The Atlantic current is slowing down.

Have you ever wondered why the ocean on the West Coast of the US is colder than the ocean on the East coast?

Los Angeles, California and Savannah, Georgia are both coastal cities at around the same latitude, sitting on the 32nd parallel. Both cities experience their warmest ocean waters in August, but if you go to the beach in LA around that time, the water temperature is barely above 65°F. In Georgia? It’s 85°F.

Let’s step out of the water and look at the weather in London. It sits between the 51st and 52nd parallels, which is quite a ways up there when you think about distances on the East Coast. Savannah is down at 32, and then 8 parallels further north, you hit NYC at the 40th, a 12 hour drive up I-95. You have to go another 10 parallels before you’re even with London, in this circle way up in Canada between the tips of Newfoundland and Labrador.

In London, July is the month with the highest average temperature at 75°F. February is the lowest at 37°F. On the opposite side of Eurasia on the Pacific Coast, Petropavlovsk-Kamchatsky on the Pacific coast of Russia is on the 53rd parallel. It’s highest average temperature is in August at a reasonable 63°F, but the lows in January are 16°F, over 20 degrees colder than London.

What’s keeping the coast along the Atlantic warmer?

Some of it is air currents and topography, but there’s also a big conveyor belt of ocean water moving heat all around the planet. Warm ocean water rides the currents up from the tropics through the Caribbean and up the East Coast of the United States where it hits Greenland and takes a hard right over to Europe. As the water cools, it sinks, and this helps keep the conveyor belt moving.

What happens if the water cools before it makes its way to Europe? What happens if too much cool water gets into the system? What if that water is freshwater of a different salinity and density from ocean water? That’s what is currently happening as the ice sheets of Greenland melt and pour into the ocean, slowing the current down until an eventual full stop.

A long-worried nightmare scenario, triggered by Greenland’s ice sheet melting from global warming, still is at least decades away if not longer, but maybe not the centuries that it once seemed, a new study in Friday’s Science Advances finds. The study, the first to use complex simulations and include multiple factors, uses a key measurement to track the strength of vital overall ocean circulation, which is slowing.

A collapse of the current — called the Atlantic Meridional Overturning Circulation or AMOC — would change weather worldwide because it means a shutdown of one of key the climate and ocean forces of the planet. It would plunge northwestern European temperatures by 9 to 27 degrees (5 to 15 degrees Celsius) over the decades, extend Arctic ice much farther south, turn up the heat even more in the Southern Hemisphere, change global rainfall patterns and disrupt the Amazon, the study said. Other scientists said it would be a catastrophe that could cause worldwide food and water shortages.

(AP News)

This is an image of how the full thermohaline cycle works now. You have the Atlantic Meridional Overturning Circulation in the north, and the Southern Ocean Overturning Circulation in the south.

You can see the warm water in red coming up the East Coast where it cools into purple and starts to sink. Once the ocean has released enough heat into the atmosphere, the water is cool enough to make the journey back down toward Antarctica and around the southern tip of Africa where it warms up again in the Indian Ocean. This warm water joins the circulation around Antarctica or moves back into the AMOC to go up the East Coast again.

At the last Panel on Climate Change at the UN, scientists agreed that this collapse probably would not happen before 2100, so we have 76 years to sit around and do nothing. I don’t mean that we should do nothing — I’m just looking at the history of humanity’s tackling of the climate issue and making an educated guess about the outcome.

It’s interesting to me that the people on these panels have children. The people running our governments have children. Even the tycoons of the fossil fuels industries creating this problem have children. And yet, the majority of people in charge of taking actual steps to stop changing the climate of our planet don’t seem to care that they are kicking the can down the road for their children and grandchildren to contend with. They are happily bringing people into a world that may be unlivable while they themselves hold the keys to ensuring their survival. They’re saying, “I want to be rich and I don’t want to be inconvenienced on this day, so I do not care that you will suffer later.”

We don’t know exactly what will happen if enough cool freshwater from Greenland stops the circulation. The historical record says this has happened before, so we do know that it will get colder in the Northern Hemisphere and hotter in the Southern, but we’re in unprecedented territory in regards to how that will affect various kinds of human societies across the globe. I guess everyone is waiting for 2100 to arrive and then we can answer those questions with certainty.