Arctic Sea Ice

Final score: 2011 vs 2007

Now that I've called the minimum, it's time to have a look at the differences between the two years with the lowest minimums in all data sets. This post will be a potpourri of different factors.

If we look at the six most important data sets - which IMHO are IJIS extent, NSIDC extent, Cryosphere Today area, Uni Bremen extent, DMI extent and PIOMAS volume - we see that this year a new record has been reached in three of them:

In the remaining three (NSIDC, IJIS and DMI extent) 2007 still holds the record low, but 2011 brushes past very closely and is firmly in second place:

If we compare the sea ice concentration maps from the University of Bremen we can see how close 2007 and 2011 match, despite differences in final shape:

The fat lady's singing

I've been speculating about this quite a while now (see update conclusion). For a minute it looked as though we were getting a grand finale, even though this melting season had quite significant hiccups starting mid-July. But the weather forecasts are now such that a turnaround (which I'm not seeing at the moment) will come too late to make the 2011 trend line go down enough on the NSIDC and IJIS graphs to break the 2007 record.

So after reading the extra update from NSIDC I'm confident enough to call the minimum (if I were less of a coward I would have done it 3-4 days ago):

 

I'll have a post comparing the two biggest melt years tomorrow.

NSIDC special update September 2011

NSIDC has just and not unexpectedly released an extra update:

Arctic sea ice nears minimum extent

In the last few days, the decline in Arctic sea ice extent has slowed. NSIDC data show Arctic sea ice extent currently at the second-lowest levels in the satellite record.

Overview of conditions
On September 10, Arctic sea ice extent was 4.34 million square kilometers (1.68 million square miles). This was 110,000 square kilometers (42,500 square miles) above the 2007 value on the same date. The record minimum Arctic sea ice extent, recorded in 2007, was 4.17* million square kilometers (1.61 million square miles).

The rate of decline has flattened considerably the last few days: Arctic sea ice is likely near its minimum value for the year. However, weather patterns could still push the ice extent lower. NSIDC scientists will make an announcement when ice extent has stopped declining and has expanded for several days in a row, indicating that the Arctic sea ice has reached its lowest extent for the year and has begun freezing over. During the first week of October, after data are processed and analyzed for the month of September, NSIDC scientists will issue a more detailed analysis of this year's melt season and the state of the sea ice.

Read the rest of the report HERE.

First uptick IJIS

This is another one of those small signs that the combination of ice thickness and warm waters are overruling the influence of weather conditions. For the first time this melting season the IJIS numeric data of sea ice extent file is showing an uptick for yesterday's extent number after revision (albeit a very small one of just 938 square km).

To show how late this is, I've made a print screen of my spreadsheet:

Here we see daily extent decreases for a particular date in the 2005-2011 period. The green cells are for first days showing an increase in extent at the end of the melting season (yellow is for century breaks).

I can't really say the weather is to blame, as there hasn't been a real Beaufort Gyre or Dipole Anomaly set-up for weeks. It must be the ice then.

2011: Arctic oddities

Here's an animation I made especially for a guest post on ClimateProgress, the special features - or oddities if you like - of this year's melting season:

To quote myself:

Both the Northwest Passage and the Northern Sea Route have opened up. As this has happened almost every year since 2007, it has become one of those new normals, but I thought I’d mention it anyway (yes, I’m being sarcastic). Shipping companies have begun sending Suezmax-class tankers through the Northern Sea Route.

More interesting is the fact that more than half of of the ice in the channels between the Queen Elizabeth Islands (that part of the Canadian Archipelago between the Northwest Passage and the Arctic Ocean) has melted out completely. This used to be the place where the thickest and oldest sea ice of the Arctic would gather, pressed together by the winds. Not anymore. Last year we saw how ice floes from the Arctic Ocean flowed between the islands when the buttresses disappeared, into warmer southerly waters. This year the winds have been blowing in the wrong direction and so the ice in those channels has simply vanished and not been replaced. There will be thinner first year ice there, meaning it will melt out earlier next year.

I forgot to mention the Laptev Bite! But that's okay, as it isn't showing as prominently on this map as on the other sea ice concentration maps. The retreat of the ice pack on the Atlantic side of the Arctic is also quite unusual, when compared to images from previous minimums.

Because the animations on ClimateProgress don't seem to work in Firefox (and IE plays them only once), I post the other one here as well, an animation of Larry Hamilton's graphs:

Daily NSIDC SIE data and graph

Another excellent post from Arctic.io:

Following this step by step guide called Whither Arctic Sea Ice? from the Earth Exploration Toolbook it is possible to download and produce daily NSIDC extent and concentration data.

Designed to familiarize educators and students with techniques for accessing and analyzing sea ice data all necessary steps like applying a look up table or animating the images are explained in great detail.

Walt Meier from the NSIDC contributed expertise from his work and it is worth to carefully read through this fictional case-study.

Continue reading at Arctic.io.

The daily minimum was reached on September 18th: 4.18 million square km. The current SIE number is 4.33 million sqaure km. This graph is now featured on the Daily Graphs page:

SIE 2011 update 20: the fat lady is still humming

During the melting season I'm regularly writing updates on the current sea ice extent (SIE) as reported by IJIS (a joint effort of the International Arctic Research Center and the Japan Aerospace Exploration Agency) and compare it to the sea ice extents in the period 2005-2010. NSIDC has a good explanation of what sea ice extent is in their FAQ. I also look at other things like sea ice area, concentration, volume, temperature and weather forecasts, anything that can be of particular interest. Check out the Arctic sea ice graphs webpage for daily updated graphs, maps and live webcam images.

September 10th 2011

The incredible has happened. In the past week the 2011 melting season has started to surpass record year 2007. First, the good people from the Polar Science Center informed us of the fact that their PIOMAS model is showing a new sea ice volume record. A day later a new all-time low on the Cryosphere Today sea ice area graph was reached. And two days after that the same thing happened on the University of Bremen sea ice extent chart.

In a sense this isn't so incredible, as we have been well aware of the fact that this could happen from the start of the melting season. But what does make it incredible, is that freak melting season 2007 is equaled and even surpassed. Four years ago, weather conditions that on average occur every 20 years or so, brought huge amounts of heat into the Arctic via air and water, flushed large amounts of ice through Fram and Nares Strait and - to top if off - compacted the ice pack so hard at the end of the melting season that the minimum extent was finally reached in the last week of September.

Up until mid-July this year's melting season resembled that of 2007, but after that things fell apart on the atmospheric front. The heat had been brought in alright, but the flushing through Nares (which opened late) and Fram was slow, and in these last weeks of the season there isn't much compaction to speak of, as the winds are too fickle to stay in place for a prolonged period.

Despite all this 2011 is right down there battling it out with 2007 on almost every graph. This is a sure sign that the ice is very weak and thin in large parts of the ice pack, which means that perfect weather conditions conducive to melting and compacting are no longer necessary to break records. The ice will melt out, regardless of what the weather does. That doesn't bode well for years to come.

We now wait and see if new minimums will be reached on the two popular extent graphs from IJIS and NSIDC. It all depends obviously on what date the minimum will be reached. In last week's SIE update I was pretty pessimistic on that score. This changed during the week, as weather forecast models were showing signs of a set-up that would extend the melting season and crush the ice pack in the process. But as nothing in the Arctic is a dead certainty (especially not the weather forecasts), things have changed again.

Sea ice extent (SIE)

Here's the current IJIS SIE graph:

In the past week SIE has been going down steadily, but slowly. 2007 had a few days of above average extent decrease and thus 2011 has still quite a few square kilometers to make up. The time to do that is next week when 2007 slows down enormously. It will take some extraordinary conditions, though not impossible. 2005 and 2010 had some really large decreases around that time.

The current difference between 2011 and the other years is as follows:

More on ice thickness from AWI

About two and half weeks ago the Alfred Wegener Institute for Polar and Marine Research (AWI) issued a press release to inform us of the fact that their research vessel and icebreaker Polarstern had arrived at the North Pole. In the blog post I dedicated to this news, I mentioned a snippet about their findings concerning ice thickness. I have finally come around to read a bit more on AWI's excellent Polarstern Blog, and have translated some more snippets about ice thickness. All the images come from the Polarstern Blog as well.

Schollensuche richtung Nordpol
the search for ice floes on the way to the North Pole

In order to document the ice conditions during our journey we observe the sea ice on an hourly basis. The ice conditions are logged following an international standard. Ice cover, type, thickness and the distribution and amount of melt ponds are recorded and documented with photographs. Ice thickness is estimated with a yardstick aboard the ship by observing the broken ice floes that are standing upright.

A broken ice floe with a thickness of approximately 1 m (image courtesy of Stefan Hendricks, Alfred Wegener Institute)

The first results from our observations show that the sea ice is relatively thin, young and unstable. Older multiyear ice, which used to be typical for this region in the past decades, makes up just 10 to 20% of the observed ice. Consequently we can travel and navigate through the ice much quicker than in the past, and do not get stuck. On top of that the journey is made easier by many stretches of open water which allow us to travel at a speed of 3 to 6 knots (5 to 10 km/h) from one measuring point to the other. This gives us more time for operating our ice and water stations.

Historical Minimum in Sea Ice Extent

The Arctic sea ice extent index calculated by a University of Bremen research team led by Dr. Georg Heygster reached a new historical low point of 4.24 million km² on September 8. The previous one-day minimum was 4.27 million km² on September 17, 2007 (Figure 1). The usual melt season is not yet over, however, so 2011 extent could decline further. All three graphs in this post will be updated through the end of the season.

 

Figure 1

The Uni Bremen sea ice index goes back only to the start of satellite observations in 1972, but the researchers suggest that ice cover may not have been this low for thousands of years before that.

A few days ago, September 6, the Arctic sea ice cover area index published by Cryosphere Today reached an historical low point as well (Figure 2).

 
Figure 2

Final poll results

The last poll from the widget in the right hand bar closed a week ago. I want to share the results with you before the final SEARCH Sea Ice Outlook comes out. Mind you, I preferred the Arctic Sea Ice blog's poll to be about IJIS daily minimum extent. The SEARCH SIO predictions are for NSIDC September average extent.

Here are the results:

The average this time around is 4.299 million square km.

These were the results for the previous polls:

Poll 1 (304 votes)

4.203 million square km

- (436 votes; closed July 15th)

4.205 million square km

Poll 2 (237 votes; closed August 20th)

4.280 million square km

Poll 3 (135 votes; closed September 1st)

4.299 million square km

Here's my complex method for processing the poll results:

I've calculated the number by multiplying the percentage number with the average of an option. For instance 'between 4.5 and 5 million' = 4.75, and for 'less than 3.5 million km2' I've used 3.25 million km2. I've added up all multiplications and divided the result by 100.

---

Again, this blog community's final prediction is 4.299 million square km.

IJIS SIE is currently at 4.561 million square km (September 7th 2011).