Environment

Climate change to trigger shift in color of world's oceans by end of the century

Climate change to trigger shif...
The changes to ocean color could be noticeable from space
The changes to ocean color could be noticeable from space
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The changes to ocean color could be noticeable from space
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The changes to ocean color could be noticeable from space

Climate change could cause more than 50 percent of Earth's oceans to change color by the end of the 21st century, according to a newly published study. The blues and greens of our planet's oceans may intensify, and could serve as an indicator for the health of marine life.

Human-triggered alterations to our planet's climate are already taking their toll on the oceans. The effects include a rise in sea temperature and ocean acidification, habitat destruction through coral bleaching and the creation of more powerful waves.

The new MIT study has revealed that climate change will also intensify the color of Earth's seas, and that the shift in hue could mark large-scale changes to the marine ecosystem.

Before talking about the significance of color to marine health, we need to understand why the ocean is blue. The answer lies in how sunlight interacts with matter. Water molecules are capable of absorbing the majority of the Sun's rays, with the exception of light located in the blue part of the electromagnetic spectrum. These unabsorbed wavelengths of light are reflected away from the molecules, making them appear blue.

However, Earth's oceans are not comprised of water alone. They are home to a stunning range of lifeforms of all shapes and sizes, all of which have unique properties and reflect different wavelengths of light. Therefore, the color of an ocean is partially a reflection of the life dwelling within, and can be used as an indicator of its health.

Among this aquatic menagerie are lifeforms called phytoplankton, a type of microscopic marine microalgae that contain significant amounts of chlorophyll. This natural pigment excels at absorbing the blue part of the electromagnetic spectrum and reflecting green light.

Enormous swarms of phytoplankton are responsible for turning vast swathes of water green. Scientists are able to use satellite imagery and data to estimate the amount of chlorophyll, and therefore the quantity of phytoplankton, present in an ocean region.

However, it is sometimes challenging to isolate the driving force behind an observed change in phytoplankton levels. Whilst it is possible that climate change could be the cause of a population swing, it could also result from natural causes, such as an El Niño event altering the level of nutrients in the marine environment.

Scientists behind the new study sought to use computer modelling to predict the effect that climate change will have on the populations of different species of phytoplankton, as ocean temperatures continue to rise. Their model takes into account how phytoplankton reflect light, and predicts how a change in microalgae populations would alter the color of the light from the water's surface.

Rather than create a computer model from scratch, the team modified an existing tool that had been used to predict phytoplankton population changes as a result of rising temperatures and ocean acidification. The model took into account phytoplankton characteristics such as feeding and growth behaviors, and was capable of simulating ocean currents and mixing dynamics.

The existing model was altered to allow it to estimate the specific wavelengths of light that would be absorbed, and those that would be reflected back out by the ocean depending on the quantity and diversity of organisms that are present in the body of water.

Results of simulations created by the team matched closely enough with past observations made by real-world satellites, for the researchers to be confident that their updated model was capable of predicting ocean colors resulting from specific environmental changes.

The scientists then simulated what parts of Earth's oceans would look like by the end of the century under a "business as usual" approach, wherein little is done to curtail greenhouse gasses, and the global temperature has risen by up to 3 °C.

In this scenario, computer modelling predicts that by the year 2100, there will be even less microalgae in the blue regions of Earth's ocean than there is today, causing it to appear a more vivid hue of blue. Meanwhile, current algae-rich areas will experience a phytoplankton bloom triggered by rising temperatures, causing them to appear greener.

"The model suggests the changes won't appear huge to the naked eye, and the ocean will still look like it has blue regions in the subtropics and greener regions near the equator and poles," says lead author Dr. Stephanie Dutkiewicz, a principal research scientist at MIT's Department of Earth, Atmospheric, and Planetary Sciences and the Joint Program on the Science and Policy of Global Change. "That basic pattern will still be there. But it'll be enough different that it will affect the rest of the food web that phytoplankton supports."

The changes should be visible to satellites in low-Earth orbit.

A paper detailing the work has been published in the journal Nature Communications.

Source: MIT

10 comments
aksdad
Please stick with science instead of hyperbole. There is no evidence that humans are "triggering" sea temperature rise, coral bleaching or "more powerful" waves. It is certain that human emissions are increasing CO2 in the atmosphere but how much it may be contributing to sea temperature rise, if at all, is undetermined. And coral bleaching is a natural phenomenon triggered by many things; one of which is rapid local warming, potentially caused by large El Niños. Bleaching is coral's survival response to changes in the environment which happen all the time in shallow reef waters. There is no evidence whatsoever that ocean waves are becoming more powerful and that humans are triggering the imagined powerful waves. Almost all these claims come from theoretical exercises in computer models based on the CMIP climate models which are not very accurate (to put it mildly) at simulating global climate.
rude.dawg
Just because the climate is changing, doesn't mean any of the changes are "human-triggered." The planet's climate has been changing for at least 4.5 billion years. Ice core samples have proven that more abrupt/rapid changes in the climate have happened before, with rates of changes that were much more rapid than the changes we're experiencing today. Temps soared by 22° within a mere 50 years, some 11,000 years ago for example. The dramatic changes from glacial to interglacial then back again is largely cyclical and primarily caused by the Earth's orbit being affected by Venus and Jupiter every 405,000 years. A computer simulation can show the whole planet turning purple and gold and still none of that proves any of the changes in the Earth's climate was or is "Human-triggered."
Pierre Collet
Whether climate change is human triggered or not is not the problem. The question can be decomposed in 2: - Is currently observed global warming menacing human development and well-being? (note that this includes biodiversity because of what we (humans) gain from bioinspired science, for instance) - If so, can we do something about it by reducing our human CO2 emissions? If yes, we should try. If no, well, let's try to ride is as well as we can...
Douglas E Knapp
Get real! Human made carbon is a fact. Stop with all the propaganda. https://en.wikipedia.org/wiki/Carbon_dioxide_in_Earth%27s_atmosphere#/media/File:Carbon_Dioxide_400kyr.png
farah
in addition to agreeing with the comments below, there is mounting evidence the earth is entering into a multi-cycle juncture of grand solar minimum with larger cosmic cycles to plunge our planet into a prolonged cooling, possible ice-age period. the problems our oceans face have little to do with temperatures and more to do with human exploitation and disregard for our Mother Earth. micro-plastics are now within almost each and every human body on the planet. we are derelicts of our responsibilities to protect and preserve this wondrous refuge afloat in an inhospitable sea of unimaginable cold and desolation.
owlbeyou
One has to consider the POV of climate change denying but the evidence is not conclusive. The Ninos, waves and storms are more frequent, unpredictable and intense, and the worldwide effluence from human activity into the ocean is a phenomenon unseen before. We've been using the sea as a drain for years and all that unnatural chemical soup (like fertilizers and more) must have a deleterious effect on the ocean, and since life began in the sea, we may be indeed slowly killing ourselves.
Thinker
I’m curious about our atmosphere. What holds it in place, what determines the line that separates our atmosphere from space? What happens when our rockets keep punching through our atmosphere, does our atmosphere escape into space? Does the penetration of our atmosphere have anything to do with our ozone layer? Does it have anything to do with our climate change? I’d love for someone to comment on the questions.
Douglas Bennett Rogers
With the greater part of the ocean being bluer, the Earth's albedo would be decreased and the temperature raised.
Robert in Vancouver
Another dire prediction based on computer models that are based on guesses, assumptions, and other computer models. This is getting silly. We are wasting so much money and effort on something that may or may not be a problem, and in any event it's beyond our control. Meanwhile, real serious research like curing cancer is severely under-funded.
Catweazle
Ah, more computer games - er, sorry - climate models... Colour me unimpressed.