Showing posts with label exponential. Show all posts
Showing posts with label exponential. Show all posts

Thursday, June 13, 2013

Arctic sea ice thickness falls by 2m in 21 days in some areas

For years, warnings have been raised about the dramatic decline of Arctic sea ice. Various posts at this blog have also analyzed the exponential nature of the decline in summer sea ice volume and the many feedbacks that fuel this decline. And for years, the conclusion has been that - without action - the sea ice looks set to disappear altogether within years.

Yet, many are still ignoring this warning, often with remarks such as "some of the ice is 5 meters thick; it would take decades for all that ice to melt!" Thick ice does indeed pile up along the northern coast of Greenland and Ellesmere Island, due to the way the ice drifts. This has lead some to argue that an S-shaped curve (sigmoid or gompertz trendline) was more appropriate, with the decline in sea ice volume slowing down as it approaches zero.

However, this argument doesn't seem make much sense, since such a S-shaped trendline would only apply to a relatively small area with very thick sea ice. Exponential curves would still remain the best fit to predict the decline of the sea ice in the Arctic Ocean at large.

Moreover, is it really more appropriate to say that summer sea ice looks set to virtually disappear within years, with just a tiny sliver of ice remaining north of Greenland and Ellesmere Island, instead of saying that the sea ice looks set to disappear altogether within years? How persistent will such a sliver really be?

One of the feedbacks of sea ice decline is that, as the decline progresses, cyclones can be expected to hit the remaining sea ice ever harder. How much damage can such cyclones and further feedbacks do? A previous post describes thin spots developing in the sea ice under the influence of a cyclone. The image below shows areas at the center of the Arctic Ocean (large circle) where thickness of the sea ice fell from 2 meters to 1 meters over a period of 21 days. Furthermore, the image below also shows that, over this period, 5m-thick ice was reduced to 3-meters thickness (top small circle), while 2m-thick ice was reduced to zero (bottom small circle).

2m falls in thickness in 21 days - click on image to enlarge
In conclusion, without action the Arctic sea ice looks set to continue to decline exponentially, while strong feedbacks such as cyclones developing when there is more open water, look set to add to the decline and cause the Arctic sea ice to disappear completely within years. For an overview of lines of action, see this post at the methane hydrates blog.

Friday, January 25, 2013

Arctic sea ice volume decline animation

Screenshot showing the exponential decline of minimum Arctic sea ice volume at the bottom end of the annual graphs
To see a 3-D animation of the decline of Arctic sea ice volume over the years, click on the play button below.

This excellent animation was produced by Andy Lee Robinson using PIOMAS data.

The image below was part of last year's post Polar jet stream appears hugely deformed. The image highlights that Arctic sea ice minimum volume in 2012 was only 19.3% what it was in 1979. The background image, prepared by Wipneus, shows an exponential trend projecting a 2013 minimum of only 2000 cubic km of sea ice, with a margin of error that allows Arctic sea ice to disappear altogether this year, i.e. in less than six  months time. 


- Polar jet stream appears hugely deformed

Monday, September 3, 2012

PIOMAS data confirm exponential trend

The Applied Physics Laboratory/Polar Science Center at the University of Washington has issued an extra release of Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) data.

Sea ice volume on August 25th, 2012, was 3500 km3, or about 500 km3 less than the prior minimum, reached on September 10th, 2011.

The image below shows that recent data for 2012 appear to match almost perfectly the expected values based on exponential trends added by Wipneus.
The image below, again based on PIOMAS data, shows trends added by Wipneus for each month of the year. The black line shows the average for the month September, pointing at zero a bit into the year 2015, while the average for August and October (the overlapping red and dark blue lines, appearing as a single purple line) point at zero before the start of the year 2016.
In conclusion, it looks like there will be no sea ice from August 2015 through to October 2015, while a further three months look set to reach zero in 2017, 2018 and 2019 (respectively July, November and June). Before the start of the year 2020, in other words, there will be zero sea ice for the six months from June through to November.

And, events may unfold even more rapidly, as discussed earlier at Getting the picture.

The image below, from the Naval Research Laboratory, shows the dramatic decline of sea ice thickness over the last 30 days.

Sunday, June 10, 2012

Arctic sea ice volume on track to reach zero around 2015

The image below shows recent data on Arctic sea ice volume, as calculated using the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS, Zhang and Rothrock, 2003) developed at the Polar Science Center, Applied Physics Laboratory, University of Washington.

As shown on the images below, by Wipneus and earlier published at the Arctic Sea Ice Blog, sea ice volume loss is on track to reach a minimum of 3000 cubic kilometers this summer.
The recent sea ice volume is in line with the exponential trend calculated by Wipneus that is pointing at zero ice volume around 2015 (image below).


Will sea ice collapse in 2014?As described in an earlier post, I believe that a trendline pointing at 2014 fits the data best (image left).

As discussed, some ice may persist close to Greenland for a few years more, since Greenland constitutes a barrier that holds the sea ice in place. Similarly, natural variability could prolong the ice longer than expected.

However, such arguments offer no reason to rule out an imminent collapse of the sea ice, since natural variability works both ways, it could bring about such a collapse either earlier or later than models indicate.

In fact, the thinner the sea ice gets, the more likely an early collapse is to occur. There is robust evidence that global warming will increase the intensity of extreme weather events, so more heavy winds and more intense storms can be expected to increasingly break up the remaining ice in future, driving the smaller parts out of the Arctic Ocean more easily. Much of the sea ice loss already occurs due to sea ice moving along the edges of Greenland into the Atlantic Ocean.

Could you think of any reason why Arctic sea ice would NOT collapse in 2014?