An updated report from Climate.gov titled Old ice in Arctic vanishingly rare shows how old ice that used to make up 20% of the arctic ice pack now only accounts for 3% of it. The culprit — warmer waters fed by a growing amount of man-made carbon dioxide in the atmosphere.
The “arctic amplification” of climate change remained in full swing in 2015, according to the 2015 Arctic Report Card. Broad areas of the Arctic were more than 5°F (3°C) warmer than average during the report card’s monitoring year (October 2014-September 2015), with temperatures over land areas record warm. The increase in temperature over Arctic regions continued to outpace the global average.
This is the explanation from NOAA Climate.gov along with animated video and graphics.
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The map at left shows the average temperature for October 2014-September 2015 compared to the 1981-2010 average. All around the Arctic, temperatures were much warmer than average, with only Greenland and a small part of northeastern Canada near or below average.
The graph beneath the map shows annual temperatures for the Arctic (areas between 60° and 90° North latitude) and the globe since 1900. Arctic temperatures (red line) are more variable from year to year than global temperatures (bigger swings above and below average). But despite the variability, a trend is clear: the Arctic has warmed more than the globe as a whole.
This amplification of climate change occurs for two main reasons. First is the feedback loop that gets underway as temperatures rise and snow and ice melt. The less snow and ice on the ground or ocean during the Arctic’s long summer days, the more sunlight the ocean and land absorb. The more they absorb, the warmer they get, and the more ice and snow melt.
Second, while the Arctic is warming, its temperature is still lower than the tropical or middle latitudes, and a colder atmosphere doesn’t radiate thermal energy back into space as efficiently as warmer parts of the atmosphere do. In other words, a colder atmosphere can’t get rid of the excess heat of global warming as well as other parts of the globe, and so it is warming faster.
Here is the explanation of the video, also from NOAA Climate.gov
Sea ice grows throughout the winter and melts throughout the summer, reaching its maximum extent in late February or March, and its minimum extent in September. The ice that survives at least one summer melt season is typically thicker and more likely to survive future summers. Since the 1980s, the amount of this perennial ice (or multiyear) has declined dramatically.
This animation tracks the relative amount of ice of different ages each week from 1990 through early November 2015. The first age class on the scale (1, darkest blue) means “first-year ice,” which formed in the most recent winter. The oldest ice (>9, white) is ice that is more than nine years old. Dark gray areas indicate open water or coastal regions where the spatial resolution of the data is coarser than the land map.
Arctic sea ice moves continually. East of Greenland, the Fram Strait is an exit ramp for ice drifting out of the Arctic Ocean. Ice loss through the Fram Strait used to be offset by ice growth in the Beaufort Gyre, northeast of Alaska, where perennial ice could persist for years.
But around the start of the 21st century, the Beaufort Gyre became less friendly to perennial ice. Warmer waters made it less likely that ice would survive its passage through the southernmost part of the gyre. By around 2008, the very oldest ice had shrunk to a narrow band along the Canadian Arctic Archipelago.
In the 2015 Arctic Report Card, scientists wrote:
In 1985, 20% of the ice pack was very old ice, but in March 2015 old ice only constituted 3% of the ice pack. Furthermore, we note that first-year ice now dominates the ice cover, comprising ~70% of the March 2015 ice pack, compared to about half that in the 1980s.
Animation by NOAA Climate.gov team, based on research data provided by Mark Tschudi, CCAR, University of Colorado. Sea ice age is estimated by tracking of ice parcels using satellite imagery and drifting ocean buoys.
Charctic Interactive Sea Ice Graph. National Snow and Ice Data Center. Accessed December 9, 2015.
Perovich, D., W. Meier, M. Tschudi, S. Farrell, S. Gerland, and S. Hendricks. (2015). Chapter 4: Sea Ice. In Jeffries, M.O., Richter-Menge, J., Overland, J.E. (2015) Arctic Report Card: Update for 2015.