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CRUCIAL GLOBAL WARMING FACT 6
The non-salty "fresh water" being added to the surfaces of the oceans is less dense than the salt water in the deeper layers, and there is nothing that will cause them to mix together, to create a new equilibrium, in less than tens or hundreds of thousands of years. So, the new fresh-water surface layer is acting like a "thermal blanket" on top of the oceans; and, that is causing catastrophic changes in deep ocean currents that played huge and critical roles, in creating the world we know and live in today. One example, "the Gulf Stream" – which made Europe warm enough to be habitable, even though most of it is as far north as the middle of Canada – has lost about 15% of its power, just in the last few decades.
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Most people don't realize how far north the entire continent of Europe is located. If studied on a globe, London is located at the same far-northern latitude as the northernmost border of Ontario, Canada (up near the Hudson Bay, in Canada). That means that all of England would be even colder than the northernmost tip of Minnesota, if it were not for a huge globe-spanning factor called The Gulf Stream, which for at least the past 10,000 years or so has carried gigantic quantities of warm water, up out of the Gulf of Mexico, and across the entire Atlantic Ocean, where it runs directly into Ireland and England, and helps warm the entire continent of Europe. It has made the climate of the European continent livable, in ways that are impossible to explain in terms that most ordinary voters can understand.
But, the Gulf Stream is going through massive, steep, and unprecedented decreases in volume and speed. Just in the past few decades, the strength and volume of warm water that is being moved across an entire ocean, by the Gulf Stream, has dropped by about 15%. And, for the same reasons that almost all of the other crisis-causing problems being created by global warming are caught up in accelerating "exponential curves" (a rough translation of that phrase: `The worse it gets, the more it's going to get even worse than that, even faster'), the strength of the Gulf Stream is going to begin dropping even faster, over the coming decades.
And, it's not just The Gulf Stream which is changing, dramatically, dangerously, and rapidly. Because of factors that directly arise from global warming, pretty much all of the "deep ocean currents" (also called "abyssal currents" and/or the "thermohaline circulation"), all around the entire planet, are beginning to also decrease and diminish.
One of the main factors driving those losses arises from what happened to the upper ocean surfaces, when trillions of tons of "fresh water" (i.e., water with low salt content) melted off of the ice sheets in Greenland and Antarctica (and when additional trillions of tons of fresh water were added to the top layers of the Arctic Ocean, as the snow and ice which formerly covered the arctic ocean and tundra regions began to rapidly melt). The simple fact is that all that "fresh water" was deposited – and, is now being added at even faster rates – on top of the salty ocean water.
That leads to huge problems, because fresh water is substantially LESS dense, and LESS heavy, than salt water. Ocean water weighs 64 pounds per cubic foot; by contrast, fresh water weighs only 62.4 pounds per cubic foot. So, there is no reason why that new layer of fresh water – which is being layered on top of the oceans, as global warming melts, destroys, and dismantles the non-salty arctic and Antarctic ice sheets and snow cover – will voluntarily or automatically mix in with the heavier and denser salt water, down deeper, below those newly-arrived surface layers with low salinity.
Instead, it appears that global warming is creating a low-salinity "insulating blanket" of fresh water, which will irrevocably alter (read: damage, and possibly destroy) the processes which created the "deep-layer" ocean currents, which – for at least the last 10,000 years or so, ever since the end of the last major "Ice Age" – kept this planet in an ideal combination of conditions, for supporting human life, and human population growth, and human happiness, civilization, society, and progress.
It's hard to predict how severe the changes will be, which are being triggered and driven by the new and different patterns of ocean currents that are being altered by global warming, especially since the creation of a new layer of fresh water, on top of the well-established layers of salt water, is happening tens of thousands of times faster than it might have happened when any of the prior "ice ages" receded in a "merely geological" (rather than "human-driven") pace. However, we can reliably say that the ocean current conditions that existed, over the past 10,000 years, were pretty much ideal, for human population growth, and for human progress and civilization. Therefore, we can pretty well predict that whatever the new conditions turn out to be, they will NOT be anywhere near as ideal as the former conditions (i.e., over the past 10,000 years) were, for enabling human population growth, and human happiness, and felicity. Instead, the only reliable prediction, in this particular area, seems to be, "If the ocean currents are shifting dramatically away from an `Ideal, for humans' pattern, into something very different, then humans, and probably nearly every other type of vertebrate life (including marine vertebrates), are destined for some rough, nasty, difficult, and unhappy conditions, over the next few thousand years, compared to what we were able to enjoy, over the past 10,000 years."
