing rapidly during the northern hemisphere winter. But not only has the Arctic been warming rapidly, this winter repeated incursions of warm air have pushed temperatures even further above average.
It has been so warm that on occasions this winter the sea ice coverage has actually temporarily shrunk, as shown by dips in the blue line in the graph below.
In the Arctic, by contrast, there is a long-term decline in sea ice due to global warming. This warming seems to be weakening the winds that circle the pole, allowing warm air to intrude into the Arctic.
And when warm air intrudes, cold air spills south. This is why parts of Asia and Europe have experienced unusually cold weather at times this winter.
As a result of the simultaneous lows at both poles, the total area of sea ice on the planet has fallen to a record low. Reconstructions of past levels of sea ice in the Arctic suggest it is likely the lowest it has been for thousands of years, says meteorologist Eric Holthaus.