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SIMBA Antarctic Sea Ice

Hi Sarah,

I was doing some research for a polar bear unit I am massaging and came about this information from the University of Illinois, Urbana-Champaign, Arctic Research Facility

 

UPDATE: Monday, October 1, 2007 - Record SH sea ice maximum and NH sea ice minimum

Just when you thought this season's cryosphere couldn't be more strange .... The Southern Hemisphere sea ice area narrowly surpassed the previous historic maximum of 16.03 million sq. km to 16.17 million sq. km. The observed sea ice record in the Southern Hemisphere (1979-present) is not as long as the Northern Hemisphere. Prior to the satellite era, direct observations of the SH sea ice edge were sporadic.

The NH sea ice area reached an historic minimum on September 16, 2007 (2.92 million sq. km), representing a 27% drop in sea ice coverage compared to the previous (2005) record NH ice minimum.

 

OK, so what's up? How can it be both the warmest and coldest? Or is it just that there might be more ice, but it's thinner? Inquiring minds HAVE to know! 

 warmly,

Maggie 

Mon, 10/08/2007 - 11:09

Sarah Anderson

Hi Maggie - thanks for sending the info...I was looking over some data I received from our "ice extent" expert on board and getting it ready to send to you. It references the University of Illinois story you mentioned. Here is a summary of what our expert, Sharon, said about ice extent...she is doing a talk later in the cruise, so I'm sure I'll have more info later. She also has a very nice set of plots that show this year's monthly data compared to the average...I'll see if I can post those.Here's Sharon's response to your original question about ice extent this year:
For the whole Southern Ocean, the monthly averaged sea ice extents for Jan-Sep 2007 rank as follows (with respect to the absolute minimum observed over 1979-2007):
Jan - 4th (lowest out of 29 years)Feb - 2ndMar - 4thApr - 4thMay - 2ndJun - 4thJul - 3rdAug - LowestSep - 7th
For monthly averaged sea ice extent for the Bellingshausen-Amundsen Sea (60W to 130W), the Jan-Sep 2007 months rank as follows:
Jan - 4thFeb - 4thMar - LowestApr - 2ndMay - LowestJun - LowestJul - LowestAug - 5th (i.e., a very short winter maximum)Sep - Lowest
(Note from Sarah, we are currently at 93W in the Bellingshausen Sea)
There is a lot of regional sea ice variability, and while the Bell-Amundsen region is experiencing exceptionally low sea ice extent (the area inside the ice edge), the western Weddell and western Ross Sea regions are experiencing near to above normal sea ice conditions.
Sharon also mentions that there is confusion in the US media about the minimum/maximum story you mention. She got some info from a colleague in the US that the professor at University of Illinois posted a retraction of his web site saying that the Southern Hemisphere sea ice is close to, but not at a maximum due to a software glitch. Based on Sharon's plots itlooks like the discrepancy is larger. As you know, most of our info about sea ice extent is based on satellite imagery, and we've definitely seen on this cruise that it's not always accurate. We've already seen with our data collection that ice thicknesses represented by the imagery don't coincide with our measurements. I still have a lot to learn about imagery,but I believe that the images we've looked at are really only good to 50 cm of ice thickness. I don't know that any of the holes we've drilled have been less than 50cm, so I think there is still a lot of work to do to "tweak" imagery to represent reality...maybe just in the Antarctic where so much less work has been done.
Have fun studying polar bears...I'm glad they aren't here! We've been watching a pair of crabeater seals on the ice just off the port side of the ship. They haven't been in the water for days now...our expert thinks the female might be pregnant and close to delivery. That would be pretty exciting to see a pup...
Keep sending your great questions!
Sarah