what would happen if north korea detonated 150 megaton nuclear bomb in some where at Atlantic ocean?

Trump would get the blame.

Are u fond of "science fiction" ?

#1 The World would be pretty amazed that they are able to do so.
#2 At least severe UN sanctions.

1. Scientists would start working on a solution to how we all ended up in some alternate reality where North Korea was able to not only build a nuke that big but actually get it all the way to the Atlantic. However, no one would be surprised that they completely missed every continent along the flight path.
2. There would be a lot of dead fish, radioactive water, and some radioactive clouds heading along to jetstream to Europe. Keep in mind that 60 years ago, the nuclear powers detonated nukes in the middle of the Pacific on a routine basis.
3. If those scientists concluded that we weren't all transported to the mirror universe, then a lot of people would be pissed at North Korea. If anyone else were president, I'd say that Kim would get a stern rebuke, but I wouldn't put it beyond Trump to turn North Korea into a parking lot.

The Atlantic is a big place, so it would depend where it happened and what impact if any the blast would have on countries bordering the Atlantic. If you are talking about somewhere near the US or Europe, it might well result in military action by the US maybe with NATO backing. I doubt the Russians or the Chinese would stand in the way of Airstrikes. If the Chinese thought a new ground war was in the offing, they might invade NK and replace the government rather than allow all that unrest on their border.

Much would depend on where in the Atlantic Ocean the bomb were to be detonated. Near any coast, or mid-ocean? And at what height above sea level?

Even if they could, why would they bother?
The only reason for launching a weapon as a demonstration is to make an enemy rethink their strategy.
The US did not make a demonstration of the bomb before bombing Japan.
The US is already aware that NK has nuclear weapons so there is no political advantage to launching a weapon.
EXCEPT that as NK is in the Pacific, to successfully get any weapon to the Atlantic would demonstrate that it has a delivery capacity. This would set alarm bells ringing amongst any nation that was considering attacking NK.

We are all dead.

Confusion--Delusion

depends where

but there would still be a lot of dead fish

(a little bit of info for "t'rone"
technically nuclear bombs itself dont "fry" anything
the emp causes electronics to fry itself - and even then only if switched on)

First, only 2 countries have bombs near that yield, 140 megaton, the US, Russia just under that with Tzar.
Korea's little poppers, perhaps 6 kiloton, about like our MIRV tactical nukes, say 5 times Heroshima.
Out in the Atlantic, probably just a dull thud on sonar. Some fallout after.
I was 60 miles from the test site when they detonated a 140 megaton device, just did swish a little water in a glass.

That would be the end of North Korea we could bomb the whole country and not even put a dent in our arsenal supply

You are being so silly. No country in the Nuclear Arms family can make a device that powerful. Russia had the biggest. I think it was about 40 megaton. They called it the Tsar bomb. Anyway: the device was so huge, it was like dropping the Hiroshima bomb in physical size equivalence (which is huge). You think if north korea was able to make such a powerful device; that they would waste its energy in the atlantic ocean with only a few fisherman spaced out every 50 square miles? You are being ridiculous, sorry. If I was north Korea: I would not waste 150 megatons of energy in the ocean, would you? It may cause a Tidal wave if the attacker is lucky to answer you question in a way you want to hear. This is also known as Tsunami. Maybe, just maybe, a device like that could do something like this. North Korea is way too behind the times to build a bomb that big though...so I am not going to lose sleep over it.

Their nukes are painfully small. Their strongest one wouldn't even destroy Manhattan. What you should worry about is them shooting one off above say, California. It would send the place back to the 19th century. All computers would be fried.

They have no way to get a bomb to the Atlantic ocean

THEY CAN'T. all Pig-Boy has are lab nuclear devices, the size of TRUCKS without their power, and not even a BOAT big enough to carry one ......................

I think that would be the end of North Korea, and it would no longer exist.

Immediate results would be rising tides and inundating much of the west coast of the U.S.
However, it's difficult to imagine what the U.S. would do to retaliate.

Free fish.