Predicting the CT Area minimum

Crysophere Today Area (CT Area) is the dataset produced by the Polar Research Group at the University of Illinois. I've stopped using it since last year, I now concentrate on NSIDC Extent and PIOMAS. But it has a peculiarity that makes it worth picking up again.

June Status: Part 1

Crucial to what I think will happen later this season is the PIOMAS data, as I wait for that the NCEP/NCAR data is now updated, and of course we have extent and area data. So here's the situation over June.

CT Area 2014 Prediction

The melt season has started off too late, there will be no CT Area anomaly cliff, and I don't believe that 2012's record will be neared or beaten. However I am making my prediction for CT Area in 2014. CT Area is Cryosphere Today Area, the data is available here.

NOTE - the final part of this blog post has been changed as an error was found in my transformation from CT Area to NSIDC Extent.

Do Not Press This Button!

Changes in Arctic sea ice are a warning to us, and in my opinion one of the best ways to see the warning is through anomalies.

Anomalies are the difference from a long term average, as usual I use the period 1980 to 1999 (20 years) for my long term average. I work out the average value of the index used for each of the 365 days in a standard year and then deduct this value from each daily value of the series 1979 to the present. This transforms the data from a large sinusoidal wave into the differences from that average sinusoidal seasonal cycle, these differences are called anomalies.


I've previously blogged on this for Cryosphere Today Area (CT Area), but thought it worth updating the graphs, this time including NSIDC Extent.

Autumn 2013

Now that PIOMAS data is out and a New Year has begun, it's worth going over some of the data regards sea ice, what I had intended to be my first post before the atmosphere going bonkers derailed my train of thought.

October Status

New PIOMAS data is now out for October, I've no intention of continuing with monthly status posts, but will do so when there's something to say. So here's an October's status blog post, and at the end there's a link to my new sea ice spreadsheet.

2013 Sea Ice Prediction Review

I have previously made two predictions, one early in the season, one late. Both were in terms of CT Area, and as CT Area is now clearly past the minimum the time has come to evaluate my predictions.

Summer 2013

Rather than do an August status post this close to the minimum, when the take-home message of the 2013 melt season is already clear, I've decided it's best to do a post on the summer melt of 2013. The actual minimum may warrant a further post, if so that will be done.

Prediction Update.

On 6 July I made my final prediction for the CT Area minimum, now at 26 August it's worth seeing how that prediction has done, so far.

Mid August Status: The fat lady draws breath

Now in mid August the potential for 2013 catching up on 2007 or 2011 is remote in my opinion, so it's worth explaining why I think that as I've been quiet for a while. Damn, just seen that Neven has posted today along similar lines, well as this is written I'll post anyway.

July Status Part 1: Cryosphere Today Area

The full data for June are now available for Cryosphere Today Area (CT Area). As usual I'm still waiting for NCEP/NCAR reanalysis to produce July average, and as PIOMAS uses NCEP/NCAR data they don't publish their main series on the first of the month. So I'll start by going over CT Area, atmosphere and volume will follow in the next few days.

If HYCOM is correct.

Looking at CT Area anomalies and the US Navy's HYCOM model, link, I suspect that August may see record losses as did 2012. This means my prediction of early this month is already looking unlikely to be correct.

What does CT Area show?

This post is a few days late due to work commitments, basically a comment on my last post, link, has raised the question; what does the Cryosphere Today Area (CT Area) index actually show?

How Fragmented is the Pack?

There's a discussion going on over at the Sea Ice Forum, link, about whether the pack this year is more fragmented than previous years. I'm with Peter Ellis on this, looking at different satellite systems and at certain areas it's possible to reach either a 'for' or 'against', conclusion. Certain features such as the Laptev/North Pole low concentration anomaly are quite exciting, although it remains to be seen what role that feature will play in the coming season.

I'm not posting to launch into a long boring discussion of the pack floe by floe. I think there's a more objective way to cut to the heart of the issue. The data I use are IJIS Sea Ice Extent index, data, and CT Area, data.

June Status Part 1: CT Area.

OK, rant over, it's time to get back to sea-ice.

Now that Cryosphere Today's area data (CT Area) are in for yesterday, it's possible to summarise the status for June. The take-home message I read from the data is that a new record is now very unlikely based on past year's behaviour due to the late start to melt, despite other indicators of pack condition (for example the Laptev to N Pole region, link). Posts on the atmospheric status (key to understanding the late melt) and PIOMAS will follow when PIOMAS and NCEP/NCAR updates come in for the month of June.

June Cliff Watch

In an earlier post I outlined the June Crash, link, or as I'll now call it in line with others, the June Cliff. It's now happening. Below is a graph of CT Area anomalies (differences from the average seasonal cycle). This will be updated regularly throughout June on this page.

2013 joins 2007, 2010, 2011 and 2012 in having a June Cliff. I'm pretty sure that 2013's June Cliff has now ended, it lasted from 6 June to 18 June. My next post on the Arctic sea ice will be the June Status post, when the PIOMAS data is out, this post will not be updated further.

As mentioned in my previous post, and discussed in the earlier post on the June Cliff (Crash) much of this drop in CT Area is not real loss of area but is due to melt ponding on the ice. This does not mean it has no impact on real area because melt ponds lower the albedo of the surface and absorb more sunlight.

While I now doubt we will see a new record this year, I expect a very exciting season. As with the May Status posts, I expect the June Status to take up more than one post.

Data as of 23/6/13.

In the figures below, Daily is the difference between successive days, Difference is the difference between area on that date and on the same date in 2012.

Date  Area    Daily   Difference
01/6 10.656 -0.035 0.716
02/6 10.581 -0.075 0.703
03/6 10.498 -0.084 0.715
04/6 10.382 -0.116 0.601
05/6 10.291 -0.091 0.535
06/6 10.223 -0.068 0.505
07/6 09.976 -0.247 0.314
08/6 09.815 -0.161 0.301
09/6 09.710 -0.105 0.369
10/6 09.714 +0.004 0.639
11/6 09.617 -0.097 0.775

12/6 09.535 -0.081 0.851
13/6 09.452 -0.083 0.898
14/6 09.384 -0.068 0.974
15/6 09.191 -0.193 0.987
16/6 08.992 -0.199 0.962
17/6 08.865 -0.127 0.918
18/6 08.722 -0.143 0.933
19/6 08.595 -0.127 0.749
20/6 08.597 +0.002 0.826
21/6 08.389 -0.208 0.651
22/6 08.403 +0.014 0.816
23/6 08.272 -0.131 0.768

Source data from Cryosphere Today, link.

Summer Acceleration

I have recently outlined the changes in the Cryosphere Today Area index (CT Area), using anomalies to examine the changes from the long term average seasonal cycle. I've shown the changes in the CT Area anomalies, link, the autumn response to increasing open water in the summer season, link, and the recent June anomaly crashes, link. I have also covered research showing the majority of surface based Arctic Amplification is a response to summer ice loss, link, and that this amplification is probably being understated by the GISS dataset, link. However I have not addressed a substantial issue, that of the summer acceleration loss of area when compared to the loss of winter area.

The CT Area June Crash

Extent is preferred by professional scientists because it is less sensitive to melt ponds impacting concentration in satellite measurements of sea ice. However I stopped using the various extent indices some time ago because I consider that in seeking to avoid such issues extent is losing valuable information.

There is a new feature of the Cryosphere Today Area series (CT Area), a June crash in anomalies, this is an important feature, which I suspect is a useful indicator of conditions that prime the ice pack for record melts.

Autumn Sea Ice Area

In my previous post I showed the post 2007 changes to the seasonal cycle of the Cryosphere Today sea ice area index (CT Area) in the context of previous decades. A notable part of this is the rapid climb of anomalies in the autumn after the lowest record area minima.

CT Area Anomalies

Cryosphere Today produce a dataset of sea ice area, which I shorthand as CT Area. Calculating the daily average over a long period gives an average sea ice area for each day (baseline average), subtracting these daily anomalies from the actual sea ice area data for each day of a given gives the daily anomaly. These daily anomalies are the differences from the average seasonal cycle. I use the period 1980 to 1999 as the baseline average period.

In this post I present graphs of the daily anomaly series from 1980 to 2012. This is a place holder for reference from future posts.

Click on any of the images to bring up full screen, with a selection menu at the bottom of the screen (this applies to all posts on this blog).