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Posted by: USSINS, 16:35 GMT le 23 mai 2010

Since the 2010 season is closing in on us, I thought I'd take a closer look at the loop current and the oil spill and how the GOM is shaping up this year. The Loop Current has now officially "pinched-off" a new, gigantic warm eddy.

This animated SSH gif (above) shows the significant size of the eddy that has spun off from the loop. This happened in July of 2005 when a large eddy spun off, drifting more northwards. Katrina came across the northern part of the loop and through the warm eddy and exploded into CAT 5 status(see QuikScatt graphics below).

The two Quikscat passes (above) show Katrina as it enters the GOM in August 2005 over sFlorida (left) and then after it passes over the loop current and eddy in the central and ncGOM (right) exploding into CAT 5 cane over these hot, deep waters before making landfall.

Loop eddys or gulf eddys are formed by the GOM loop current - "the ring of fire." This a warm current that enters the GOM from the Caribbean between the Yucatan Peninsula and Cuba. The current forms a "loop" as it bends to exit the GOM through the Florida Straights between Cuba and Florida and into the Gulf Stream up the Atlantic coast.

The "pinching-off" process from the loop generally takes at least a few days and can take up to a several weeks. On average, eddys separate from the loop current about every 9.5 months, occasionally separating as short as six and as much as 11 months. And, these warm rings can range in size from 200-400 miles wide. This new eddy appears to be a very large one, possibly 250-300 miles wide.

When these large warm-core, clockwise eddys spin off from the loop they spin these smaller eddys off, usually sending them rotating anti-clockwise and creating upwelling. A large warm-core eddy can spin off several cyclonic eddys - in this case, these eddys could help bring more oil to the surface.

This may be good news (at least temporarily for southern FL with the spill), but this large warm eddy could have a broader, damaging effect in the weeks, months ahead to other parts of the GOM. It is difficult to tell in which direction this new eddy would spin towards, but the ultimate, general motion is usually more west, but they can initially move more northerly (like with Katrina in 2005) before ultimately drifting westwards. If it spins towards the spill source, imo, its down-welling motion could pull more surface oil downwards more quickly and more widespread under the surface. This could possibly even make the surface slicks less visible, but obviously, no less dangerous. In fact, a warm eddy in those areas could possibly even delay any breakdown help from oil-eating bacteria, etc, as these warm-core eddys are generally lifeless compared to their cold-core counterparts which are rich in nutrients and life.

Of course, movement and direction, too, will also be greatly influenced by surface winds, but the gist is, I think it's possible that this large eddy, spinning off others for upwelling, could just add to the mess dispersing oil in various ways.

This huge, warm eddy spun off from the loop shortens the northerly reach the loop can make (sometimes as far north as 27-28N). The new general current, nearer 24-25N northerly edge, is now far removed from the spill source and spreading oil, saving or at least delaying oil moving through the current by the Keys and into the Gulf Stream.

But, what may be good for S. FL may wind up being even more harmful for the northern GOM coast including the FL panhandle and westwards to TX as the eddy will effectively "stir the pot." Oil could move greater distances, faster, but deeper and possibly less visible at the surface and with the new cold-cores that spin up, bring oil to the surface at various places. It may be possible, unfortunately, that the new large warm-core eddy could serve to temporarily mask our disastrous problem if it's able to downwell surface slicks.

Of course, in addition to complicating the spill problems, a large eddy breaking off going into hurricane season adds more fuel to the fire for approaching tropical systems. GOM temps will warm a bit sooner, and there will be a larger reservoir of substantially warmer and deeper water that will act as a generous source of fuel for tropical storms and hurricanes. And, as the season progresses, it's also likely that the loop current will have drifted more northwards again, effectively increasing the area of hazard.

Considerable comparison to SST's now and in 2005. Let's hope that isn't the scenario that unfolds this season!

Updated: 15:46 GMT le 28 mai 2010

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