(Bryce) Global weather patterns are regulated by ocean currents, but warming water is causing
those currents to change.
This is one of a handful of earth system tipping elements that climate experts fear could set
off incomprehensible devastation.
(Dr. Francis) I'm sure most people have heard about the ocean conveyor belt which is basically
the system of ocean currents that flow all around the world's oceans.
There are two places really that that push that current to flow.
One of them is in the North Atlantic.
And the idea here is that when fall and winter come along the ocean surface waters get cold
and they freeze.
And when they freeze, they eject the salt out of the water.
And that heavy, salty, cold water that comes out of that freezing process is very heavy
relative to the other water in the area, and so it sinks really rapidly.
And it creates this downward flow of water which then basically turns south and starts
heading towards the southern Atlantic and meets up with other currents along the way.
And another area where this happens is off the coast of Antarctica, where also you get
some very cold air temperatures and ocean water freezing.
So the concern is that in the area around Greenland, the water has been becoming fresher
partly because of the water that's being melted from the Greenland ice sheet.
(Medley) "Over the past few days we've seen a significant amount of, actually, liquid
water on the surface that have both accumulated in small ponds, and probably approaching the
size of lakes especially near the edge of the ice sheet.
An interesting thing is that the melt season actually in Greenland started pretty much
end of April, beginning of May--which, in the grand scheme of things, is very close
to a month earlier than average.
My name is Brooke Medley.
I'm the deputy project scientist for Operation Ice Bridge.
Last April and May, we were actually flying in Greenland out of Kangerlussuaq on the NASA
P-3.
This was somewhat of a unique year where we expected to be going early enough where we
would see the typical dry snow conditions.
But, rather, we were met with a much different scenario where we saw all these spectacular
blue ponds of beautiful liquid water just pooling on top of the surface.
The ice sheet is actually experiencing almost an additional month of melt because it started
so early here.
Part of it is actually driven by the fact that it's very warm right now, but also that
there was not a lot of snowfall last winter.
And so what that means is when the snow does melt it very quickly exposes darker ice, which
can then melt even faster.
Just a significant increase in the total amount of water that we just see in general over
the course of 2019.
There was so much melt that it actually ended up being the second largest meltwater production
year for the Greenland ice sheet since 1980.
It's actually quite simple: the longer your melt season that means you can just have more
time to accumulate more melt, and the only place for this water to go is into the oceans."
(Dr. Francis) Also, there's more fresh water flowing from rivers into the Arctic ocean.
That fresher water then comes out into the North Atlantic in that passage between Europe
and Greenland there.
And so we're finding this area of fresher than normal water just south of Greenland
and the reason it's looking colder than average there is because when that fresh water is
sitting there it floats because fresh water is lighter than the salt water.
It sits on top and it prevents that freezing process and that creation of that very salty,
dense water from happening, it slows it down anyway.
(Bryce) You can see that on the map--that's the most contrasting, rapidly contrasting
color area.
(Dr. Francis) Exactly.
(Bryce) It's very clear.
(Dr. Francis) Yes it is.
And it even has a name.
It's called the 'Cold Blob.'
(Bryce) The cold blob?
(Dr. Francis) Yes, it's a very technical term.
(Bryce) Because it just sits.
(Dr. Francis) Yeah, it's been there for several years and it's a very interesting area.
A lot of people are studying it because not only does it have this effect on the ocean
circulation, but it also is causing weather patterns to change in the North Atlantic and
in Europe.
Because whenever you change temperature patterns in the ocean or on land you affect winds.
And when you affect winds, you affect weather.
(Bryce) The water moving through the Atlantic Meridional Overturning Circulation flows at
a rate of 20 million cubic meters per second.
Studies show that, since the 1950s, this rate has slowed by 15%.
That 3 million cubic meters per second loss is equivalent to three times the flow rate
of all the rivers in the world.
If this already massive decrease continues - which seems likely - and the AMOC stalls
completely - it would disrupt the entire climate system.
We know this because it's happened before.
Past changes in Atlantic overturning have caused some of the strongest and most rapid
climate shifts, such as a southward shift of the tropical rainfall belt, and warming
of the southern ocean and Antarctica.
(Dr. Steffensen) The last 11,000 years - that since the Ice Age - this our interglacial
period, has been unreasonably stable--and we don't know why?
With an enhanced greenhouse effect from the burning of fossil fuels - CO2 and methane
and so on - you would have a gradual increase in temperature.
That's what all the models show you, it's sort of a gradual increase in temperature.
But that's assuming that the climate plays nice.
And we actually know from the ice cores that the climate does not play nice all the time.
We have tons of examples of climate changes where we see complete reorganization of the
atmospheric circulation from one year to the next and that will be extremely hurtful for
any agricultural activity in the world--because the weather will change and will not change
back.
What we know from the sudden climate changes in the past is that these abrupt changes represent
a reconfiguration of the entire atmospheric pattern.
What if, with the emission of greenhouse gases, that we trigger a situation when this system
all of a sudden goes into a feedback?
If you reconfigure the transport patterns of high pressures and low pressure systems
over North America and, for instance, Europe--but particularly North America and the Midwest,
and all of a sudden it stops to rain.
And it hits the Midwest and the U.S. and it leads to massive crop failure.
That's going to impact the entire world.
We don't know.
We don't know where the threshold is.
But we are rats inside the experiment.
(Bryce) You can support the Climate Change Solutions show and unlock every full episode
through the link below.
The small membership fee also gives you access to my research links so you can easily learn
much more.
Until next time, thanks for watching.
I'm Bryce Plank.