Our oceans are interconnected to form a single, powerful engine driven by sunlight and affected by changes in water temperature, salinity, gravity and tectonic plate movements. From the ocean floor to tropical coral reefs, estuaries and Arctic ice floes, they redistribute energy from the equator to the poles, affecting the global climate. This plays a vital part in supporting all marine life, from tiny plankton to massive whales.
We are ocean
On 7 December 1972, Apollo 17 was 29,000 km on its way to the Moon, in perfect alignment with the Earth and Sun to take the first ever picture of our fully illuminated planet. It showed just one planet, one atmosphere and one ocean, with no borders. The ideal icon to promote public awareness of our global ecosystem and its fragility. The message we send to the universe is: “We are ocean.”
We need tolook at a different map projection to realise it is one ocean, not the five we normally refer to (Pacific, Atlantic, Indian, Arctic, Southern). This is key to understanding the complex links between climate and ocean changes. The map preferred by the Woods Hole Oceanographic Institution in the USA is the Spilhaus projection, introduced in 1942. Insert map here. This has been adapted to show ocean surface temperature.
Descending into the ocean
If we descend into the ocean and view it horizontally, from top to bottom, we see a warm layer of 25 to 30°C in the top few metres of tropical areas. Here the ocean is gathering and storing the heat energy from the sun. As it penetrates the water, the red light is absorbed in the first 4 metres or so, then the green down to 10 metres, followed by the blue from 20 metres or so. This is why, from above, the ocean appears to be blue.
Some of this energy evaporates above, warming the atmosphere, and the rest heats the water below. Infra-red energy is absorbed and re-radiated back into the atmosphere. As you descend, there are cooler layers of water, down to, for example, 4°C at 3000 metres. There is also a relatively very small amount of geothermal energy from below. But the ocean is too big to mix up without some external influence.
Currents churning the water
One influence is ocean currents formed by surface winds on the water, the rotation of the Earth, gravitational effects, storms and earthquakes. One famous current is the Humboldt, which brings cold water and nutrients from the Antarctic up the eastern side of South America to the Galapagos Islands. As it moves north, the warm layer is pushed away from the land, allowing the cold water and nutrients to rise, be exposed to sunlight and attract fish. This is an example of our ocean acting as an engine, churning the water to make life possible. To learn how this affected the price of bacon in Britain in the 1970s, watch How does the ocean help shape our world? with Helen Czerski.
Now you also know that but for the blue machine, there would no white cliffs of Dover and no concrete for our buildings. Here is a map of the currents in the Arctic Ocean, currently a focus of political attention. I will be following the Operation Firecrest deployment of HMS Prince of Wales and the NATO maritime support group led by the UK, in conjunction with US and Canadian forces, to this area during the Spring.
Variables of the ocean
The temperature and salinity of ocean water vary with latitude, depth and season. At mid-latitudes (45 to 55 degrees), the average temperature can drop to 10 to 13°C, and near 60 degrees latitude, to 0 degrees C. At a depth of 200 metres, the average temperature is 2°C, dropping to 3.5°C at 1 kilometre and 1°C at 5 kilometres. Temperature and salinity also control water density, which drives ocean circulation.
Above the surface, sight is our primary sense. We can see a couple talking across the street, but we can’t hear their conversation. Under water, sound is the primary sense due to the rapid loss of light at depth.
In air, sound travels at 343 metres per second at 20°C. In water, it travels at 1500 to 1531 metres per second due to the greater density and elasticity. This is why it can travel much further and more efficiently in water, and marine species, such as whales, have evolved to use sound for communication. Light and sound can be described as the messengers of the ocean, while heat is a passenger and marine life is the voyager seeking nutrition and safety.
Earth’s contribution to universal entropy
Without water, none of us could exist, and neither could the structures we build. Water is the strangest liquid. Without water, I could not have sat here in Queensland, Australia while watching the Winter Olympics in Italy, having experienced much tropical rain and a cyclone, while New South Wales is covered by forest fires, and Portugal and Spain suffer floods.
The complex interaction of the ocean, the atmosphere and biology plays a crucial part in our planet’s life support system. The energy added continuously to the ocean circulation is only a fraction of that going into the atmospheric circulation, which in turn is only a fraction of that arriving from the Sun. Earth is exporting entropy to the universe, and it is this entropy export that effectively ‘pays’ for all the wonderfully ordered structure (mountains, trees, us) that we have on Earth.
The laws of thermodynamics state that entropy (the measure of a system’s energy that is unavailable for ‘mechanical’ work) must always increase with time. For example, as the universe expands, the available energy is spread more widely, leaving less available for ‘work’. Whether this will lead to the heat death of the universe is open to debate. But what overwhelming evidence from scientific research shows is that if we don’t change our activities to reduce our impact on global warming, we are failing to realise that we are a significant part of Earth’s life support system.
Our responsibility to ocean life
As an ex-naval aircraft engineer with experience in research, development, trial and operational use of anti-submarine warfare technology, I am now acutely aware of the effects of putting sound in the ocean due to our ignorance. Whether these effects result from this warfare technology or the propulsion sounds of ships carrying trade and people over vast distances, we should be listening to the whales, not disrupting their communication, and finally put a stop to the whaling industry. Whether you are a farmer, fisherman, energy supplier or distributor, you must consider: “Am I working with the ocean or against it?”
Further information
I am indebted to Dr Helen Czerski, British physicist, oceanographer and regular broadcaster of BBC videos and podcasts on oceanography based on practical research. She is the key British educator on oceanography as Tim Peake is on space exploration. I highly recommend her book, The Blue Machine, on how the ocean shapes our world, available on amazon.co.uk in paperback, audio and Kindle format.
