Friday, 22 February 2013


I've previously posted about the current state of the ice in January 2013. As I've just reminded myself of the ASCAT system that has replaced QuikScat, I thought I'd reproduce images from PIOMAS gridded data and the drift age model (DAM) together with ASCAT satellite images.

All images are for December. ASCAT from here, select 'ice' then 'arctic'. DAM from here. And PIOMAS produced by myself from PIOMAS gridded data available from here.

ASCAT is the Advanced Scatterometer satellite system, a radar that operates in a frequency band (C-band ~5.3GHz) where multi-year ice shows up as white (high signal return), first year ice shows up as grey (less of a signal return). Compare the ASCAT multi-year ice with thicker December PIOMAS ice and DAM regions of older ice.

2010 ASCAT

2010 DAM


2011 ASCAT

2011 DAM


2012 ASCAT

2012 DAM


The agreement looks good. The ice state at the end of 2012 looks bad - and that's confirmed by satellite, not just models.

PS - knew I had the link somewhere - here's an ftp directory of ASCAT images, various regions and NH.


Neven said...

Great stuff, Chris. Do you have any idea when the Maslanik-Tschudi maps will be updated? I want to know if they show, like the NRL's ACNFS model, a lot of the MYI shoved towards Beaufort.

That's the number one thing to know before the melting season starts. Then it's the melt ponds.

Chris Reynolds said...


I don't know, I was under the impression that they were updated monthly. I can email Dr Tschudi if you like as I did let him know about the failed annual increment. But in the meantime to keep an eye on MYI we can use ASCAT.

Comparing ASCAT day 355 and day 52 it is clear that the MYI has flattened towards the CAA and spread out towards Banks Island. So what you report is supported. This behaviour is typical for winter. BTW it is also supported by PIPS (which I normally call HYCOM).

Kevin O'Neill said...

Chris, when I did a search for "Quikscat archive" the site came up on the top of the list. I found the ftp directories for the images and the ftp directory for the raw data easily.

The images are explicitly stated as not for science - browse only.

I didn't look into it any further than that - but I'd bet there's a tool available to process the raw data as well.

I didn't want to go any further into it with A-Team over at Neven's, but signal processing is NOT just the purview of one person or team. For instance, SIE and SIA per AMSR-E had no less than 8 different algorithms in use

Chris Reynolds said...


Yes I hit that eventually. First I went looking for quikscat sea ice, then added images to that, the other stuff. Finally I tried the search term you used. Then I searched that site for quikscat and came up with a page full of stuff, amongst which was the raw data.

Raw data? Not what I want. I don't want to go through all the hassle of processing that just to answer this little question. So I started hunting through all the other links. Various iterations later I went back to the top google hit you stated and searched for quikscat images - that's when I found it.

Google searching has parallels with the weak anthropic principle.

Sorry but I agree with A-Team. For years the quikscat team provided large images of Arctic ice. There isn't a good reason for these not to be archived somewhere. If those images were good enough during the mission they're good enough now. For researchers (like Ron Kwok) they'll use the processed data, for the rest of us images are needed.