researchers at the massachusetts institute of technology (mit) in cambridge and nasa have studied how the oceans act as heat sinks slowing down the effects of greenhouse gases on the warming of the atmosphere and their report indicates that the oceans absorb gases twice as quickly as heat energy and that the additional heat not only slows down ocean currents but also reduces the ability of oceans to absorb gases or heat.
mit and nasa are studying the effect of heat on ocean currents and oceans' ability to absorb
greenhouse gases and heat energy. (mit/youtube)
according to a report on the mit website, researchers used the nasa giss ocean model and the mit general circulation model to simulate major currents in the atlantic ocean, including the atlantic meridional overturning circulation (which includes the gulf stream) that carries warm waters to greenland where it dives to 1,000 meters below the surface to cool and traveling back 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,” the article explained.
it continued, “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.”
scientists used two independent models and shipboard observations of chlorofluorocarbons to begin the study and see how much gas is absorbed from the atmosphere into the ocean. because currents rely on temperature gradients, global warming slows down the movement of water.
this study will help researchers refine studies of future effects of global warming by adding new computer models to the overall examination of how warming oceans affect absorption of greenhouse gases and heat.
“this is especially true for projections that stretch tens or 100 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,” the article explained. “when that happens some portion of them will return to the atmosphere after their long underwater journey around the planet.”
one of the researchers called this eventual release of greenhouse gases and energy the “warming in the pipeline” or the “warming commitment.”
the research was published in june in geophysical research letters. the abstract stated:
“the central role played by the ocean's atlantic meridional overturning circulation (amoc) in the uptake and sequestration of transient tracers is studied in a series of experiments with the goddard institute for space studies and massachusetts institute of technology ocean circulation models. forced by observed atmospheric time series of cfc-11, both models exhibit realistic distributions in the ocean, with similar surface biases but different response over time.
“to better understand what controls uptake, we ran idealized forcing experiments in which the amoc strength varied over a wide range, bracketing the observations. we found that differences in the strength and vertical scale of the amoc largely accounted for the different rates of cfc-11 uptake and vertical distribution thereof.
“a two-box model enables us to quantify and relate uptake efficiency of passive tracers to amoc strength and how uptake efficiency decreases in time. we also discuss the relationship between passive tracer and heat uptake efficiency, of which the latter controls the transient climate response to anthropogenic forcing in the north atlantic.
“we find that heat uptake efficiency is substantially less (by about a factor of 5) than that for a passive tracer.”
learn more in the video below: