WASHINGTON (AP) — The BP oil spill left an oily "bathub ring" on the sea floor that's about the size of Rhode Island, new research shows.

The study by David Valentine, the chief scientist on the federal damage assessment research ships, estimates that about 10 million gallons of oil coagulated on the floor of the Gulf of Mexico around the damaged Deepwater Horizons oil rig.

Valentine, a geochemistry professor at the University of California Santa Barbara, said the spill from the Macondo well left other splotches containing even more oil. He said it is obvious where the oil is from, even though there were no chemical signature tests because over time the oil has degraded.

"There's this sort of ring where you see around the Macondo well where the concentrations are elevated," Valentine said. The study, published in Monday's Proceedings of the National Academy of Sciences, calls it a "bathtub ring."

Oil levels inside the ring were as much as 10,000 times higher than outside the 1,200-square-mile ring, Valentine said. A chemical component of the oil was found on the sea floor, anywhere from two-thirds of a mile to a mile below the surface.

The rig blew on April 20, 2010, and spewed 172 million gallons of oil into the Gulf through the summer. Scientists are still trying to figure where all the oil went and what effects it had.

BP questions the conclusions of the study. In an email, spokesman Jason Ryan said, "the authors failed to identify the source of the oil, leading them to grossly overstate the amount of residual Macondo oil on the sea floor and the geographic area in which it is found."

It's impossible at this point to do such chemical analysis, said Valentine and study co-author Christopher Reddy, a marine chemist at Woods Hole Oceanographic Institute, but all other evidence, including the depth of the oil, the way it laid out, the distance from the well, directly point to the BP rig.

Outside marine scientists, Ed Overton at Louisiana State University and Ian MacDonald at Florida State University, both praised the study and its conclusions.

The study does validate earlier research that long-lived deep water coral was coated and likely damaged by the spill, Reddy said. But Reddy and Valentine said there are still questions about other ecological issues that deep.

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Seth Borenstein can be followed at http://twitter.com/borenbears

Oil spill left 'bathtub ring' on ocean floor

An estimated 10 million gallons of oil remains in the Gulf of Mexico near the damaged rig, scientists say.
Size of Rhode Island

Ex-administration officials sharply critical of Obama, failure to help Syrian rebels earlier

“The administration not only was warned by everybody back in January, it actually announced that it was going to intensify support against ISIS with the Iraqi armed forces. And it did almost nothing,” says James Jeffrey, who served as U.S. ambassador to Iraq between 2010 and 2012, in "Frontline's" "The Rise of ISIS," which airs on PBS Tuesday night (check local listings) and is previewed here exclusively on Yahoo News.

Jeffrey is one of a number of ex-administration officials who appear in the film and sharply criticize the decisions of the president they once served. Former U.S. Ambassador to Syria Robert Ford and former Defense Secretary Leon Panetta both take issue with Obama’s refusal to arm moderate rebels in Syria who — it is now argued — could have acted as a counterweight to the Islamic State (also called ISIS or ISIL).

“I think we made the wrong decision in not providing assistance to the rebels,” Panetta bluntly says at one point.

The film, reported by correspondent Martin Smith, offers a richly detailed account of how the Iraqi government of Prime Minister Nouri al-Maliki alienated the country’s disenfranchised Sunni population, making reckless accusations of terrorism against Sunni leaders — including the country’s Vice Prime Minister Tariq al-Hashimi. Those allegations— flatly denied by al-Hashimi on camera — were based on the testimony of bodyguards who, it is strongly suggested, were tortured.

With little pressure or engagement from Washington, al-Maliki’s anti-Sunni agenda —driven by his “paranoia,” as one of Smith’s interlocutors says — paved the way for ISIS radicals to march through huge swaths of Iraqi territory this spring, seizing arsenals of U.S.-made weapons from a collapsing Iraqi army. This, of course, was the same army that the U.S. spent billions arming and training. In fact, terrorism expert Ken Katzman suggests in the film, they were a phantom led by do-nothing officers.

“They were people who were — they were fat cats, I call them,” Katzman, a Congressional Research Service terrorism analyst, says in the film. “They were people who were earning good money to basically sit at a desk and smoke cigarettes and drink good liquor all day.”

In the end, Smith reports, it took only 800 ISIS militants, with the help of local Ba’athist military cadres, to secure Mosul, a city of 1.8 million people.

“If you go back and you look at the record of what we were providing to the Iraqis, there was a steady increase, whether you're talking about Hellfire missiles, the Apaches,” says Rhodes. “They were held up by Congress; we sought the expedition of that delivery to the Iraqis.”

Perhaps the most striking exchange in the film comes as Smith presses Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, on whether the administration’s current policy of airstrikes at Islamic State targets will achieve Obama’s goal of “destroying” the Islamic State — without deploying U.S. ground troops.

"Are you an optimist at this point, that this really can work?" Smith asks him.

“No, I'm not an optimist,” says Dempsey in a less-than-confidence-building response. While the campaign’s strategy may be right, “every campaign's assumptions have to be revisited as the campaign evolves. Some of these assumptions are no doubt going to be challenged."

Documentary: Obama did little to stop rise of IS

Former ambassador to Iraq James Jeffrey says the White House was warned about the militant group.
'Made the wrong decision'

A month ago, ISIS’s advance looked unstoppable. Now it’s been stopped.

A Kurdish fighter poses next to a destroyed ISIS truck. (Ahmad Al-Rubaye/AFP/Getty Images)

Watching the news, you could be forgiven for thinking that ISIS is an unstoppable juggernaut, sweeping Iraq and Syria in an unending, unstoppable, terrible blitzkrieg.

But you'd be wrong. The truth is that ISIS's momentum is stalled: in both Iraq and Syria, the group is being beaten back at key points. There are initial signs — uncertain, sketchy, but hopeful — that the group is hurting more than you may think, and has stalled out in the war it was for so long winning. ISIS isn't close to being destroyed. But they are reeling.

ISIS's defeats in Iraq are more important than its gains

(Institute for the Study of War)

In mid-October, ISIS advanced to within 16 miles of the Baghdad airport. Many observers (and many Iraqis), fearing an ISIS assault on Baghdad itself, understandably panicked. But to Michael Knights, the Lafer Fellow at the Washington Institute for Near East Policy, the ISIS advance meant something else.

"The threat posed to Baghdad this autumn is emerging less because [ISIS] is winning the war in Iraq," he wrote in Politico Magazine, "and more because it might be slowly but steadily losing it."

To understand what Knights means, you have to understand the basic dynamic of the see-saw war between ISIS and the Iraqi government. The war has been bifurcated: while ISIS has been making big inroads in the western, heavily Sunni Anbar province, it's being pushed back in the other major battlefields around the country, including Rabia, a northwest border town linking ISIS's holdings in Iraq and Syria.

"THEY APPEAR TO HAVE HIT THEIR LIMITATIONS"

In late October, ISIS suffered a defeat in an even more crucial area. Iraqi government forces took Jurf al-Sakhar, a town (in the area labeled Northern Babil in the above map) that Knights describes as an ISIS stronghold. This was a real defeat. As Reutersput it, "the victory could allow Iraqi forces to prevent the Sunni insurgents from edging closer to the capital, sever connections to their strongholds in western Anbar province, and stop them infiltrating the mainly Shi'ite Muslim south."

The question, then, is whether ISIS's recent victories in Anbar have been more important than its defeats. That's not obvious. It's also not obvious that its advances in Anbar can be translated into victories elsewhere; the Anbar campaign owes a lot to the tactical acumen of one commander, the Chechen fighter Abu Umar al-Shishani. "You have Shishani running wild in Anbar, employing very different tactics than ISIS is employing in the rest of Iraq and Syria," says Daveed Gartenstein-Ross, a senior fellow at the Foundation for the Defense of Democracies.

The contrast makes ISIS's setbacks outside of Anbar look even more significant. Shishani doesn't control broader ISIS strategy, nor does he seem capable of turning it around even if he did run it. "In terms of their offensive operations, Anbar is going well," Gartenstein-Ross says. "Everywhere else, they appear to have hit their limitations."

ISIS's siege of Kobane has been a disaster

Kurdish fighters in Kobane. (Ahmet Sik/Getty Images)

In Syria, ISIS isn't facing the same kind of concerted counter-offensive that it is in Iraq. But it's suffering from a self-inflicted wound: the stupid, counterproductive siege of Kobane, a Kurdish town in Syria on the border with Turkey.

For months, ISIS has been trying and failing to take Kobane. Its recent push, beginning on around September 16, looked likely to succeed. But Kurdish fighters, with heavy American support, have pushed ISIS back. Kobane could still fall, but the Kurdish resistance has shattered the perception of ISIS invincibility — a crucial element of its recruiting pitch.

"The [loss of] prestige in the jihadi movement could do a lot of damage to them," Garteinstein-Ross suggests. "ISIS can draw so many recruits because they're seen as the strong horse, because they're winning. [Kobane] shifts that perception."

Moreover, they've thrown a ton of manpower into Kobane. "They may have lost 4,000 fighters trying to take Kobane," Gartenstein-Ross says. He cautions that the 4,000 number is a spitball estimate; the Syrian Observatory for Human Rights estimates that about 500 ISIS fighters have died since September 16. But there's been fighting over Kobane since August 2013.

The loss of prestige and of personnel compound one another. The more people ISIS loses, the more it needs new fighters. But the defeats make people less likely to volunteer. ISIS has already beenconscripting local Syrians and Iraqis to fill its ranks; they may need to conscript even more to make up for the losses, and the involuntary fighters - some of them children - will likely be less effective than voluntary recruits.

Three reasons the war may soon get even worse for ISIS

An airstrike near Kobane. (Kutluhan Cucel/Getty Images)

There are at least three major causes of ISIS's recent defeats. Each gives us reason to believe that ISIS may only become more vulnerable as time goes on.

First, while American airstrikes are not going to defeat ISIS, they have seriously limited the group's ability to conduct offensive operations. "Airpower has made it difficult for ISIS to concentrate its forces in large numbers," Jason Lyall, a political scientist at Yale University and an expert on counterinsurgency, writes via email. "It has made it more dangerous to reposition its equipment and forces, slowing down its reaction times and complicating its command and control. As a result, ISIS is a far more dispersed force than it was in June."

The harder it is for ISIS to fight in the open, the harder it is for it to put together troop-intensive drives to conquer territory. If ISIS can't expand, it can only preserve what it has or retract.

Second, ISIS's enemies are adapting. ISIS "is a military power mostly because of the weakness and unpreparedness of its enemies," Knights writes in West Point's Sentinel journal. ISIS's advances depend on its ability to launch lightning-quick strikes against opponents that aren't ready for it. Iraqi and Kurdish forces, with American support, are finally learning how to counter these tactics.

"AIRPOWER ALONE IS INSUFFICIENT TO DEFEAT ISIS"

Third, ISIS's so-called caliphate has hamstrung its military options. "When they declared the caliphate, their legitimacy came to rest on the continuing viability of their state," Gartenstein-Ross writes.

If ISIS didn't have to run the caliphate, its smart strategic move would be to melt into the surrounding populations, wait for Iraqi and Syrian troops to enter the area, and then fight them as an insurgency. But the obligations of running a caliphate means that the fighters need to stay visible and out in the open —leaving them exposed and vulnerable.

But don't count ISIS out yet

Kashmiri demonstrators hold up an ISIS flag during a demonstration against Israeli military operations in Gaza, in downtown Srinagar on July 18, 2014. (Tauseef Mustafa/AFP/Getty Images)

These setbacks are significant, as is the group's slowing momentum. But to be clear, none of it specifically points to ISIS getting closer to collapsing. "On balance, ISIS is probably in a stronger position today than it was" in mid-July, Lyall writes. ISIS has consolidated control over its core strongholds, such as Mosul in Iraq and Raqaa in Syria.

"It would be a mistake to read too much into these local reversals" in Iraq, Lyall writes. "ISIS has proven adaptive, especially in moving its forces around on the battlefield and in coordinating multi-pronged offensives. A temporary setback in one area may only mean that ISIS is repositioning for a wider effort somewhere else."

Things like US air strikes are good for stalling ISIS's advance, but to be clear, they are not going to defeat the group. "Airpower alone is insufficient to defeat ISIS or even degrade it seriously," Lyall cautions. "Instead, its role is to make ISIS work harder to control and extend its territory while buying time for the Iraqi Army."

So it's best to see the recent ISIS setbacks as evidence that ISIS is vulnerable rather than as a harbinger of any looming collapse. The fact that is being rolled back in some areas indicates that the group can be budged, but the group's total defeat is unlikely, absent a collapse in Sunni civilian support and more effective opposition in Syria.

"I don't think these latest losses are things that ISIS is incapable of recovering from," Gartenstein-Ross says. "There are always ebbs and flows in any war, and I expect there to be [ISIS] gains. But overall, they're a weaker organization than they were at the beginning of August."

Watch: Obama's 2014 evolution on ISIS, in under 3 minutes

Myth #9: ISIS is invincible