NSIDC Arctic sea ice news July 2010

The National Snow and Ice Data Centre has just released its July analysis of Arctic conditions in the past month. Here are some excerpts:

Average ice extent for July was 8.39 million square kilometers (3.24 million square miles), 1.71 million square kilometers (660,000 square miles) below the 1979 to 2000 mean, but 260,000 square kilometers (100,000 square miles) above the average for July 2007, the lowest July in the thirty-two-year satellite record.

Stormy, cloudy, and relatively cool weather persisted through the month, which helped slow the rate of ice loss. The daily rate of decline for July was 77,000 square kilometers (29,700 square miles) per day, close to the 1979 to 2000 average of 84,400 square kilometers (32,600 square miles).

(...)

Cool, stormy weather this July has made it less likely that the upcoming 2010 sea ice minimum will set a new record. It would take a very unusual set of conditions in August to create a new record low.

If the daily rate of decline this August follows the average August rate of decline for 1979 to 2000, the daily sea ice minimum in September would be 5.00 million square kilometers (1.93 million square miles), considerably higher than the record minimum of 4.13 million square kilometers (1.59 million square miles) observed for September 16, 2007. A daily rate of decline identical to 2007 would yield a September minimum of 4.43 million square kilometers (1.71 million square miles); while daily decline rates similar to 2008 (the largest ever observed for August), would yield a September minimum of 4.08 million square kilometers (1.58 million square miles). If the daily rate of decline is similar to 2006, the slowest in recent years, the minimum would be 5.27 million square kilometers (2.03 million square miles).

(...)

Older, thicker ice melting in the southern Beaufort Sea

This past winter's negative phase of the Arctic Oscillation transported old ice (four, five, and more years old) from an area north of the Canadian Archipelago. The ice was flushed southwards and westward into the Beaufort and Chukchi seas, as noted in our April post. Ice age data show that back in the 1970s and 1980s, old ice drifting into the Beaufort Sea would generally survive the summer melt season. However, the old, thick ice that moved into this region is now beginning to melt out, which could further deplete the Arctic’s remaining store of old, thick ice. The loss of thick ice has been implicated as a major cause of the very low September sea ice minima observed in recent years.

Here's the graph:

 

Read the whole summary here.

Comments

[Nick Barnes]

Off-topic: Check out today's MODIS of the NWP and the northern archipelago:
http://rapidfire.sci.gsfc.nasa.gov/subsets/?subset=Arctic_r04c02.2010216.terra
There's a lot of cloud, but some detail is visible through it. Blink with this one from the end of June to identify the coastlines:
http://rapidfire.sci.gsfc.nasa.gov/subsets/?subset=Arctic_r04c02.2010180.terra

There is snow on many of the islands, but there is also open water. There's a big swathe of it south of Ellef Ringnes island, and a narrower swathe of it all around the western side of that island right up to Cape Isacsen on the Arctic Ocean. Some patches of open water near some of the other islands.

[Neven]

I noticed it too one minute ago, Nick. I can't wait for those clouds to move aside again.

[Neven]

ECMWF is forecasting some big highs over the Canadian Archipelago 5 days from now. If this comes about, we will have our seat right next to the pitch to watch the game unfold.

Unisys doesn't agree, I think.

Jim Dowling, where are you?

[siili]

USCGC Healy just entered the arctic ocean http://www.sailwx.info/shiptrack/shipposition.phtml?call=NEPP
on the way to a very ambitious and long lasting cruise to map the seafloor in the Canada basin http://continentalshelf.gov/missions/10arctic/welcome.html and there probably encounter the last surviving old ice of the entire arctic ocean.

[Phil263]

@ siili
MODIS actually have some good holes through the clouds, showing ice streatching almost all the way from Wrangel to Alaska, not showing on Bremen...

I found the same discrepancy between the NOAA analysis for Alaska and the maps from the Canadian ice service here and here , and Uni Bremen sattelite images . Does anybody know what these maps are based on?

[siili]

From what i remember the biggest difference is the purpose of the maps, Bremen and others like that are primarily made out of an effort to understand the science of the arctic system, they are, once the code is written, running automatic without human interference and gives maps based on e.g. a fixed 15% concentration limit using the chsen algoritm and detector.

The Iceservices has a very different mission, to support shipping and other professional operation, and then it is very important not to miss any ice which might be a problem to any vessel venturing into ice infested waters. So they use all detectors available, microwaves passive and active from all satellites,optical, ship reports, the lot. And they have very skilled people looking at all this data before constructing the charts.

So no wonder they show more ice.

[siili]

A short background to remote sensing of ice using passive microwaves, used by e.g. Bremen, JAXA, and NSIDC.

All objects radiate at different wavelengths, mainly dependent on the temperature of the object, the mainly in the optical, the earth mainly in the infrared. In the microwave wavelength range, how much an object emitts is not mainly due to the temperature of the object but instead on the texture,or roughness of it. Smooth surfaces like calm water emitts little mircowaves, rough surfaces like stormy water a lot, and stuff inbetween like land and ice emitts inbetween. In the image this is mapped to shades of gray. There are also other tricks like polarisation state, but let's save that for now.

I have not found many basic images from mircowaves, but one example showing similar effects is from a variant tecniqe, using ACTIVE micowaves i.e. RADAR
http://www.seaice.dk/iwicos/latest/envisat.GMM3d.n.20100805.gif

There are some "stripes" in the Beaufort that might be from cloud effects. Otherwise the brokenup state of the ice is very clearly seen all the way in to the hole at the pole caused by the orbital plane of the satellite. Also note the filamentary ice close to Bering strait and compare it to visual MODIS images.

Due to the use of Synthetic Aperture Radar (SAR) , the resolution in much better than passive detectors, which usually have 25km, in this image it's 1km in the original data and in the image probably limited by the pixelsize.

[Phil263]

Thanks Siili, great picture!