2016 End of Season Arctic Sea Ice Report

I've been waiting to talk about the state of the Arctic until we had reached the minimum extent, and we have either reached it or will shortly, depending on which measure you look at, more on that below. Also, if you'd like to see many more images of the state of the Arctic, click here.

The freezing and melting of sea ice has a large effect on the circulations of the seas and oceans. Here's an excerpt from the NSIDC about that importance:
"Salt plays an important role in ocean circulation. In cold, polar regions, changes in salinity affect ocean density more than changes in temperature. When salt is ejected into the ocean as sea ice forms, the water's salinity increases. Because salt water is heavier, the density of the water increases and the water sinks. The exchange of salt between sea ice and the ocean influences ocean circulation across hundreds of kilometers." 

I wanted to share a post from a meteorologist that I think takes a very honest look at the state of the ice, and he said this today. 

"Now that it looks like we've reached the minimum on all metrics, time for a quick review.


I posted predictions for CT SIA on June 30th this year like I've been doing since 2013. For the first time, this year fell outside the 5-95% confidence intervals. A 5% result would have been a min of 2.58 million sq km on CT SIA, and we finished down near 2.42 million sq km which was actually closer to 2012 (the lowest year) than 2011 (2nd lowest). I'll get back to this in a minute.


For extent, it is a bit harder, but loosely converting area to extent made the low of roughly 4.1 million sq km (on NSIDC... a bit lower on Jaxa around 4.02) a result that would occur about 20-25% of the time given the information we had on 6/30. So the extent was low, but not well outside of the typical confidence intervals.


Getting back to the extreme area result.... the first culprit you would look at is the weather. However, the weather wasn't hostile to the ice in July/August this summer. There were a few hostile periods, but they were largely transient and we would have needed to see off-the-charts extreme. So weather isn't really a valid explanation. That leaves two other variables that may have played a large factor.... bottom melt and reduced ice thickness from an exceptionally warm January-May period. PIOMAS didn't really have exceptionally thin ice, though the CAB region close to the pole was a bit thin and this is actually where a lot of the area damage occurred as we had a big fragmented pool of floes that was the major contributor of the area loss in August. Cryosat2 was a bit thinner here as well. But we've had very thin ice here before too that experienced summer weather worse than 2016 and yet we didn't see this. In 2013, the ice was significantly thinner in much of the CAB region near the pole, though it did have weather more favorable for ice retention than 2016 did. But still, that leads me to believe we may have had more bottom melt too this season. We don't have a lot of reliable data on this, and some scattered buoys is about it. There is some literature that suggests stronger El Ninos causes an influx of warmer waters at depth into the arctic ocean, but it's not very robust.


At any rate, it will be interesting to gather more data as it become available in the early winter with Cryosat2. I think a combination of exceptional warmth in spring and above average bottom melt likely contributed to the extreme result. Something like this may have to be taken into account in the future when making predictions."

UPDATE 09/15/16 - Here's an additional comment from another meteorologist:

"Statistical tie for 2nd place with 2007 on NSIDC.http://nsidc.org/arcticseaicenews/
That September ice extent nevertheless fell to second lowest in the satellite record is hence surprising. Averaged for July through August, air temperatures at the 925 hPa level (about 2,500 feet above sea level) were 0.5 to 2 degrees Celsius (1 to 4 degrees Fahrenheit) below the 1981 to 2010 long-term average over much of the central Arctic Ocean, and near average to slightly higher than average near the North American and easternmost Siberian coasts. Reflecting the stormy conditions, sea level pressures were much lower than average in the central Arctic during these months.


Why did extent fall to a tie for second lowest with 2007? The 2016 Arctic melt season started with a record low maximum extent in March, and sea ice was measured at record low monthly extents well into June. Computer models of ice thickness, and maps of sea ice age both indicated a much thinner ice pack at the end of winter. Statistically, there is little relationship between May and September sea ice extents after removing the long-term trend, indicating the strong role of summer weather patterns in controlling sea ice loss. However, the initial ice thickness may play a significant role. As noted in our mid-August post, the upper ocean was quite warm this summer and ocean-driven melting is important during late summer. The science community will be examining these issues in more detail in coming months."

UPDATE: 09/15/16 - More comments from the mets

2016 finished 3rd by their metrics. Additionally, NSIDC fails to never mentioned sea ice extent minimum values before 2012 were based on a nine day trailing mean. Since then we have a 5 day trailing mean, which makes the minimum extent value appear lower than it would be had there been a 9 day trailing mean. The 2016 arctic sea ice extent minimum based on a 9 day trailing mean is 4.18 million square kilometers. For those wondering the daily NSIDC arctic sea ice daily minimum value was September 7th, 2016. In layman's terms the 5 day running mean for 2007 was adjusted to 4.15 million square kilometers years after the actual minimum. Even if you take the 9 day running mean of 2007's adjusted data, 2016 is higher. 

(Press release of the running mean change)
http://nsidc.org/arcticseaicenews/2012/04/daily-graph-changes/


http://nsidc.org/arcticseaicenews/2007/10/589/#26September
http://nsidc.org/arcticseaicenews/

This is an animated image of the sea ice, beginning the last week of August through September 12th. You can see the ice beginning to make it's winter comeback, so we know the minimum extent was reached earlier this month. 
UPDATE 09/15/16 - "​The early rapid freeze up continues. We are now in 4th place in northern hemisphere sea ice extent (JAXA) as of September 14th, 2016. We are potentially setting up for one of the longest arctic sea ice freeze seasons on record."
​

Arctic Sea Ice Extent

Arctic Temperatures - 265 K is about 17ºF