2017 Arctic sea ice recap
The National Snow and Ice Data Center has <a href="https://nsidc.org/arcticseaicenews/" target=n>released</a> their final 2017 data for Arctic sea ice.
Following a record low sea ice extent for the winter of 2016/17, the annual seasonal minimum sea ice extent (occurred on Sept. 13) ended up as the 8th lowest on record. Satellite measured records go back to 1979.
Also of note, sea ice extent for December 2017 was the 2nd lowest on record.
One striking piece of data is the fact that ice-over dates are steadily getting later in the calendar year in the Beaufort and Chukchi seas. The NOAA charts below show the clear trend in regards to the ice-over dates, which is due in part to an increase in the upper ocean heat at the end of the summer.
<img src="https://vortex.accuweather.com/adc2004/pub/includes/columns/climatewx/2018/590x708_01101710_figure4.png"/>
Ice-over dates are defined as the first day that the ice concentration is greater than 95 percent in the region.
These later ice-over dates are causing the ice growth season to shorten, which is leading to thinner ice by the end of the summer. This thinner, younger ice is more likely to melt completely during the summer compared to thicker, older ice.
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Longer term Arctic sea ice extent trends</strong>
NOAA has recently published monthly estimates of Arctic sea ice going all the way back to 1850. Clearly, the older data is limited, but the trend is clear. Sea ice extent has steadily declined, especially over the past 30 years.
<img src="https://vortex.accuweather.com/adc2004/pub/includes/columns/climatewx/2018/590x336_01101724_figure5.png"/>
The second image below shows the lowest September minimum Arctic sea ice extents during 50-year intervals going back to 1850. Again, the trend is unmistakable.
<img src="https://vortex.accuweather.com/adc2004/pub/includes/columns/climatewx/2018/590x323_01101725_figure5b-2.png"/>
