Feature | June 13, 2017
NASA-MIT study evaluates efficiency of oceans as heat sink, atmospheric gases sponge
Credit: NASA’s Goddard Space Flight Center.
By Ellen Gray,
NASA’s Goddard Space Flight Center
The world’s oceans are like brakes slowing down the full effects of greenhouse gas warming of the atmosphere. Over the last ten years, one-fourth of human-emissions of carbon dioxide as well as 90 percent of additional warming due to the greenhouse effect have been absorbed by the oceans. Acting like a massive sponge, the oceans pull from the atmosphere heat, carbon dioxide and other gases, such as chlorofluorocarbons, oxygen and nitrogen and store them in their depths for decades to centuries and millennia.
New NASA research is one of the first studies to estimate how much and how quickly the ocean absorbs atmospheric gases and contrast it with the efficiency of heat absorption. Using two computer models that simulate the ocean, NASA and MIT scientists found that gases are more easily absorbed over time than heat energy. In addition, they found that in scenarios where the ocean current slows down due to the addition of heat, the ocean absorbs less of both atmospheric gases and heat, though its ability to absorb heat is more greatly reduced. The results were published in Geophysical Research Letters, a journal of the American Geophysical Union.
“As the ocean slows down, it will keep uptaking gases like carbon dioxide more efficiently, much more than it will keep uptaking heat. It will have a different behavior for chemistry than it has for temperature,” said Anastasia Romanou, lead author and climate scientist at NASA’s Goddard Institute for Space Studies and Columbia University in New York City.
Credit: NASA’s Goddard Space Flight Center.
She and colleagues at the Massachusetts Institute of Technology in Cambridge, Massachusetts used the NASA GISS ocean model and the MIT General Circulation Model to simulate one of the Atlantic’s major current systems that delivers absorbed heat and gases to the depths.
In the Atlantic Ocean, the Gulf Stream is part of what’s called the Atlantic Meridional Overturning Circulation, a conveyor belt of ocean water that carries warm water from Florida to Greenland where it cools and sinks to 1000 meters (about 3281 feet) or more before traveling back down the coast to the tropics. On its northward journey, the water at the surface absorbs gases like carbon dioxide and chlorofluorocarbons (CFCs) – the latter are, to a large extent, the gases responsible for the ozone hole over Antarctica – as well as excess heat from the atmosphere. When it sinks near Greenland, those dissolved gases and heat energy are effectively buried in the ocean for years to decades and longer. Removed from the atmosphere by the ocean, the impact of their warming on the climate has been dramatically reduced.
To understand and quantify the ocean’s sponge-like capabilities, the researchers used the two independent models of Atlantic Ocean currents together with shipboard observations of chlorofluorocarbons as a starting point. Chlorofluorocarbons are what’s called a passive tracer.
The red line on the map shows the Gulf Stream current, the surface portion of the Atlantic Meridional Overturning Circulation. Shown in shades of blue are the concentrations of CFCs at depth in the ocean. Nearer to the equator, the CFCs only occur at the surface. As the Gulf Stream current moves north, they begin to be drawn down to depth with the downward pull of the conveyor belt. Image credit: NASA/Jenny Hottle.
“I think of it as a colored dye,” said co-author John Marshall, a professor of oceanography at the Massachusetts Institute of Technology. “If I have a bucket of water and just stir it around and put some food coloring in it, the dye goes down into the water, and it doesn’t influence the circulation of the water.”
In the real world as well as in the model, this allows scientists to “see” how much of the gas is absorbed from the atmosphere into the ocean and then follow it as it travels around the world in the currents. Adding heat to the ocean, in contrast, slows down the overturning circulation because ocean currents depend on temperature gradients – moving from warmer locations to cooler locations – that weaken under global warming as cooler waters heat up. This means that estimating how much heat the ocean absorbs by only using a tracer may not be accurate.
“The results show that we need to think differently about how the ocean responds to taking up heat and passive tracers or greenhouse gases. Then we need to study them in parallel but using different methods,” Romanou said.
These results from the computer models of the Atlantic Meridional Overturning Circulation are one of the many moving parts that come together in global climate models. By refining scientists’ understanding of how efficiently gases and heat are taken up, the finding will improve global climate model projections for future climate scenarios, said Marshall. This is especially true for projections that stretch tens or a hundred years into the future, when those tracers and other gases that behave similarly like carbon dioxide, as well as excess heat energy, reach the upward turn of the conveyor belt and return to the surface. When that happens some portion of them will return to the atmosphere after their long underwater journey around the planet.
“Most of the excess heat from climate change will go into the ocean eventually, we think,” Romanou said. “Most of the excess chemical pollutants and greenhouse gases will be buried in the ocean. But the truth is that the ocean recirculates that extra load and, at some point, will release some of it back to the atmosphere, where it will keep raising temperatures, even if future carbon dioxide emissions were to be much lower than they are now.”
This eventual release of buried gases and heat from the oceans is sometimes called the “warming in the pipeline” or “warming commitment” that people will eventually have to contend with, Romanou said.
Reference
Romanou, A., J. Marshall, M. Kelley, and J. Scott, 2017: Role of the ocean’s AMOC in setting the uptake efficiency of transient tracers. Geophys. Res. Lett., early on-line, doi:10.1002/2017gl072972.
Media contacts
Leslie McCarthy, NASA Goddard Institute for Space Studies, New York, N.Y., 212-678-5507, leslie.m.mccarthy@nasa.gov
Michael Cabbage, NASA Goddard Institute for Space Studies, New York, N.Y., 212-678-5516, mcabbage@nasa.gov
Is space cold or hot? There are no molecules in space so our common definitions of hot/cold/heat/energy don’t apply.
The temperatures of objects in space, e.g. the earth, moon, space station, mars, venus, etc. are determined by the radiation flowing past them. In the case of the earth, the solar irradiance of 1,368 W/m^2 has a Stefan Boltzmann black body equivalent temperature of 394 K. That’s hot. Sort of.
But an object’s albedo reflects away that heat and reduces that temperature.
The earth’s albedo reflects away 30% of the sun’s 1,368 W/m^2 energy leaving 70% or 958 W/m^2 to “warm” the earth and at a S-B BB equivalent temperature of 361 K, 33 C colder than the earth with no atmosphere or albedo.
The earth’s albedo/atmosphere doesn’t keep the earth warm, it keeps the earth cool.
Over 3,000!! (up 1,200 since 6/9) views on my WriterBeat papers which were also sent to the ME departments of several prestigious universities (As a BSME & PE felt some affinity.) and a long list of pro/con CAGW personalities and organizations.
NOBODY has responded explaining why my methods, calculations and conclusions in these papers are incorrect. BTW that is called SCIENCE!!
SOMEBODY needs to step up and ‘splain my errors ‘cause if I’m correct (Q=UAdT runs the atmospheric heat engine) – that’s a BIGLY problem for RGHE.
Step right up! Bring science.
http://writerbeat.com/articles/14306-Greenhouse—We-don-t-need-no-stinkin-greenhouse-Warning-science-ahead-
http://writerbeat.com/articles/15582-To-be-33C-or-not-to-be-33C
http://writerbeat.com/articles/16255-Atmospheric-Layers-and-Thermodynamic-Ping-Pong
Nick,
As the earth is a sphere, didn’t you forget to take into account that you need to reduce the flat earth surface radiation of 1,368 W/m^2 with a factor 4?
Solar IR is changed to heat by the ground. The ground is short term storage. the ground heats up the oceans. The oceans are long term storage and are conveyors.
I am not sure how you are supposing that heat is transferred from ground surfaces into the ocean water?
And I do not think conveyors is a very good word to use for ocean currents. The conveyor belt is a continuous loop in which one part is connected to all the other parts and pulling on one part or pushing on one part will move all the other parts by necessity.
The oceans are not like conveyor belts, they’re huge pools of water that are very deep, and have complex shapes, multiple layers with various degrees of mixing between the layers, and have currents in them, and that are constantly changing.
Are they implying that NASA has found the hidden heat?
If they put more emphasis on solar variations adding heat to the oceans they might actually find out the truth, instead of chasing this flawed CO2 hypothesis. I wish NASA would abandon climate research and focus on what we (The Taxpayers) pay them to do.
Indeed. NASA doing climate science is like climate scientists probing Uranus. However much the latter may want to do that it’s really not their business to be going where no man has gone before. NASA should stick to space and aeronautics and let climate scientists play with their virtual reality video games.
Somebody ought to teach these people some physical chemistry, Absorption of gases, heat, etc. by water occurs at the gas/water interface – something called the ‘surface’, which is far more efficient when the surface-to-volume ratio is high, as on a raindrop. The rain falling on the oceans in the tropics and temperate zones is saturated (or nearly so) with atmospheric gases – some of which (CO2, NOx) are more soluble in water than others (N2, O2, ozone). Raindrops are also in thermal equilibrium with the air, so they transport atmospheric heat into the ocean. The rain ‘scrubs’ the air. The main driver of ocean currents is gravity – specifically the tidal forces of the sun and moon acting on the earth and the oceans – which is why the main circulation is always eastward on that part of the circuit nearest the equator.
Any model of chemical and thermal transport in the oceans that does not include the influence of rainfall and tides is hopelessly oversimplified.
Gravity !
Who knew ?
tadchem,
Solubility of CO2 in fresh water is very low, as there is no buffer capacity in fresh water. Even without extra pollution from SO2 and NOx, the pH would drop to around 4.
Most CO2 is released from warm equatorial waters, together with water vapor. When that condenses to rain, it needs several hundred m3 air to form 1 l of rain, what it absorbs from the CO2 at that height is negligible. If that rains out, falls on the ground and evaporates, that gives 1 ppmv CO2 extra in the first m3 of the atmosphere…
Only if you take into account the massive quantities of water transported via the atmosphere, there may be an appreciable amount of CO2 circulating with it, but mostly between the oceans and the oceans, thus a null operation… What falls on land still needs millions of years to form the beautiful caves we see everywhere in carbonate rocks and the returning waters are in many cases buffered with (bi)carbonates…
I’m hardly a scientist, and please feel free to educate me if my ignorance is unbearable, but…
Doesn’t what they’re proposing run counter to CAWG dogma? The dogma says, “If left unchecked, DOOM”. Wouldn’t the world’s oceans in this scenario be the ultimate ‘check’ on CAGW? Am I still supposed to believe that the human race will be extinct by 2100 if we don’t eliminate all fossil fuel consumption by 2030?
I’m so confused.
Ignorance is far more bearable than stupid. I speak from the former perspective.
If I were speaking from the latter perspective, then I wouldn’t even know it.
AJ_74,
According to the Bern model, used in near all climate model’s calculations for the IPCC, the deep oceans get saturated when they have absorbed about 10% of all our CO2 emissions. Thus according to them a lot of CO2 remains in the atmosphere for very long periods…
The problem is that this only may be true when you burn all know reserves of gas and oil and a lot of available coal, but by far not for smaller total emissions.
The original calculations were made for the above scenario when 3000 GtC CO2 was released and worse for 5000 GtC CO2, thus including enormous amounts of coal.
Currently we have burned fossil fuels in the past 165 years, emitting some total 370 GtC CO2 in the atmosphere. If we should cease all emissions, that will ultimately end mostly in the deep oceans, where already some 37,000 GtC in different forms is present. Thus all our emissions together will increase the deep oceans with less than 1% (minus what is buried permanently in vegetation). In equilibrium with the atmosphere, that also will end 1% higher, thus 293 ppmv CO2 instead of 290 ppmv for the current ocean surface temperature…
There is until now not the slightest sign of saturation of the deep oceans, thus wait and see what the future brings…
Given the ratio of Co2 in the deep oceans compared to emissions of humans, there will not be a signal by the time oil runs out, dear lord!
and truth be told we know nothing about the deep oceans, relatively speaking, we are 5th graders on that topic
“Mark – Helsinki July 14, 2017 at 12:34 pm”
We know more about the moon than we do deep ocean.
“AJ_74 July 14, 2017 at 10:00 am
I’m hardly a scientist, and please feel free to educate me if my ignorance is unbearable, but…
The dogma says, “If left unchecked, DOOM”.”
Let me correct you there;
The dogma says, “If left UNTAXED, DOOM”.
Do these authors even consider the amount of CO2 the oceans are capable of absorbing on a semi-permanent to permanent basis? Good grief, there are entire mountain ranges build of marine limestone in the Western U.S. Do the authors give any thought to the capacity of marine organisms to steal CO2 and turn it into rock?
Isn’t the largest long term Carbon sink CaCO3? As seen in limestone and chalk (The White Cliffs of Dover for instance) CaCO3 created naturally for shells of marine organisms, snails, and eggs, corals and many other sources.
Heat sink analogy is a bogus concept and with concepts reality leaves the room.
I suspect night time and clouds on the night side of the planet have a large influence on the energy budget.
I think this is the route for radiation to head out into space, and is regulated by clouds.
What if CFCs aren’t just a passive tracer?
Does anyone remember that from the ’60s through the ’90s we gaily sprayed and leaked chlorofluorocarbons (CFCs) into the atmosphere? And that Mario Molina told us that this was a no-no because in so doing we were destroying our all-important ozone shield? That allowed solar ultraviolet radiation (UV-B) to stream through the thinned ozone layer (remember the ozone hole?) and cause all sorts of horrible things like bad sunburn and genetic damage. UV-B is HOT!
So, we very sensibly shut down CFC production with the Montreal Protocol. No one thought, however, that this ultra-hot ultraviolet radiation could also cause global warming. No, because “obviously” the cause of global warming was rising carbon dioxide! Funnily enough, shortly after the Montreal Protocol, global warming went into “hiatus” mode, but carbon dioxide just kept on rising. The climate scientists were baffled. What happened? They tried to pretend that the so-called “hiatus” didn’t really exist, and they even performed various data manipulations to make it go away.
But it didn’t. It’s a reality. And guess what: almost all the chlorine from all the CFCs we put into the atmosphere is still up there, destroying ozone catalytically, and chlorine has a very long residence time in the atmosphere.
So, you see, the inconvenient “hiatus”and its elevated temperatures will be with us for quite some time to come, but eventually, the chlorine will precipitate out and global cooling will begin, while carbon dioxide continues on its merry way upward, doing nothing at all to the climate.
So,it seems that all the climate scientists are, like Don Quijote, tilting at the wrong windmill. “It’s chlorine, stupid, not carbon dioxide.”
Extended periods of darkness has more to do with lack of ozone at the poles. Sunlight is necessary for ozone production. 🌞