Global Warming/Climate Change

An Ocean of Unknown

Photo copyright: Simon Nash

Carbon dioxide emissions from human activities are acidifying the oceans and threaten a mass extinction of sea life, a top ocean scientist warns.

Dr Carol Turley from Plymouth Marine Laboratory says it is impossible to know how marine life will cope, but she fears many species will not survive. – BBC

That’s a quote from today’s BBC news. To follow is a quote from an updated intro to a well-loved book – one first published 140 years ago:

“The deepest parts of the ocean are totally unknown to us,”… “What goes on in those distant depths? What creatures inhabit, or could inhabit, those regions twelve or fifteen miles beneath the surface of the water? It’s almost beyond conjecture.”

Jules Verne (1828–1905) published the French equivalents of these words in 1869, and little has changed since. 126 years later, a Time cover story on deep–sea exploration made much the same admission: “We know more about Mars than we know about the oceans.” – from the introduction to Jules Verne’s “Twenty Thousand Leagues Under the Sea”

Given Jules Verne’s deep interest in science and the unknown, and his eagerness to pass this enthusiasm and sense of mystery to young and old, I can’t help but wonder how he would react if he could see us now. If scientists are correct, we may well be adversely impacting creatures we’ve never even laid eyes upon, let alone classified.

The Southern Ocean has been absorbing less CO2 from the atmosphere since 1981, even though levels have increased 40 percent due to burning of fossil fuels. Oceans absorb half of all human carbon emissions, but the Southern Ocean is taking up less and less and is reaching its saturation point, reported an international research team in the journal Science.

This is the first evidence of the long-feared positive feedbacks that could rapidly accelerate the rate of climate change, pushing impacts to the extreme end of the scale. – IPS

I know what you’re going to ask – “why do they mention the ‘Southern Ocean’ in particular?” Here’s the scoop:

Carbon dioxide in the atmosphere can dissolve in water, and the colder and more turbulent regions of the oceans tend to absorb carbon dioxide, while the warmer and less turbulent regions release it, carbon dioxide being less soluble in warm water than in cold water. – Institute of Science in Society

The IPS article mentions one obvious impact of oceans reaching a CO2 saturation point – my paraphrased summary being that we’re losing an enormous, and free, CO2 offset mechanism.

As dire as this may be, it doesn’t stop there. In nature, nothing is linear. Another consequence of excess ocean CO2 levels is increased ocean acidification.

Ocean acidification is the name given to the ongoing decrease in the pH of the Earth’s oceans, caused by their uptake of anthropogenic carbon dioxide from the atmosphere. Between 1751 and 1994 surface ocean pH is estimated to have decreased from approximately 8.179 to 8.104 (a change of -0.075) – Wikipedia

There are, of course, implications to this acidification trend:

  • Under normal conditions, calcite and aragonite are stable in surface waters since the carbonate ion is at supersaturating concentrations. However, as ocean pH falls, so does the concentration of this ion, and when carbonate becomes undersaturated, structures made of calcium carbonate are vulnerable to dissolution. Research has already found that corals, coccolithophore algae, coralline algae, foraminifera, shellfish and pteropods experience reduced calcification or enhanced dissolution when exposed to elevated CO2. (Wikipedia).
  • Many forms of sea life extract carbon and oxygen from seawater and combine them with calcium to produce calcium carbonate (CaCO3). This is used to produce shells and other hard body parts by a variety of organisms, such as coral, clams, oysters, and some microscopic plants and animals. When these organisms die, their shells and body parts sink to the seabed. Over very long periods of time, enormous numbers of dead organisms can create thick layers of carbonate-rich deposits on the ocean floor. – Schlumberger

Another effect of global warming is a reduction in the upward movement of the nutrient-rich deeper stratum – with implications for one of the most important ingredients in our ‘biological soup’: phytoplankton.

Global warming of the surface layers of the oceans reduces the upward transport of nutrients. Computer simulations predict that plankton growth will become unstable when the supply of nutrients is reduced…. Plankton plays a key role in the oceans. It forms the basis of the marine food web. Moreover, phytoplankton (microscopically small algae) consumes the greenhouse gas carbon dioxide during photosynthesis. Because the oceans cover more than 70% of the earth’s surface, marine phytoplankton is quantitatively important for reducing the greenhouse effect on earth. Phytoplankton growth depends on light and on nutrients such as nitrogen and phosphorus. These nutrients are supplied from deeper ocean layers, and are slowly mixed upwards. In large parts of the oceans, phytoplankton is concentrated at about 100 meters depth. Phytoplankton grows well at this depth, because there is a sufficient supply of light from above and a sufficient supply of nutrients from below…. However, warm surface layers reduce mixing of the ocean waters. This vertical stratification of the water column is widespread in the oceans. A larger temperature difference between two water layers implies less mixing of chemicals between these water layers. Global warming of the surface layers of the oceans, owing to climate change, strengthens the stratification and thereby reduces the upward mixing of nutrients. – Global Warming could Destabilize Plankton in Oceans

Phytoplankton absorb Carbon Dioxide and release Oxygen. In fact phytoplankton produce as much Oxygen as all the trees in the world, and they remove 3 billion tonnes of Carbon Dioxide every year. – SAHFOS

The global importance of phytoplankton cannot be overstated. – NASA

For phytoplankton to thrive there must be an appropriate supply of nutrients. Too little, and the phytoplankton will fail to grow, too much all at once from agricultural runoffs sewage or other industrial pollutants, and algal blooms will result that could become toxic to fish, livestock and humans eating shellfish that feed on the phytoplankton and accumulate the toxins [12]. Moreover, the water must not be too warm, or too acid. All these conditions are deteriorating on account of global warming, bringing the prospect of a collapse in the marine biota, and turning the oceans into a massive carbon source that would further aggravate global warming…. – Institute of Science in Society

It must be said that the interactions of oceans, and ocean life, are a relatively new study. Not enough is known to pretend to give a half-decent picture of the potential reactions to climate change by the vast oceans and the creatures that inhabit them. If our experience of terrestrial environments (which, in themselves, are still full of mystery) is anything to go by, however, then there will be no quick fix to restoring equilibrium to the sea.

Oceans are vast, deep, and mysterious. They cover 71 percent of the earth’s surface and contain approximately 97 percent of the earth’s water. The average depth of the ocean is almost 4,000 metres, and nearly half the area is over 3,000 metres deep.

The oceans are home to the majority of plant and animal life on earth, accounting for 90 percent of the world’s living biomass, and many new species are being discovered from the depths. The Census of Marine Life (COML), an international alliance of scientists from 70 countries, discovered some 13 000 new species in 2003 alone. – Institute of Science in Society

CO2 absorption by our oceans is a natural part of the great carbon cycle. It is – like many other pieces of this huge, interdependent jig-saw puzzle that is our biologically diverse world – yet another service to humanity that we tend to take for granted, until we begin to lose it. If the world is our host, and we are its guests, our activities over the last century are a serious breach of etiquette. We have overstepped our bounds. And, if our own needs must take precedence in this discussion, let’s not forget that the ocean’s great bounty directly nourishes untold millions of our own species.

"I believe we may be heading for a mass extinction, as the rate of change in the oceans hasn’t been seen since the dinosaurs.

"It may have a major impact on food security. It really is imperative that we cut emissions of CO2." – BBC

A natural carbon equilibrium is being tipped out of balance, and we would do well to take heed. There is an ocean of unknown out there.



  1. Scary stuff Craig…no wonder our Reefs are dying. It has been all over the news the last couple of days how the ocean is warming up much faster than previously anticipated. Saw a doco recently too that believes that if carbon emissions aren’t drastically reduced in the next decade, it will be too late – climate change will just drive itself. Now is the time for action, but unfortunately the message doesn’t seem to be getting across where it’s needed.

  2. If everyone would just stop breathing for one day we could tackle this CO2 problem. There are many problems that we have created on this planet. I have done extensive research on both sides of the table regarding global climate change. In my opinion the world is putting to much focus on global climate change instead of the real problems. GMO is one of them. There are many others that could be listed of which there is only one side and definite serious problems arising from them. Why are people not spending time on these issues. I never hear of anyone talking about the destruction of our trees and forests anymore. I found it interesting that Al Gore owns a company whose sole purpose is the clearing of forests for development purposes. The so called know it all on global climate change is probably contributing more to the problem than any other single person. It seems the chemical polution of our water is far more damaging than CO2. Here in the United States our methods of dealing with sewage is completely backwards. Pharmaceuticals gone bad are being dumped in our waterways to dispose of them. The list goes on.

  3. Reef bleaching is serious stuff Peta. In 1998, for example, “up to 90 percent of coral reefs died in some areas of the Indian Ocean” (ENS Newswire). With hotter years to come, these ecosystems may well collapse entirely. In regards to tackling climate change too late, check this and this out.

    Thanks for your comment Jacob. Yes, you’re right – if we all stopped breathing (i.e. the human race disappeared), nature would restore itself eventually. I don’t see that as an option though.

    In regards to which problem is worse – they’re all serious, and they’re all also inter-related. Chemical pollution of our water is largely due to industrial agriculture, for example, and industrial agriculture also happens to be the biggest user of water, destroyer of topsoil – and, significantly, the biggest consumer of fossil fuels and thus the biggest contributor to climate change.

    We also cover the topics you’ve mentioned – water, GMO’s, soil loss, deforestation, chemical pollution, plant diversity, and much more. People need to know about it all – including climate change.

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