One third of Arctic ice cap now missing; Midwestern floods; tropical update

By: Dr. Jeff Masters , 12:46 PM GMT on August 24, 2007

Sea ice in the Arctic continues its record decline, thanks to unusually cloud-free conditions and above-average temperatures. For August 21, the National Snow and Ice Data Center estimated that fully one third of the Arctic ice cap was missing, compared to the average levels observed on that date from 1979-2000. Sea ice extent was 4.92 million square kilometers on August 21, and the 1979-2000 average for the date was about 7.3 million square kilometers. Arctic sea ice has fallen below the record low absolute minimum of 4.92 million square kilometers set in 2005 by about 8%, with another 3-5 weeks of the melting season still remaining. Reliable records of sea ice coverage go back to 1979.

Figure 1. Extent of the polar sea ice on August 21, compared to the average for the date from the 1979-2000 period (pink line). Image credit: National Snow and Ice Data Center.

With one third of the Arctic ice cap already gone, and another month of melting to go, we need to consider what effect this will have on weather, climate, and sea level rise. Well, we don't need to worry about sea level rise, since the polar sea ice is already in the ocean, and won't appreciably change sea level when it melts. However, the remarkable melting of the ice cap will likely lead to unusual weather patterns this fall and winter. The lack of sea ice will put much more heat and moisture into the polar atmosphere, affecting the path of the jet stream and the resultant storm tracks. Expect a much-delayed arrival of winter to the Northern Hemisphere again this year, which may lead to further accelerated melting of the ice cap in future years.

Last week, I remarked that the most recent images from the North Pole webcam show plenty of melt water and rainy conditions near the Pole. It turns out that was misleading, since the webcam is on a ship that was headed towards the pole, but had not reached it. There have been rainy conditions at the Pole this summer, and there is some open water there, but this is not uncommon in summer. Shifting ice frequently opens up leads (cracks) with open sea water at the Pole. It was one of these open leads that British swimmer Lewis Gordon Pugh swam in for 18 minutes this July to draw attention to global climate change.

Figure 2. Total rainfall from August 10-22 as estimated by NASA's TRMM satellite.

Midwest flooding
To get an idea of the magnitude of the flooding that has hit the Midwestern U.S. during the past ten days, take a look at the total amount of rain from August 10-22 (Figure 2). We can blame Tropical Storm Erin for the rain in Texas and Oklahoma (up to 11 inches), and for the nine flooding deaths that occurred in those states. However, the unbelievable rain amounts in excess of 20 inches in Minnesota and Wisconsin were primarily due to a frontal system--with the help of some copious moisture pumped northwards by the counter-clockwise circulation around Erin while it spun over Oklahoma.

Tropical update
There are no threat areas in the Atlantic to discuss. Two of our four reliable forecast models, the NOGAPS and ECMWF, are predicting that a tropical depression could form off the coast of Nicaragua on Sunday. The models forecast that this system would move inland over Nicaragua and Honduras by Monday.

I'll have an update on Saturday morning.
Jeff Masters

After Hurricane Dean (sprinter)
Bulldozer trying to clear sand and debris from Norman Manley Highway(Airport Road)
After Hurricane Dean
Findlay Ohio flood (prairieview)
The flood is over, now the cleanup
Findlay Ohio flood

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1147. Rick54
5:55 PM CDT on August 25, 2007
Bottom line, the current Arctic ice loss trend is very troubling.

Even more troubling to my mind is the potential for change in the world's weather systems due to changes in albedo in the arctic.
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1146. hosweather
10:55 PM GMT on August 25, 2007
The CMC is not alone. The MM5 also develops both the CV wave and the disturbance just N of the Colombia\Venezuela border.

It will be interesting to see the next 00Z runs.
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1143. hosweather
10:21 PM GMT on August 25, 2007
According to ryang's link, the GFS drops development of the CV wave after 96 hours. Currently only the CMC has continuing development placing this system just N of PR in 240 hours. BTW, nice convection currently building over this wave.

CMC could end up with two firsts in a row--Erin and Felix. But then I did say I'm a CMC fan.
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1142. IKE
5:36 PM CDT on August 25, 2007
Posted By: pacegrl64 at 5:31 PM CDT on August 25, 2007.
a watched pot never boils!

I agree too.....I have a hard time sitting in front of a computer screen watching clouds spin. Maybe they'll be something in a few days.
Member Since: June 9, 2005 Posts: 23 Comments: 37995
10:34 PM GMT on August 25, 2007
p g 64 thats so true
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1140. IKE
5:32 PM CDT on August 25, 2007
I'll have an update on Saturday morning.
Jeff Masters


Hope everything is OK Dr. Masters.
Member Since: June 9, 2005 Posts: 23 Comments: 37995
1139. pacegrl64
10:28 PM GMT on August 25, 2007
a watched pot never boils!
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1138. stoormfury
10:21 PM GMT on August 25, 2007
check out this rotation SW of the Cape Verdes

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10:19 PM GMT on August 25, 2007
on the verge of insanity tcc i have visions of people grasping there comp desk screaming aimlessly into there monitors with eyes proturing from there eye sockets sombes from weeks of lack of sleep wishcasting on everything that moves tryin to make sense out of something that makes no sense at all
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1135. boobless
10:25 PM GMT on August 25, 2007
Not to say no rain, just no convective currents
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1134. sunnyandshear
10:24 PM GMT on August 25, 2007
A hurricane stiking any of the prone areas could make windstorm insurance unaffordable for most of the gulf coast and Florida residents. Rates now are backbreaking for commercial properties in Florida and forcing many industries to consider getting out(Piper, Wellcraft) Elected leaders need to consider the odds and act now. We have enough lighted public tneeis courts,
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1133. boobless
10:19 PM GMT on August 25, 2007
LFC based on a surface-based parcel finding itself in a cooler enviroment. No convection under your setup.
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1132. boobless
10:13 PM GMT on August 25, 2007
Posted By: StormW at 9:51 PM GMT on August 25, 2007.

Here's fuel for thought on the GW stuff...if the

Arrgh. This Q hurts my head. First guess to a part of your question:
ELR and DAR-same.
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1127. FatPenguin
10:08 PM GMT on August 25, 2007
Posted By: definer at 9:48 PM GMT on August 24, 2007.

How can we talk about a "remarkable" ice melt and also state that reliable sea ice records only go back to 1979? Seems to me this could be another example of an "answer" ("global warming") looking for a question.

With less than 30 years of reliable data to compare to, it seems that, while the amount of melt does seem more than average, we can only talk about it in the terms of the last 30 years and state we simply don't know what was seen before. For instance, we don't have any records to indicate the amount of melt that took place during the 1930s, a period that we do know was warmer than what we see now.


For Ken (and anyone else)
For a minute, ignore everything else and think about the ultimate effect of a summertime ice-free Arctic Ocean....Greenland will start losing ice a lot faster.

If the current trend doesn't reverse itself, then eventually you have an ice-free Greenland. Prior to 2006, I've seen estimates around 1,500 years from now or a little sooner.

With the increased rate of Arctic ice loss for the last two years, it could be a lot sooner than 1,500 years.

Keep in mind that total Greenland ice loss equates to about 20 feet of ocean rise. It will only take about 2 to 3 feet of rise to start causing dramatic issues for coastal cities around the world. In other words, it may take less than 100 years to see dangerous ocean levels if the current trend in the Arctic sea ice melt don't stop, or reverse itself. That might happen. There's still a lot of mystery involved with explaining previous ice ages.

My estimates are rough and amateur, but I think they're fair. In late September we will hear from the scientists that do have good estimates. We may even get an unscheduled revised report from the IPCC.

Bottom line, the current Arctic ice loss trend is very troubling.
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9:56 PM GMT on August 25, 2007
Ya Know, 2005 slipped up on everybody. Then when the forcast to be almost as bad in 2006 was a bust (average after all) everybody lost faith in the system. This year they forcast an above average and conditions looked that way, unfortunatlely the weather isn't going to comply with wishcasters. It may well turn out to be a slow season, then again it may ramp up unexpectantly. I for one hope for another slow season. If you are bored with the weather I suggest a good book or movie. If you want you could join the people in the mid-west that are getting pounded. Now that's a storm to try to track, pop up and fast moving.
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1124. ryang
6:04 PM AST on August 25, 2007
If the wave keeps up, an invest is possible tomorrow night?
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1122. ryang
6:02 PM AST on August 25, 2007
By the way, the GFS develops the CV wave, maybe only a depression?
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1120. Weather456
9:58 PM GMT on August 25, 2007
One thing, I notice, some of u all are watching the tropics too hard for development. I think the season is goin just fine, relax and let the season do its stuff, we'll have periods of active weather and periods of calm weather. We cant have tropical cyclones every day or none everyday.
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1119. ryang
6:01 PM AST on August 25, 2007
Everyone forgot the TWO?

ABNT20 KNHC 252119
530 PM EDT SAT AUG 25 2007







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1117. extreme236
10:00 PM GMT on August 25, 2007
well im leaving. BBL
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1116. runningfromthestorms
9:56 PM GMT on August 25, 2007
StormW - I know so little about this topic but it would seem that we would not have those features you mentioned - just a hot, moist environment everywhere - how boring would that be? I am fascinated by thunderstorms, by their power and beauty and would miss them
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1112. extreme236
9:57 PM GMT on August 25, 2007
Amy you cant say anyone overcasting until the year is done. You dont know for sure your right. Your not a psychic. Anything can happen
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1108. taistelutipu
9:52 PM GMT on August 25, 2007
Since the tropics are so quiet at the moment, may I ask one question about the SAL: it seems to me that there is also one west of Mexico (first picture on that website: Saharan Air Layer Analysis which currently appears to be quite strong. How come that the SAL extends over the American continent into the East Pacific? But there is a huge gap between the SAL around the African coast and the one in the E-Pacific. Can someone of you weather experts explain this to me, please *bats eyelashes*
Thanks alot!
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1107. extreme236
9:52 PM GMT on August 25, 2007
People just need to stop wishcasting and downcasting. Lets all be neutral. Lets just watch everything
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1105. extreme236
9:50 PM GMT on August 25, 2007
Who knows Amy? Maybe you will be wrong. Maybe I will be wrong. Maybe NOAA will be wrong. But I am not willing to call something a dud when its not even past the peak yet
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1103. extreme236
9:49 PM GMT on August 25, 2007
Amy, you act like you KNOW there wont be any activity between now and then. You can guess, but please dont act like you know for sure
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1101. extreme236
9:48 PM GMT on August 25, 2007
Member Since: August 2, 2007 Posts: 19 Comments: 19234
9:46 PM GMT on August 25, 2007
Oh! by the way the nws loop can take a while to load even on broadband. Be patient, it's worth it.
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1098. extreme236
9:46 PM GMT on August 25, 2007
I know amy. But september is in a week so we are just going to have to watch. A lot can happen in a week
Member Since: August 2, 2007 Posts: 19 Comments: 19234

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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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