Arctic Sea Ice

Polls August 2012

ATTENTION: new polls in the right hand bar, closing August 20th.

I guess the latest SEARCH Sea Ice Outlook hasn't come out yet because participating forecasters want to see the full effect of this storm on the sea ice extent numbers before submitting their final estimate for the September average sea ice extent as calculated by the National Snow and Ice Data Center. But we need some new polls over here, so I'm putting out this post.

As you all know, we're doing two polls, because only betting on the September average is kind of boring, as we'd have to wait until October to see the final result. It's more fun to track the daily numbers, and so there's a poll for Cryosphere Today sea ice area as well.

I chose this dataset because IJIS switched from the AMSR-E to the WindSat sensor, and their SIE numbers are oscillating a bit too much to trust comparisons to other years. There are not any other daily updated, freely accessible data sets out there (NSIDC has one now, but I had already started the polls by then) and as Cryosphere Today is an old and trustworthy player in the whole sea ice cover calculation business, I've decided to go for a daily minimum sea ice area poll.

Here are the results from last month's poll:

The NSIDC minimum monthly/September sea ice extent received 238 votes. The average* of all votes was 4.24 million square km.

These are the NSIDC September monthly average SIE minimums (data here) in the 2005-2011 period:

• 2005: 5.57 million square km
• 2006: 5.92 million square km
• 2007: 4.30 million square km
• 2008: 4.73 million square km
• 2009: 5.39 million square km
• 2010: 4.93 million square km
• 2011: 4.61 million square km

The average* for the Cryosphere Today minimum daily sea ice area (279 votes) was 2.93 million square km.

These are the Cryosphere Today daily SIA minimums (data here) in the 2005-2011 period:

• 2005: 4.09 million square km
• 2006: 4.03 million square km
• 2007: 2.92 million square km
• 2008: 3.00 million square km
• 2009: 3.42 million square km
• 2010: 3.07 million square km
• 2011: 2.90 million square km

There are new polls in the right hand bar, that will close on August 20th. Because of recent developments I've changed the options. If you want, you can re-vote later on by going to the polls directly (here for NSIDC minimum monthly SIE, and here for CT minimum daily SIA). For an explanation of the differences between the polls, go to this blog post.

* This is my complex method for processing the poll results and calculating the average:

I've calculated the number by multiplying the percentage number with the average of an option. For instance 'between 4.0 and 4.2 million' = 4.1, and for 'less than 2.8 million km2' I've used 2.7 million km2. I've added up all multiplications and divided the result by 100.

Polls July 2012

ATTENTION: new polls in the right hand bar, closing July 31st.

With the release of the July SIO report I also release the results of the two ASI blog polls in the right hand bar, that closed on June 30th. First off the poll for the NSIDC minimum monthly/September sea ice extent that received 271 votes. The average* of all votes was 4.29 million square km.

These are the NSIDC September monthly average minimums in the 2005-2011 period:

• 2005: 5.57 million square km
• 2006: 5.92 million square km
• 2007: 4.30 million square km
• 2008: 4.73 million square km
• 2009: 5.39 million square km
• 2010: 4.93 million square km
• 2011: 4.61 million square km

The average* for the Cryosphere Today minimum daily sea ice area (310 votes) was 3.05 million square km.

These are the Croysphere Today daily minimums in the 2005-2011 period:

• 2005: 4.09 million square km
• 2006: 4.03 million square km
• 2007: 2.92 million square km
• 2008: 3.00 million square km
• 2009: 3.42 million square km
• 2010: 3.07 million square km
• 2011: 2.90 million square km

I voted 'between 3.0 and 3.2 million km2' for the CT SIA daily minimum, and 'between 4.25 and 4.5 million km2' for the NSIDC monthly minimum.

There are new polls in the right hand bar, that will close on July 31st. If you want, you can re-vote by going to the polls directly (here for NSIDC minimum monthly SIE, and here for CT minimum daily SIA). For an explanation of the differences between the polls, go to this blog post.

SEARCH Outlook Contribution May 2012

My SEARCH contribution follows. However, I want to say this is the best statistical scheme I have found and doesn't necessarily mean I believe it. If I was submitting a huristic estimate then I would be saying:

I find myself concerned at the rapid drop in area and the appearance of the ice. High area in March April and May in southerly locations should have reflected more solar radiation and kept things cool. Despite this Chukchi isn't far behind normal. The volume is about the same as last year but spread more thinly into southerly locations. The time for that to slow down retreat of areas like Chukchi has almost past and it seems to me as if the thinner ice at more northerly locations will now cause faster retreat so that areas like Chukchi can catch up if not overtake. On the Atlantic side, so far the weather has prevented fast retreat in these weak ice area. That is unlikely to continue indefinitely and despite the weather the Barents and Kara are still looking very weak compared to past years. I think there has been high outflow through Fram strait, and high Atlantic water heat content inflow recently and low snow cover in April and May around the arctic basin.

Polls 2012: daily and monthly minimum

Now that the melting season is underway and we have had the opportunity to study the prelude, this is a good moment to start guessing the minimum. But there are different kinds of minimum: area, extent, daily minimum, average September minimum. Of course, the difference between extent and area is well-known and area tends to be lower than extent. There's also a difference between the day in September with the lowest extent/area, and an average of all September days.

Personally I'm a big fan of minimum daily extent/area polls, because that makes it more exciting around the time of the minimum (not having to wait until October for the final result to come in). On the other hand, the monthly SEARCH Sea Ice Outlook reports, where science pros and knowledgeable amateurs submit their guesses, garner more interest every year. And these are for the NSIDC September (monthly average) minimum extent. Okay, so let's do two polls then. But which datasets?

Last year the polls were focused on IJIS minimum daily sea ice extent, but because of the switch to WindSat it's not sure yet how 'trustworthy' or consistent it is. That means there's only one option left and that's the Cryosphere Today sea ice area numbers (to be found here).

These are the daily minimums in the 2005-2011 period: