It is dissipating just as it showed up — rather unexpectedly.

For two years, an enormous expanse of extremely warm water in the northern Pacific Ocean has wreaked havoc on marine life from Alaska to Mexico, and altered weather patterns across North America, causing droughts and intensifying hurricanes.

It also helped produce this year’s powerful El Nino.

The phenomenon has beleaguered and mesmerized oceanographers. So much so that dozens of them gathered at the Scripps Institution of Oceanography in San Diego in April to discuss it and its impacts.

Now, this blob — as it has come to be known — is starting to dissipate.

That’s good news, right?

Yes, and no.

“From an oceanographer’s perspective, we are eager to see normal conditions come back in the Pacific,” says Richard Dewey, associate director of science with Ocean Networks Canada, an initiative of the University of Victoria.

The blob has been extraordinary, in intensity and longevity, he says. “We are talking about a million square kilometres of ocean that is 3 C warmer … that represents a lot of heat.”

He’ll be relieved to see it go, he says, adding it will take a few months for it to disappear.

The problem is that the blob is a terrifying glimpse into what the future, driven by a changing climate, likely holds for us, says Dewey.

Blobs like this one could become frequent. If this warm blob is something that occurs every 10 years as opposed to every 100 years, it will mean a major change for the northeastern Pacific, he says.

“Climate change is affecting large-scale atmospheric systems, all the way from the tropics to the Arctic,” he points out.

The blob was first identified in the fall of 2013 when a huge body of water in the Pacific did not cool down as expected and remained significantly warmer than average.

Nick Bond of the University of Washington named it the blob and the moniker stuck.

Water transfer from the tropics to the northern Pacific happens all the time, says Paul Pastelock, a senior meteorologist with AccuWeather in Stormstown, Pa. Usually, storms come in and bring up cold water from deeper layers that cool down the surface, he says.

In this case, there were almost no storms and the warm water stayed put, continuing to get warmer. The water’s stubborn layering also meant nutrients didn’t mix, devastating the ecology.

The blob also altered the jet stream air currents that drive storms from the upper atmosphere.

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In the summer, these changes caused prolonged dryness, especially in Western Canada. Wildfires broke out early, stayed on late. Farmers fretted over their crops.

In the winter, they prompted the jet stream to split. “One part went way, way up to Alaska and northern Canada and another down to Southern California and in between you don’t have any rain or any snow … hardly at all,” says Pastelock.

Why the blob developed and stubbornly stayed for this long isn’t clear.

One theory is linked to the Arctic, which has gone through rapid climate change. In 2012, a year before the blob showed up, the Arctic Ocean recorded its lowest sea-ice extent on record, allowing a significant amount of heat to be absorbed by open water. As a result, the entire northern hemisphere seems to have gone through extreme changes.

In the past few weeks however, the area has seen a series of storms, helping break up the blob.

This too caught experts by surprise.

“It weakened so fast and so much,” says Pastelock.

The blob may be dissipating but its persistence raises a question: was it a one-off “or are we going to see this kind of phenomenon in other ocean basins,” wonders Dave Phillips, Environment Canada’s senior climatologist.

On a lighter note, Phillips says the blob will be responsible for “at least three dozen PhDs as people learn more about it, understand what caused it and the impacts it had … the fact that we have been able to observe it, is very exciting.”

For Dewey, there is lesson.

Climate change, he says, won’t necessarily mean steady warming. “What we have learned in the past years is that nature may not behave uniformly. There could be major shifts in our weather patterns that last for long periods and dramatically impact regions differently. It could mean events we haven’t seen before, events that are unexpected.”

Like the blob.

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