World Oceans Day 1: Let’s get physical

Department of Conservation —  18/05/2021 — 1 Comment

World Oceans Day is on the 8th of June. This day is an opportunity to celebrate all the ways that the ocean supports our lives and livelihoods and highlight the significant challenges we face in ocean conservation. Here’s part one of a series of blogs about this day.

This first blog is dedicated to celebrating the vast big blue that surrounds us and exploring its role in climate change mitigation and adaptation.

By Irene Llabres Pohl, Technical Advisor Mountains to Sea

Satellite view of the pacific ocean, which holds over half the world’s oceanic water
📡: Google Earth

 Planet Ocean

… is what Earth should be called.

The ocean covers more than 70% of Earth’s surface and provides 99% of the habitat for life on Earth. From creepy crawlies in rock pools, to fascinating long-distance migrations of many marine animals, there’s no doubt that the ocean casts its spells on most of us.

But did you know that the ocean itself rocks the entire climate system? Let’s dive right into a few of the ways that the physics of the ocean rule the Earth.

The planet’s thermostat

The ocean contains 96% of the earth’s water.

Since water stores energy incredibly well, the ocean plays a key role in climate regulation.

Major surface ocean currents move heat away from the tropics towards the icy poles where the water cools and sinks, flowing back along the seafloor. This giant ocean heat conveyor belt slowly turns over water in the entire ocean, from top to bottom, over thousands of years.

Because the ocean takes in such huge quantities of heat and releases it very slowly, it has a regulating effect on Earth’s overall climate, akin to how our blood and circulatory system regulate our body temperature. It’s ultimately the main reason that we enjoy a stable and life-sustaining climate.

Figure of global ocean circulation shown in the Spielhaus map projection
📈: Michael P. Meredith/ British Antarctic Survey

^ Finally, a map that has Aotearoa on it.

The world’s largest waterfall is underwater

That’s right, the worlds largest waterfall is the Denmark Strait Cataract, and it’s underwater.

At key locations in the ocean conveyor belt, surface water become cold and dense and sinks. In the north Atlantic, the water spills over an underwater cliff and falls a mind-blowing 3500 m into the deep North Atlantic, putting its land-based competitor, Venezuela’s Angel Falls at 980 m, to shame. Oceanographers estimate 6 billion litres per second flow down this waterfall.

This channel of Mauritus in the Indian ocean gives you good visual of what an underwater waterfall would look like
📡: Image Google Earth

Ocean and rainfall

Scientists estimate that at least 50% of rainfall on land originates from evaporation in the ocean.

In Aotearoa, fully surrounded by ocean; we can assume that the vast majority of water falling from the sky came from the surrounding seas.

So wherever you are today, if it is raining, take a second to appreciate that the sea might be much closer than you think.

Like this:

Screengrab from the 2013 cinematic masterpiece, Sharknado
📷: NBC

But also, not like this. We’re joking. Scientists make jokes too.

Back to rain:

Marine biodiversity also has a role to play in regulating rainfall. Scientists think some types of marine algae release chemical compounds into the atmosphere which cause water droplets and clouds to form.

That’s just a small side-gig for these tiny sea creatures, in addition to providing 50% of the oxygen we breath and the food basis for all life in the sea.

A spring bloom south-east of Cook Strait in October 2009. Credit: NASA Earth Observatory
📡:: NASA Earth Observatory

Let that (carbon) sink in

The ocean also plays a critical role in climate regulation by absorbing carbon dioxide (CO2).

CO2 can be used by phytoplankton for photosynthesis, or by organisms such as pāua and corals to build their shells and skeletons. Over decades, the ocean acts as a massive carbon sink.

Since CO2 is a key greenhouse gas, by taking in CO2 the ocean has a direct effect on how much solar energy is trapped in the atmosphere. The ocean is (for the time being) literally taking the heat out of climate change.

Is Earth’s climate always the same?

No, the Earth has natural climate cycles that occur at multiple time scales, from years to decades (think El Niño/La Niña), centuries and millennia. Some are due to differences in solar energy reaching us because of periodic changes in the Earth’s orbit around the sun. When that happens, the whole climate system and in particular ocean currents adjust to restore balance, just like a heat pump cranks up or down if we change the desired temperature.

To learn more about how the ocean functions, check out the ‘One Planet, One Ocean’ course by the UN’s Sustainable Development Goals Academy, provided for free on distance learning platform edX.

In part 2 next week we will break down how the ocean is responding to human-induced climate change.


To learn more about our work in the oceans space, head here: https://www.doc.govt.nz/nature/habitats

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  1. World Oceans Day: Taking the heat out of global warming | Conservation blog Conservation blog - May 25, 2021

    […] week in our first blog in this series, we discussed how the ocean regulates our climate. Now, we’re diving […]

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