Arctic sea ice melting season begins
The annual Arctic melting season has begun. We've just passed the Spring Equinox, so the North Pole is now in 24-hour daylight. Will the melting of Arctic sea ice this year surpass last year's record? Well, we have a greater areal extent of ice over the Arctic this month compared to April of last year, thanks to some cool Arctic temperatures this winter. In particular, the ice in the Bering Straight between Alaska and Russia extends quite a bit further south than in 2007. This extra ice will likely delay the melting season a bit this year, giving some hope that we won't surpass last year's record melt. However, if weather similar to last summer occurs--unusually clear skies and high pressure over the Arctic--this extra ice will not help much, because it is all thin, first-year ice. It is the thick, 2-9 year old ice that is most able to resist summer melting, and the amount of old multi-year ice is only about half of what it was in 2007. This is apparent from images taken by the QuikSCAT satellite, which carries the SeaWinds scatterometer. This instrument emits a pulse of microwave energy that bounces off the ice and returns to the satellite. Old, multi-year ice is thicker, and reflects a different amount of microwave energy back to the satellite than thin ice, resulting in a whiter image. Thin, first-year ice appears a darker grey. It is apparent from Figure 1 that we have only about half of the old, multi-year ice that we had last year. In fact, thin first-year ice extends past the North Pole, raising the distinct possibility that this year's melt will allow one to sail a ship all the way to the North Pole in September, for the first time since humans began testing Arctic waters with ships in 1497. In addition, a large region of the old ice north of Alaska is highly fractured, making it vulnerable to melting.
Figure 1. QuikSCAT images of the Arctic from April 4, 2007 and April 4, 2008. The boundary of old, multi-year ice is marked in yellow, and 2008 has about half the old ice of 2007. Image credit: NOAA/NESDIS/ORA.
How did we lose so much old ice in the past year?
Part of the lost old ice melted during the record-breaking melt season of 2007, which was fueled both by global warming and a natural (but unusual) sunny summer. Another big chunk of old ice was lost due to natural wind patterns between September 2007 and March 2008. An animation of the sea ice available from Environment Canada's sea ice page (click on "Updated QuikScat animation") reveals that strong winds pushed large amounts of old ice out of the Arctic southward along the east coast of Greenland. So, we can't blame the melting of the Arctic sea ice entirely on global warming--natural weather patterns also played a significant role.
The forecast
It's impossible to guess what the dominant Arctic weather pattern will be this summer, and what level of melting we will get. With the loss of so much old ice over the past year, though, even an average summer has the potential to melt much more ice this summer compared to last summer--all the way to the North Pole. There's also a good chance that we'll see the fabled Northwest Passage open up again, since most of the ice along the Passage is young, first-year ice. We'll just have to wait and see how the summer unfolds.
Jeff Masters
Reader Comments
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But historically,we see the Lower Gom,BoC,..for early season development,and it can be extreme as early as June. Allison Showed us that in 2001.A Tropical Storm.
Just 54 days till the hurricane season.
i this want an update on what the BERMUDA HIGH is doing
Upper level divergence may account for the system's fanned-out look.
Not those lil Burps from the Gulf Stream like Andrea was.
Tropical Storm Allison was a tropical storm that devastated southeast Texas in June of the 2001 Atlantic hurricane season. The first storm of the season, Allison lasted unusually long for a June storm, remaining tropical or subtropical for 15 days. The storm developed from a tropical wave in the northern Gulf of Mexico on June 4, 2001, and struck the northern Texas coast shortly thereafter. It drifted northward through the state, turned back to the south, and re-entered the Gulf of Mexico. The storm continued to the east-northeast, made landfall on Louisiana, then moved across the southeast United States and Mid-Atlantic. Allison was the first storm since Tropical Storm Frances in 1998 to strike the northern Texas coastline.[1]
The storm dropped heavy rainfall along its path, peaking at over 40 inches (1,000 mm) in Texas. The worst flooding occurred in Houston, where most of Allison's damage occurred: 30,000 became homeless after the flooding destroyed 2,744 homes. Downtown Houston was inundated with flooding, causing severe damage to hospitals and businesses. Twenty-three people died in Texas. Throughout its entire path, Allison caused $6.4 billion (2007 USD) in damage and 41 deaths. Aside from Texas, the places worst hit were Louisiana and southeastern Pennsylvania..
And June 4 is only 4 days into the season,....Id say that's early.
Tropical Storm Allison Link
There are three conceptual tropical wave models:
The African Easterly Waves - Ethiopia to the Cape Verdes
Inverted V Tropical Waves - Cape Verdes to the Lesser Antilles
Rheil's Tropical Waves - The Eastern Caribbean to Central America
There are several features that distinguish AEW from those waves found over the TRP ATL and CARIB.
They have two areas of max vort in the low levels poleward and equatorward the axis. In the other wave models, the area of max vort is found along the axis.
Low level convergence is ahead of the wave axis instead of behind. Most of the bad weather occurs ahead of the axis unlike the Rhiel's tropical wave where most of the bad weather occurs behind the wave axis.
Form near 15E, tracked westward as anomalous convective signitures and they do not have a surface vort/circulaton until they reach the coast.
Lastly, as these waves enter the Eastern ATL, they weaken due to the stable enviroment (dust and cool ssts).
Juan Link
Track and rain totals. Link
Satellite Pic,Juan Link
Good to see the folks gathering round the old keyboard.
Nice to see 236,Caneaddict, again. Been a while.
Nothing like a good raincloud to excite the troops ! This one is interesting though, and I for one am looking at it from the point of view that-
the SAL has been less than recent previous years
the water temps are warm
the wet season in Africa has been relatively low rainfall in areas spawning waves
the ITCZ is showing more moisture than normal
The above would seem to be conditions that would normally contradict each other to some degree.
Thats what I find so interesting here now.
.
Blob Reply: Yes it is fading quickly.
I think an earlier discussion suggested that it would hold together to around 50 W.
The water temps are plenty warm in the area, yet it has not been able to maintain the convection it had earlier.
Any ideas ?
Pottery i see our rain chances are high for the coming weekend,from that trough.
Stormdude77 where are you from?
I'm located in Barbados, and yes... that trough will increase rain chances this weekend (across the Windward islands)...
How is your dry season shaping up so far? Do you know its been unsually wet here in Trinidad
OK place your bets what places will get hit by a devastating hurricane in the next five years
1. the Carolinas
2. Texas
3. New England
4. Puerto Rico
5. North East Coast of Florida
also 2 majors that year
Link
It's very dry here (only 182 mm of rain so far for the year). During the last four years, that amount has been nearly doubled (at the end of March; especially in 2005 and 2006)
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